Volume 45,Issue 3,2016 Table of Contents
2016, 45(3):537-541.
Abstract:
Nickel-based alloys and austenitic stainless steels are widely used in the structures of primary circuit of nuclear power plants. Environmentally assisted cracking (EAC) of these materials is one of the most significant potential safety hazards in the primary circuit of nuclear power plants. Researches showed that EAC in nickel-based alloy is a process of oxide film rupture and reform at the tip of EAC in the high temperature water environment of nuclear power plants. To understand the micro-mechanical state at the tip of EAC, the stress and strain in the oxide film and the base metal at the EAC tip is simulated and discussed by using a commercial finite element analysis code, which provides a foundation to improve the quantitative predication accuracy of EAC growth rate of nickel-based alloys and austenitic stainless steels in the important structures of nuclear power plants.
Nickel-based alloys and austenitic stainless steels are widely used in the structures of primary circuit of nuclear power plants. Environmentally assisted cracking (EAC) of these materials is one of the most significant potential safety hazards in the primary circuit of nuclear power plants. Researches showed that EAC in nickel-based alloy is a process of oxide film rupture and reform at the tip of EAC in the high temperature water environment of nuclear power plants. To understand the micro-mechanical state at the tip of EAC, the stress and strain in the oxide film and the base metal at the EAC tip is simulated and discussed by using a commercial finite element analysis code, which provides a foundation to improve the quantitative predication accuracy of EAC growth rate of nickel-based alloys and austenitic stainless steels in the important structures of nuclear power plants.
2016, 45(3):542-547.
Abstract:
Strain rate sensitivity (SRS) of CuZr-based bulk metallic glass composites (BMGCs) containing a B2-CuZr phase with different volume fractions were investigated by performing uniaxial compression tests in a strain-rate-jump mode. It was found that the SRS exponents of the BMGCs could vary from negative to positive within the strain-rate range from 3.7×10?5 s?1 to 3.7×10?3 s?1 with increasing the B2-CuZr phase volume fraction. However, the positive SRS exponent of the BMGC with a higher B2-CuZr phase volume fraction of up to about 80% was still unexpectedly low. This was attributed to the limited strain-rate-dependence of mechanical behavior of the B2-CuZr phase, which was induced by the martensitic transformation effect of the phase during deformation. It appears that the SRS ceiling of the CuZr-based BMGCs is controlled by the B2-CuZr phase.
Strain rate sensitivity (SRS) of CuZr-based bulk metallic glass composites (BMGCs) containing a B2-CuZr phase with different volume fractions were investigated by performing uniaxial compression tests in a strain-rate-jump mode. It was found that the SRS exponents of the BMGCs could vary from negative to positive within the strain-rate range from 3.7×10?5 s?1 to 3.7×10?3 s?1 with increasing the B2-CuZr phase volume fraction. However, the positive SRS exponent of the BMGC with a higher B2-CuZr phase volume fraction of up to about 80% was still unexpectedly low. This was attributed to the limited strain-rate-dependence of mechanical behavior of the B2-CuZr phase, which was induced by the martensitic transformation effect of the phase during deformation. It appears that the SRS ceiling of the CuZr-based BMGCs is controlled by the B2-CuZr phase.
2016, 45(3):548-554.
Abstract:
Grain size is one of the crucial parameters in the microstructure analysis of high strength aluminum alloy. This information is commonly derived based on manual processes. However, these manual processes may take long time and are error prone. Nowadays，the rapid development of the digital image processing and the pattern recognition technologies provides a new methodology for the quantitative metallographic analysis. Artificial intelligence utilized in realizing automatic metallographic analysis can overcome the drawbacks of the manual processes. Through this paper we present a new method of digital image processing for determining the grain size of the metallographic images. To derive the grain size of the digital metallographic images, the digital image processing is applied to extract grain boundary by proposing a new edge detection algorithm based on the fuzzy logic. Extensive metallographic images with different qualities were tested to validate this method. Practical application use cases are presented here. The grain size is calculated in accordance with American Society for Testing Material (ASTM) standards.
Grain size is one of the crucial parameters in the microstructure analysis of high strength aluminum alloy. This information is commonly derived based on manual processes. However, these manual processes may take long time and are error prone. Nowadays，the rapid development of the digital image processing and the pattern recognition technologies provides a new methodology for the quantitative metallographic analysis. Artificial intelligence utilized in realizing automatic metallographic analysis can overcome the drawbacks of the manual processes. Through this paper we present a new method of digital image processing for determining the grain size of the metallographic images. To derive the grain size of the digital metallographic images, the digital image processing is applied to extract grain boundary by proposing a new edge detection algorithm based on the fuzzy logic. Extensive metallographic images with different qualities were tested to validate this method. Practical application use cases are presented here. The grain size is calculated in accordance with American Society for Testing Material (ASTM) standards.
2016, 45(3):555-560.
Abstract:
Vacuum diffusion bonding of TiC cermet/304 stainless steel was conducted and Ti-Nb-Cu multi-interlayer was intended to achieve active bonding and residual stress relieving. Detailed microstructure characterization and mechanical properties assessment was carried out to evaluate the bonding technology. It was found that an obvious transition zone was formed at the interfaces and the detailed interfacial products were (Ti,Nb), remnant Nb, remnant Cu and Cu(s.s). The shear strength of TiC/Ti-Nb-Cu/304SS joint up to 84.6 MPa by controlling heating to 925℃ and hold for 20 min under a pressure of 8MPa. Failure occurred within TiC cermet near the interface in a brittle manner. The results indicated that Ti/Nb/Cu can be effectively reduce the harmful effects of intermetallic compounds on the joint performance, and the Nb interlayer plays a major role in the relief of the residual stress.
Vacuum diffusion bonding of TiC cermet/304 stainless steel was conducted and Ti-Nb-Cu multi-interlayer was intended to achieve active bonding and residual stress relieving. Detailed microstructure characterization and mechanical properties assessment was carried out to evaluate the bonding technology. It was found that an obvious transition zone was formed at the interfaces and the detailed interfacial products were (Ti,Nb), remnant Nb, remnant Cu and Cu(s.s). The shear strength of TiC/Ti-Nb-Cu/304SS joint up to 84.6 MPa by controlling heating to 925℃ and hold for 20 min under a pressure of 8MPa. Failure occurred within TiC cermet near the interface in a brittle manner. The results indicated that Ti/Nb/Cu can be effectively reduce the harmful effects of intermetallic compounds on the joint performance, and the Nb interlayer plays a major role in the relief of the residual stress.
2016, 45(3):561-566.
Abstract:
N-doped TiO2 nanotube (NT) arrays were prepared by anodization in electrolytes containing HF, 1-n-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM]BF4) ionic liquid and water. The ionic liquid, [BMIM]BF4, was used as the nitrogen source. The surface morphology and composition of samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and UV-Vis diffuse reflectance spectra (DRS). Photocatalytic activity of N-doped TiO2 NT arrays was investigated by degradation of methylene blue (MB) under spherical xenon lamp. The degradation rate of MB over N-doped TiO2 NT arrays was obviously higher than that over undoped TiO2 NT arrays. The results are caused by the increased oxygen vacancies and the decreased band gap.
N-doped TiO2 nanotube (NT) arrays were prepared by anodization in electrolytes containing HF, 1-n-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM]BF4) ionic liquid and water. The ionic liquid, [BMIM]BF4, was used as the nitrogen source. The surface morphology and composition of samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and UV-Vis diffuse reflectance spectra (DRS). Photocatalytic activity of N-doped TiO2 NT arrays was investigated by degradation of methylene blue (MB) under spherical xenon lamp. The degradation rate of MB over N-doped TiO2 NT arrays was obviously higher than that over undoped TiO2 NT arrays. The results are caused by the increased oxygen vacancies and the decreased band gap.
2016, 45(3):567-570.
Abstract:
The effect of annealing temperature on the microstructure evolution of Zr48Cu36Ag8Al8 bulk metallic glass was investigated by using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Results show that the as-cast Zr48Cu36Ag8Al8 alloy by rapid solidi?cation exhibits a typical characteristic of the amorphous structure. After annealed at 703K / 20min, a homogeneous amorphous matrix was separated into two different glassy phases, namely, phase separation occurred. Because phase separation structure competed with amorphous matrix during isothermal annealing, this structure easily decomposed and transformed into the crystalline phase AlZr2 and AlAg3with annealing temperature increasing. The microstructure of Zr48Cu36Ag8Al8 bulk metallic glass undergoes the local structure difference, phase separation and nano-crystallization during heat treatment in the supercooled liquid region, which implies that the microstructure of Zr48Cu36Ag8Al8 bulk metallic glass is sensitive to the annealing temperature. In addition, the formation of phase separation can accelerate the formation of nano-crystals.
The effect of annealing temperature on the microstructure evolution of Zr48Cu36Ag8Al8 bulk metallic glass was investigated by using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Results show that the as-cast Zr48Cu36Ag8Al8 alloy by rapid solidi?cation exhibits a typical characteristic of the amorphous structure. After annealed at 703K / 20min, a homogeneous amorphous matrix was separated into two different glassy phases, namely, phase separation occurred. Because phase separation structure competed with amorphous matrix during isothermal annealing, this structure easily decomposed and transformed into the crystalline phase AlZr2 and AlAg3with annealing temperature increasing. The microstructure of Zr48Cu36Ag8Al8 bulk metallic glass undergoes the local structure difference, phase separation and nano-crystallization during heat treatment in the supercooled liquid region, which implies that the microstructure of Zr48Cu36Ag8Al8 bulk metallic glass is sensitive to the annealing temperature. In addition, the formation of phase separation can accelerate the formation of nano-crystals.
2016, 45(3):571-574.
Abstract:
Pb (Zr0.95Ti0.05)O3(PZT95/5 for short) anti-ferroelectric nano-powder was prepared by sol-gel method，and the effects of calcinations temperatures on structural stability of perovskite for PZT(95/5) was systematically investigated in this paper. Based on the results of TGA-DSC, calcinations temperature range of dried gel was identified as 550℃ to 750℃. XRD results illustrated that the peak intensity of the main crystalline phase gradually increasing, while that of the impurity phase decreasing, eventually disappeared with the increasing of the calcinations temperature T1. When calcined at 750℃, single phase of perovskite for PZT(95/5) was formed. Observed under SEM, with the increasing of T1, powder synthesized becomes finer and more uniform progressively. And when calcined at 750℃, the average particle size of PZT(95/5) nan-powder is about 100 nm.
