Volume 42,Issue 10,2013 Table of Contents
2013, 42(10):1981-1987.
Abstract:
The electrode alloys with the chemical compositions of La0.8-xPrxMg0.2Ni3.35Al0.1Si0.05 (x=0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and annealing. The effects of Pr substitution on the structure and electrochemical hydrogen storage characteristics of the alloys were investigated. The results indicate that the as-cast and the annealed alloys consist of Ce2Ni7-type hexagonal (La, Mg)2Ni7 phase and CaCu5-type hexagonal LaNi5 phase as well as a little residual phase LaNi3. The substitution of Pr for La observably affects the electrochemical hydrogen storage characteristics of the alloys. The discharge capacity and the high rate discharge ability (HRD) of the as-cast and the annealed alloys first increase and then decline with the growing of Pr content. The as-cast and the annealed (x=0.3) alloys yield the largest discharge capacities of 363.1 and 389.7 mAh/g, respectively. The electrochemical cycle stability of the as-cast and the annealed alloys markedly grows with the rising of Pr content. The capacity retaining rate (S100) at 100th charging and discharging cycle is enhanced from 64.96% to 77.94% for the as-cast alloy, and from 72.82% to 91.81% for the as-annealed alloy by raising Pr content from 0 to 0.4
The electrode alloys with the chemical compositions of La0.8-xPrxMg0.2Ni3.35Al0.1Si0.05 (x=0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and annealing. The effects of Pr substitution on the structure and electrochemical hydrogen storage characteristics of the alloys were investigated. The results indicate that the as-cast and the annealed alloys consist of Ce2Ni7-type hexagonal (La, Mg)2Ni7 phase and CaCu5-type hexagonal LaNi5 phase as well as a little residual phase LaNi3. The substitution of Pr for La observably affects the electrochemical hydrogen storage characteristics of the alloys. The discharge capacity and the high rate discharge ability (HRD) of the as-cast and the annealed alloys first increase and then decline with the growing of Pr content. The as-cast and the annealed (x=0.3) alloys yield the largest discharge capacities of 363.1 and 389.7 mAh/g, respectively. The electrochemical cycle stability of the as-cast and the annealed alloys markedly grows with the rising of Pr content. The capacity retaining rate (S100) at 100th charging and discharging cycle is enhanced from 64.96% to 77.94% for the as-cast alloy, and from 72.82% to 91.81% for the as-annealed alloy by raising Pr content from 0 to 0.4
2013, 42(10):1988-1992.
Abstract:
The method of molten salt denucleating was applied to study the rapid solidification of IN718 superalloy. The highest undercooling up to 250 K was produced, and the microstructure evolution with undercooling was investigated. Based on the calculations of the dendritic tip radius, the dendrite growth velocity and undercooling, the solidification behavior and structure transition mechanisms were analyzed by adopting BCT dendrite growth model. Result show that the solidification morphologies of the undercooled IN718 superalloy are dependent on the degree of undercooling. Within the achieved undercooling, 0~250 K, the solidification microstructure of IN718 undergoes twice grain refinement. When 0 K≤ΔT＜63 K, it is the first grain refinement; when 63 K≤ΔT＜90 K, with the increasing of undercooling, grain coarsening comes into being; when 90 K≤ΔT＜250 K, it is the second grain refinement, and aforementioned dendritic structure transforms into granular grain with average grain size about 5.5 μm
The method of molten salt denucleating was applied to study the rapid solidification of IN718 superalloy. The highest undercooling up to 250 K was produced, and the microstructure evolution with undercooling was investigated. Based on the calculations of the dendritic tip radius, the dendrite growth velocity and undercooling, the solidification behavior and structure transition mechanisms were analyzed by adopting BCT dendrite growth model. Result show that the solidification morphologies of the undercooled IN718 superalloy are dependent on the degree of undercooling. Within the achieved undercooling, 0~250 K, the solidification microstructure of IN718 undergoes twice grain refinement. When 0 K≤ΔT＜63 K, it is the first grain refinement; when 63 K≤ΔT＜90 K, with the increasing of undercooling, grain coarsening comes into being; when 90 K≤ΔT＜250 K, it is the second grain refinement, and aforementioned dendritic structure transforms into granular grain with average grain size about 5.5 μm
2013, 42(10):1993-1998.
