Volume 46,Issue 1,2017 Table of Contents
2017, 46(1):1-6.
Abstract:
With the melting temperature of 2323 K and withdrawing rate of 100 μm/s, Nb-Ti-Si based ultrahigh temperature alloy has been directionally solidified with the use of crucibles. The directionally solidified (DS) specimens were subsequently heat-treated in two ways: either at 1723 K/50 h (HT1) or at 1623 K/50 h 1723 K/50 h 1373 K/50 h (HT2) respectively. XRD, SEM and EDS have been employed to investigate the influence of heat-treatments on the microstructures and fractographies of the directionally solidified alloys. The results show that after heat-treatment, the volume fraction of the large-size primary silicides decreases. Both kinds of heat-treatments could effectively alleviate or even eliminate the segregation in the alloys. The original boundaries between the (Nb,X)5Si3 Nbss eutectic cells in the DS specimens have thoroughly disappeared after heat-treatments. Specifically, silicides have been more evenly distributed after HT2 than HT1. Compared with DS specimens, the average room temperature fracture toughness of the specimens has increased by 12.3% to 19.2 MPa?m1/2 while the average tensile strength has increased by 26.6% and the maximum value reaches 933.2 MPa after HT2. These improvements could be mainly attributed to the more effective dispersion strengthening of (Nb,X)5Si3 silicide particles and the shape change as well as size increase of the ductile Nbss phases after HT2.
With the melting temperature of 2323 K and withdrawing rate of 100 μm/s, Nb-Ti-Si based ultrahigh temperature alloy has been directionally solidified with the use of crucibles. The directionally solidified (DS) specimens were subsequently heat-treated in two ways: either at 1723 K/50 h (HT1) or at 1623 K/50 h 1723 K/50 h 1373 K/50 h (HT2) respectively. XRD, SEM and EDS have been employed to investigate the influence of heat-treatments on the microstructures and fractographies of the directionally solidified alloys. The results show that after heat-treatment, the volume fraction of the large-size primary silicides decreases. Both kinds of heat-treatments could effectively alleviate or even eliminate the segregation in the alloys. The original boundaries between the (Nb,X)5Si3 Nbss eutectic cells in the DS specimens have thoroughly disappeared after heat-treatments. Specifically, silicides have been more evenly distributed after HT2 than HT1. Compared with DS specimens, the average room temperature fracture toughness of the specimens has increased by 12.3% to 19.2 MPa?m1/2 while the average tensile strength has increased by 26.6% and the maximum value reaches 933.2 MPa after HT2. These improvements could be mainly attributed to the more effective dispersion strengthening of (Nb,X)5Si3 silicide particles and the shape change as well as size increase of the ductile Nbss phases after HT2.
2017, 46(1):7-11.
Abstract:
The ionic conductivity of Li3PO4 dispersed Li0.5La0.5TiO3 (LLTO) composite solid electrolyte was examined by using complex impedance analysis. The X-ray powder diffraction (XRD), scanning electron microscope (SEM) observation and relative density measurement were also performed to study the dispersion of the second phase into the LLTO electrolyte. It was found that the addition of Li3PO4 into LLTO matrix leads to a decrease of the ionic conductivity, though the composites added by the Li3PO4 particles show a high compactness. The reasons for the conductivity deterioration were clarified based on the lattice structure of LLTO, misconstrues at the grain boundary regions, and the lithium content. The variation of the lithium content and microstructures in the LLTO matrix dispersed by Li3PO4 particles are mostly responsible for the behaviors in the ionic conduction.
The ionic conductivity of Li3PO4 dispersed Li0.5La0.5TiO3 (LLTO) composite solid electrolyte was examined by using complex impedance analysis. The X-ray powder diffraction (XRD), scanning electron microscope (SEM) observation and relative density measurement were also performed to study the dispersion of the second phase into the LLTO electrolyte. It was found that the addition of Li3PO4 into LLTO matrix leads to a decrease of the ionic conductivity, though the composites added by the Li3PO4 particles show a high compactness. The reasons for the conductivity deterioration were clarified based on the lattice structure of LLTO, misconstrues at the grain boundary regions, and the lithium content. The variation of the lithium content and microstructures in the LLTO matrix dispersed by Li3PO4 particles are mostly responsible for the behaviors in the ionic conduction.
2017, 46(1):12-16.
Abstract:
Directional solidified Mg-1.5Gd (wt.%) magnesium alloy was carried out to investigate the effects of the growth rate on the microstructures under controlled solidification conditions. A Bridgman-type directional solidification furnace with liquid metal cooling (LMC) technology was used to solidify the specimens, which could provide steady state conditions with a constant temperature gradient (40K/mm) at a wide range of growth rate (10-200μm/s). The microstructures were observed to be cellular structures, and the relationship between cellular spacing (λ) and growth rate (V) was established in the form: λ= 130.2827V-0.2228 by using a linear regression analysis, which was in good agreement with the calculated values by Trivedi model. The thermodynamics solidification path calculations by Scheil model and experimental observations confirm that the solidification microstructure in the alloy consists of primary α(Mg) phase and binary eutectic α(Mg) Mg5Gd phase. Meanwhile, the microsegregation of the alloying element predicted by the Scheil model agrees reasonably with the electron probe microanalysis (EPMA) measurements.
Directional solidified Mg-1.5Gd (wt.%) magnesium alloy was carried out to investigate the effects of the growth rate on the microstructures under controlled solidification conditions. A Bridgman-type directional solidification furnace with liquid metal cooling (LMC) technology was used to solidify the specimens, which could provide steady state conditions with a constant temperature gradient (40K/mm) at a wide range of growth rate (10-200μm/s). The microstructures were observed to be cellular structures, and the relationship between cellular spacing (λ) and growth rate (V) was established in the form: λ= 130.2827V-0.2228 by using a linear regression analysis, which was in good agreement with the calculated values by Trivedi model. The thermodynamics solidification path calculations by Scheil model and experimental observations confirm that the solidification microstructure in the alloy consists of primary α(Mg) phase and binary eutectic α(Mg) Mg5Gd phase. Meanwhile, the microsegregation of the alloying element predicted by the Scheil model agrees reasonably with the electron probe microanalysis (EPMA) measurements.
2017, 46(1):17-22.
Abstract:
The surface of AZ91D magnesium alloy was treated using HJ-III type ultrasonic impact treating (UIT) machine and the grain refining mechanism of ultrasonic impact treating was investigated by means of HTEM. The wear resistance of AZ91D magnesium alloy was experimentally studied both for the treated and un-treated samples respectively. The effect of UIT on the microstructure, and micro-hardness were also investigated using SEM and micro-hardness tester. The experimental results indicate that the severe plastic deformation in the surface of AZ91D was formed by UIT, the thickness of the plastic deformation layer is about 120 祄, and the grains are highly refined and compressive residual stress in the surface of AZ91D was also obtained. The wear resistance and micro-hardness of AZ91D alloy could be greatly improved via UIT. The wear resistance and micro-hardness are promoted by increasing the UIT current and time, which indicates that the UIT is a useful method to increase the hardness and wear resistance of AZ91D alloy.
The surface of AZ91D magnesium alloy was treated using HJ-III type ultrasonic impact treating (UIT) machine and the grain refining mechanism of ultrasonic impact treating was investigated by means of HTEM. The wear resistance of AZ91D magnesium alloy was experimentally studied both for the treated and un-treated samples respectively. The effect of UIT on the microstructure, and micro-hardness were also investigated using SEM and micro-hardness tester. The experimental results indicate that the severe plastic deformation in the surface of AZ91D was formed by UIT, the thickness of the plastic deformation layer is about 120 祄, and the grains are highly refined and compressive residual stress in the surface of AZ91D was also obtained. The wear resistance and micro-hardness of AZ91D alloy could be greatly improved via UIT. The wear resistance and micro-hardness are promoted by increasing the UIT current and time, which indicates that the UIT is a useful method to increase the hardness and wear resistance of AZ91D alloy.
2017, 46(1):23-27.
Abstract:
The TiO2/Al2O3 composite coatings were successfully prepared on the surface of Ti-6Al-4V alloy by means of micro-arc oxidation in the Na2SiO3-(NaPO3)6-NaAlO2 solution. Its growth process revealed that O2- reacted rapidly with Ti4 (from substrate) along the reaction channels to form TiO2, and because of the addition of AlO2-, Al2O3 and Al2TiO5 were simultaneously formed. Al2TiO5 was immediately decomposed into rutile TiO2 and α-Al2O3 owing to the high thermal energy caused by discharge. Finally the prepared composite phase coatings were mainly composed of anatase TiO2, rutile TiO2 and α-Al2O3 via XRD analysis. Furthermore, the wear resistance of the TiO2/Al2O3 composite coatings enhanced about 9.5 times than that of Ti-6Al-4V alloy owing to the existence of ceramic layer.
The TiO2/Al2O3 composite coatings were successfully prepared on the surface of Ti-6Al-4V alloy by means of micro-arc oxidation in the Na2SiO3-(NaPO3)6-NaAlO2 solution. Its growth process revealed that O2- reacted rapidly with Ti4 (from substrate) along the reaction channels to form TiO2, and because of the addition of AlO2-, Al2O3 and Al2TiO5 were simultaneously formed. Al2TiO5 was immediately decomposed into rutile TiO2 and α-Al2O3 owing to the high thermal energy caused by discharge. Finally the prepared composite phase coatings were mainly composed of anatase TiO2, rutile TiO2 and α-Al2O3 via XRD analysis. Furthermore, the wear resistance of the TiO2/Al2O3 composite coatings enhanced about 9.5 times than that of Ti-6Al-4V alloy owing to the existence of ceramic layer.
2017, 46(1):28-34.
Abstract:
Abstract: The microstructure evolution and composition distribution of the industrially cast Al-Cu-Li alloy during single-step and tow-step homogenization were investigated in detail by means of optical microscopy(OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC).The results show that severe dendrite segregation exists in the Al-Cu-Li as-cast alloy. Cu distribute unevenly from the grain boundary to inside. But the change of Mg, Zn, Mn and Ag are not obvious. In the grain boundary, there are distributed a large number of coarse nonequilibrium eutectic phases Al2Cu, Al2Cu dissolved a small amount of Mg and Al2CuMg phase. After?optimized two-step?homogenization treatment, most of the nonequilibrium?eutectic?phase and second phase(Al2CuMg and Al2CuLi)?dissolved?into ɑ(Al) matrix. A small amount of Fe-rich and Mn-rich phase are still distributed at the grain boundaries. Al2CuMg phase melting point lower than?the melting point of Al2Cu phase. Al2CuMg and Al2Cu phase gradually dissolved into matrix at 495℃ and 515℃, respectively. The suitable homogenization treatment for the Al-Cu-Li alloy is 495℃×24h 515℃×24h. The results of homogenization can be described by homogenization kinetic analysis, which agrees well with experimental observation.
Abstract: The microstructure evolution and composition distribution of the industrially cast Al-Cu-Li alloy during single-step and tow-step homogenization were investigated in detail by means of optical microscopy(OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC).The results show that severe dendrite segregation exists in the Al-Cu-Li as-cast alloy. Cu distribute unevenly from the grain boundary to inside. But the change of Mg, Zn, Mn and Ag are not obvious. In the grain boundary, there are distributed a large number of coarse nonequilibrium eutectic phases Al2Cu, Al2Cu dissolved a small amount of Mg and Al2CuMg phase. After?optimized two-step?homogenization treatment, most of the nonequilibrium?eutectic?phase and second phase(Al2CuMg and Al2CuLi)?dissolved?into ɑ(Al) matrix. A small amount of Fe-rich and Mn-rich phase are still distributed at the grain boundaries. Al2CuMg phase melting point lower than?the melting point of Al2Cu phase. Al2CuMg and Al2Cu phase gradually dissolved into matrix at 495℃ and 515℃, respectively. The suitable homogenization treatment for the Al-Cu-Li alloy is 495℃×24h 515℃×24h. The results of homogenization can be described by homogenization kinetic analysis, which agrees well with experimental observation.
2017, 46(1):35-38.