Pb (Zr0.95Ti0.05)O3(PZT95/5 for short) anti-ferroelectric nano-powder was prepared by sol-gel method，and the effects of calcinations temperatures on structural stability of perovskite for PZT(95/5) was systematically investigated in this paper. Based on the results of TGA-DSC, calcinations temperature range of dried gel was identified as 550℃ to 750℃. XRD results illustrated that the peak intensity of the main crystalline phase gradually increasing, while that of the impurity phase decreasing, eventually disappeared with the increasing of the calcinations temperature T1. When calcined at 750℃, single phase of perovskite for PZT(95/5) was formed. Observed under SEM, with the increasing of T1, powder synthesized becomes finer and more uniform progressively. And when calcined at 750℃, the average particle size of PZT(95/5) nan-powder is about 100 nm.
2016, 45(3):575-580.
Abstract:
The microstructure evolution of titanium alloy was decided with deformation rate in cold-deformation process, and substructure significantly influences phase transformation behavior in isothermal aging treatment. The microstructure evolution in cold-deformation and aging behavior of the TB8 alloy was investigated by X-ray diffraction (XRD), Vickers hardness (HV), field emission scanning electron microscope (FESEM) and differential scanning calorimeter (DSC). The high value of FWHM resulted from the combination of the grain distortion and dislocations, and the enhancement of the distortion and dislocations was indicated by increasing of HV value. The phase transformations of this study have reversed the effect of cold-deformation on transformation behavior of α phase precipitation in the β matrix. It suggested that there existed a possibility of a special behavior in the aging transformation of cold-deformation titanium alloy.
The microstructure evolution of titanium alloy was decided with deformation rate in cold-deformation process, and substructure significantly influences phase transformation behavior in isothermal aging treatment. The microstructure evolution in cold-deformation and aging behavior of the TB8 alloy was investigated by X-ray diffraction (XRD), Vickers hardness (HV), field emission scanning electron microscope (FESEM) and differential scanning calorimeter (DSC). The high value of FWHM resulted from the combination of the grain distortion and dislocations, and the enhancement of the distortion and dislocations was indicated by increasing of HV value. The phase transformations of this study have reversed the effect of cold-deformation on transformation behavior of α phase precipitation in the β matrix. It suggested that there existed a possibility of a special behavior in the aging transformation of cold-deformation titanium alloy.
2016, 45(3):581-587.
Abstract:
The present investigation mainly focuses on effects of centrifugal forces and casting modulus on structures and mechanical properties of Ti-6Al-4V alloy formed under different vertical centrifugal casting conditions in graphite molds. Mold rotating rates of 0, 110 and 210 rpm are considered with experimental method. Results show that, grain size and lamellar thickness decrease with the decreasing of modulus or increasing of centrifugal force, and tensile strengths are considerably enhanced with the decreasing of modulus or increasing of centrifugal force, but the elongation shows the opposite changing trend. The quantitative relationships among gravity coefficient, casting modulus and structures or mechanical properties of Ti-6Al-4V alloy have been obtained. As the comparison of Ti-6Al-4V alloy cast in graphite mold under gravity field, the structures of steeped casting in metal mold are also investigated. It was found that the grain size or lamellar thickness in both two molds shows the same changing trend with the cooling rate, and the quantitative relationships between structures and cooling rates have been obtained.
The present investigation mainly focuses on effects of centrifugal forces and casting modulus on structures and mechanical properties of Ti-6Al-4V alloy formed under different vertical centrifugal casting conditions in graphite molds. Mold rotating rates of 0, 110 and 210 rpm are considered with experimental method. Results show that, grain size and lamellar thickness decrease with the decreasing of modulus or increasing of centrifugal force, and tensile strengths are considerably enhanced with the decreasing of modulus or increasing of centrifugal force, but the elongation shows the opposite changing trend. The quantitative relationships among gravity coefficient, casting modulus and structures or mechanical properties of Ti-6Al-4V alloy have been obtained. As the comparison of Ti-6Al-4V alloy cast in graphite mold under gravity field, the structures of steeped casting in metal mold are also investigated. It was found that the grain size or lamellar thickness in both two molds shows the same changing trend with the cooling rate, and the quantitative relationships between structures and cooling rates have been obtained.
2016, 45(3):588-592.
Abstract:
High emissivity coatings used in high temperature condition are attracting great attention in the worldwide to effectively transfer heat by radiation. Here we prepared a new high emissivity coating by using spray painting method. The coating contains amorphous borosilicate glass, Mg2B2O5, MoSi2 and SiB4 and has the thickness of about 50μm. The coating exhibits excellent thermal shock resistance (more than 100 thermal cycles from 950 oC to water temperature). The average emissivity of the coating is 0.905?.024 at 950 oC and has a slight degradation after 100 thermal cycles.
High emissivity coatings used in high temperature condition are attracting great attention in the worldwide to effectively transfer heat by radiation. Here we prepared a new high emissivity coating by using spray painting method. The coating contains amorphous borosilicate glass, Mg2B2O5, MoSi2 and SiB4 and has the thickness of about 50μm. The coating exhibits excellent thermal shock resistance (more than 100 thermal cycles from 950 oC to water temperature). The average emissivity of the coating is 0.905?.024 at 950 oC and has a slight degradation after 100 thermal cycles.
2016, 45(3):593-598.
Abstract:
In this paper, we investigated the effect of counterface of ZrO2, Si3N4 and SiC ceramics on the tribological behavior of 1Cr18Ni9Ti steel under 90% hydrogen peroxide solution. The results showed that the tribological properties of 1Cr18Ni9Ti steel were strongly dependent on the counterfaces. The adhesion behavior affects the tribocouple of 1Cr18Ni9Ti/ZrO2, leading to a high coefficient of friction (COF) fluctuating from 0.17 to 0.27 and the highest wear loss of 1Cr18Ni9Ti steel. The reactions of oxidation and hydrolysis protect the worn surface of 1Cr18Ni9Ti/SiC, inducing a low COF 0.035 and the lowest wear loss of 1Cr18Ni9Ti steel. Both the adhesion behavior and reactions play important roles in the wear behavior of 1Cr18Ni9Ti/Si3N4, leading to a complex COF and between-in wear loss of 1Cr18Ni9Ti steel. As for the counterparts, ZrO2 ceramic showed severe wear, and Si3N4 ceramic preserved the obviously lowest wear volume.
In this paper, we investigated the effect of counterface of ZrO2, Si3N4 and SiC ceramics on the tribological behavior of 1Cr18Ni9Ti steel under 90% hydrogen peroxide solution. The results showed that the tribological properties of 1Cr18Ni9Ti steel were strongly dependent on the counterfaces. The adhesion behavior affects the tribocouple of 1Cr18Ni9Ti/ZrO2, leading to a high coefficient of friction (COF) fluctuating from 0.17 to 0.27 and the highest wear loss of 1Cr18Ni9Ti steel. The reactions of oxidation and hydrolysis protect the worn surface of 1Cr18Ni9Ti/SiC, inducing a low COF 0.035 and the lowest wear loss of 1Cr18Ni9Ti steel. Both the adhesion behavior and reactions play important roles in the wear behavior of 1Cr18Ni9Ti/Si3N4, leading to a complex COF and between-in wear loss of 1Cr18Ni9Ti steel. As for the counterparts, ZrO2 ceramic showed severe wear, and Si3N4 ceramic preserved the obviously lowest wear volume.
2016, 45(3):599-605.
Abstract:
Structure and thermal stability of nano-sized dispersoids in Al-(Zr)-(Pr)-(Cr) alloys have been revealed by conventional and high-resolution transmission electron microscopy. Al-0.16Zr-0.26Pr-0.18Cr alloy (wt.%) illustrates significant precipitation strengthening, thermal stability and inhibit-recrystallization ability by forming a relatively high density of coherent and well-dispersed Pr-containing (Al, Cr)3Zr dispersoids (15 - 20 nm) with L12 structure. The dispersoid is coherent even exposed at 500℃ for 400 h. Pr-containing (Al, Cr)3Zr dispersoid is finer and coarsening-resistant around 500 癈, as compared with L12-structured Al3Zr and Pr-containing Al3Zr dispersoid.
Structure and thermal stability of nano-sized dispersoids in Al-(Zr)-(Pr)-(Cr) alloys have been revealed by conventional and high-resolution transmission electron microscopy. Al-0.16Zr-0.26Pr-0.18Cr alloy (wt.%) illustrates significant precipitation strengthening, thermal stability and inhibit-recrystallization ability by forming a relatively high density of coherent and well-dispersed Pr-containing (Al, Cr)3Zr dispersoids (15 - 20 nm) with L12 structure. The dispersoid is coherent even exposed at 500℃ for 400 h. Pr-containing (Al, Cr)3Zr dispersoid is finer and coarsening-resistant around 500 癈, as compared with L12-structured Al3Zr and Pr-containing Al3Zr dispersoid.
2016, 45(3):606-611.
Abstract:
Weld bead geometry and porosity of AA2219-T851 high strength aluminum alloy welds with ER2319 wire produced by different cold metal transfer (CMT) processes and its heat input were investigated. The results show that, a narrow finger-shaped geometry is observed using the conventional CMT process and a large number of gas pores exist in the lower and upper part of welds. Compared to that of CMT process, the weld melting area is increased using CMT-P process, and it is beneficial to reduce the porosity effectively with an appropriate heat input. Finger-shaped geometry with lower melting depth using CMT-ADV process and spherical-shaped bead geometry with lower dilution using CMT-PADV process is achieved, respectively. The gas pore is reduced predominantly and even eliminated due to the lower heat input and effective oxide cleaning of wire ends for the two processes.
Weld bead geometry and porosity of AA2219-T851 high strength aluminum alloy welds with ER2319 wire produced by different cold metal transfer (CMT) processes and its heat input were investigated. The results show that, a narrow finger-shaped geometry is observed using the conventional CMT process and a large number of gas pores exist in the lower and upper part of welds. Compared to that of CMT process, the weld melting area is increased using CMT-P process, and it is beneficial to reduce the porosity effectively with an appropriate heat input. Finger-shaped geometry with lower melting depth using CMT-ADV process and spherical-shaped bead geometry with lower dilution using CMT-PADV process is achieved, respectively. The gas pore is reduced predominantly and even eliminated due to the lower heat input and effective oxide cleaning of wire ends for the two processes.
2016, 45(3):612-616.
Abstract:
The formation mechanisms of garnet-like Li7La3Zr2O12 (LLZO) phase using LiOH?H2O as raw materials are investigated symmetrically by XRD and DTA/TG measurements. It was found that reaction mechanisms of the LLZO formation are as follows: 7Li2O 3La2O3 4ZrO2=2Li7La3Zr2O12 The production of LLZO phase takes place at about 680oC observed from the XRD patterns, in agreement with the thermic peak at 700oC in DTA/TG curves, which arises from the formation of LZZO phase. The stable existence temperature range of LLZO phase is wide, from 720 to 1000oC. However, LLZO is thermally unstable at the high temperatures (>1000oC) due to a serious loss of lithium element, and it discomposes into pyrochlore phase La2Zr2O7. And the amount of the decomposed products increased, and LLZO decreased gradually with the increase of the calcination temperature. When the reactant mixture was calcined at the low temperature, the produced phases were identified to be lanthanum compounds because La2O3 absorbs moisture and CO2 very easily. The chemical reactions at lower temperature are mainly related with the reactions among lanthanum compounds. LLZO powder was synthesized by solid state reaction at 800℃. It is found that the LLZO crystal belongs to the tetragonal symmetry. SEM observations show that the obtained LLZO powder was nano-sized.