Abstract:
The influence of Y on the microstructure, the mechanical property and the corrosion resistance of Mg-9Li-3Al alloy was investigated by optical microscopy, scanning electronic microscopy (SEM), X-ray diffraction (XRD), mechanical properties testing and electrochemical measurement. The results show that the addition of Y can change the microstructure form of the α phase and reduce its volume fraction. Meanwhile, the binary Al2Y phase is mainly distributed inside the β phase and the α phase is formed. The addition of Y can effectively improve the ultimate tensile strength (UTS) and the elongation (EL) of the alloy. Upon 1.6 wt% Y addition, the UTS of the alloy is up to 190 MPa; the maximal EL reaches 19.3% when the content of Y is 2wt%. The corrosion resistances of the alloy are found to decrease upon Y content less than 1.2wt% and then increase upon Y content from 1.2wt% to 2.0wt%.
The influence of Y on the microstructure, the mechanical property and the corrosion resistance of Mg-9Li-3Al alloy was investigated by optical microscopy, scanning electronic microscopy (SEM), X-ray diffraction (XRD), mechanical properties testing and electrochemical measurement. The results show that the addition of Y can change the microstructure form of the α phase and reduce its volume fraction. Meanwhile, the binary Al2Y phase is mainly distributed inside the β phase and the α phase is formed. The addition of Y can effectively improve the ultimate tensile strength (UTS) and the elongation (EL) of the alloy. Upon 1.6 wt% Y addition, the UTS of the alloy is up to 190 MPa; the maximal EL reaches 19.3% when the content of Y is 2wt%. The corrosion resistances of the alloy are found to decrease upon Y content less than 1.2wt% and then increase upon Y content from 1.2wt% to 2.0wt%.
2013, 42(10):1999-2003.
Abstract:
Mg-14Li-1Al (LA141), LA141-0.3Y, LA141-0.3Sr and LA141-0.3Y-0.3Sr alloys were prepared and their electrochemical behavior in 0.7 mol/L NaCl solutions was investigated by means of potentiodynamic polarization, potentiostatic current-time and electrochemical impedance spectroscopy measurements as well as by scanning electron microscope examination. The effects of gallium oxide as an electrolyte additive on the potentiostatic discharge performances of these magnesium alloys were studied. The discharge activities and utilization efficiencies of these alloys increase in the order: LA141LA141-0.3Sr>LA141-0.3Y>LA141-0.3Y-0.3Sr. Scanning electron microscopy indicates that the alloy elements Y and Sr can prevent the formation of dense oxide film on the alloy surface and accelerate the peeling off the oxide products. In the respect of improving the electrochemical performance Y is more obvious than Sr and it is the most significant when Y and Sr are alloyed in magnesium at the same time. LA141-0.3Y-0.3Sr exhibits the best performance in terms of activity and utilization efficiency and the most loose oxide products on alloy surface.
Mg-14Li-1Al (LA141), LA141-0.3Y, LA141-0.3Sr and LA141-0.3Y-0.3Sr alloys were prepared and their electrochemical behavior in 0.7 mol/L NaCl solutions was investigated by means of potentiodynamic polarization, potentiostatic current-time and electrochemical impedance spectroscopy measurements as well as by scanning electron microscope examination. The effects of gallium oxide as an electrolyte additive on the potentiostatic discharge performances of these magnesium alloys were studied. The discharge activities and utilization efficiencies of these alloys increase in the order: LA141
2013, 42(10):2004-2008.
Abstract:
Ag and Nb were chosen as modifying elements, and their effects on the microstructure, antibacterial property and corrosion resistance of 316L were studied by antibacterial experiment, electrochemical experiment and microscopic analysis. The results show that niobium can refine the grains of 316L effectively and improve the distribution of silver in the matrix. The 316L stainless steel containing an appropriate amount of silver has an excellent antibacterial efficacy to S. aureus and its microbiological corrosion resistance is improved while an excessive silver is prone to form segregation and degrade the corrosion resistance. When 316L the stainless steel contains about 0.04wt%~0.06 wt% Ag and 0.1 wt% Nb, an optimized matching among microstructure, corrosion resistance and antibacterial properties can be obtained.