Abstract:
Tapered Cu50Zr42Al8 alloy with good glass-forming ability were fabricated by copper mould suction casting. Cubic AlCu2Zr and B2-ZrCu, thermal-induced martensitic B19’-ZrCu phases form on the glass matrix along the radial direction structure. Size effects on micro-mechanical properties and a unique crack healing behavior were studied. Micro-hardness of monolithic BMG displays "smaller is softer" trend, that is, the softer surface and harder center. Whereas the lager size composites possess a softer center and harder surface, due to the integrative action of the secondary phases. Amorphous matrix is toughened by TRIP effect of shape-memory phase as well as weakened and embrittled by AlCu2Zr crystal. After annealed, self-heal of Vickers indentation crack occurs as the thermoelastic transformation of shape-memory crystals. As loading, stress-induced martensites transform from B2 to B19’, along with volume expansion. Annealed upon the reverse transformation temperature, B19’ to B2 transform accompanied by a volume shrinkage, and a restoring force is set up to drive the crack closure.
Tapered Cu50Zr42Al8 alloy with good glass-forming ability were fabricated by copper mould suction casting. Cubic AlCu2Zr and B2-ZrCu, thermal-induced martensitic B19’-ZrCu phases form on the glass matrix along the radial direction structure. Size effects on micro-mechanical properties and a unique crack healing behavior were studied. Micro-hardness of monolithic BMG displays "smaller is softer" trend, that is, the softer surface and harder center. Whereas the lager size composites possess a softer center and harder surface, due to the integrative action of the secondary phases. Amorphous matrix is toughened by TRIP effect of shape-memory phase as well as weakened and embrittled by AlCu2Zr crystal. After annealed, self-heal of Vickers indentation crack occurs as the thermoelastic transformation of shape-memory crystals. As loading, stress-induced martensites transform from B2 to B19’, along with volume expansion. Annealed upon the reverse transformation temperature, B19’ to B2 transform accompanied by a volume shrinkage, and a restoring force is set up to drive the crack closure.
2017, 46(1):39-44.
Abstract:
The surface tension of liquid Ti-Al alloys at 1758 K was determined by the improved sessile drop method. The surface tension of liquid Ti-Al alloys were calculated using the Butler’s model and several modified ideal solution models. Results showed that the surface tension of liquid Ti-Al alloy decreases with increased Al concentration. Experimental results agree well with both the Butler’s model and the modified ideal solution model. The segregation of Al atoms to the surface occurs at all bulk concentrations of Ti-Al alloys. Al with lower surface tension prefers to segregate on the surface of liquid Ti-Al alloy, whereas Ti with higher surface tension prefers to segregate inside the molten alloy. The effect of surface active solute on the surface tension of liquid Ti-Al alloy was also discussed. Sulfur was found to have a larger effect on the surface tension of alloy. The surface tension of liquid Ti-Al alloy decreases with increased sulfur concentration. Sulfur concentration on the surface is higher than in the bulk. Thus, the adsorption of sulfur for Ti-Al alloys is a positive adsorption.
The surface tension of liquid Ti-Al alloys at 1758 K was determined by the improved sessile drop method. The surface tension of liquid Ti-Al alloys were calculated using the Butler’s model and several modified ideal solution models. Results showed that the surface tension of liquid Ti-Al alloy decreases with increased Al concentration. Experimental results agree well with both the Butler’s model and the modified ideal solution model. The segregation of Al atoms to the surface occurs at all bulk concentrations of Ti-Al alloys. Al with lower surface tension prefers to segregate on the surface of liquid Ti-Al alloy, whereas Ti with higher surface tension prefers to segregate inside the molten alloy. The effect of surface active solute on the surface tension of liquid Ti-Al alloy was also discussed. Sulfur was found to have a larger effect on the surface tension of alloy. The surface tension of liquid Ti-Al alloy decreases with increased sulfur concentration. Sulfur concentration on the surface is higher than in the bulk. Thus, the adsorption of sulfur for Ti-Al alloys is a positive adsorption.
2017, 46(1):45-50.
Abstract:
Microstructure, bio-corrosion properties of as-cast Mg-2Zn-0.5Ca-Y series alloy was investigated for biomedical application in detail by optical microscopy, scanning electronic microscopy(SEM) , immersion tests and electrochemical measurements in NaCl solution (3.5wt.％) and Hank''s solution. The morphology of the Mg-2Zn-0.5Ca-Y series magnesium alloy shows that the corrosion behavior is not uniform and corrosion layer with many cracks were on their surface after immersion tests . The corrosion resistance of as-cast Mg-2Zn-0.5Ca-Y series alloy increased with the addition of the rare earth element Y and Mg-2Zn-0.5Ca-1.0Y alloy is the best. All of the potentiodynamic polarization curves obtained in the tests in Hank''s solution and NaCl solution showed current plateaus which were due to the presence of a protective corrosion product film. The electrochemical impedance curves of the alloy in the test solutions had only one capacitive loop. The appearance of a capacitive loop at high frequency was due to the existence of stable double-layer capacitance. The capacitive loop at low frequency was attributed to diffusion control at film-free areas.
Microstructure, bio-corrosion properties of as-cast Mg-2Zn-0.5Ca-Y series alloy was investigated for biomedical application in detail by optical microscopy, scanning electronic microscopy(SEM) , immersion tests and electrochemical measurements in NaCl solution (3.5wt.％) and Hank''s solution. The morphology of the Mg-2Zn-0.5Ca-Y series magnesium alloy shows that the corrosion behavior is not uniform and corrosion layer with many cracks were on their surface after immersion tests . The corrosion resistance of as-cast Mg-2Zn-0.5Ca-Y series alloy increased with the addition of the rare earth element Y and Mg-2Zn-0.5Ca-1.0Y alloy is the best. All of the potentiodynamic polarization curves obtained in the tests in Hank''s solution and NaCl solution showed current plateaus which were due to the presence of a protective corrosion product film. The electrochemical impedance curves of the alloy in the test solutions had only one capacitive loop. The appearance of a capacitive loop at high frequency was due to the existence of stable double-layer capacitance. The capacitive loop at low frequency was attributed to diffusion control at film-free areas.
2017, 46(1):51-56.
Abstract:
Medical forged CoCrMo alloy was treated by DC plasma nitriding process to alter its surface characteristics and improve mechanical and tribological properties. The phase compositions, microstructures, surface microhardness, and wettability were characterized by using X-ray diffraction, scanning electron microscope, micro-hardness tester, and optical dynamic/static contact angle meter. Friction and wear characteristics were investigated on ball-on-disc tribotester under dry sliding conditions. The experimental analyses confirmed that plasma nitriding process is promising in producing thicker, harder, highly hydrophilic and more wear resistance layers on CoCrMo alloy for biomedical applications. At lower nitriding temperatures and shorter time, the nitrided layer structure was composed of σ-CoCr and CrN phases. At higher nitriding temperatures and longer time, σ-CoCr and CrN as well as Cr2N phases appeared to occur in nitrided specimens. With increasing nitriding temperatures and time, case depth thickness, surface roughness, microhardness and wear resistance increased while water contact angle decreased and became highly hydrophilic. Compared with untreated CoCrMo alloy, all nitrided specimens showed an important reduction in wear rate and wear scar width, and the nitrided specimen at 800 ℃-8h exhibited the lowest wear rate and better dry-sliding wear resistance. The wear mechanisim for untreated specimen was mainly adhesive wear while the nitrided specimens changed the wear mechanisim to fatigue wear, abrasive wear and slight adhesive wear because of breakage of nitrided layers. From the experimental results shown in this paper, it is concluded that the improvements of mechanical and tribological properties are attributed to thicker case depth and hard σ-CoCr, CrN and Cr2N phases formed in forged CoCrMo alloy. Moreover, the wettability of nitrided specimen was mainly determined by its surface roughness.
Medical forged CoCrMo alloy was treated by DC plasma nitriding process to alter its surface characteristics and improve mechanical and tribological properties. The phase compositions, microstructures, surface microhardness, and wettability were characterized by using X-ray diffraction, scanning electron microscope, micro-hardness tester, and optical dynamic/static contact angle meter. Friction and wear characteristics were investigated on ball-on-disc tribotester under dry sliding conditions. The experimental analyses confirmed that plasma nitriding process is promising in producing thicker, harder, highly hydrophilic and more wear resistance layers on CoCrMo alloy for biomedical applications. At lower nitriding temperatures and shorter time, the nitrided layer structure was composed of σ-CoCr and CrN phases. At higher nitriding temperatures and longer time, σ-CoCr and CrN as well as Cr2N phases appeared to occur in nitrided specimens. With increasing nitriding temperatures and time, case depth thickness, surface roughness, microhardness and wear resistance increased while water contact angle decreased and became highly hydrophilic. Compared with untreated CoCrMo alloy, all nitrided specimens showed an important reduction in wear rate and wear scar width, and the nitrided specimen at 800 ℃-8h exhibited the lowest wear rate and better dry-sliding wear resistance. The wear mechanisim for untreated specimen was mainly adhesive wear while the nitrided specimens changed the wear mechanisim to fatigue wear, abrasive wear and slight adhesive wear because of breakage of nitrided layers. From the experimental results shown in this paper, it is concluded that the improvements of mechanical and tribological properties are attributed to thicker case depth and hard σ-CoCr, CrN and Cr2N phases formed in forged CoCrMo alloy. Moreover, the wettability of nitrided specimen was mainly determined by its surface roughness.
11 Effect of alloy element Al on the corrosion behavior of Ni-10 wt. % Fe based alloy in molten NaCl
2017, 46(1):57-62.
Abstract:
NaCl and its mixed salt have many advantages as medium of solar energy phase change thermal storage at moderate and high temperature. But molten chloride has sharp corrosive action on metal thermal storage vessel. The corrosion behavior of three kinds of Ni-10 wt. % Fe based sample (1#, 2# and 3#) in 850℃ molten NaCl was studied. The content of Al in 1#, 2# and 3# sample is 0.0 wt. %、5.0 wt. % and 10.0 wt. %, respectively. The components of NaCl after corroding and corrosion products on samples surface were analyzed. Elements change trend and corrosion characteristic on cross section of the three samples were contrasted. Corrosion mechanisms were discussed finally. Results show that the kinetics curves of the three kinds of sample obey liner rule. The average mass loss rate reduce when Al is added in sample. The rate of 2# and 3# is only 12% and 20% of 1#, respectively. There are two reasons for the value reduction: first, Al will be oxidized prior to oxidization of Fe or Ni, and the atomic mass of Al is small. Second, Al2O3 is very stable at high temperature as corrosion products. However, when the content of Al is very high (for example 10 wt. % in here) in Ni-10 wt. % Fe based alloy, Al oxidized on sample surface provides convenient condition for Al atom transmission from sample matrix to surface.Al2O3 film becomes thick and exfoliates easily. The exfoliation led to the average mass loss rate increase in turn. The study establishes foundation for new corrosion resistance alloy research in molten salt.
NaCl and its mixed salt have many advantages as medium of solar energy phase change thermal storage at moderate and high temperature. But molten chloride has sharp corrosive action on metal thermal storage vessel. The corrosion behavior of three kinds of Ni-10 wt. % Fe based sample (1#, 2# and 3#) in 850℃ molten NaCl was studied. The content of Al in 1#, 2# and 3# sample is 0.0 wt. %、5.0 wt. % and 10.0 wt. %, respectively. The components of NaCl after corroding and corrosion products on samples surface were analyzed. Elements change trend and corrosion characteristic on cross section of the three samples were contrasted. Corrosion mechanisms were discussed finally. Results show that the kinetics curves of the three kinds of sample obey liner rule. The average mass loss rate reduce when Al is added in sample. The rate of 2# and 3# is only 12% and 20% of 1#, respectively. There are two reasons for the value reduction: first, Al will be oxidized prior to oxidization of Fe or Ni, and the atomic mass of Al is small. Second, Al2O3 is very stable at high temperature as corrosion products. However, when the content of Al is very high (for example 10 wt. % in here) in Ni-10 wt. % Fe based alloy, Al oxidized on sample surface provides convenient condition for Al atom transmission from sample matrix to surface.Al2O3 film becomes thick and exfoliates easily. The exfoliation led to the average mass loss rate increase in turn. The study establishes foundation for new corrosion resistance alloy research in molten salt.