The formation mechanisms of garnet-like Li7La3Zr2O12 (LLZO) phase using LiOH?H2O as raw materials are investigated symmetrically by XRD and DTA/TG measurements. It was found that reaction mechanisms of the LLZO formation are as follows: 7Li2O 3La2O3 4ZrO2=2Li7La3Zr2O12 The production of LLZO phase takes place at about 680oC observed from the XRD patterns, in agreement with the thermic peak at 700oC in DTA/TG curves, which arises from the formation of LZZO phase. The stable existence temperature range of LLZO phase is wide, from 720 to 1000oC. However, LLZO is thermally unstable at the high temperatures (>1000oC) due to a serious loss of lithium element, and it discomposes into pyrochlore phase La2Zr2O7. And the amount of the decomposed products increased, and LLZO decreased gradually with the increase of the calcination temperature. When the reactant mixture was calcined at the low temperature, the produced phases were identified to be lanthanum compounds because La2O3 absorbs moisture and CO2 very easily. The chemical reactions at lower temperature are mainly related with the reactions among lanthanum compounds. LLZO powder was synthesized by solid state reaction at 800℃. It is found that the LLZO crystal belongs to the tetragonal symmetry. SEM observations show that the obtained LLZO powder was nano-sized.
2016, 45(3):617-622.
Abstract:
This paper presents a method for measuring the creep stress exponent of Ti6Al4V alloy in room temperature using nanoindentation with constant . As to find out the effect of the loading rate and the maximum load to the result, the diamond Berkovich indenter was loaded to different maximum loads with different loading rates, then the maximum load was held as a constant for 5 minutes, and the stress exponent of the material in room temperature was discovered based on the relationship between the indentation strain rate and the hardness during the hold period. It shows that the effects of the loading rate and the maximum load are so small to the result that they can be ignored, and the creep stress exponent of Ti6Al4V in room temperature got from the experiment is between 7.0513~7.216.
This paper presents a method for measuring the creep stress exponent of Ti6Al4V alloy in room temperature using nanoindentation with constant . As to find out the effect of the loading rate and the maximum load to the result, the diamond Berkovich indenter was loaded to different maximum loads with different loading rates, then the maximum load was held as a constant for 5 minutes, and the stress exponent of the material in room temperature was discovered based on the relationship between the indentation strain rate and the hardness during the hold period. It shows that the effects of the loading rate and the maximum load are so small to the result that they can be ignored, and the creep stress exponent of Ti6Al4V in room temperature got from the experiment is between 7.0513~7.216.
2016, 45(3):623-628.
Abstract:
Deposit Ti film on polished Mo, quartz and single crystal silicon subserate by using electron beam evaporation. Analized the surface morphology and microstructures of substrates and the thin film by AFM, XRD and SEM.The results shown that : The Ti film’s surface morphology and microstructure were greatly influenced by the substrate materials. The surface of the Ti film on the polished MO substrates had some fluctuations. The Ti film nucleated on the substrate firstly, and then vertically grown upwards in the form of columnar grain. The surface of Ti film on the polished quartz substrate was smooth, and the particles and the interfaces were clearly distinguished by the layer of equiaxed grains on the interface. The surface of Ti film on the single crystal silicon substrate was the roughest one. However, the surface of the crystal silicon was the smoothest one. There were peaks of TiSi2 controlled by Ti/Si interface silicide growth dynamics.
Deposit Ti film on polished Mo, quartz and single crystal silicon subserate by using electron beam evaporation. Analized the surface morphology and microstructures of substrates and the thin film by AFM, XRD and SEM.The results shown that : The Ti film’s surface morphology and microstructure were greatly influenced by the substrate materials. The surface of the Ti film on the polished MO substrates had some fluctuations. The Ti film nucleated on the substrate firstly, and then vertically grown upwards in the form of columnar grain. The surface of Ti film on the polished quartz substrate was smooth, and the particles and the interfaces were clearly distinguished by the layer of equiaxed grains on the interface. The surface of Ti film on the single crystal silicon substrate was the roughest one. However, the surface of the crystal silicon was the smoothest one. There were peaks of TiSi2 controlled by Ti/Si interface silicide growth dynamics.
2016, 45(3):629-634.
Abstract:
Abstract: Nanoscale WC-Co composite powders were synthesized by in situ reduction and carbonization reactions at different temperatures and subsequent consolidated in the spark plasma sintering (SPS) system, the nanocrystalline WC-Co cemented carbide bulk materials were obtained. Systematic tests and analyses show that the cemented carbides consolidated from the powders synthesized at low temperature has obvious orientation distribution of WC characteristic planes. The area fraction of the (0001) plane vertical to the sintering pressure direction occupies up to 40%, but only 10.72% parallel to the sintering pressure direction. In contrast, the cemented carbide bulk materials consolidated from the powders synthesized at higher temperatures do not exhibit the orientational distribution of characteristic planes.
Abstract: Nanoscale WC-Co composite powders were synthesized by in situ reduction and carbonization reactions at different temperatures and subsequent consolidated in the spark plasma sintering (SPS) system, the nanocrystalline WC-Co cemented carbide bulk materials were obtained. Systematic tests and analyses show that the cemented carbides consolidated from the powders synthesized at low temperature has obvious orientation distribution of WC characteristic planes. The area fraction of the (0001) plane vertical to the sintering pressure direction occupies up to 40%, but only 10.72% parallel to the sintering pressure direction. In contrast, the cemented carbide bulk materials consolidated from the powders synthesized at higher temperatures do not exhibit the orientational distribution of characteristic planes.
18 First-principle studies of AlCoCrCuFexNi high entropy alloys with the different mole fractions of Cu
2016, 45(3):635-639.
Abstract:
The structural properties, elastic properties, and the heat of formations for the high entropy alloys (HEAs) AlCoCrCuxFeNi were studied by density functional theory and plane-wave pseudopotental technique with generalized gradient approximation (GGA), the crystal structure was built with the Virtual Crystal Approximation (VCA). The calculated results indicate that the mass density of HEA AlCoCrCuxFeNi increases with the increasing mole fraction of Cu, the lattice parameter is the largest when the mole fraction of Cu is 1.5. The mechanical stability of the HEA AlCoCrCuxFeNi is nothing to do with the mole fraction of Cu. The heat of formation decreases with the increasing mole fraction of Cu, but the HEAs AlCoCrCuxFeNi are thermodynamically stable due to their negative heats of formation.
The structural properties, elastic properties, and the heat of formations for the high entropy alloys (HEAs) AlCoCrCuxFeNi were studied by density functional theory and plane-wave pseudopotental technique with generalized gradient approximation (GGA), the crystal structure was built with the Virtual Crystal Approximation (VCA). The calculated results indicate that the mass density of HEA AlCoCrCuxFeNi increases with the increasing mole fraction of Cu, the lattice parameter is the largest when the mole fraction of Cu is 1.5. The mechanical stability of the HEA AlCoCrCuxFeNi is nothing to do with the mole fraction of Cu. The heat of formation decreases with the increasing mole fraction of Cu, but the HEAs AlCoCrCuxFeNi are thermodynamically stable due to their negative heats of formation.
2016, 45(3):640-643.
Abstract:
In this paper, the microstructures and mechanical properties of extruded Mg-6xZn-xY alloys at the extrusion ratio of 81:1 are quantitatively investigated. The results show that I-phase content gradually increases, the average grain size of α -Mg matrix decreases first and then increases, with the increasing Zn, Y content. The α -Mg average grain size of Mg-6Zn-1Y alloy is minimum of 2.9 μm, and the size distribution is most uniform, the standard deviation of α -Mg grain size also reached the minimum of 0.77 μm. With increasing Zn, Y content, yield strength and tensile strength of Mg-Zn-Y alloy increase, and elongation decreases. Compare with α-Mg grain refinement, the content of fine I-phase increases significantly to improve the strength of Mg-6xZn-xY alloy.
In this paper, the microstructures and mechanical properties of extruded Mg-6xZn-xY alloys at the extrusion ratio of 81:1 are quantitatively investigated. The results show that I-phase content gradually increases, the average grain size of α -Mg matrix decreases first and then increases, with the increasing Zn, Y content. The α -Mg average grain size of Mg-6Zn-1Y alloy is minimum of 2.9 μm, and the size distribution is most uniform, the standard deviation of α -Mg grain size also reached the minimum of 0.77 μm. With increasing Zn, Y content, yield strength and tensile strength of Mg-Zn-Y alloy increase, and elongation decreases. Compare with α-Mg grain refinement, the content of fine I-phase increases significantly to improve the strength of Mg-6xZn-xY alloy.
2016, 45(3):644-649.
Abstract:
In this paper, the morphological character of AlMn intermetallics in Mg-3Al alloys and the mechanism of Manganese’s effect on heterogeneous nucleation of aluminum carbide (A14C3) were studied by using OM, SEM, EDS and DTA. Results show that A14C3 particles are produced by carbon inoculation and act as the potent heterogeneous nuclei for primary Mg. The ?-Mg grain can be greatly refined with carbon inoculation when the content of Mn is below 0.32wt%. The minimum average grain size of 66 μm can be obtained due to the formation of numerous small ball-like and short rod-like AlMn intermetallics, which is helpful to grain refinement. In contrast, coarser cross petals-like AlMn intermetallics will be formed if the content of Mn is increased to 0.56wt.%. Therefore, the A14C3 particles are easily poisoned by excess Mn solute and turn to be complex Al-Mn-C-O compounds, which are not effective heterogeneous nuclei of primary Mg, hence leading to the coarsening of ?-Mg grain.
In this paper, the morphological character of AlMn intermetallics in Mg-3Al alloys and the mechanism of Manganese’s effect on heterogeneous nucleation of aluminum carbide (A14C3) were studied by using OM, SEM, EDS and DTA. Results show that A14C3 particles are produced by carbon inoculation and act as the potent heterogeneous nuclei for primary Mg. The ?-Mg grain can be greatly refined with carbon inoculation when the content of Mn is below 0.32wt%. The minimum average grain size of 66 μm can be obtained due to the formation of numerous small ball-like and short rod-like AlMn intermetallics, which is helpful to grain refinement. In contrast, coarser cross petals-like AlMn intermetallics will be formed if the content of Mn is increased to 0.56wt.%. Therefore, the A14C3 particles are easily poisoned by excess Mn solute and turn to be complex Al-Mn-C-O compounds, which are not effective heterogeneous nuclei of primary Mg, hence leading to the coarsening of ?-Mg grain.