Ag and Nb were chosen as modifying elements, and their effects on the microstructure, antibacterial property and corrosion resistance of 316L were studied by antibacterial experiment, electrochemical experiment and microscopic analysis. The results show that niobium can refine the grains of 316L effectively and improve the distribution of silver in the matrix. The 316L stainless steel containing an appropriate amount of silver has an excellent antibacterial efficacy to S. aureus and its microbiological corrosion resistance is improved while an excessive silver is prone to form segregation and degrade the corrosion resistance. When 316L the stainless steel contains about 0.04wt%~0.06 wt% Ag and 0.1 wt% Nb, an optimized matching among microstructure, corrosion resistance and antibacterial properties can be obtained.
2013, 42(10):2009-2013.
Abstract:
The Mg-10Y master alloys made by different processes but with the same composition have obviously different modifying efficiencies and structure heredity effects. The results indicate that there exist differences in the microstructures and grain sizes of Mg-10Y master alloys in the states of conventional casting, as-extruded, heat-treated and rapid solidification. The Mg-10Y master alloys are added to AZ31 magnesium alloy as modifier and an obvious refinement is observed. The final magnesium alloys are all composed of α-Mg, Mg17Al12, Al2Y and Al3Y phases. Similar structures exist in both the Mg-10Y master alloys and the final magnesium alloys. After addition of as-extruded Mg-10Y master alloy, the mechanical properties of AZ31 alloy reach the maximum at room temperature, whose ultimate tensile strength is up to 199.3 MPa and the elongation is up to 9.2%. The corresponding differences of the microstructures and the mechanical properties between Mg-10Y master alloys and AZ31 magnesium alloy are related to the structure heredity of Mg-10Y master alloys.
The Mg-10Y master alloys made by different processes but with the same composition have obviously different modifying efficiencies and structure heredity effects. The results indicate that there exist differences in the microstructures and grain sizes of Mg-10Y master alloys in the states of conventional casting, as-extruded, heat-treated and rapid solidification. The Mg-10Y master alloys are added to AZ31 magnesium alloy as modifier and an obvious refinement is observed. The final magnesium alloys are all composed of α-Mg, Mg17Al12, Al2Y and Al3Y phases. Similar structures exist in both the Mg-10Y master alloys and the final magnesium alloys. After addition of as-extruded Mg-10Y master alloy, the mechanical properties of AZ31 alloy reach the maximum at room temperature, whose ultimate tensile strength is up to 199.3 MPa and the elongation is up to 9.2%. The corresponding differences of the microstructures and the mechanical properties between Mg-10Y master alloys and AZ31 magnesium alloy are related to the structure heredity of Mg-10Y master alloys.
2013, 42(10):2014-2018.
Abstract:
α-Fe2O3 hexagonal micro-platelets were prepared via a simple hydrothermal process in the presence of an organic solvent PEG400. The synthetic method was based on the hydrothermal oxidative decomposition and the recrystallization of Fe(OH)3 precursor in a basic solution of NaOH. The crystalline structures and morphologies of the as-obtained samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of the alkali environment during the hydrothermal reaction on product morphology were investigated. According to the results, α-Fe2O3 hexagonal micro-platelets could be directly prepared in a basic solution of NaOH (2.5 mol/L) when using PEG400 in the reaction system. The product morphology changes from rodlike to platelike shape when the alkali concentration increases from 1 mol/L to 2.5 mol/L. Therefore, the use of PEG400 and the hydrothermal growth alkali concentration play an important role in the formation of such platelike microstructure of α-Fe2O3. When the α-Fe2O3 hexagonal micro-platelets are used in Li-ion battery, it exhibits an initial reversible capacity of 674.9 mAh·g-1
α-Fe2O3 hexagonal micro-platelets were prepared via a simple hydrothermal process in the presence of an organic solvent PEG400. The synthetic method was based on the hydrothermal oxidative decomposition and the recrystallization of Fe(OH)3 precursor in a basic solution of NaOH. The crystalline structures and morphologies of the as-obtained samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of the alkali environment during the hydrothermal reaction on product morphology were investigated. According to the results, α-Fe2O3 hexagonal micro-platelets could be directly prepared in a basic solution of NaOH (2.5 mol/L) when using PEG400 in the reaction system. The product morphology changes from rodlike to platelike shape when the alkali concentration increases from 1 mol/L to 2.5 mol/L. Therefore, the use of PEG400 and the hydrothermal growth alkali concentration play an important role in the formation of such platelike microstructure of α-Fe2O3. When the α-Fe2O3 hexagonal micro-platelets are used in Li-ion battery, it exhibits an initial reversible capacity of 674.9 mAh·g-1
2013, 42(10):2019-2022.