2017, 46(1):63-67.
Abstract:
W/ZrC cermets were fabricated by Displacive Compensation of Porosity (DCP) and Hot Pressing (HP), and then they were heat treated at 2600°C for 1 h. Microstructure changes of W/ZrC cermets before and after heat treatment were investigated. Results showed that both of two W/ZrC cermets had an increase of open porosity, a linear expansion and a weight loss after the heat treatment. Annealed DCP-derived W/ZrC cermets were still composed of dispersive W phases and continuous ZrC phases, but residual WC, W2C and Zr-Cu alloy were gone, instead, a large increase of pores and a sharp reduction of W phases appearing. While a new phase of W2C was formed in annealed HP-derived W/ZrC cermets, and W grains had a tendency to congregate together to form a big agglomerate phase.
W/ZrC cermets were fabricated by Displacive Compensation of Porosity (DCP) and Hot Pressing (HP), and then they were heat treated at 2600°C for 1 h. Microstructure changes of W/ZrC cermets before and after heat treatment were investigated. Results showed that both of two W/ZrC cermets had an increase of open porosity, a linear expansion and a weight loss after the heat treatment. Annealed DCP-derived W/ZrC cermets were still composed of dispersive W phases and continuous ZrC phases, but residual WC, W2C and Zr-Cu alloy were gone, instead, a large increase of pores and a sharp reduction of W phases appearing. While a new phase of W2C was formed in annealed HP-derived W/ZrC cermets, and W grains had a tendency to congregate together to form a big agglomerate phase.
2017, 46(1):68-72.
Abstract:
Manganese molybdates MnMoO4?xH2O (x=0.9,1.5) could be obtained by the method of a microemulsion based on a quaternary system（CTAB/ water / pentane / isoamyl alcohol) under different manganese precursors. According to XRD , the DSC and TG traces, it was proved that MnMoO4?0.9H2O could be prepared under the precursor manganese of MnCl2?4H2O, and the other precursor manganese of C4H6MnO4?4H2O was MnMoO4?1.5H2O. And it was showed that ω([CTAB]/[H2O]) and the different manganese precursors had great influence of the microstructure of the final product. It could be well known from the solid ultraviolet spectra that the band-gap energy of MnMoO4?0.9H2O could reach up to 3.08eV, and MnMoO4?1.5H2O was 3.04eV.
Manganese molybdates MnMoO4?xH2O (x=0.9,1.5) could be obtained by the method of a microemulsion based on a quaternary system（CTAB/ water / pentane / isoamyl alcohol) under different manganese precursors. According to XRD , the DSC and TG traces, it was proved that MnMoO4?0.9H2O could be prepared under the precursor manganese of MnCl2?4H2O, and the other precursor manganese of C4H6MnO4?4H2O was MnMoO4?1.5H2O. And it was showed that ω([CTAB]/[H2O]) and the different manganese precursors had great influence of the microstructure of the final product. It could be well known from the solid ultraviolet spectra that the band-gap energy of MnMoO4?0.9H2O could reach up to 3.08eV, and MnMoO4?1.5H2O was 3.04eV.
2017, 46(1):73-77.
Abstract:
Composite containing metal fibers would be applied widely in the field of electromagnetic interference for excellent electromagnetic shielding effectiveness (EMSE). In the study, two kinds of composite, the 316L fibers/epoxy resin composite and the Cu fibers/epoxy resin composite, were achieved using infiltration and mechanical stirring methods, respectively. The EMSE of composite was assessed. The results show that the EMSE of 316L fibers/epoxy resin composite increases gradually with the aspect ratio of fibers increasing from 200 to 1000, while it decreases quickly with that from 1000 to 3000. Furthermore, the EMSE of the composite increases gradually as the content of fibers increases from 10wt% to 25wt%. Additionally, for the 316L fibers/epoxy resin composite, the optimum parameters of 316L fibers are the diameter of ?8μm, the content of 25wt% and the aspect ratio of 1000, and the highest EMSE of the composite is about -78dB. For the Cu fibers/epoxy resin composite, the optimum parameters of Cu fibers are the diameter of ?120μm and the content of 2.0wt%.
Composite containing metal fibers would be applied widely in the field of electromagnetic interference for excellent electromagnetic shielding effectiveness (EMSE). In the study, two kinds of composite, the 316L fibers/epoxy resin composite and the Cu fibers/epoxy resin composite, were achieved using infiltration and mechanical stirring methods, respectively. The EMSE of composite was assessed. The results show that the EMSE of 316L fibers/epoxy resin composite increases gradually with the aspect ratio of fibers increasing from 200 to 1000, while it decreases quickly with that from 1000 to 3000. Furthermore, the EMSE of the composite increases gradually as the content of fibers increases from 10wt% to 25wt%. Additionally, for the 316L fibers/epoxy resin composite, the optimum parameters of 316L fibers are the diameter of ?8μm, the content of 25wt% and the aspect ratio of 1000, and the highest EMSE of the composite is about -78dB. For the Cu fibers/epoxy resin composite, the optimum parameters of Cu fibers are the diameter of ?120μm and the content of 2.0wt%.
15 Improved Electrochemical performance of LiMnBO3/C composite synthesized by wet impregnating method
2017, 46(1):78-82.
Abstract:
Hexagonal-LiMnBO3/C composite was prepared by the wet impregnating method using the 3D-network ketchen black (KB) as both temple and conductive framework. The crystal structure, morphology and specific surface area were characterized by X-ray diffraction, scanning electron microscopy and nitrogen sorption measurements, respectively. The electrochemical properties of the composite were studied by galvanostatic charge/discharge and cyclic voltammetry measurements. When tested at C/20 rate for Li ion insertion/extraction properties, LiMnBO3/C composite exhibits good cycle capability with discharge capacity retention of 87.4% at the 30th cycle. As the current rate increases from C/20, C/10 to C/5, good rate capability was obtained for all rates with initial discharge specific capacities of 138.8, 124.5 and 100.5 mA h g-1, respectively.
Hexagonal-LiMnBO3/C composite was prepared by the wet impregnating method using the 3D-network ketchen black (KB) as both temple and conductive framework. The crystal structure, morphology and specific surface area were characterized by X-ray diffraction, scanning electron microscopy and nitrogen sorption measurements, respectively. The electrochemical properties of the composite were studied by galvanostatic charge/discharge and cyclic voltammetry measurements. When tested at C/20 rate for Li ion insertion/extraction properties, LiMnBO3/C composite exhibits good cycle capability with discharge capacity retention of 87.4% at the 30th cycle. As the current rate increases from C/20, C/10 to C/5, good rate capability was obtained for all rates with initial discharge specific capacities of 138.8, 124.5 and 100.5 mA h g-1, respectively.
2017, 46(1):83-89.
Abstract:
Abstract: A research on mechanics and high cycle fatigue properties of the third generation Al-Li alloy 2198-T8 has been carried out. Comparing with the same series Al-Li alloys with different heat treatments and other aluminum alloys used in airplanes, the material 2198-T8 shows a various improvement on tensile strength and yield strength and a better performance in ant-fatigue, but the dispersion of fatigue data increases with the decreasing stress level. In order to explore the internal mechanism of this phenomenon deeply, the advanced testing measurements including scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) have been applied. The results reveal that the propagation, the movement and the pileup of dislocations are the main reasons for fatigue crack initiation, and fatigue crack could be easily formed in the rough zone of persistent slip band (PSB ) and dislocation extrusion area. Under different stress states, the fracture caused by the material’s internal defect are fatal, having a huge impact on the fatigue life, which can reduce the fatigue life much more than 90%. Different crack initiation mechanisms can make the fatigue life changed greatly, which explains the problem of dispersion in fatigue data reasonably.
Abstract: A research on mechanics and high cycle fatigue properties of the third generation Al-Li alloy 2198-T8 has been carried out. Comparing with the same series Al-Li alloys with different heat treatments and other aluminum alloys used in airplanes, the material 2198-T8 shows a various improvement on tensile strength and yield strength and a better performance in ant-fatigue, but the dispersion of fatigue data increases with the decreasing stress level. In order to explore the internal mechanism of this phenomenon deeply, the advanced testing measurements including scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) have been applied. The results reveal that the propagation, the movement and the pileup of dislocations are the main reasons for fatigue crack initiation, and fatigue crack could be easily formed in the rough zone of persistent slip band (PSB ) and dislocation extrusion area. Under different stress states, the fracture caused by the material’s internal defect are fatal, having a huge impact on the fatigue life, which can reduce the fatigue life much more than 90%. Different crack initiation mechanisms can make the fatigue life changed greatly, which explains the problem of dispersion in fatigue data reasonably.
2017, 46(1):90-96.
Abstract:
Abstract: X2A66 was tested in isothermal compression experiment by using the Gleeble-3500 thermal simulator with the deformation temperature range of 350～470癈 and the strain rate range of 0.001～10s-1. The alloy peak stress constitutive equation and processing map were established by utilizing hyperbolic sine function and dynamic materials model. The results show that flow stress of X2A66 decreases with the increase of deformation temperature and increases with the increase of strain rate. In addition, the strain rate has no effect on temperature sensitivity of X2A66 and high strain rate which is above 0.1s-1. In X2A66 isothermal compression experiment, the relationship between the peak flow stress and strain rate satisfies hyperbolic sine function and the constitutive equation is : =5.09?09[sinh(0.019σ)]4.54414exp(-145.377/RT) In the range of test parameters, the instability zones of X2A66 alloy are mainly concentrated in area of high strain rate. The peak area of dissipation efficiency is the strain rate range of 0.001～10 s-1 and the deformation temperature range of 700-743K, which is the best thermal processing zone for X2A66.
Abstract: X2A66 was tested in isothermal compression experiment by using the Gleeble-3500 thermal simulator with the deformation temperature range of 350～470癈 and the strain rate range of 0.001～10s-1. The alloy peak stress constitutive equation and processing map were established by utilizing hyperbolic sine function and dynamic materials model. The results show that flow stress of X2A66 decreases with the increase of deformation temperature and increases with the increase of strain rate. In addition, the strain rate has no effect on temperature sensitivity of X2A66 and high strain rate which is above 0.1s-1. In X2A66 isothermal compression experiment, the relationship between the peak flow stress and strain rate satisfies hyperbolic sine function and the constitutive equation is : =5.09?09[sinh(0.019σ)]4.54414exp(-145.377/RT) In the range of test parameters, the instability zones of X2A66 alloy are mainly concentrated in area of high strain rate. The peak area of dissipation efficiency is the strain rate range of 0.001～10 s-1 and the deformation temperature range of 700-743K, which is the best thermal processing zone for X2A66.
2017, 46(1):97-103.
Abstract:
Two vertical sections of the Fe-C-Ta system with 0.1wt.%，0.5wt.% ta were experimentally investigated by DTA, and the phase transformation sequences of the alloys Fe-2.93C-0.1Ta and Fe-2.31C-0.5Ta were analyzed. A thermodynamic calculation of this system was carried out using CALPHAD technique. The results show that the thermodynamically calculated results agree well with the experimental data. There are four nonvariant reactions in the liquidus projection of Fe-C-Ta system in the Fe-rich corner: Liquid bcc ?fcc TaC，Liquid ? bcc Fe2Ta TaC，Liquid ? Fe3C TaC fcc，Liquid Ta2C ? TaC Fe2Ta. The temperature of the nonvariant reactions is as following: 1443.26℃, 1413.90 ℃,1122.42 ℃, 1508.64℃.The eutectoid reaction occurred at 726.6℃of the alloys Fe-2.93C-0.1Ta and Fe-2.31C-0.5Ta.
Two vertical sections of the Fe-C-Ta system with 0.1wt.%，0.5wt.% ta were experimentally investigated by DTA, and the phase transformation sequences of the alloys Fe-2.93C-0.1Ta and Fe-2.31C-0.5Ta were analyzed. A thermodynamic calculation of this system was carried out using CALPHAD technique. The results show that the thermodynamically calculated results agree well with the experimental data. There are four nonvariant reactions in the liquidus projection of Fe-C-Ta system in the Fe-rich corner: Liquid bcc ?fcc TaC，Liquid ? bcc Fe2Ta TaC，Liquid ? Fe3C TaC fcc，Liquid Ta2C ? TaC Fe2Ta. The temperature of the nonvariant reactions is as following: 1443.26℃, 1413.90 ℃,1122.42 ℃, 1508.64℃.The eutectoid reaction occurred at 726.6℃of the alloys Fe-2.93C-0.1Ta and Fe-2.31C-0.5Ta.