2016, 45(3):650-655.
Abstract:
In order to identify the failure mechanism of the IPMC and prolong service life, researching the prepared Ag-IPMC to analyze the changes of surface chemical components before and after the failure of IPMC. Three parts of active Ag-IPMC surfaces and five inactive Ag-IPMC surfaces selected were spectroscopy scanned by EDS to analyze the change rules of surface chemical components before and after the failure of IPMC and study the influence of changes of surface chemical components on movement failure. Results indicate that there was no oxide of Ag in the clad layer of active Ag-IPMC surfaces, and the Ag clad layer had a fine electrical conductivity, which provided an environment of steady electric field for the ion exchange in inophragma; the Ag content of inactive Ag-IPMC surfaces decreased, and Ag in clad layer reacted with O and S under the function of current, which generated the oxides and sulfides, making the structure of clad layer generate the phenomenon similar to fracture, and the increase of contact resistance of Ag-IPMC surfaces leaded to the failure of Ag-IPMC.
In order to identify the failure mechanism of the IPMC and prolong service life, researching the prepared Ag-IPMC to analyze the changes of surface chemical components before and after the failure of IPMC. Three parts of active Ag-IPMC surfaces and five inactive Ag-IPMC surfaces selected were spectroscopy scanned by EDS to analyze the change rules of surface chemical components before and after the failure of IPMC and study the influence of changes of surface chemical components on movement failure. Results indicate that there was no oxide of Ag in the clad layer of active Ag-IPMC surfaces, and the Ag clad layer had a fine electrical conductivity, which provided an environment of steady electric field for the ion exchange in inophragma; the Ag content of inactive Ag-IPMC surfaces decreased, and Ag in clad layer reacted with O and S under the function of current, which generated the oxides and sulfides, making the structure of clad layer generate the phenomenon similar to fracture, and the increase of contact resistance of Ag-IPMC surfaces leaded to the failure of Ag-IPMC.
2016, 45(3):656-661.
Abstract:
The tensile fractography of polycrystalline beryllium with zero and ＞5% elongations at room temperature was systematically examined by scanning electron microscopy. The results show that the tensile fracture of polycrystalline beryllium is of flat surface and no necking. Regardless of elongations of polycrystalline beryllium, its macroscopic fractography has fibrous and radical zones, and its microscopic fractography has cleavage fracture patterns produced by cracks propagating along some specific crystallographic surfaces, together with tear ridges produced by some plastic deformation. Therefore, tensile fracture of polycrystalline beryllium is of quasi-cleavage one. In which, for the polycrystalline beryllium with ＞5% elongation, the boundaries between fibrous and radical zones in the fracture area are not clear, and radial patterns are tiny and of multiple directions. The main crack source is not obvious in the fractograph, and the fracture is caused by the confluence of multiple cracks. In contrast, for the polycrystalline beryllium with zero elongation, the boundaries between fibrous and radical zones in the fracture area are clear, and the radial patterns are coarse with one direction. The radical patterns are mainly across almost all regions of the fracture area, together with very limited fibrous zones. There is obviously main crack source, where some kinds of microstructure defects exist, and the fracture is mainly controlled by a single crack propagating. It can thus be concluded that the elongation of polycrystalline beryllium mainly arises from the microcrack nucleation stage. Microstructure defects lead microcracks to prematurely reach the critical size of crack propagation, which is the main reason responsible for the poor ductility of polycrystalline beryllium at room temperature.
The tensile fractography of polycrystalline beryllium with zero and ＞5% elongations at room temperature was systematically examined by scanning electron microscopy. The results show that the tensile fracture of polycrystalline beryllium is of flat surface and no necking. Regardless of elongations of polycrystalline beryllium, its macroscopic fractography has fibrous and radical zones, and its microscopic fractography has cleavage fracture patterns produced by cracks propagating along some specific crystallographic surfaces, together with tear ridges produced by some plastic deformation. Therefore, tensile fracture of polycrystalline beryllium is of quasi-cleavage one. In which, for the polycrystalline beryllium with ＞5% elongation, the boundaries between fibrous and radical zones in the fracture area are not clear, and radial patterns are tiny and of multiple directions. The main crack source is not obvious in the fractograph, and the fracture is caused by the confluence of multiple cracks. In contrast, for the polycrystalline beryllium with zero elongation, the boundaries between fibrous and radical zones in the fracture area are clear, and the radial patterns are coarse with one direction. The radical patterns are mainly across almost all regions of the fracture area, together with very limited fibrous zones. There is obviously main crack source, where some kinds of microstructure defects exist, and the fracture is mainly controlled by a single crack propagating. It can thus be concluded that the elongation of polycrystalline beryllium mainly arises from the microcrack nucleation stage. Microstructure defects lead microcracks to prematurely reach the critical size of crack propagation, which is the main reason responsible for the poor ductility of polycrystalline beryllium at room temperature.
2016, 45(3):662-666.
Abstract:
Cu-Cr and Cu-Mo alloyed powders of different constitutes were investigated by X-ray diffraction (XRD) and TEM.Mo mainly dissovles in Cu lattice, and the solid solubility extension of Mo in Cu by mechanical alloying is limited. As Mo content increases, Cu grain size decreases, and the saturated amount of Mo in Cu increases. Amorphous phase appears in the Cu-80%Mo alloyed powder. Cu-Cr solid solution belongs to nano grain boudary solution. The alloyed product of Cu-50wt%Cr is affected by milling intensity. Cu nano crystallites and Cr oxides are formed with high milling intensity.
Cu-Cr and Cu-Mo alloyed powders of different constitutes were investigated by X-ray diffraction (XRD) and TEM.Mo mainly dissovles in Cu lattice, and the solid solubility extension of Mo in Cu by mechanical alloying is limited. As Mo content increases, Cu grain size decreases, and the saturated amount of Mo in Cu increases. Amorphous phase appears in the Cu-80%Mo alloyed powder. Cu-Cr solid solution belongs to nano grain boudary solution. The alloyed product of Cu-50wt%Cr is affected by milling intensity. Cu nano crystallites and Cr oxides are formed with high milling intensity.
2016, 45(3):667-670.
Abstract:
We tested the PCT curves of Zr-0 alloy under different temperature and calculated thermodynamic parameters according thermodynamic equilibrium of deuteride equation. The results show that the Equilibrium pressure, The maximum amount of deuterium absorbtion and desorption increases with Elevated temperature. The equilibrium pressure and the maximum amount of deuterium absorbtion are 0.12MPa, 5.2%（mass％）.The maximum amount of deuterium desorption is 2.2%（mass％）when the temoerature is 900℃.The Standard molar entropy change of Zr-0 alloy separate out ZrD is -32.74J/mol, the standard molar enthalpy change is -47.68kJ/mol, the ZrD separated out equilibrium temperature is 1183℃(1456K). The Standard molar entropy change of Zr-0 alloy separate out ZrD1.66 is -290.86J/mol, the standard molar enthalpy change is -326.55kJ/mol, the ZrD separated out equilibrium temperature is 850℃(1123K). The calculated results are consistent with the experimental results..
We tested the PCT curves of Zr-0 alloy under different temperature and calculated thermodynamic parameters according thermodynamic equilibrium of deuteride equation. The results show that the Equilibrium pressure, The maximum amount of deuterium absorbtion and desorption increases with Elevated temperature. The equilibrium pressure and the maximum amount of deuterium absorbtion are 0.12MPa, 5.2%（mass％）.The maximum amount of deuterium desorption is 2.2%（mass％）when the temoerature is 900℃.The Standard molar entropy change of Zr-0 alloy separate out ZrD is -32.74J/mol, the standard molar enthalpy change is -47.68kJ/mol, the ZrD separated out equilibrium temperature is 1183℃(1456K). The Standard molar entropy change of Zr-0 alloy separate out ZrD1.66 is -290.86J/mol, the standard molar enthalpy change is -326.55kJ/mol, the ZrD separated out equilibrium temperature is 850℃(1123K). The calculated results are consistent with the experimental results..
2016, 45(3):677-680.
Abstract:
The corrosion behavior of Inconel 625 alloy haved been investigated in molten (Li,K)2CO3 and (Li,K)2CO3 Y2O3 at 650℃ by using SEM and XRD.It was shown that the corrosion rate of Inconel 625 alloy in molten (Li,K)2CO3 is faster than that of Inconel 625 alloy in the (Li,K)2CO3 Y2O3 at 650℃.The excellent corrosion resistance of the Inconel 625 alloy in (Li,K)2CO3 Y2O3 at 650℃ was related to the formation of a protective oxide film with NiCr2O4、Y2O3、NiO、Cr2O3.
The corrosion behavior of Inconel 625 alloy haved been investigated in molten (Li,K)2CO3 and (Li,K)2CO3 Y2O3 at 650℃ by using SEM and XRD.It was shown that the corrosion rate of Inconel 625 alloy in molten (Li,K)2CO3 is faster than that of Inconel 625 alloy in the (Li,K)2CO3 Y2O3 at 650℃.The excellent corrosion resistance of the Inconel 625 alloy in (Li,K)2CO3 Y2O3 at 650℃ was related to the formation of a protective oxide film with NiCr2O4、Y2O3、NiO、Cr2O3.
2016, 45(3):681-687.
Abstract:
Space winding helix parametric equation, metal rubber and its blank meso structure numerical model were established with real raw material and process parameters of product based on automatic blank twine technology. Forming force, mould friction force, mould stress, product size, springback value, solid phase volume fraction, contact point number, material meso structure and tissue distribution were predicted by numerical model. Forecast results are coincident to experiment. Numerical model is physically significant and reliable definitely. The model is directive for manufacture of metal rubber and makes it possible to research metal rubber in meso scale.
Space winding helix parametric equation, metal rubber and its blank meso structure numerical model were established with real raw material and process parameters of product based on automatic blank twine technology. Forming force, mould friction force, mould stress, product size, springback value, solid phase volume fraction, contact point number, material meso structure and tissue distribution were predicted by numerical model. Forecast results are coincident to experiment. Numerical model is physically significant and reliable definitely. The model is directive for manufacture of metal rubber and makes it possible to research metal rubber in meso scale.
2016, 45(3):688-695.