Abstract:
The thermal conductivity and the tensile properties of Mg-3Zn-xSn (x=0.5, 1.5, 2.5, 3.5, wt%) alloys were studied. The thermal conductivities of the alloys with different contents of Sn were measured at 25 °C and 100 °C. The results clearly show that the thermal conductivity decreases with the increase of Sn content, and increases with the rise of temperature. Meanwhile, the ultimate tensile strength and the elongation of the alloys increase with the increase of Sn content. With the increase of Sn content the thermal conductivity of the alloys decreases, while the mechanical properties increase.
The thermal conductivity and the tensile properties of Mg-3Zn-xSn (x=0.5, 1.5, 2.5, 3.5, wt%) alloys were studied. The thermal conductivities of the alloys with different contents of Sn were measured at 25 °C and 100 °C. The results clearly show that the thermal conductivity decreases with the increase of Sn content, and increases with the rise of temperature. Meanwhile, the ultimate tensile strength and the elongation of the alloys increase with the increase of Sn content. With the increase of Sn content the thermal conductivity of the alloys decreases, while the mechanical properties increase.
2013, 42(10):2023-2026.
Abstract:
The c-axis textured aluminum nitride (AlN) thin films with columnar grains perpendicular to Molybdenum(Mo)/ Polyimide(PI)/Si(111) substrate could be obtained through reactive magnetron sputtering at room temperature. The full width at half maximum of the X-ray diffraction rocking curves and E2 (high) peak of Raman spectrum of the AlN thin films were 2.2° and 18.6?cm-1, respectively. The thin film bulk acoustic resonators (FBARs) with Mo/AlN/Mo/PI/Si (111) configuration were fabricated, and a PI/Mo heterostructure was used as acoustic isolation layer for the FBARs. The resonant frequency response of the FBARs was measured using a vector network analyzer, and an effective coupling coefficient of 5.4% was achieved.
The c-axis textured aluminum nitride (AlN) thin films with columnar grains perpendicular to Molybdenum(Mo)/ Polyimide(PI)/Si(111) substrate could be obtained through reactive magnetron sputtering at room temperature. The full width at half maximum of the X-ray diffraction rocking curves and E2 (high) peak of Raman spectrum of the AlN thin films were 2.2° and 18.6?cm-1, respectively. The thin film bulk acoustic resonators (FBARs) with Mo/AlN/Mo/PI/Si (111) configuration were fabricated, and a PI/Mo heterostructure was used as acoustic isolation layer for the FBARs. The resonant frequency response of the FBARs was measured using a vector network analyzer, and an effective coupling coefficient of 5.4% was achieved.
Li Jiayan
,
Xie Ming
,
Yang Youcai
,
Zhang Jiming
,
Chen Yongtai
,
Liu Manmen
,
Wang Saibei
,
Hu Jieqiong
,
Nin Ping
2013, 42(10):2027-2033.
Abstract:
The effect of Zr, Mo and Y adding on mechanical and electrical properties of Au-Pd, Pt-Ir and Pd-Ru systems was investigated. The alloys were prepared in a vacuum high frequency melting furnace. X-ray diffraction and metallographic microscopy were employed to detect the microstructures. Electric bridge and eddy current conductive instrument were used to test the electrical resistivity, and the mechanical properties of the alloys were tested by AG-X100KN type tensile testing machine. The results show that adding of rare metal elements in Au-Pd, Pt-Ir and Pd-Ru systems could refine structures of the alloys effectively, increase their melting points, densities and electrical resistivities, and improve mechanical properties of the alloys, but the elongations of the alloys is decreased.