2017, 46(1):104-110.
Abstract:
The as-cast state microstructure was analyzed by XRD、OM、SEM and TEM. The results show that V-5Cr-5Ti alloy was fabricated by vacuum electron-beam melting ,it has coarse grain, the grain has the characteristics of dendritic crystal made by lamellar secondary phase. The lattice parameters of metal vanadium and V-5Cr-5Ti alloy is 0.30316nm and 0.30375nm, the swelling of V cell volume is 0.58%. There are two kinds of the secondary phase in as-cast alloy:1) Short strip secondary phase, has FCC structure, the lattice parameter is 0.4182~0.4228nm; 2) Elliptical-shaped secondary phase, has FCC structure, the lattice parameter is 0.4186~0.4242nm; In the process of solidification, Ti and C formed metastable interstitial phase (Ti2C), which has FCC structure, or V and C formed metastable interstitial phase (V2C), which has HCP structure; Then, atoms substituted by each other. Finally, the secondary phases are vanadium and chromium-alloyed precipitations of titanium oxycarbonitride, which chemical formula can be expressed as (Ti2-CON).
The as-cast state microstructure was analyzed by XRD、OM、SEM and TEM. The results show that V-5Cr-5Ti alloy was fabricated by vacuum electron-beam melting ,it has coarse grain, the grain has the characteristics of dendritic crystal made by lamellar secondary phase. The lattice parameters of metal vanadium and V-5Cr-5Ti alloy is 0.30316nm and 0.30375nm, the swelling of V cell volume is 0.58%. There are two kinds of the secondary phase in as-cast alloy:1) Short strip secondary phase, has FCC structure, the lattice parameter is 0.4182~0.4228nm; 2) Elliptical-shaped secondary phase, has FCC structure, the lattice parameter is 0.4186~0.4242nm; In the process of solidification, Ti and C formed metastable interstitial phase (Ti2C), which has FCC structure, or V and C formed metastable interstitial phase (V2C), which has HCP structure; Then, atoms substituted by each other. Finally, the secondary phases are vanadium and chromium-alloyed precipitations of titanium oxycarbonitride, which chemical formula can be expressed as (Ti2-CON).
2017, 46(1):111-116.
Abstract:
Macroscopic subdivision, microscopic subdivision and boundary misorientation angle of cold drawn Ag single crystal with <110> parallel to axis direction have been investigated by EBSD and TEM systematically in the present paper. The results show that with strain increasing, the macroscopic subdivision of cold drawn Ag single crystal becomes severe, the number of deformation band increases, and the width and spacing of deformation bands decrease. When the strains are higher than 0.94, the fiber microstructure parallel to the aixs direction of wires forms gradually as the strains increase. Contrasting to the alloys with the SFE approximate to Ag, the suppression of cross-slip and climb decreases in cold drawn Ag single crystal. Except for the deformation twins, there are abundant of incidental dislocation boundaries and geometry necessary dislocation boundaries in the drawn Ag. The results of boundary misorientation angle show that dislocation slip is the dominate deformation mechanism at low strains. At the medium strains, dislocation slip and twinning compete with each other. At high strains, twinning becomes predominate deformation mechanism.
Macroscopic subdivision, microscopic subdivision and boundary misorientation angle of cold drawn Ag single crystal with <110> parallel to axis direction have been investigated by EBSD and TEM systematically in the present paper. The results show that with strain increasing, the macroscopic subdivision of cold drawn Ag single crystal becomes severe, the number of deformation band increases, and the width and spacing of deformation bands decrease. When the strains are higher than 0.94, the fiber microstructure parallel to the aixs direction of wires forms gradually as the strains increase. Contrasting to the alloys with the SFE approximate to Ag, the suppression of cross-slip and climb decreases in cold drawn Ag single crystal. Except for the deformation twins, there are abundant of incidental dislocation boundaries and geometry necessary dislocation boundaries in the drawn Ag. The results of boundary misorientation angle show that dislocation slip is the dominate deformation mechanism at low strains. At the medium strains, dislocation slip and twinning compete with each other. At high strains, twinning becomes predominate deformation mechanism.
2017, 46(1):117-121.
Abstract:
Abstract:To eliminate the prediction errors of the recovery stress model of NiTi SMAs caused by the incomplete reverse martensitic transformation, an improved prediction model of recovery stress had been developed based on the one-dimensional Constitutive Behavior model proposed by Brinson for shape memory alloys (SMAs). This model regarded the martensitic recovery factor as an internal variable and took the stress and temperature into account as influencing factors to martensitic content of SMAs. The curve of recovery stress of NiTi SMAs with different initial strains versus temperature was measured by experiment. Compared with the experimental results, the computation result showed that the model had a certain accuracy to calculate the recovery stress-temperature curve.
Abstract:To eliminate the prediction errors of the recovery stress model of NiTi SMAs caused by the incomplete reverse martensitic transformation, an improved prediction model of recovery stress had been developed based on the one-dimensional Constitutive Behavior model proposed by Brinson for shape memory alloys (SMAs). This model regarded the martensitic recovery factor as an internal variable and took the stress and temperature into account as influencing factors to martensitic content of SMAs. The curve of recovery stress of NiTi SMAs with different initial strains versus temperature was measured by experiment. Compared with the experimental results, the computation result showed that the model had a certain accuracy to calculate the recovery stress-temperature curve.
2017, 46(1):122-126.
Abstract:
Nanocomposite permanent magnets have been extensively researched because of their unusually high remanence, high energy products and low cost, but little research has elucidated the underlying mechanism for microstructure improvement. Nanocomposite Nd9.5Fe79-xCo5NbxB6.5(x=0, 1, 2, 3) alloys were prepared by melt-spinning at a rate of 18m/s cooperating with subsequent annealing. The effects of Nb content on microstructure and magnetic properties for the alloys have been studied by XRD, VSM, TEM and 3DAP. The results shown that the Jr firstly increases with increasing Nb content from 0.92T up to 0.94T at x=1, then decreases obviously with further Nb addition. The iHc increases monotonically and then remains relatively lower increasing ratio. The (BH)max appears to increase from 104kJ/m3 at x=0 to a maximum of 120kJ/m3 at x=2, then decreases sharply. An intergranular NbFeB phase with a chemical composition near the Nb: Fe: B stoichiometry of 26: 48: 26 between the Nd2Fe14B interfaces was found for Nd9.5Fe77Co5Nb2B6.5 by 3DAP technique, which provides direct evidence of magnetic properties improvement.
Nanocomposite permanent magnets have been extensively researched because of their unusually high remanence, high energy products and low cost, but little research has elucidated the underlying mechanism for microstructure improvement. Nanocomposite Nd9.5Fe79-xCo5NbxB6.5(x=0, 1, 2, 3) alloys were prepared by melt-spinning at a rate of 18m/s cooperating with subsequent annealing. The effects of Nb content on microstructure and magnetic properties for the alloys have been studied by XRD, VSM, TEM and 3DAP. The results shown that the Jr firstly increases with increasing Nb content from 0.92T up to 0.94T at x=1, then decreases obviously with further Nb addition. The iHc increases monotonically and then remains relatively lower increasing ratio. The (BH)max appears to increase from 104kJ/m3 at x=0 to a maximum of 120kJ/m3 at x=2, then decreases sharply. An intergranular NbFeB phase with a chemical composition near the Nb: Fe: B stoichiometry of 26: 48: 26 between the Nd2Fe14B interfaces was found for Nd9.5Fe77Co5Nb2B6.5 by 3DAP technique, which provides direct evidence of magnetic properties improvement.
2017, 46(1):127-134.
Abstract:
This paper reports the use of micro-arc oxidation(MAO) to prepare porous oxide coatings on the surface of titanium and large plastic deformed titanium. The bio-tribological properties of the MAO coatings were evaluated under different lubrication medium conditions, namely dry friction, stimulated body liquid, and calf serum. The effect of structure refinement of the titanium substrate on the friction wear properties of the coating surface was also investigated. The MAO coating obtained from large plastic deformed titanium exhibits higher abrasion resistance than the MAO coating on titanium because of improved friction wear properties. To be more specific, the structure refinement of the titanium substrate results in more crystal defects and provides more energy for nucleation on the MAO coating,which makes the TiO2 coating formed through the reaction harder, the coating surface more compact, uniform, and smooth.The friction coefficient and degree of wear of the MAO coating formed from large plastic deformed titanium under calf serum lubrication are better than those under dry friction and stimulated body liquid. This finding could be attributed to more effective lubrication and cooling, as well as to the roles of the coatings formed on the friction surface through chemical reaction and physical adsorption under calf serum lubrication.
This paper reports the use of micro-arc oxidation(MAO) to prepare porous oxide coatings on the surface of titanium and large plastic deformed titanium. The bio-tribological properties of the MAO coatings were evaluated under different lubrication medium conditions, namely dry friction, stimulated body liquid, and calf serum. The effect of structure refinement of the titanium substrate on the friction wear properties of the coating surface was also investigated. The MAO coating obtained from large plastic deformed titanium exhibits higher abrasion resistance than the MAO coating on titanium because of improved friction wear properties. To be more specific, the structure refinement of the titanium substrate results in more crystal defects and provides more energy for nucleation on the MAO coating,which makes the TiO2 coating formed through the reaction harder, the coating surface more compact, uniform, and smooth.The friction coefficient and degree of wear of the MAO coating formed from large plastic deformed titanium under calf serum lubrication are better than those under dry friction and stimulated body liquid. This finding could be attributed to more effective lubrication and cooling, as well as to the roles of the coatings formed on the friction surface through chemical reaction and physical adsorption under calf serum lubrication.
2017, 46(1):135-142.
Abstract:
In this study, various amount of Mn elements (x=0.4, 0.8, 1.2, 1.6, 2.0, wt. %) was added to Mg-10Gd-6Y-1.6Zn alloys. We investigated the effect of Mn elements and extrusion ratio on the microstructures and mechanical properties of the alloys. The results show that in the hot extrusion Mg-10Gd-6Y-1.6Zn-xMn alloys, the metastable 18R structure turned into a stable 14H structure of the long period stacking ordered (LPSO) structures. Large extrusion ratio can significantly improve mechanical properties of the alloys at room temperature. When 0.8 wt.% Mn element was added to the alloy, its tensile strength of no-aged status is 386 MPa, and its elongation is about 10%.
In this study, various amount of Mn elements (x=0.4, 0.8, 1.2, 1.6, 2.0, wt. %) was added to Mg-10Gd-6Y-1.6Zn alloys. We investigated the effect of Mn elements and extrusion ratio on the microstructures and mechanical properties of the alloys. The results show that in the hot extrusion Mg-10Gd-6Y-1.6Zn-xMn alloys, the metastable 18R structure turned into a stable 14H structure of the long period stacking ordered (LPSO) structures. Large extrusion ratio can significantly improve mechanical properties of the alloys at room temperature. When 0.8 wt.% Mn element was added to the alloy, its tensile strength of no-aged status is 386 MPa, and its elongation is about 10%.
2017, 46(1):143-149.
Abstract:
Aim at the existing problem of the growth of WC particles in the traditional reduction and carbonization process, adopted the method of carbon-hydrogen coreduction-carbonization to prepare nano-level powders and studied the effects of the n(C)/n(W) of precursors and reaction temperature on the properties of WC. The results show that the carbon content of WC is related to the n(C)/n(W) of precursors, and the optimum molar ratio is 3.6. The average particle size of WC is closely related to reduction temperature and carbonization temperature duo to the transformation of W to WC has structural heredity. Pressure of water vapor in the system decreases due to the reaction of H2O and C with the reduction temperature increases from 680 ℃ to 800 ℃, and which inhibited the volatilization-deposition growth of W particles in hydrogen reduction process. Therefore, the average particle size of WC decreases with increasing reduction temperature. The high temperature can promote the grain boundary migration of WC particles and the combination growth of nano W particles, and the average particle size of WC increases with increasing carbonization temperature. When the n(C)/n(W) of precursor is 3.6, the average particle size of WC powders is 87.3 nm after reduction and carbonization at 800 ℃ and 1100 ℃, respectively.