Abstract:
Isothermal compression tests of 316LN stainless steel at temperatures ranging from 1000 to 1200 oC and strain rates from 0.01 to 10 s-1 were performed on Gleeble thermo-simulation machine. Based on hyperbolic sine function, the constitutive equations of 316LN stainless steel and hot processing maps during the hot deformation process were established. The flow stresses were corrected via considering the temperature rise induced by plastic deformation and friction during the test process. In addition, by taking the influence of strain on flow stress into account, a unified constitutive model for predicting flow stress was proposed. The flow stress predicted by the constitutive equations shows good agreement with the corrected stress under the situation that R is 0.992 and ARRE is 4.43%. According to dynamic material model presented by Prasad, hot processing maps for hot working condition were established based on exploring the effect of power dissipation and instability coefficient associated with various kinds of temperatures and stain rates. Subsequently, efficiency of power dissipation and instability coefficient were interpreted based on hot processing maps under a series of strain, temperatures and strain rates. The results show that efficiency of power dissipation increases gradually with the increasing temperature and the decreasing stain rate, and note that the maxium of efficiency of power disspation is 0.38. An optimun zone for 316LN stainless steel is obtained and verified effectively by the analysis of microstructure.
Isothermal compression tests of 316LN stainless steel at temperatures ranging from 1000 to 1200 oC and strain rates from 0.01 to 10 s-1 were performed on Gleeble thermo-simulation machine. Based on hyperbolic sine function, the constitutive equations of 316LN stainless steel and hot processing maps during the hot deformation process were established. The flow stresses were corrected via considering the temperature rise induced by plastic deformation and friction during the test process. In addition, by taking the influence of strain on flow stress into account, a unified constitutive model for predicting flow stress was proposed. The flow stress predicted by the constitutive equations shows good agreement with the corrected stress under the situation that R is 0.992 and ARRE is 4.43%. According to dynamic material model presented by Prasad, hot processing maps for hot working condition were established based on exploring the effect of power dissipation and instability coefficient associated with various kinds of temperatures and stain rates. Subsequently, efficiency of power dissipation and instability coefficient were interpreted based on hot processing maps under a series of strain, temperatures and strain rates. The results show that efficiency of power dissipation increases gradually with the increasing temperature and the decreasing stain rate, and note that the maxium of efficiency of power disspation is 0.38. An optimun zone for 316LN stainless steel is obtained and verified effectively by the analysis of microstructure.
28 Study on microstructure and mechanical properties of joints of a new Al-Zn-Mg-Cu alloy welded by TIG
2016, 45(3):696-701.
Abstract:
In this study, sheets of a new Al-Zn-Mg-Cu alloy have been welded using automatic TIG welding with filler wire. The microstructure characteristics and mechanical properties of weld joints were analyzed. Results showed that the fusion zone (FZ) is comprised of non-dendritic equiaxed grain zone (EQZ) and coarser dendritic equiaxed grains, and the fusion boundary does not appear to nucleate epitaxially from the heat affected zone (HAZ) substrate, the compound T (AlZnMgCu) phase precipitates discretely on grain boundaries; the HAZ is divided into the solid solution zone that is close to the FZ and overaging zone which is farther away from the FZ because of an alteration of the strengthening precipitates, they possess different microhardness values, grains in the HAZ are elongated as same as the base metal (BM) and not coarser compared with the BM; The minimum microhardness of the joint is obtained in the FZ and the value is approximately 120HV, and that of the BM is about 184HV, the ultimate tensile strength of joints is 421.75MPa which is 65.08% of that of the BM, samples of the tensile test fracture at the FZ and the fractured surface is ductile fracture characteristics, small particles whose composition is almost same with the compound T phase are observed at the bottom of dimples.
In this study, sheets of a new Al-Zn-Mg-Cu alloy have been welded using automatic TIG welding with filler wire. The microstructure characteristics and mechanical properties of weld joints were analyzed. Results showed that the fusion zone (FZ) is comprised of non-dendritic equiaxed grain zone (EQZ) and coarser dendritic equiaxed grains, and the fusion boundary does not appear to nucleate epitaxially from the heat affected zone (HAZ) substrate, the compound T (AlZnMgCu) phase precipitates discretely on grain boundaries; the HAZ is divided into the solid solution zone that is close to the FZ and overaging zone which is farther away from the FZ because of an alteration of the strengthening precipitates, they possess different microhardness values, grains in the HAZ are elongated as same as the base metal (BM) and not coarser compared with the BM; The minimum microhardness of the joint is obtained in the FZ and the value is approximately 120HV, and that of the BM is about 184HV, the ultimate tensile strength of joints is 421.75MPa which is 65.08% of that of the BM, samples of the tensile test fracture at the FZ and the fractured surface is ductile fracture characteristics, small particles whose composition is almost same with the compound T phase are observed at the bottom of dimples.
29 Mathematical Temperature Field Model about Cast AZ31B Magnesium Alloy during Hot Rolling of Plate
2016, 45(3):702-708.
Abstract:
The cast magnesium alloy AZ31B cylindrical samples of high temperature compression tests were taken under the deformation temperature 250-450℃and strain rate 0.005-5 using Gleeble-1500D thermal/mechanical simulation testing machine. Based on the high precision flow stress models and the rigid-plastic finite element analysis software, numerical analysis of coupled thermal-stress of hot rolling process under different initial rolling temperatures, different rolling reductions and different rolling speeds was carried on. Under different conditions, models of temperature field of magnesium plate deformation region were established by using mathematical analysis methods. The results showed that, under different conditions of hot rolling processes and rolling zone, regional distribution of rolling deformation temperature was so different that mathematical models of temperature field should be divided into different process conditions to establish. The mechanism of temperature controlled online was more simple by using mathematical equations to characterize the magnesium alloy heat transfer process ,and heat transfer mechanism of magnesium plate rolling in wide ranges was accurately characterized.
The cast magnesium alloy AZ31B cylindrical samples of high temperature compression tests were taken under the deformation temperature 250-450℃and strain rate 0.005-5 using Gleeble-1500D thermal/mechanical simulation testing machine. Based on the high precision flow stress models and the rigid-plastic finite element analysis software, numerical analysis of coupled thermal-stress of hot rolling process under different initial rolling temperatures, different rolling reductions and different rolling speeds was carried on. Under different conditions, models of temperature field of magnesium plate deformation region were established by using mathematical analysis methods. The results showed that, under different conditions of hot rolling processes and rolling zone, regional distribution of rolling deformation temperature was so different that mathematical models of temperature field should be divided into different process conditions to establish. The mechanism of temperature controlled online was more simple by using mathematical equations to characterize the magnesium alloy heat transfer process ,and heat transfer mechanism of magnesium plate rolling in wide ranges was accurately characterized.
2016, 45(3):709-714.
Abstract:
Abstract：The method of boriding by molten salt electrolysis was applied for TC4 titanium alloy to improve the surface hardness. Using a mixture of sodium tetraborate and sodium carbonate as the base ingredients of molten electrolyte, the experiment was carried out with the Voltage of 1.49V; the effects of boriding temperature on the microstructure of the boridng layer and the reaction mechanism were studied. DSC-TG analysis was conducted on the mixture of sodium tetraborate and sodium carbonate with different composition to analyze the changes when heating the mixed salts, XRD was used for chemical phase analysis of the molten salt and the borides coating, SEM and EDS were applied to observe microstructure and analyze the element content of the borides coating. It was found that a dense and uniform boriding layer was obtained on the TC4 titanium alloy with the main composition of TiB2 and TiB when the boriding temperature was 900℃ with process duration for 110min; the surface micro hardness of the boriding sample reached to 2.4GPa; NaBO2 was detected in the electrolyte after electrolysis; TiB2 was firstly produced in the bording layer then TiB was formed beneath it.
Abstract：The method of boriding by molten salt electrolysis was applied for TC4 titanium alloy to improve the surface hardness. Using a mixture of sodium tetraborate and sodium carbonate as the base ingredients of molten electrolyte, the experiment was carried out with the Voltage of 1.49V; the effects of boriding temperature on the microstructure of the boridng layer and the reaction mechanism were studied. DSC-TG analysis was conducted on the mixture of sodium tetraborate and sodium carbonate with different composition to analyze the changes when heating the mixed salts, XRD was used for chemical phase analysis of the molten salt and the borides coating, SEM and EDS were applied to observe microstructure and analyze the element content of the borides coating. It was found that a dense and uniform boriding layer was obtained on the TC4 titanium alloy with the main composition of TiB2 and TiB when the boriding temperature was 900℃ with process duration for 110min; the surface micro hardness of the boriding sample reached to 2.4GPa; NaBO2 was detected in the electrolyte after electrolysis; TiB2 was firstly produced in the bording layer then TiB was formed beneath it.
2016, 45(3):715-719.
Abstract:
The influence of partial replacement of Fe by Mo element on thermal stability and soft magnetic properties of the Fe–Nb–B amorphous alloys was investigated in detail. The results indicated that the crystallization behavior is dependent on the Mo content. It undergoes two-stage crystallization events for the alloys containing 1 at.% Mo and 3 at.% Mo, while it undergoes only single crystallization event for the alloys containing 5 at.% Mo. The addition of Mo element is benefit to increase the glass transition temperature Tg and onset crystallization temperature Tx1. As the Mo content increases, the thermal stability is enhanced and the glass forming ability (GFA) decreases slightly. The Fe70Nb6B23Mo1 alloy is found to reveal the largest GFA with low the glass transition temperature Tg (=830 K) and wide supercooled liquid region ΔTx (=53 K), which agrees well with that predicted by thermodynamic parameter PHS. The Fe71-xNb6B23Mox (x=1, 3, 5) amorphous ribbons show good soft magnetic properties with high saturation magnetization (Ms) and low coercivity (Hc), and the Ms value is in the range 60–84 emu/g. The Fe71-xNb6B23Mox (x=1, 3, 5) amorphous alloys exhibit a correspondence between thermal stability and soft magnetic properties.
The influence of partial replacement of Fe by Mo element on thermal stability and soft magnetic properties of the Fe–Nb–B amorphous alloys was investigated in detail. The results indicated that the crystallization behavior is dependent on the Mo content. It undergoes two-stage crystallization events for the alloys containing 1 at.% Mo and 3 at.% Mo, while it undergoes only single crystallization event for the alloys containing 5 at.% Mo. The addition of Mo element is benefit to increase the glass transition temperature Tg and onset crystallization temperature Tx1. As the Mo content increases, the thermal stability is enhanced and the glass forming ability (GFA) decreases slightly. The Fe70Nb6B23Mo1 alloy is found to reveal the largest GFA with low the glass transition temperature Tg (=830 K) and wide supercooled liquid region ΔTx (=53 K), which agrees well with that predicted by thermodynamic parameter PHS. The Fe71-xNb6B23Mox (x=1, 3, 5) amorphous ribbons show good soft magnetic properties with high saturation magnetization (Ms) and low coercivity (Hc), and the Ms value is in the range 60–84 emu/g. The Fe71-xNb6B23Mox (x=1, 3, 5) amorphous alloys exhibit a correspondence between thermal stability and soft magnetic properties.