The effect of Zr, Mo and Y adding on mechanical and electrical properties of Au-Pd, Pt-Ir and Pd-Ru systems was investigated. The alloys were prepared in a vacuum high frequency melting furnace. X-ray diffraction and metallographic microscopy were employed to detect the microstructures. Electric bridge and eddy current conductive instrument were used to test the electrical resistivity, and the mechanical properties of the alloys were tested by AG-X100KN type tensile testing machine. The results show that adding of rare metal elements in Au-Pd, Pt-Ir and Pd-Ru systems could refine structures of the alloys effectively, increase their melting points, densities and electrical resistivities, and improve mechanical properties of the alloys, but the elongations of the alloys is decreased.
2013, 42(10):2034-2038.
Abstract:
The effects of cold rolling reduction 20%~90% on the phase structure, microstructure, crystal orientation, mechanical properties and Young’s modulus of a low modulus biomedical b titanium alloy were investigated by tensile tests and XRD, EBSD and TEM. The changes of the microstructure and mechanical behavior of the deformed titanium alloy were described. The formation of nanocrystallines in the deformation bands of b titanium alloy with BCC crystal structure during cold rolling was analyzed and a new viewpoint that nanostructure and texture jointly influence the Young’s modulus of b titanium alloy was suggested.
The effects of cold rolling reduction 20%~90% on the phase structure, microstructure, crystal orientation, mechanical properties and Young’s modulus of a low modulus biomedical b titanium alloy were investigated by tensile tests and XRD, EBSD and TEM. The changes of the microstructure and mechanical behavior of the deformed titanium alloy were described. The formation of nanocrystallines in the deformation bands of b titanium alloy with BCC crystal structure during cold rolling was analyzed and a new viewpoint that nanostructure and texture jointly influence the Young’s modulus of b titanium alloy was suggested.
2013, 42(10):2039-2042.
Abstract:
A finite element model for single track laser cladding Al2O3 ceramic on Ti6Al4V substrate was established using ANSYS software. By observing the molten pool's morphology and measuring the temperature, the simulation shows a good agreement with the experiment, which indicates that the model is reliable. Furthermore, the variation of temperature gradient during the cooling stage and the effect of preheating on temperature gradient were both analyzed. The results show that the temperature gradient decreases with the temperature decreasing during the cooling stage. When the temperature drops to the plasticity point of alumina, the edge of the bonding between layer and substrate exhibits a higher temperature gradient. So it is easy to form cracks at the edge of the bonding. And preheating substrate could reduce the temperature gradient sharply. The higher the preheating temperature is, the lower the temperature gradient is. So it is possible to restrain the crack formation by preheating substrate.
A finite element model for single track laser cladding Al2O3 ceramic on Ti6Al4V substrate was established using ANSYS software. By observing the molten pool's morphology and measuring the temperature, the simulation shows a good agreement with the experiment, which indicates that the model is reliable. Furthermore, the variation of temperature gradient during the cooling stage and the effect of preheating on temperature gradient were both analyzed. The results show that the temperature gradient decreases with the temperature decreasing during the cooling stage. When the temperature drops to the plasticity point of alumina, the edge of the bonding between layer and substrate exhibits a higher temperature gradient. So it is easy to form cracks at the edge of the bonding. And preheating substrate could reduce the temperature gradient sharply. The higher the preheating temperature is, the lower the temperature gradient is. So it is possible to restrain the crack formation by preheating substrate.
2013, 42(10):2043-2047.
Abstract:
Split Hopkinson bar was used to study the dynamic mechanical properties of three tungsten heavy alloys (93W-4.9Ni-2.1Fe) with a wide range of strain rates (102~103 s-1) and temperatures (298~623 K), and the true stress-true strain curves can be obtained. The results reveal that fine-grained 93W-4.9Ni-2.1Fe-0.03%Y enters into the unstable plastic stage in advance, compared with other two 93W-4.9Ni-2.1Fe under the same conditions. According to experimental data, modified Johnson-Cook constitutive equations were fitted out and the fitting is better than the original Johnson-Cook model, with maximum relative error –3.4%. Comparing the constitutive parameters of three fine-grained tungsten heavy alloys, fine-grained tungsten alloy is considered to be possible to form adiabatic shear band (ASB).