Aim at the existing problem of the growth of WC particles in the traditional reduction and carbonization process, adopted the method of carbon-hydrogen coreduction-carbonization to prepare nano-level powders and studied the effects of the n(C)/n(W) of precursors and reaction temperature on the properties of WC. The results show that the carbon content of WC is related to the n(C)/n(W) of precursors, and the optimum molar ratio is 3.6. The average particle size of WC is closely related to reduction temperature and carbonization temperature duo to the transformation of W to WC has structural heredity. Pressure of water vapor in the system decreases due to the reaction of H2O and C with the reduction temperature increases from 680 ℃ to 800 ℃, and which inhibited the volatilization-deposition growth of W particles in hydrogen reduction process. Therefore, the average particle size of WC decreases with increasing reduction temperature. The high temperature can promote the grain boundary migration of WC particles and the combination growth of nano W particles, and the average particle size of WC increases with increasing carbonization temperature. When the n(C)/n(W) of precursor is 3.6, the average particle size of WC powders is 87.3 nm after reduction and carbonization at 800 ℃ and 1100 ℃, respectively.
2017, 46(1):150-156.
Abstract:
Mo(Si1-x,Alx)2/Al2O3 composites were prepared by combustion synthesis and hot-pressing sintering process. The combustion characteristics, phase composition, microstructure and mechanical properties of Mo(Si1-x,Alx)2/Al2O3 composites were investigated. The results show that the combustion synthesis mode, determined by image analysis, is spiral combustion in MoSi2 sample, however, those are chaos combustion in Mo(Si1-x,Alx)2/Al2O3 samples. X-ray diffraction analysis confirms that the main phase composition of combustion products are changed from tetragonal MoSi2 to hexagonal Mo(Si,Al)2 with the increasing of aluminum, and the diffraction peaks of Al2O3 can be identified in Mo(Si1-x,Alx)2/Al2O3 samples. The fracture toughness and bending strength are the maximum for Mo(Si0.90,Al0.10)2/10vol.%Al2O3, 4.25 MPa.m1/2 and 346 MPa, respectively, by a factor of 39% and 60% than the monolith MoSi2. The toughening and strengthening mechanism can be attributed to solid solution of aluminum alloying, alumina particle reinforcement, the remove of glass phase and intergranular fracture.
Mo(Si1-x,Alx)2/Al2O3 composites were prepared by combustion synthesis and hot-pressing sintering process. The combustion characteristics, phase composition, microstructure and mechanical properties of Mo(Si1-x,Alx)2/Al2O3 composites were investigated. The results show that the combustion synthesis mode, determined by image analysis, is spiral combustion in MoSi2 sample, however, those are chaos combustion in Mo(Si1-x,Alx)2/Al2O3 samples. X-ray diffraction analysis confirms that the main phase composition of combustion products are changed from tetragonal MoSi2 to hexagonal Mo(Si,Al)2 with the increasing of aluminum, and the diffraction peaks of Al2O3 can be identified in Mo(Si1-x,Alx)2/Al2O3 samples. The fracture toughness and bending strength are the maximum for Mo(Si0.90,Al0.10)2/10vol.%Al2O3, 4.25 MPa.m1/2 and 346 MPa, respectively, by a factor of 39% and 60% than the monolith MoSi2. The toughening and strengthening mechanism can be attributed to solid solution of aluminum alloying, alumina particle reinforcement, the remove of glass phase and intergranular fracture.
2017, 46(1):157-163.
Abstract:
A novel PbO2 electrode doped with rare earth of Nd (Nd-PbO2) was prepared by electrodepositon technique. The microstructure and electrochemical properties of the doped electrode were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fluorospectrophotometry (FP), Linear-sweep voltammetry (LSV), accelerated lifetime (ALT) and cyclic voltammetry (CV). SEM, XRD and XPS analysis reveal that the Nd-PbO2 electrode is covered by β-PbO2 with tetragonal crystal structure and the main chemical valence of Nd is 3 , and the morphology and elementary composition of the electrode surface have changed at different degrees. Electrochemical performance tests show that doping with Nd can increase oxygen evolution reaction and stability of PbO2 electrode. The results of CV and AOII degradation experiments indicate that Nd-PbO2 electrode can enhance the direct anodic oxidation, which is helpful to mineralize AOII. Besides, the FP analysis reveals that the electrocatalytic activity of the Nd-PbO2 electrode in the degradation of organic materials is higher than that of the PbO2 electrode because more hydroxyl radicals can be generated on its surface.
A novel PbO2 electrode doped with rare earth of Nd (Nd-PbO2) was prepared by electrodepositon technique. The microstructure and electrochemical properties of the doped electrode were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fluorospectrophotometry (FP), Linear-sweep voltammetry (LSV), accelerated lifetime (ALT) and cyclic voltammetry (CV). SEM, XRD and XPS analysis reveal that the Nd-PbO2 electrode is covered by β-PbO2 with tetragonal crystal structure and the main chemical valence of Nd is 3 , and the morphology and elementary composition of the electrode surface have changed at different degrees. Electrochemical performance tests show that doping with Nd can increase oxygen evolution reaction and stability of PbO2 electrode. The results of CV and AOII degradation experiments indicate that Nd-PbO2 electrode can enhance the direct anodic oxidation, which is helpful to mineralize AOII. Besides, the FP analysis reveals that the electrocatalytic activity of the Nd-PbO2 electrode in the degradation of organic materials is higher than that of the PbO2 electrode because more hydroxyl radicals can be generated on its surface.
2017, 46(1):164-170.
Abstract:
Abstract: In order to improve the refining and modification effect of A356 aluminum alloy, reduce the cost, carry melt mixing refining and modification on A356 aluminum alloy, and compared with traditional technique. The experimental results showed that the melt mixing refining and modification treatment has a better effect. In the process of the mutually melt mixing can fully for particles and energy exchange, the second phase particles spontaneously from higher chemical potential phase into the lower chemical potential phase，reduce the total free energy of system, make the system to achieve balance. Due to the change of the solute in the liquid phase concentration, change the equilibrium of the solute distribution coefficient K0, change its crystallization precipitation, reduce the enrichment of segregation of second phase particles, and significantly improve the refining and modification effect.
Abstract: In order to improve the refining and modification effect of A356 aluminum alloy, reduce the cost, carry melt mixing refining and modification on A356 aluminum alloy, and compared with traditional technique. The experimental results showed that the melt mixing refining and modification treatment has a better effect. In the process of the mutually melt mixing can fully for particles and energy exchange, the second phase particles spontaneously from higher chemical potential phase into the lower chemical potential phase，reduce the total free energy of system, make the system to achieve balance. Due to the change of the solute in the liquid phase concentration, change the equilibrium of the solute distribution coefficient K0, change its crystallization precipitation, reduce the enrichment of segregation of second phase particles, and significantly improve the refining and modification effect.
2017, 46(1):171-176.
Abstract:
Metal hydride (MHx) is typically under extreme non-equilibrium irradiations when used as a neutron moderator in nuclear reactor, an ion source in laser, a target material for neutron generator, and other devices. This work proposes using an extreme non-equilibrium high intensity pulsed ion beam (HIPIB) to evaluate the effects on mechanic properties of TiD2 film under non-equilibrium irradiations. Both microscratch and microhardness were measured for the original and irradiated samples. Results reflect that frictional coefficient on the surface of scratch test is reduced under repetitive irradiations, and repeated melting of the surface layer makes the scratch revealing a more smoothed and densified texture, and the release of D can also improve both of its hardness and toughness, alleviating the plastic deformations.
Metal hydride (MHx) is typically under extreme non-equilibrium irradiations when used as a neutron moderator in nuclear reactor, an ion source in laser, a target material for neutron generator, and other devices. This work proposes using an extreme non-equilibrium high intensity pulsed ion beam (HIPIB) to evaluate the effects on mechanic properties of TiD2 film under non-equilibrium irradiations. Both microscratch and microhardness were measured for the original and irradiated samples. Results reflect that frictional coefficient on the surface of scratch test is reduced under repetitive irradiations, and repeated melting of the surface layer makes the scratch revealing a more smoothed and densified texture, and the release of D can also improve both of its hardness and toughness, alleviating the plastic deformations.
2017, 46(1):177-182.
Abstract:
The aim of this paper was to overcome the problem of the poor tribological properties such as high friction coefficient and low hardness of Ti6Al4V. Cladding of metal matrix composites (MMC) layer on Ti-6Al-4V substrate by coincident wire-powder laser deposition was conducted in the paper. During experiment, powder was fed from a coaxial nozzle and wire was fed from a lateral nozzle into the deposition melt pool. Microstructure of compound layer was analyzed by SEM, EDS, XRD. It has shown that compound layer mainly comprises WC, W2C, TiC, α-Ti, W phase. TiC、W2C phase was formed with different morphology at different location of MMC layer. W2C, W and TiC layer can be found at the interface of WC/Ti matrix,. The hardness of compound layer is 570HV0.2 ，which is about 2 times of the hardness of substrate. The friction coefficient of MMC layer was 0.3, while the friction coefficient of Ti substrate was 0.5. Compared to the substrate, the friction coefficient of MMC layer reduced distinctively.
The aim of this paper was to overcome the problem of the poor tribological properties such as high friction coefficient and low hardness of Ti6Al4V. Cladding of metal matrix composites (MMC) layer on Ti-6Al-4V substrate by coincident wire-powder laser deposition was conducted in the paper. During experiment, powder was fed from a coaxial nozzle and wire was fed from a lateral nozzle into the deposition melt pool. Microstructure of compound layer was analyzed by SEM, EDS, XRD. It has shown that compound layer mainly comprises WC, W2C, TiC, α-Ti, W phase. TiC、W2C phase was formed with different morphology at different location of MMC layer. W2C, W and TiC layer can be found at the interface of WC/Ti matrix,. The hardness of compound layer is 570HV0.2 ，which is about 2 times of the hardness of substrate. The friction coefficient of MMC layer was 0.3, while the friction coefficient of Ti substrate was 0.5. Compared to the substrate, the friction coefficient of MMC layer reduced distinctively.
2017, 46(1):183-188.
Abstract:
The mechanical properties and micro-structures of a Mg, Ag and Zn multi-microalloyed Al-Li alloy with isothermal T8 aging and non-isothermal (cooling) T8 aging were studied. The results showed that the main strengthening precipitates were T1 (Al2CuLi), some ?? (Al2Cu) and ??(Al3Li) precipitates played a supplementary strengthening effect. Compared to the isothermal T8 aging, the cooling T8 aging enhanced the Al-Li alloy strength but did not lower its elongation. In addition, the precipitation and growth of T1 precipitates were slower during cooling T8 aging process due to its lowered temperature. Meanwhile, the fraction of ?? and ?? precipitates were higher in the alloy with cooling T8 peak aging, which caused a higher supplementary strengthening effect.
The mechanical properties and micro-structures of a Mg, Ag and Zn multi-microalloyed Al-Li alloy with isothermal T8 aging and non-isothermal (cooling) T8 aging were studied. The results showed that the main strengthening precipitates were T1 (Al2CuLi), some ?? (Al2Cu) and ??(Al3Li) precipitates played a supplementary strengthening effect. Compared to the isothermal T8 aging, the cooling T8 aging enhanced the Al-Li alloy strength but did not lower its elongation. In addition, the precipitation and growth of T1 precipitates were slower during cooling T8 aging process due to its lowered temperature. Meanwhile, the fraction of ?? and ?? precipitates were higher in the alloy with cooling T8 peak aging, which caused a higher supplementary strengthening effect.
2017, 46(1):189-194.