32 Investigation on Micro Friction Stir welded Lap joint of Thin Al-alloy/SiC Reinforced Al Composite
Jing Zhang
,
Xiaosong Feng
,
Hui Huang
,
Huihui Zhao
,
Chengcong Zhang
,
Yanyan Xiong
,
Fengbo Dong
,
Lijie Guo
2016, 45(3):720-726.
Abstract:
The micro friction stir welding (μ-FSW) of lap joint of thin Al-alloy plate with a thickness of 0.5mm and SiC reinforced Al composite were investigated, concentrating on the process characteristics, macro-morphology of weld cross-section and mechanical properties of the joints. The mechanisms of migration interface morphology formation and joint failure were revealed. The results show that with suitable indentation depth, wels of good appearance can be obtained in a wide range of process window. The weld cross-section shows a special “Hoop shape” migration interface morphology, caused by the characteristics of μ-FSW process and SiC particles. The joint failure mode is the tensile fracture of “thinning area” at the upper rim of migration interface. And the joint mechanical properties are directly related to the loading direction, which is caused by the different metal plastic flow behaviors under different loading directions
The micro friction stir welding (μ-FSW) of lap joint of thin Al-alloy plate with a thickness of 0.5mm and SiC reinforced Al composite were investigated, concentrating on the process characteristics, macro-morphology of weld cross-section and mechanical properties of the joints. The mechanisms of migration interface morphology formation and joint failure were revealed. The results show that with suitable indentation depth, wels of good appearance can be obtained in a wide range of process window. The weld cross-section shows a special “Hoop shape” migration interface morphology, caused by the characteristics of μ-FSW process and SiC particles. The joint failure mode is the tensile fracture of “thinning area” at the upper rim of migration interface. And the joint mechanical properties are directly related to the loading direction, which is caused by the different metal plastic flow behaviors under different loading directions
2016, 45(3):727-731.
Abstract:
In this study, graphene oxide(GO)/hydroxyapatite(HA) composite coatings have been firstly fabricated by a modified electrocodeposition technique on titanium substrate. The microstructure and phase constituents of the composite coatings were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectra. The in vitro cellular response was detected by the morphology of MG63 cells which were inoculated onto the coatings. The addition of GO into HA coatings increased the crystallinity of hydroxyaptite. In addition, in vitro cell culture assessment shows a better biocompatibility of the composite coatings compared with the pure HA coating.
In this study, graphene oxide(GO)/hydroxyapatite(HA) composite coatings have been firstly fabricated by a modified electrocodeposition technique on titanium substrate. The microstructure and phase constituents of the composite coatings were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectra. The in vitro cellular response was detected by the morphology of MG63 cells which were inoculated onto the coatings. The addition of GO into HA coatings increased the crystallinity of hydroxyaptite. In addition, in vitro cell culture assessment shows a better biocompatibility of the composite coatings compared with the pure HA coating.
2016, 45(3):732-736.
Abstract:
Mg-10Gd-3Y-1.2Zn-0.5Zr alloy was prepared by adding 1.2wt%Zn in Mg-10Gd-3Y-0.5Zr alloy. The microstructures and mechanical properties as well as fracture behaviors of the alloys at the different conditions were studied by using optical microscopy, scanning electron microscopy and tensile testing machine.The results indciated that the cast case showed a poor plasticity, however, T4 alloys had a good plasticity, and the plasticity of T6 state was between the cast and T4 conditions. All the specimens mainly attributed to brittle cleavage fracture, and the bonding strength at interface of grain boundary and lamellar phase was stronger than the compound interface.Compare to the T6 mechanical properties at three different temperatures, it was found that improving solution temperature could improve the alloy strength, however, the elongation rate reduced slightly. The Zn can promote the growth of lamellar phase, however, only a limited role for plastic characteristics of the matrix could be observed.
Mg-10Gd-3Y-1.2Zn-0.5Zr alloy was prepared by adding 1.2wt%Zn in Mg-10Gd-3Y-0.5Zr alloy. The microstructures and mechanical properties as well as fracture behaviors of the alloys at the different conditions were studied by using optical microscopy, scanning electron microscopy and tensile testing machine.The results indciated that the cast case showed a poor plasticity, however, T4 alloys had a good plasticity, and the plasticity of T6 state was between the cast and T4 conditions. All the specimens mainly attributed to brittle cleavage fracture, and the bonding strength at interface of grain boundary and lamellar phase was stronger than the compound interface.Compare to the T6 mechanical properties at three different temperatures, it was found that improving solution temperature could improve the alloy strength, however, the elongation rate reduced slightly. The Zn can promote the growth of lamellar phase, however, only a limited role for plastic characteristics of the matrix could be observed.
2016, 45(3):737-741.
Abstract:
In this paper, the field activated and pressure assisted synthesis (FAPAS) were used for preparing the ultra-hard, super-abrasive AlMgB14∕TiB2 composite ceramic. We analyzed how the ultra-fine TiB2 particles influence microstructure and toughness of samples by using scanning electron microscopy (SEM), energy dispersive analysis (EDS) and X-ray diffraction (XRD) respectively. The wear resistence and tribological behavior of AlMgB14∕TiB2 composite materials at 25℃, 300℃,500℃ were characterized throughing high-temperature friction and wear test. The results show that the average hardness of AlMgB14∕TiB2 composite materials reached 32.5 GPa after adding 30 wt% submicron scale TiB2 particles. The fracture toughness was seen to increase from 3.0 to 3.95MPa? m1/2. Friction coefficient ranged from 0.4 to 0.5 at room temperature and 300℃ , this figure exhibited approximately 0.65 in the case of 500℃ sliding operation. The specific wear rate ranged from 1.27?0-6 mm-3/（N?m）to 6.62 mm-3/（N﹒m）.With increasing the test temperature, The tribological properties of AlMgB14∕TiB2 composite materials changed, As a result of the friction surface oxide lubrication, friction coefficient decreased at 300℃，the wear mechanism from abrasive wear at room temperature to adhesive wear .
In this paper, the field activated and pressure assisted synthesis (FAPAS) were used for preparing the ultra-hard, super-abrasive AlMgB14∕TiB2 composite ceramic. We analyzed how the ultra-fine TiB2 particles influence microstructure and toughness of samples by using scanning electron microscopy (SEM), energy dispersive analysis (EDS) and X-ray diffraction (XRD) respectively. The wear resistence and tribological behavior of AlMgB14∕TiB2 composite materials at 25℃, 300℃,500℃ were characterized throughing high-temperature friction and wear test. The results show that the average hardness of AlMgB14∕TiB2 composite materials reached 32.5 GPa after adding 30 wt% submicron scale TiB2 particles. The fracture toughness was seen to increase from 3.0 to 3.95MPa? m1/2. Friction coefficient ranged from 0.4 to 0.5 at room temperature and 300℃ , this figure exhibited approximately 0.65 in the case of 500℃ sliding operation. The specific wear rate ranged from 1.27?0-6 mm-3/（N?m）to 6.62 mm-3/（N﹒m）.With increasing the test temperature, The tribological properties of AlMgB14∕TiB2 composite materials changed, As a result of the friction surface oxide lubrication, friction coefficient decreased at 300℃，the wear mechanism from abrasive wear at room temperature to adhesive wear .
2016, 45(3):742-748.
Abstract:
ZrC nano-particles with varied mass fractions were introduced into the CFRP (carbon fiber-reinforced plastics) green body by a slurry infiltration technique. After the pyrolysis of CFRP green body, the C/C-ZrC preform with different microstructure features were obtained. By infiltrating the liquid silicon into the C/C-ZrC preform, the C/C-SiC-ZrC composites were successfully fabricated. The morphologies of C/C-ZrC perform and C/C-SiC-ZrC were observed by scanning electron microscopy (SEM). The porosity was measured by using the Archimedes method. The mechanical properties were evaluated by means of three point bending and single edge notched-beam (SENB) tests, respectively. The morphologies of C/C-ZrC perform show that the ZrC nano-particles distributed homogeneously in the fiber bundle area and had a obvious influence on the microstructure. The measurement of mechanical properties found that the C/C-SiC-ZrC composites with a mass fraction of 5% nano-particles presented the highest value in the flexural strength and fractural toughness. While the mass fraction of nano-particles exceeds the 5%, both the flexural strength and fracture toughness of composites decreased. Combing the mechanical properties with the microstructure analysis, the high mechanical properties could be attributed to the more homogeneous distribution of SiC phase and the moderate fiber/matrix interfacial bonding strength.
ZrC nano-particles with varied mass fractions were introduced into the CFRP (carbon fiber-reinforced plastics) green body by a slurry infiltration technique. After the pyrolysis of CFRP green body, the C/C-ZrC preform with different microstructure features were obtained. By infiltrating the liquid silicon into the C/C-ZrC preform, the C/C-SiC-ZrC composites were successfully fabricated. The morphologies of C/C-ZrC perform and C/C-SiC-ZrC were observed by scanning electron microscopy (SEM). The porosity was measured by using the Archimedes method. The mechanical properties were evaluated by means of three point bending and single edge notched-beam (SENB) tests, respectively. The morphologies of C/C-ZrC perform show that the ZrC nano-particles distributed homogeneously in the fiber bundle area and had a obvious influence on the microstructure. The measurement of mechanical properties found that the C/C-SiC-ZrC composites with a mass fraction of 5% nano-particles presented the highest value in the flexural strength and fractural toughness. While the mass fraction of nano-particles exceeds the 5%, both the flexural strength and fracture toughness of composites decreased. Combing the mechanical properties with the microstructure analysis, the high mechanical properties could be attributed to the more homogeneous distribution of SiC phase and the moderate fiber/matrix interfacial bonding strength.
2016, 45(3):749-754.
Abstract:
In this paper, WC-12Co particles were deposited on aluminum, copper and stainless steel substrates by High Velocity Oxy-fuel (HVOF) process. Both the surface and the cross-sectional morphology of the two-phase semi-molten particles were observed and analyzed by Scanning electron microscopy (SEM). The collision model of the two-phase particles with matrix was simplified as the process interacting with substrate of liquid phase Co and solid phase WC, and an improved mathematical model was established to calculate the relative deformation ratio λ of the substrate to the splat. It was found that WC-Co particles deposited on aluminum, copper and stainless steel substrates exhibited hemispherical-like, pie-like and sputtering-like morphologies, respectively, and different shaped WC-Co particles had different λ values. Compared with forming hemispherical-like (λ>1) and sputtering-like particles (λ<1), moderate deformation occurred in both particles and substrates when pie-like (λ=1) particles were formed, which was beneficial for increasing the effective contact area between particle and substrate, thus improving the bond strength.