Abstract:
In this study, Mg-4.4Zn-0.3Zr-0.4Y (wt.%) alloy ingots were prepared by two casting processes with different cooling rates: air cooling cast (AC cast) and water cooling cast (WC cast). Then, these two types of Mg-4.4Zn-0.3Zr-0.4Y alloy ingots were extruded under the same conditions, and the effect of different cooling rates on microstructure and mechanical properties of extruded alloy was studied. The results showed that the cooling rate of melt during cast processing has a great effect on microstructure and mechanical properties of extruded alloy. Compared with AC cast alloy, the lamellar eutectic structure and dendrite cell size of WC cast alloy are significantly refined, while the formation of W-phase (Mg3Y2Zn3) was suppressed and the volume fraction of I-phase (Mg3YZn6) increased in WC cast alloy. After extrusion deformation, the WC cast Mg-4.4Zn-0.3Zr-0.4Y alloy has finer dynamically recrystallized grain size, finer and more uniformly fragmented I-phase particles distributed in matrix and grain boundaries, decreased {0002} basal texture intensity and increased {101 ?2} texture intensity than that in the extruded AC cast alloy. The yield strength and tensile strength of extruded WC cast Mg-4.4Zn-0.3Zr-0.4Y alloy reached 297.0MPa and 327.3MPa, which increased by 46.4MPa and 21.4MPa compared with that of the extruded AC cast alloy, respectively. The extruded WC cast Mg-4.4Zn-0.3Zr-0.4Y alloy showed an elongation of 14.8%, which is 4.7% improvement compared with that of the extruded AC cast alloy.
In this study, Mg-4.4Zn-0.3Zr-0.4Y (wt.%) alloy ingots were prepared by two casting processes with different cooling rates: air cooling cast (AC cast) and water cooling cast (WC cast). Then, these two types of Mg-4.4Zn-0.3Zr-0.4Y alloy ingots were extruded under the same conditions, and the effect of different cooling rates on microstructure and mechanical properties of extruded alloy was studied. The results showed that the cooling rate of melt during cast processing has a great effect on microstructure and mechanical properties of extruded alloy. Compared with AC cast alloy, the lamellar eutectic structure and dendrite cell size of WC cast alloy are significantly refined, while the formation of W-phase (Mg3Y2Zn3) was suppressed and the volume fraction of I-phase (Mg3YZn6) increased in WC cast alloy. After extrusion deformation, the WC cast Mg-4.4Zn-0.3Zr-0.4Y alloy has finer dynamically recrystallized grain size, finer and more uniformly fragmented I-phase particles distributed in matrix and grain boundaries, decreased {0002} basal texture intensity and increased {101 ?2} texture intensity than that in the extruded AC cast alloy. The yield strength and tensile strength of extruded WC cast Mg-4.4Zn-0.3Zr-0.4Y alloy reached 297.0MPa and 327.3MPa, which increased by 46.4MPa and 21.4MPa compared with that of the extruded AC cast alloy, respectively. The extruded WC cast Mg-4.4Zn-0.3Zr-0.4Y alloy showed an elongation of 14.8%, which is 4.7% improvement compared with that of the extruded AC cast alloy.
2017, 46(1):195-200.
Abstract:
TiO2 films were prepared on the surface of diamond through sol-gel method. The effect of heat treatment temperature on morphology, phase composition, phase transition, bonding with diamond, and oxidation resistance of diamond coated with TiO2 films of TiO2 film of diamond surface were characterized through SEM, FTIR , Raman spectroscopy, X-ray diffraction analysis, XPS, TG-DSC, fracturing strength. The results showed that when the heat treatment temperature rose to 600℃, TiO2 film of diamond surface would change from amorphous state to a dense anatase films and Ti-O-C chemical bond was formed between TiO2 and diamond substrate. When the heat treatment temperature rose to 800℃, TiO2 film was still anatase phase, graphitization of diamond substrate generared, graphitization C could form Ti-O-C chemical bond with TiO2 film, however, TiO2 film began to emerge cracks. Meanwhile, the heat treatment temperature of TiO2 films had a greater impact on the oxidation resistance of diamond in the air. When the heat treatment temperature was at 600℃, diamond initial oxidation temperature reached a maximum 754 ℃.After diamond coated with TiO2 films oxidized at 800℃ for 0.5h in the air, the weight loss rate and compressive strength was 6.7wt.% and 15.7N, respectively.
TiO2 films were prepared on the surface of diamond through sol-gel method. The effect of heat treatment temperature on morphology, phase composition, phase transition, bonding with diamond, and oxidation resistance of diamond coated with TiO2 films of TiO2 film of diamond surface were characterized through SEM, FTIR , Raman spectroscopy, X-ray diffraction analysis, XPS, TG-DSC, fracturing strength. The results showed that when the heat treatment temperature rose to 600℃, TiO2 film of diamond surface would change from amorphous state to a dense anatase films and Ti-O-C chemical bond was formed between TiO2 and diamond substrate. When the heat treatment temperature rose to 800℃, TiO2 film was still anatase phase, graphitization of diamond substrate generared, graphitization C could form Ti-O-C chemical bond with TiO2 film, however, TiO2 film began to emerge cracks. Meanwhile, the heat treatment temperature of TiO2 films had a greater impact on the oxidation resistance of diamond in the air. When the heat treatment temperature was at 600℃, diamond initial oxidation temperature reached a maximum 754 ℃.After diamond coated with TiO2 films oxidized at 800℃ for 0.5h in the air, the weight loss rate and compressive strength was 6.7wt.% and 15.7N, respectively.
34 Effect of Annealing Process on the Corrosion Resistance of Zr-0.8Sn-0.25Nb-0.35Fe-0.1Cr-0.05Ge Alloy
2017, 46(1):201-206.
Abstract:
The corrosion resistance of Zr-0.8Sn-0.25Nb-0.35Fe-0.1Cr-0.05Ge alloy samples with different annealing processes has been studied in super-heated steam at 400 ℃/10.3 MPa by autoclave test. The microstructure of the samples was investigated by TEM/EDS and SEM. The results show that partial recrystallization occurs in the samples annealed at 500 ℃, and the effect of annealing time on the size of second phase particles(SPPs) is not obvious; while complete recrystallization occurs in the samples annealed at 580 ℃, as the prolongation of annealing time, the size of SPPs enlarged in Zr-0.8Sn-0.25Nb-0.35Fe-0.1Cr-0.05Ge alloy. There exist Zr(Nb,Fe,Cr)2 SPPs with a hexagonal close packed structure, tetragonal Zr3Ge and orthogonal Zr3Fe SPPs. The corrosion resistance of Zr-0.8Sn-0.25Nb-0.35Fe-0.1Cr-0.05Ge alloy in super-heated steam at 400 ℃/10.3 MPa is improved with the prolongation of annealing time and increase of annealing temperature.
The corrosion resistance of Zr-0.8Sn-0.25Nb-0.35Fe-0.1Cr-0.05Ge alloy samples with different annealing processes has been studied in super-heated steam at 400 ℃/10.3 MPa by autoclave test. The microstructure of the samples was investigated by TEM/EDS and SEM. The results show that partial recrystallization occurs in the samples annealed at 500 ℃, and the effect of annealing time on the size of second phase particles(SPPs) is not obvious; while complete recrystallization occurs in the samples annealed at 580 ℃, as the prolongation of annealing time, the size of SPPs enlarged in Zr-0.8Sn-0.25Nb-0.35Fe-0.1Cr-0.05Ge alloy. There exist Zr(Nb,Fe,Cr)2 SPPs with a hexagonal close packed structure, tetragonal Zr3Ge and orthogonal Zr3Fe SPPs. The corrosion resistance of Zr-0.8Sn-0.25Nb-0.35Fe-0.1Cr-0.05Ge alloy in super-heated steam at 400 ℃/10.3 MPa is improved with the prolongation of annealing time and increase of annealing temperature.
2017, 46(1):207-212.
Abstract:
The nano-cooper powder and graphene are mixed by the way of mechanical wet ball-milling. Then the graphene/cooper (G/Cu) composite materials is prepared by the Spark Plasma Sintering method(SPS). The microstructure and organization structure of graphene and cooper power are analyzed by means of SEM, XRD and other test methods to explore the relationship between the variation of graphene and cooper power and the ball-milling process. It has found that when the ball-milling time increased to 8h, the grapnene nanoplates have a better combination and distribution on cooper substrate. The improvement of performance is relatively best. The tensile yield strength of the G/Cu composite is 183MPa, increased by 52.5%compared with Cu matrix; the compres yield strength is improve more nearly 1.4 times from 150MPa to 365Mpa; the hardness is also increased to 135HV; the conductivity IACS of the composites reaches 65.5%. The comprehensive performance increased significantly.
The nano-cooper powder and graphene are mixed by the way of mechanical wet ball-milling. Then the graphene/cooper (G/Cu) composite materials is prepared by the Spark Plasma Sintering method(SPS). The microstructure and organization structure of graphene and cooper power are analyzed by means of SEM, XRD and other test methods to explore the relationship between the variation of graphene and cooper power and the ball-milling process. It has found that when the ball-milling time increased to 8h, the grapnene nanoplates have a better combination and distribution on cooper substrate. The improvement of performance is relatively best. The tensile yield strength of the G/Cu composite is 183MPa, increased by 52.5%compared with Cu matrix; the compres yield strength is improve more nearly 1.4 times from 150MPa to 365Mpa; the hardness is also increased to 135HV; the conductivity IACS of the composites reaches 65.5%. The comprehensive performance increased significantly.
2017, 46(1):213-218.
Abstract:
After machining metallic parts, there will be residual stresses generated by machining in surface layers of the machined parts, the deformations caused by surface residual stresses have a strong effect to the parts accuracy. In order to predict the deformations caused by surface residual stresses generated by milling Ti6Al4V parts, this paper presents a method for measuring the equivalent surface residual stresses and the effective depth to solve this problem. The material in the surface opposite to the machined surface were removed twice, the depth and the neutral layer of the workpiece were changed, the change of the bending deflections and the strains measured from the machined surface were measured after that, and then the equivalent surface residual stresses and the effective depth can be calculated out. FEA (finite element analysis) was used to validated the correctness of this method, the results calculated by FEA correspond well to those measured in the experiments, so it can be concluded that the results got from the method proposed in this paper are correct, they can be used to evaluated the surface residual stresses generated by milling and predicted the deformations caused by surface residual stresses, as to predict if the parts accuracy can meet the requirement.
After machining metallic parts, there will be residual stresses generated by machining in surface layers of the machined parts, the deformations caused by surface residual stresses have a strong effect to the parts accuracy. In order to predict the deformations caused by surface residual stresses generated by milling Ti6Al4V parts, this paper presents a method for measuring the equivalent surface residual stresses and the effective depth to solve this problem. The material in the surface opposite to the machined surface were removed twice, the depth and the neutral layer of the workpiece were changed, the change of the bending deflections and the strains measured from the machined surface were measured after that, and then the equivalent surface residual stresses and the effective depth can be calculated out. FEA (finite element analysis) was used to validated the correctness of this method, the results calculated by FEA correspond well to those measured in the experiments, so it can be concluded that the results got from the method proposed in this paper are correct, they can be used to evaluated the surface residual stresses generated by milling and predicted the deformations caused by surface residual stresses, as to predict if the parts accuracy can meet the requirement.
2017, 46(1):219-224.
Abstract:
Orignal CQDs and functionalized CQDs with SOCl2 (Cl-CQDs ) were prepared in a autoclave, and silver nanoparticles were synthesized using ethylene glycol as a reducing agent. Ag /CQDs and Ag /Cl-CQDs were synthesized by simple mixing respectively. The samples were detected by TEM and FTIR. Fluorescence and absorption spectra were recorded on a fluorescence spectrophotometer and UV-Vis spectrometer, respectively. The results showed that the average diameter of CQDs was about 3.5 nm, and the mean diameter of roundish silver nanoparticles was about 18 nm. Fluorescence quenching happened after incorporating Ag into CQDs, and absorption capacity was strengthen in visible solar wavelength range. Comparing with single Ag and CQDs, Photocatalytic property of composite catalysts became stronger. The composite catalyst with a mass ratio of Ag /CQDs of 1/2 had the highest catalytic efficiency. Ag/Cl-CQDs can promote the degradation of methyl orange, and 50 mL, 50 mg/L methyl orange was degraded in 12 minutes.
Orignal CQDs and functionalized CQDs with SOCl2 (Cl-CQDs ) were prepared in a autoclave, and silver nanoparticles were synthesized using ethylene glycol as a reducing agent. Ag /CQDs and Ag /Cl-CQDs were synthesized by simple mixing respectively. The samples were detected by TEM and FTIR. Fluorescence and absorption spectra were recorded on a fluorescence spectrophotometer and UV-Vis spectrometer, respectively. The results showed that the average diameter of CQDs was about 3.5 nm, and the mean diameter of roundish silver nanoparticles was about 18 nm. Fluorescence quenching happened after incorporating Ag into CQDs, and absorption capacity was strengthen in visible solar wavelength range. Comparing with single Ag and CQDs, Photocatalytic property of composite catalysts became stronger. The composite catalyst with a mass ratio of Ag /CQDs of 1/2 had the highest catalytic efficiency. Ag/Cl-CQDs can promote the degradation of methyl orange, and 50 mL, 50 mg/L methyl orange was degraded in 12 minutes.
2017, 46(1):225-230.
Abstract:
Seven zirconium alloys with copper and manganese additions in Zircaloy-4 were prepared by vacuum non-consumable arc melting method. The specimens were corroded by autoclave tests in lithiated water with 0.01 M LiOH at 360?C/18.6 MPa or in super-heated steam at 400 ?C/10.3 MPa. In comparison to the corrosion behavior of Zircaloy-4, the annealed Zircaloy-4 specimens obtained from commercial products and the remelted Zircaloy-4 specimens were also corroded together with the seven zirconium alloys specimens. The results show that the corrosion resistance was improved obviously by the addition of 0.05%~0.18% Cu or 0.07%~0.35% Mn, or 0.08%Cu and 0.09%Mn during the specimens corroded in lithiated water at 360?C. No transition occurred on the curve of the weight gain versus exposure time. Therefore the corrosion resistance of the seven alloy specimens was superior to that of Zircaloy-4. But the corrosion resistance of the specimens by the addition of Cu or Mn was worse than that of Zircaloy-4 during the specimens corroded in super-heated steam at 400?C. The tendency towards the degradation of corrosion resistance by the addition of Cu and Mn increased with the increase of the contents of Cu and Mn. The detrimental effect on the corrosion resistance by the addition of Mn is more obvious than that by the addition of Cu. The reason that the different effects on the corrosion resistance by the addition of Cu and Mn during the specimens corroded in different conditions was discussed and explained based on the relations between the anisotropic growth of oxide film and the addition of alloying elements.
Seven zirconium alloys with copper and manganese additions in Zircaloy-4 were prepared by vacuum non-consumable arc melting method. The specimens were corroded by autoclave tests in lithiated water with 0.01 M LiOH at 360?C/18.6 MPa or in super-heated steam at 400 ?C/10.3 MPa. In comparison to the corrosion behavior of Zircaloy-4, the annealed Zircaloy-4 specimens obtained from commercial products and the remelted Zircaloy-4 specimens were also corroded together with the seven zirconium alloys specimens. The results show that the corrosion resistance was improved obviously by the addition of 0.05%~0.18% Cu or 0.07%~0.35% Mn, or 0.08%Cu and 0.09%Mn during the specimens corroded in lithiated water at 360?C. No transition occurred on the curve of the weight gain versus exposure time. Therefore the corrosion resistance of the seven alloy specimens was superior to that of Zircaloy-4. But the corrosion resistance of the specimens by the addition of Cu or Mn was worse than that of Zircaloy-4 during the specimens corroded in super-heated steam at 400?C. The tendency towards the degradation of corrosion resistance by the addition of Cu and Mn increased with the increase of the contents of Cu and Mn. The detrimental effect on the corrosion resistance by the addition of Mn is more obvious than that by the addition of Cu. The reason that the different effects on the corrosion resistance by the addition of Cu and Mn during the specimens corroded in different conditions was discussed and explained based on the relations between the anisotropic growth of oxide film and the addition of alloying elements.
2017, 46(1):231-236.
Abstract:
Solid oxide proton conductors display lower activation energy than conventional oxygen-ion conductorswith a good development prospect. BaZr0.1Ce0.7Y0.2O2.9(BZCY)-(Li/Na)2CO3 composite electrolytes were prepared with BZCY powders synthesized by homogeneous coprecipitation. The structure and electrical properties of composite electrolytes were preliminarily studied. The conductivities of the composites reach 0.095Scm-1 at 600 oC and 0.071Scm-1 at 450oC in air, 0.126Scm-1 and 0.075Scm-1 in humidified hydrogen. The maximum power densities reach 741mWcm-2 at 600 oC and 258mWcm-2 at 450 oC.
Solid oxide proton conductors display lower activation energy than conventional oxygen-ion conductorswith a good development prospect. BaZr0.1Ce0.7Y0.2O2.9(BZCY)-(Li/Na)2CO3 composite electrolytes were prepared with BZCY powders synthesized by homogeneous coprecipitation. The structure and electrical properties of composite electrolytes were preliminarily studied. The conductivities of the composites reach 0.095Scm-1 at 600 oC and 0.071Scm-1 at 450oC in air, 0.126Scm-1 and 0.075Scm-1 in humidified hydrogen. The maximum power densities reach 741mWcm-2 at 600 oC and 258mWcm-2 at 450 oC.
tanzhilong
,
fenghaiquan
,
zhangjunmin
,
wangchuanjun
,
wenming
,
guanweiming
,
guojunmei
,
lichenhui
2017, 46(1):237-241.
Abstract:
The CIGS quaternary alloy target was prepared through Spark Plasma Sintering(SPS) using Cu(In0.7Ga0.3)Se2 single-phase powder which was compounded under 650℃. The influence of sintering technological parameter ,such as sintering temperature, holding time and sintering pressure on performance of target was studied. The results showed that the target was a Cu(In0.7Ga0.3)Se2 single-phase when sintering temperature was above 500℃, and the grain size was increased , both of density and resisitivity was a linear increase with the sintering temperature increasing. The grain size, density and resistivity were also increasing with holding time. However, the density was increased, the resistivity was decreased with the sintering pressure increasing. In conclusion, the resisitivity is 50Ω?cm, density is above 98%, when sintering temperature is 600℃，sintering pressure is 30 MPa，holding time is 5mins.
The CIGS quaternary alloy target was prepared through Spark Plasma Sintering(SPS) using Cu(In0.7Ga0.3)Se2 single-phase powder which was compounded under 650℃. The influence of sintering technological parameter ,such as sintering temperature, holding time and sintering pressure on performance of target was studied. The results showed that the target was a Cu(In0.7Ga0.3)Se2 single-phase when sintering temperature was above 500℃, and the grain size was increased , both of density and resisitivity was a linear increase with the sintering temperature increasing. The grain size, density and resistivity were also increasing with holding time. However, the density was increased, the resistivity was decreased with the sintering pressure increasing. In conclusion, the resisitivity is 50Ω?cm, density is above 98%, when sintering temperature is 600℃，sintering pressure is 30 MPa，holding time is 5mins.
2017, 46(1):242-246.
Abstract:
The precursor of ammonium metatungstate(AMT) coated titanium carbide(TiC) were prepared by titration method, in which the suspension composed of the saturated solution of AMT, TiC micropowder and the dispersants was titrated with the anhydrous ethanol. The as-synthesized precursors were reduced in high-purity hydrogen atmosphere and then the tungsten coated TiC composite powder was prepared. The as-prepared powder was characterized by XRD and SEM. The results showed that the well-dispersed globularlike composite powders were produced when N,N-dimethyl formamide (DMF) and PEG used as the dispersant for TiC and saturated solution of AMT and the precursor reduced in the high-purity hydrogen atmosphere at 600 ℃ for 1h and 800 ℃ for 30 min. And the bulk samples were prepared by spark plasma sintering (SPS) and their SEM morphology, relative density and mechanical properties were investigated. The results showed that TiC particles were uniformly distributed in the matrix W when the samples sintered by spark plasma sintering (SPS) at 1600 ℃ for 2 min, that the relative density, flexural strength, micro-hardness and fracture toughness of the samples achieved 94.6 %, 739 MPa, 4.86GPa and 7.87MPa?m1/2, respectively.
The precursor of ammonium metatungstate(AMT) coated titanium carbide(TiC) were prepared by titration method, in which the suspension composed of the saturated solution of AMT, TiC micropowder and the dispersants was titrated with the anhydrous ethanol. The as-synthesized precursors were reduced in high-purity hydrogen atmosphere and then the tungsten coated TiC composite powder was prepared. The as-prepared powder was characterized by XRD and SEM. The results showed that the well-dispersed globularlike composite powders were produced when N,N-dimethyl formamide (DMF) and PEG used as the dispersant for TiC and saturated solution of AMT and the precursor reduced in the high-purity hydrogen atmosphere at 600 ℃ for 1h and 800 ℃ for 30 min. And the bulk samples were prepared by spark plasma sintering (SPS) and their SEM morphology, relative density and mechanical properties were investigated. The results showed that TiC particles were uniformly distributed in the matrix W when the samples sintered by spark plasma sintering (SPS) at 1600 ℃ for 2 min, that the relative density, flexural strength, micro-hardness and fracture toughness of the samples achieved 94.6 %, 739 MPa, 4.86GPa and 7.87MPa?m1/2, respectively.
2017, 46(1):247-251.
Abstract:
The effects of process parameters on macro-morphology, microstructure, mechanical properties of the joints, which were frabricated by friction stir welding (FSW) using 3mm 2A14 aluminium alloy and TC4 titanium alloy with a 0.05mm Zn ribbon as intermediate layer, were studied. The results indicate that the well-formed joints can fabricated by friction stir welding with the parameters that welding velocity is 75 mm/min, rotation speed is 375~950 r/min and offset between the center of pin and interface of two plate is 2.5mm. The surface roughness reduces with increase of rotatation speed and then increases, while the tensile strength of joints decrease gradually as the increase of rotation speed. However, as increase of welding velocity, the surface roughness increases, and the tesile strength decreases. When the welding velocity, rotation speed and offset are 75mm/min, 375 r/min and 2.5mm, respectively, the maximum tensile strength exceed to 237.3 MPa, nearly 57.7% of the alluminum alloy.
The effects of process parameters on macro-morphology, microstructure, mechanical properties of the joints, which were frabricated by friction stir welding (FSW) using 3mm 2A14 aluminium alloy and TC4 titanium alloy with a 0.05mm Zn ribbon as intermediate layer, were studied. The results indicate that the well-formed joints can fabricated by friction stir welding with the parameters that welding velocity is 75 mm/min, rotation speed is 375~950 r/min and offset between the center of pin and interface of two plate is 2.5mm. The surface roughness reduces with increase of rotatation speed and then increases, while the tensile strength of joints decrease gradually as the increase of rotation speed. However, as increase of welding velocity, the surface roughness increases, and the tesile strength decreases. When the welding velocity, rotation speed and offset are 75mm/min, 375 r/min and 2.5mm, respectively, the maximum tensile strength exceed to 237.3 MPa, nearly 57.7% of the alluminum alloy.
2017, 46(1):252-256.
Abstract:
The Pd/γ-Al2O3 catalysts with different Pd content were prepared by impregnation, and effects of Pd content on hydrodeoxygenation and saturated hydrogenation performance over catalysts were studied by XRD, H2-TPR, BET and other analytical characterization techniques and a reaction system with methyl oleate as model compounds. The results showed that the proper Pd content can help to improve Pd dispersion in the support, and reduce the strength of the interaction of PdO-Al2O3. So hydrodeoxygenation and saturated hydrogenation performance of catalysts can be improved and hydrodeoxygenation way is easily carried out by decarboxylation or decarbonylation way; Catalytic hydrodeoxygenation and saturated hydrogenation conversion of 2%Pd/γ-Al2O3 is 100%, and its catalytic hydrodeoxygenation was performed according to full decarboxylation or decarbonylation way.