In this paper, WC-12Co particles were deposited on aluminum, copper and stainless steel substrates by High Velocity Oxy-fuel (HVOF) process. Both the surface and the cross-sectional morphology of the two-phase semi-molten particles were observed and analyzed by Scanning electron microscopy (SEM). The collision model of the two-phase particles with matrix was simplified as the process interacting with substrate of liquid phase Co and solid phase WC, and an improved mathematical model was established to calculate the relative deformation ratio λ of the substrate to the splat. It was found that WC-Co particles deposited on aluminum, copper and stainless steel substrates exhibited hemispherical-like, pie-like and sputtering-like morphologies, respectively, and different shaped WC-Co particles had different λ values. Compared with forming hemispherical-like (λ>1) and sputtering-like particles (λ<1), moderate deformation occurred in both particles and substrates when pie-like (λ=1) particles were formed, which was beneficial for increasing the effective contact area between particle and substrate, thus improving the bond strength.
2016, 45(3):755-759.
Abstract:
The synthesis of Bi dopped Mg2Si1-xSnx (0.4≦x≦0.6) solid solution thermoelectric materials with high purity was achieved by microwave-assisted solid state reaction followed by the field activated and pressure assisted synthesis (FAPAS), and its microstructure and transport properties were observed and evaluated. It indicates that the replacement of Mg used in traditional processes by MgH2 powder significantly reduces the temperature of the solid state reaction and further inhibits the oxidation and volatilization of magnesium. Meanwhile, the low-temperature and rapid heating from microwave restrain the grain growth effectively; as a result the pure product with an average grain size of 200nm has been reached. Thermoelectric performance was tested in the temperature range of 300-750K. It indicates that the solid solution with fine lamellar structure and the doping of Bi significantly lower the thermal conductivity and improve the electric properties simultaneously. The 1.5at.% Bi doped Mg2Si0.4Sn0.6 got the maximum ZT of 0.91 at 600K.
The synthesis of Bi dopped Mg2Si1-xSnx (0.4≦x≦0.6) solid solution thermoelectric materials with high purity was achieved by microwave-assisted solid state reaction followed by the field activated and pressure assisted synthesis (FAPAS), and its microstructure and transport properties were observed and evaluated. It indicates that the replacement of Mg used in traditional processes by MgH2 powder significantly reduces the temperature of the solid state reaction and further inhibits the oxidation and volatilization of magnesium. Meanwhile, the low-temperature and rapid heating from microwave restrain the grain growth effectively; as a result the pure product with an average grain size of 200nm has been reached. Thermoelectric performance was tested in the temperature range of 300-750K. It indicates that the solid solution with fine lamellar structure and the doping of Bi significantly lower the thermal conductivity and improve the electric properties simultaneously. The 1.5at.% Bi doped Mg2Si0.4Sn0.6 got the maximum ZT of 0.91 at 600K.
39 Effect of La, Zr micro-alloying on the microstructure and mechanical properties of Al-Mg-Zr alloy
2016, 45(3):760-764.
Abstract:
Al-Mg-Ti alloys containing La, Zr elements were prepared by cast metallurgy. Effects of La, Zr additions on microstructure and mechanical properties of Al-Mg-Ti alloy were investigated by property test, optical microscopy, scanning electron microscopy, energy spectrum and X-ray diffraction. The results show that the addition of 0.2%Zr can positively refine the grain size，which indicates the composite refining effect of Ti, Zr is compatible，and the brittle phases of Al3Zr precipitated in matrix can significantly increase the hardness of the alloys, but weaken the effect of grain refinement on the strength and ductility of the alloy. The combined addition of 0.2%La and 0.2%Zr possesses the most excellent grain refining effect, the average grain size of the alloy is dropped to only about 55μm and the addition of La can effectively avoid the precipitation and coarsening of brittle phase of Al3Zr, which makes the strength and ductility of the alloy improved significantly, and makes the hardness increased little.
Al-Mg-Ti alloys containing La, Zr elements were prepared by cast metallurgy. Effects of La, Zr additions on microstructure and mechanical properties of Al-Mg-Ti alloy were investigated by property test, optical microscopy, scanning electron microscopy, energy spectrum and X-ray diffraction. The results show that the addition of 0.2%Zr can positively refine the grain size，which indicates the composite refining effect of Ti, Zr is compatible，and the brittle phases of Al3Zr precipitated in matrix can significantly increase the hardness of the alloys, but weaken the effect of grain refinement on the strength and ductility of the alloy. The combined addition of 0.2%La and 0.2%Zr possesses the most excellent grain refining effect, the average grain size of the alloy is dropped to only about 55μm and the addition of La can effectively avoid the precipitation and coarsening of brittle phase of Al3Zr, which makes the strength and ductility of the alloy improved significantly, and makes the hardness increased little.
2016, 45(3):765-770.
Abstract:
Fe24 XCo24-XCr15Mo14C15B6Y2(X=0,2,4,6,8) bulk amorphous alloys were prepared by a non-consumable arc-melting furnace, the thermal expansion coefficient and thermal conductivity of the amorphous alloy were tested by thermal expansion test instrument and laser indeed thermal conductivity tester, and the results were compared with the differential scanning calorimetry (DSC). Linear thermal expansion behavior with the temperature change of FeCo-based amorphous alloys with different Co content and effect of different Co element content and different organizations on thermal conductivity of FeCo-base amorphous alloy were investigated, respectively. The results show that with the decrease of Co content, FeCo-base amorphous alloys exist two crystallization processes, and the initial and the secondary crystallization temperature increase in turn. Thermal expansion coefficient of Fe24Co24Cr15Mo14C15B6Y2 has the third maximum points around 875 ℃. At 25 ℃, thermal conductivity of the Fe24 XCo24-XCr15Mo14C15B6Y2(X=0,2,4,6,8) iron cobalt base amorphous alloy is in 7.12~7.35 W/(m.K) range, thermal conductivity of the Fe24 XCo24-XCr15Mo14C15B6Y2(X=0,2,4,6,8) iron cobalt base amorphous alloys treated at 700 ℃ range from 7.5 W/(m.K) to 9.46 W/(m.K). However, thermal conductivity of Fe24 XCo24-XCr15Mo14C15B6Y2(X=0,2,4,6,8) iron cobalt base amorphous alloys treated at 920 ℃ have a maximum value when X is up to 2 at%.
Fe24 XCo24-XCr15Mo14C15B6Y2(X=0,2,4,6,8) bulk amorphous alloys were prepared by a non-consumable arc-melting furnace, the thermal expansion coefficient and thermal conductivity of the amorphous alloy were tested by thermal expansion test instrument and laser indeed thermal conductivity tester, and the results were compared with the differential scanning calorimetry (DSC). Linear thermal expansion behavior with the temperature change of FeCo-based amorphous alloys with different Co content and effect of different Co element content and different organizations on thermal conductivity of FeCo-base amorphous alloy were investigated, respectively. The results show that with the decrease of Co content, FeCo-base amorphous alloys exist two crystallization processes, and the initial and the secondary crystallization temperature increase in turn. Thermal expansion coefficient of Fe24Co24Cr15Mo14C15B6Y2 has the third maximum points around 875 ℃. At 25 ℃, thermal conductivity of the Fe24 XCo24-XCr15Mo14C15B6Y2(X=0,2,4,6,8) iron cobalt base amorphous alloy is in 7.12~7.35 W/(m.K) range, thermal conductivity of the Fe24 XCo24-XCr15Mo14C15B6Y2(X=0,2,4,6,8) iron cobalt base amorphous alloys treated at 700 ℃ range from 7.5 W/(m.K) to 9.46 W/(m.K). However, thermal conductivity of Fe24 XCo24-XCr15Mo14C15B6Y2(X=0,2,4,6,8) iron cobalt base amorphous alloys treated at 920 ℃ have a maximum value when X is up to 2 at%.
2016, 45(3):771-775.
Abstract:
Abstract: The duplex treatment consisting of plasma surface alloyed with copper followed by thermal diffusion under the bombardment of glow was carried out on Ti-6Al-4V. The antibacterial properties against Gram-negative E.coli ATCC10536 and Gram-positive S.aureus ATCC25923 of the untreated and duplex-treated stainless steel were investigated by using a spread plate method. Meanwhile, the wearing resistance is also tested. The X-Ray Diffraction(XRD)、scanning electron microscope(SEM) and Energy Dispersive Spectrometer(EDS) are exploited in order to observe and analyze the phase structure and the elementary composition of the coats,and the optical microscopy with 3D function is used to detect the wear depth. The results show that the copper concentration on alloyed surface is about 11wt% and the thickness of alloyed layer is about12μm. And alloyed surface exhibits excellent antibacterial properties against both E.coli and S.aureus . And the wearing resistance is improved significantly.
Abstract: The duplex treatment consisting of plasma surface alloyed with copper followed by thermal diffusion under the bombardment of glow was carried out on Ti-6Al-4V. The antibacterial properties against Gram-negative E.coli ATCC10536 and Gram-positive S.aureus ATCC25923 of the untreated and duplex-treated stainless steel were investigated by using a spread plate method. Meanwhile, the wearing resistance is also tested. The X-Ray Diffraction(XRD)、scanning electron microscope(SEM) and Energy Dispersive Spectrometer(EDS) are exploited in order to observe and analyze the phase structure and the elementary composition of the coats,and the optical microscopy with 3D function is used to detect the wear depth. The results show that the copper concentration on alloyed surface is about 11wt% and the thickness of alloyed layer is about12μm. And alloyed surface exhibits excellent antibacterial properties against both E.coli and S.aureus . And the wearing resistance is improved significantly.
2016, 45(3):771-775.
Abstract:
Osmium surface was planarized by chemical mechanical polishing (CMP), the effect of different surfactants on the results of polishing was investigated via a series of home-made slurries. The influence of surfactants on the process of CMP was studied by electrochemical dynamics and X-ray photoelectron spectroscopy, the morphology of Os surface was characterized by atomic force microscopy (AFM). The results are following: when adding TMAOH in slurry, the MRR of Os decreases from 5.8 nm/min to 2.9 nm/min and the surface roughness (Ra) increases from 2.1 nm to 4.8 nm; although PEG400, SHMP and SDS can increase the MRR, they cannot improve the surface quality; SLS and CTAB can increase the MRR and decrease the surface roughness; especially, CTAB can increase MRR to 14.6nm/min and decrease surface roughness (Ra) to 0.57 nm.
Osmium surface was planarized by chemical mechanical polishing (CMP), the effect of different surfactants on the results of polishing was investigated via a series of home-made slurries. The influence of surfactants on the process of CMP was studied by electrochemical dynamics and X-ray photoelectron spectroscopy, the morphology of Os surface was characterized by atomic force microscopy (AFM). The results are following: when adding TMAOH in slurry, the MRR of Os decreases from 5.8 nm/min to 2.9 nm/min and the surface roughness (Ra) increases from 2.1 nm to 4.8 nm; although PEG400, SHMP and SDS can increase the MRR, they cannot improve the surface quality; SLS and CTAB can increase the MRR and decrease the surface roughness; especially, CTAB can increase MRR to 14.6nm/min and decrease surface roughness (Ra) to 0.57 nm.
2016, 45(3):776-781.
Abstract:
NiCrAlYSi bond coating has been deposited on DZ125 alloy substrates by arc ion plating. YSZ has been deposited on the bond coating by EB-PVD technology. The microstructure and interface morphology of the sandpapered (SS), polished (PS), vibratory polished (VS) and grit-blasted samples (GS) have been investigated and compared in detail. The results indicate that the bond coating surface has been polished and the roughness has been decreased due to the effect of surface treatments. Furthermore, effect of surface treatments on bond strength is studied which the bond strength has been increased by different surface treatments. The durability of these systems by different surface treatments has been measured and compared. Based on the electron microscopy observations, the failure mechanisms of thermal barrier coatings have been investigated by the various stages of cycle life.
NiCrAlYSi bond coating has been deposited on DZ125 alloy substrates by arc ion plating. YSZ has been deposited on the bond coating by EB-PVD technology. The microstructure and interface morphology of the sandpapered (SS), polished (PS), vibratory polished (VS) and grit-blasted samples (GS) have been investigated and compared in detail. The results indicate that the bond coating surface has been polished and the roughness has been decreased due to the effect of surface treatments. Furthermore, effect of surface treatments on bond strength is studied which the bond strength has been increased by different surface treatments. The durability of these systems by different surface treatments has been measured and compared. Based on the electron microscopy observations, the failure mechanisms of thermal barrier coatings have been investigated by the various stages of cycle life.
2016, 45(3):782-787.
Abstract:
Ultra-long copper microwires have been prepared by a facile hydrothermal method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), nitrogen sorption isotherms. The results show that the ultra-long copper microwires have a five-fold symmetric twin crystal structure. It is proposed that both the selective adsorption of CTAB on {100} facets and the internal tension of copper crystals synergistically lead to the formation of the copper microwires. Moreover, the apparent rate constant (ka=0.00484 min-1) of copper microwires is 3.5 times as high as that (ka=0.0014 min-1) over bulk Cu for for the H2O2-assisted RhB decoloring reaction, which has been mainly ascribed to its larger surface area and microscale size. The adopted method can be potentially used for mass production of copper microwires because of the high yield and the simple operation.
Ultra-long copper microwires have been prepared by a facile hydrothermal method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), nitrogen sorption isotherms. The results show that the ultra-long copper microwires have a five-fold symmetric twin crystal structure. It is proposed that both the selective adsorption of CTAB on {100} facets and the internal tension of copper crystals synergistically lead to the formation of the copper microwires. Moreover, the apparent rate constant (ka=0.00484 min-1) of copper microwires is 3.5 times as high as that (ka=0.0014 min-1) over bulk Cu for for the H2O2-assisted RhB decoloring reaction, which has been mainly ascribed to its larger surface area and microscale size. The adopted method can be potentially used for mass production of copper microwires because of the high yield and the simple operation.
2016, 45(3):788-792.
Abstract:
AA new solid state joining method named as rigid restraint thermal self-compressing bonding is proposed. Solid joints can be produced using localized heating method without the use of external force. The butted surfaces of the rigid restrained plates is locally heated to produce a thermal elastic-plastic stress-strain field to compress the zones to be bonded, and in its turn to facilitate the diffusion of interface atoms to form solid joint. Experiments were conducted on TC4 titanium plates to show the feasibility of rigid restraint thermal self-compressing bonding using electron beam as heat source. Thermal cycles of rigid restraint thermal self-compressing bonding were measured. Microstructure and mechanical properties of bonded joint were investigated. Moreover, effects of temperature on rigid restraint thermal self-compressing bonding were analyzed. Results show that perfect solid state joint can be performed. The effects of thermal cycles and the peak temperature on microstructure and mechanical properties of bonded joint are notable. Peak temperature lower than the β transus temperature of TC4 alloy is recommended to perform homogeneous microstructure of the solid state bonded joint with high mechanical properties equal to base metal.
AA new solid state joining method named as rigid restraint thermal self-compressing bonding is proposed. Solid joints can be produced using localized heating method without the use of external force. The butted surfaces of the rigid restrained plates is locally heated to produce a thermal elastic-plastic stress-strain field to compress the zones to be bonded, and in its turn to facilitate the diffusion of interface atoms to form solid joint. Experiments were conducted on TC4 titanium plates to show the feasibility of rigid restraint thermal self-compressing bonding using electron beam as heat source. Thermal cycles of rigid restraint thermal self-compressing bonding were measured. Microstructure and mechanical properties of bonded joint were investigated. Moreover, effects of temperature on rigid restraint thermal self-compressing bonding were analyzed. Results show that perfect solid state joint can be performed. The effects of thermal cycles and the peak temperature on microstructure and mechanical properties of bonded joint are notable. Peak temperature lower than the β transus temperature of TC4 alloy is recommended to perform homogeneous microstructure of the solid state bonded joint with high mechanical properties equal to base metal.
2016, 45(3):793-797.
Abstract:
The deformation behavior of TC27 titanium alloy at the strain rate of 0.01~10s-1 and the temperature of 900~1150℃ was investigated and established the constitutive equation during the hot compression in the machine of Thermecmastor-Z. The conclusion indicates that the material was sensitivity to temperature and strain rate. At the beginning of deformation, the flow stress increases quickly with the augment of true strain and decreases slowly when stress reaches to the maximum value, finally, tending to relatively stable condition. The flow stress decreased with the increase of temperature and increased with the increase of strain rate. The change of flow stress with strain rate and temperature can be described by the constitutive equation during hot compression processing. The active energy of deformation is 300 kJ/mol
The deformation behavior of TC27 titanium alloy at the strain rate of 0.01~10s-1 and the temperature of 900~1150℃ was investigated and established the constitutive equation during the hot compression in the machine of Thermecmastor-Z. The conclusion indicates that the material was sensitivity to temperature and strain rate. At the beginning of deformation, the flow stress increases quickly with the augment of true strain and decreases slowly when stress reaches to the maximum value, finally, tending to relatively stable condition. The flow stress decreased with the increase of temperature and increased with the increase of strain rate. The change of flow stress with strain rate and temperature can be described by the constitutive equation during hot compression processing. The active energy of deformation is 300 kJ/mol
2016, 45(3):802-809.
Abstract:
Gd2Ti2O7:Ce nanoparticles were prepared by co-precipitation method of different initial solution concentrations; The phase composition, particle morphology and luminescence properties of the samples were characterized by XRD, TG-DTA and SEM. Powders’ thermal analysis kinetics and activation energy in the synthesis process were also calculated at different heating rates. It is shown that there are three stages in the process of the precursor's phase transformations during heating, initial solution concentrations are 0.08mol/L and 0.04mol/L respectively. The average apparent activation energies of the precursors’ three reaction stages are 42.43、145.58、381.98 kJ?mol-1 and 51.28、161.51、446.30kJ?mol-1 using the Doyle-Ozawa and Kissinger methods separately. Meanwhile, the grain growth activation energies of two different concentrations are 12.58 kJ?mol-1 and 19.54 kJ?mol-1 severally. It is concluded that Gd2Ti2O7:Ce nanoparticles with higher surface activity have the best luminescence property when calcined at 1173K for 2h, especially the samples doped 0.7 mol% Ce is optimal at the concentration of 0.08mol/L.
Gd2Ti2O7:Ce nanoparticles were prepared by co-precipitation method of different initial solution concentrations; The phase composition, particle morphology and luminescence properties of the samples were characterized by XRD, TG-DTA and SEM. Powders’ thermal analysis kinetics and activation energy in the synthesis process were also calculated at different heating rates. It is shown that there are three stages in the process of the precursor's phase transformations during heating, initial solution concentrations are 0.08mol/L and 0.04mol/L respectively. The average apparent activation energies of the precursors’ three reaction stages are 42.43、145.58、381.98 kJ?mol-1 and 51.28、161.51、446.30kJ?mol-1 using the Doyle-Ozawa and Kissinger methods separately. Meanwhile, the grain growth activation energies of two different concentrations are 12.58 kJ?mol-1 and 19.54 kJ?mol-1 severally. It is concluded that Gd2Ti2O7:Ce nanoparticles with higher surface activity have the best luminescence property when calcined at 1173K for 2h, especially the samples doped 0.7 mol% Ce is optimal at the concentration of 0.08mol/L.
2016, 45(3):810-814.
Abstract:
Electrocatalytic oxidation technology is an effective method for recalcitrant organic wastewater treatment developed in recent years. Antimony-doped tin oxide coating on Ti substrate as anodes (Ti/SnO2-Sb) attract more attention because of its higher electrochemical oxidation activity for organic contaminants. In this review，the progress of modified Ti/SnO2-Sb by doping with rare earth metals, non-rare earth metal and carbon nanotubes (CNTs) are summarized. The mechanism of Ti/SnO2-Sb electrode electrocatalytic activity, current efficiency and electrode life effect by dopant is outlined, the research situations of Ti/SnO2-Sb and the modified Ti/SnO2-Sb electrode applied for removing organic pollutants is introduced, and the noteworthy direction of doping and application of Ti/SnO2-Sb electrode is prospected.
Electrocatalytic oxidation technology is an effective method for recalcitrant organic wastewater treatment developed in recent years. Antimony-doped tin oxide coating on Ti substrate as anodes (Ti/SnO2-Sb) attract more attention because of its higher electrochemical oxidation activity for organic contaminants. In this review，the progress of modified Ti/SnO2-Sb by doping with rare earth metals, non-rare earth metal and carbon nanotubes (CNTs) are summarized. The mechanism of Ti/SnO2-Sb electrode electrocatalytic activity, current efficiency and electrode life effect by dopant is outlined, the research situations of Ti/SnO2-Sb and the modified Ti/SnO2-Sb electrode applied for removing organic pollutants is introduced, and the noteworthy direction of doping and application of Ti/SnO2-Sb electrode is prospected.
2016, 45(3):815-820.
Abstract:
Abstract: Nickel-aluminum bronze (NAB) are extensively used for marine equipment of propeller, pump, valve etc because of the high mechanical properties and excellent corrosion resistance. The improved corrosion fatigue property of NAB under complex ocean condition lies in the core of producing marine equipment with high service performance. In this study, the development of NAB on microstructure, the corrosion behavior, hot working, surface coating and modification etc were summarized and pointing out the problems of these studies on real produce and direction for further investigation.
Abstract: Nickel-aluminum bronze (NAB) are extensively used for marine equipment of propeller, pump, valve etc because of the high mechanical properties and excellent corrosion resistance. The improved corrosion fatigue property of NAB under complex ocean condition lies in the core of producing marine equipment with high service performance. In this study, the development of NAB on microstructure, the corrosion behavior, hot working, surface coating and modification etc were summarized and pointing out the problems of these studies on real produce and direction for further investigation.