The Pd/γ-Al2O3 catalysts with different Pd content were prepared by impregnation, and effects of Pd content on hydrodeoxygenation and saturated hydrogenation performance over catalysts were studied by XRD, H2-TPR, BET and other analytical characterization techniques and a reaction system with methyl oleate as model compounds. The results showed that the proper Pd content can help to improve Pd dispersion in the support, and reduce the strength of the interaction of PdO-Al2O3. So hydrodeoxygenation and saturated hydrogenation performance of catalysts can be improved and hydrodeoxygenation way is easily carried out by decarboxylation or decarbonylation way; Catalytic hydrodeoxygenation and saturated hydrogenation conversion of 2%Pd/γ-Al2O3 is 100%, and its catalytic hydrodeoxygenation was performed according to full decarboxylation or decarbonylation way.
2017, 46(1):257-261.
Abstract:
La0.9Sr0.1Ga0.8Mg0.2O2.85(LSGM) powders were synthesized by solid state reaction, glycine-nitrate process and acrylamide polymerization, respectively. Novel composite electrolytes were obtained by mixing LSGM powders with binary carbonates. The conductivity behavior of LSGM-carbonate composite electrolytes has a transition temperature. The conductivities of the composites are much higher than that of pure LSGM, reaching 0.122Scm-1 at 600℃ and 0.08Scm-1 at 450℃，The maximum power densities reach 617mWcm-2 at 600℃ and 311mWcm-2 at 450℃ for SOFC with LSGM-carbonate composite electrolytes. The output performance and OCV is influenced by LSGM morphology,size and carbonate content. and the composite electrolyte with 20 wt % carbonate show the best performance.
La0.9Sr0.1Ga0.8Mg0.2O2.85(LSGM) powders were synthesized by solid state reaction, glycine-nitrate process and acrylamide polymerization, respectively. Novel composite electrolytes were obtained by mixing LSGM powders with binary carbonates. The conductivity behavior of LSGM-carbonate composite electrolytes has a transition temperature. The conductivities of the composites are much higher than that of pure LSGM, reaching 0.122Scm-1 at 600℃ and 0.08Scm-1 at 450℃，The maximum power densities reach 617mWcm-2 at 600℃ and 311mWcm-2 at 450℃ for SOFC with LSGM-carbonate composite electrolytes. The output performance and OCV is influenced by LSGM morphology,size and carbonate content. and the composite electrolyte with 20 wt % carbonate show the best performance.
2017, 46(1):262-265.
Abstract:
La0.4Sr0.6Co0.2Fe0.7Nb0.1O3-δ(LSCFN)，a perovskite oxide materials, have been synthesized by the solid state reaction method .The electrolyte-supported symmetrical solid oxide fuel cells were fabricated by tape-casting and screen-printing procedure using YSZ as electrolyte, GDC as interlayer and LSCFN as both anode and cathode. The crystal structure and chemical stability were examined by X-ray diffraction (XRD) and microstructure was inspected by scanning electron microscopy (SEM). The electrical properties of single cell were tested by using humidified 3% H2 and CH4 as fuel respectively, ambient air as oxidant and tested the stability in humidified 3% CH4 at 850℃.The results show that LSCFN appeared to be chemically compatible with GDC to at least 1400℃. The maximum power density was 254 mW cm-2 and 105 mW cm-2 in humidified H2 and CH4 at 850℃, respectively. Stable performance was sustained for at least for 100 h operating in humidified CH4. These results suggest that the LSCFN can potentially serve as an electrode for symmetrical SOFCs with YSZ electrolyte.
La0.4Sr0.6Co0.2Fe0.7Nb0.1O3-δ(LSCFN)，a perovskite oxide materials, have been synthesized by the solid state reaction method .The electrolyte-supported symmetrical solid oxide fuel cells were fabricated by tape-casting and screen-printing procedure using YSZ as electrolyte, GDC as interlayer and LSCFN as both anode and cathode. The crystal structure and chemical stability were examined by X-ray diffraction (XRD) and microstructure was inspected by scanning electron microscopy (SEM). The electrical properties of single cell were tested by using humidified 3% H2 and CH4 as fuel respectively, ambient air as oxidant and tested the stability in humidified 3% CH4 at 850℃.The results show that LSCFN appeared to be chemically compatible with GDC to at least 1400℃. The maximum power density was 254 mW cm-2 and 105 mW cm-2 in humidified H2 and CH4 at 850℃, respectively. Stable performance was sustained for at least for 100 h operating in humidified CH4. These results suggest that the LSCFN can potentially serve as an electrode for symmetrical SOFCs with YSZ electrolyte.
2017, 46(1):266-269.
Abstract:
Mg-9Li-0.5Ca alloy with an eutectic structure was prepared by alloying Mg-9Li alloys with 0.5 wt.% Ca element and employing the magnetic levitation melting and copper mould suction casting method. Microstructure observation results show that ?-Mg phase in the conventional Mg-9Li alloy are coarse plates, oriented randomly and distributed homogeneously in the ?-Li matrix. While a eutectic structure consisting of alternating lamellae of ?-Mg and ?-Li phases was formed in Mg-9Li-0.5Ca alloy, which exists as grains, i.e. eutectic colonies. Within each colony ?-Mg phase are present in the form of long fibers (the length-to-diameter ratio of ~100) and such lamellae are oriented in essentially the specific direction. Also, large amounts of nano- or ultrafine-scale Mg2Ca particles are dispersed uniformly in ?-Mg and ?-Li grains and the ?-Mg/?-Li phase interface. As a consequence, Mg-9Li-0.5Ca alloy with such eutectic structure exhibits a significantly enhanced mechanical property with the yield strength increased by 3%, the tensile strength by 3.5% and the percent elongation by 50% compared to Mg-9Li alloy. It was inferred that small amount of Ca addition and a relatively fast cooling rate from the copper mould suction casting result in the formation of fine（?-Mg ?-Li）eutectic structure which greatly improves the mechanical property of Mg-9Li-0.5Ca alloy.
Mg-9Li-0.5Ca alloy with an eutectic structure was prepared by alloying Mg-9Li alloys with 0.5 wt.% Ca element and employing the magnetic levitation melting and copper mould suction casting method. Microstructure observation results show that ?-Mg phase in the conventional Mg-9Li alloy are coarse plates, oriented randomly and distributed homogeneously in the ?-Li matrix. While a eutectic structure consisting of alternating lamellae of ?-Mg and ?-Li phases was formed in Mg-9Li-0.5Ca alloy, which exists as grains, i.e. eutectic colonies. Within each colony ?-Mg phase are present in the form of long fibers (the length-to-diameter ratio of ~100) and such lamellae are oriented in essentially the specific direction. Also, large amounts of nano- or ultrafine-scale Mg2Ca particles are dispersed uniformly in ?-Mg and ?-Li grains and the ?-Mg/?-Li phase interface. As a consequence, Mg-9Li-0.5Ca alloy with such eutectic structure exhibits a significantly enhanced mechanical property with the yield strength increased by 3%, the tensile strength by 3.5% and the percent elongation by 50% compared to Mg-9Li alloy. It was inferred that small amount of Ca addition and a relatively fast cooling rate from the copper mould suction casting result in the formation of fine（?-Mg ?-Li）eutectic structure which greatly improves the mechanical property of Mg-9Li-0.5Ca alloy.
2017, 46(1):270-273.
Abstract:
Two types of thin films were deposited by the magnetron sputtering method. After annealing at 650 ℃, the samples were tested and analyzed by XRD and VSM respectively. The Mo/Nd/NdFeB/Nd/Mo multilayer thin films with the thickness ratio of NdFeB/Nd=6/5 show high coercivity. The parallel and perpendicular coercivity of multilayer films were 14.5kOe and 10.5kOe respectively. The Mo/[NdFeB/Nd]n/Mo (n=2,5,8,10,NdFeB/Nd=6/5) alternative multilayer thin films with n=8 show good hard magnetic properties .The parallel and perpendicular coercivity of alternative multilayer thin films were 21.3kOe and 16.7kOe respectively. The magnetic properties of the alternative multilayer film with thickness ratio of NdFeB/Nd=6/5 was enhanced in comparison with multilayer film.
Two types of thin films were deposited by the magnetron sputtering method. After annealing at 650 ℃, the samples were tested and analyzed by XRD and VSM respectively. The Mo/Nd/NdFeB/Nd/Mo multilayer thin films with the thickness ratio of NdFeB/Nd=6/5 show high coercivity. The parallel and perpendicular coercivity of multilayer films were 14.5kOe and 10.5kOe respectively. The Mo/[NdFeB/Nd]n/Mo (n=2,5,8,10,NdFeB/Nd=6/5) alternative multilayer thin films with n=8 show good hard magnetic properties .The parallel and perpendicular coercivity of alternative multilayer thin films were 21.3kOe and 16.7kOe respectively. The magnetic properties of the alternative multilayer film with thickness ratio of NdFeB/Nd=6/5 was enhanced in comparison with multilayer film.
2017, 46(1):274-277.
Abstract:
Gold-based alloys were prepared by electromagnetic stirring and conventional die casting respectively. The effects of electromagnetic field on as-cast microstructure and central defects of gold-based alloy were investigated. The results show that the dendritic structure of the gold-based alloy billets prepared by electromagnetic stirring is more uniform and smaller than that by conventional casting, Meanwhile, Such defects as shrinkage cavity and porosity that frequently occur in the central region of gold-based alloy ingot produced by conventional die casting are eliminated. Moreover, the effects of electromagnetic stirring on the mechanism of refinement of the solidification structure and elimination of central defects were also discussed.
Gold-based alloys were prepared by electromagnetic stirring and conventional die casting respectively. The effects of electromagnetic field on as-cast microstructure and central defects of gold-based alloy were investigated. The results show that the dendritic structure of the gold-based alloy billets prepared by electromagnetic stirring is more uniform and smaller than that by conventional casting, Meanwhile, Such defects as shrinkage cavity and porosity that frequently occur in the central region of gold-based alloy ingot produced by conventional die casting are eliminated. Moreover, the effects of electromagnetic stirring on the mechanism of refinement of the solidification structure and elimination of central defects were also discussed.
2017, 46(1):278-281.
Abstract:
Because of excellent properties, U - Zr alloy will be used widely more and more in the future. To meet the large amounts of U - Zr alloy routine analysis, Energy Dispersion X-ray Fluorescence was used to determine zirconium content in U-Zr alloy in the present study. The thin-layer samples were prepared through dissolution, transferring and drying. Compared to traditional methods, this method shares simplicity, rapidness, as well as accuracy. It can be used in the determination of Zr content in the range of 6%-18% in U-Zr alloy. The relative standard deviation (RSD) (n=6) is not above 1.0%. The extended-uncertainty (k=2) is not above 3%.
Because of excellent properties, U - Zr alloy will be used widely more and more in the future. To meet the large amounts of U - Zr alloy routine analysis, Energy Dispersion X-ray Fluorescence was used to determine zirconium content in U-Zr alloy in the present study. The thin-layer samples were prepared through dissolution, transferring and drying. Compared to traditional methods, this method shares simplicity, rapidness, as well as accuracy. It can be used in the determination of Zr content in the range of 6%-18% in U-Zr alloy. The relative standard deviation (RSD) (n=6) is not above 1.0%. The extended-uncertainty (k=2) is not above 3%.
2017, 46(1):282-288.
Abstract:
The development of long-lifetime and high-performance thermal barrier coatings (TBCs) has been a very urgent task for China due to the need of high-power aero-engines and new-generation supersonic air craft. The failure caused by the penetration of CaO-MgO-Al2O3-SiO2 (CMAS) has been given more and more attention during recent years. This paper reviewed the latest experimental results on the failure mechanism and corrosion resistance of coatings deposited by atmospheric plasma spraying (APS) or electron beam physical vapor deposition (EBPVD) with the aim of fabricating the high-performance TBCs.
The development of long-lifetime and high-performance thermal barrier coatings (TBCs) has been a very urgent task for China due to the need of high-power aero-engines and new-generation supersonic air craft. The failure caused by the penetration of CaO-MgO-Al2O3-SiO2 (CMAS) has been given more and more attention during recent years. This paper reviewed the latest experimental results on the failure mechanism and corrosion resistance of coatings deposited by atmospheric plasma spraying (APS) or electron beam physical vapor deposition (EBPVD) with the aim of fabricating the high-performance TBCs.