Split Hopkinson bar was used to study the dynamic mechanical properties of three tungsten heavy alloys (93W-4.9Ni-2.1Fe) with a wide range of strain rates (102~103 s-1) and temperatures (298~623 K), and the true stress-true strain curves can be obtained. The results reveal that fine-grained 93W-4.9Ni-2.1Fe-0.03%Y enters into the unstable plastic stage in advance, compared with other two 93W-4.9Ni-2.1Fe under the same conditions. According to experimental data, modified Johnson-Cook constitutive equations were fitted out and the fitting is better than the original Johnson-Cook model, with maximum relative error –3.4%. Comparing the constitutive parameters of three fine-grained tungsten heavy alloys, fine-grained tungsten alloy is considered to be possible to form adiabatic shear band (ASB).
2013, 42(10):2048-2052.
Abstract:
The mechanism of surface self-nanocrystallization and the evolution of grain size for TC17 were investigated by means of X-ray diffraction (XRD), micro-hardness testing and transmission electron microscope (TEM). The results show that the nanostructures are obtained by the supersonic fine particles bombarding (SFPB), and have obvious working-hardening on the surface layer of TC17 alloy. Compared with the matrix material, the surface microhardness is increased by one time. The thickness of the nanostructured layer increases with the extension of SFPB treatment time and finally is stabilized when the SFPB treatment time is more than 30 min. The size of equiaxed nano-crystallites is approximately 16.3 nm, which exhibits a random crystallographic orientation on the top surface layer. The surface self-nanocrystallization could be attributed to dislocation glide and division. Under the multidirectional loads of repeating actions, a large number of dislocations are formed. The dislocation slippage, dislocation accumulation and interaction of dislocation form the dislocation cells or walls. The dislocations continue to slip, and then form subboundary or subgrain. With increasing the strain, more and more dislocations are born and annihilated in the subboundary, so that the subboundary and subgrain transform into grain boundary and grain. When the forming and annihilating rate of the dislocations achieve the balance, the grains achieve to nanometer level.
The mechanism of surface self-nanocrystallization and the evolution of grain size for TC17 were investigated by means of X-ray diffraction (XRD), micro-hardness testing and transmission electron microscope (TEM). The results show that the nanostructures are obtained by the supersonic fine particles bombarding (SFPB), and have obvious working-hardening on the surface layer of TC17 alloy. Compared with the matrix material, the surface microhardness is increased by one time. The thickness of the nanostructured layer increases with the extension of SFPB treatment time and finally is stabilized when the SFPB treatment time is more than 30 min. The size of equiaxed nano-crystallites is approximately 16.3 nm, which exhibits a random crystallographic orientation on the top surface layer. The surface self-nanocrystallization could be attributed to dislocation glide and division. Under the multidirectional loads of repeating actions, a large number of dislocations are formed. The dislocation slippage, dislocation accumulation and interaction of dislocation form the dislocation cells or walls. The dislocations continue to slip, and then form subboundary or subgrain. With increasing the strain, more and more dislocations are born and annihilated in the subboundary, so that the subboundary and subgrain transform into grain boundary and grain. When the forming and annihilating rate of the dislocations achieve the balance, the grains achieve to nanometer level.
2013, 42(10):2053-2056.
Abstract:
The surface morphology, corrosion resistance, fretting friction, wear properties and bioactivity of electrochemically polished surface on conventional Ti and ultrafine-grained Ti were investigated. The results show that compared to the electrochemically polished surface of conventional Ti, the electrochemically polished surface of ultrafine-grained titanium has more nano-scale corrosion pits, higher corrosion resistance (corrosion rate of the latter is 2/5 of the former) in the Kokubo simulated body fluid, lower friction coefficient (0.12 vs. 0.15), higher wear resistance (wear scar width of the latter is 4/5 of the former), and a slightly higher bioactivity (growth rate of Ca-P layer in simulated body fluid about 21.03 vs. 18.40 g/m2). It is believed that the above mentioned improvements were caused by the increase of crystal defects (internal energy) due to ultrafine microstructure.
The surface morphology, corrosion resistance, fretting friction, wear properties and bioactivity of electrochemically polished surface on conventional Ti and ultrafine-grained Ti were investigated. The results show that compared to the electrochemically polished surface of conventional Ti, the electrochemically polished surface of ultrafine-grained titanium has more nano-scale corrosion pits, higher corrosion resistance (corrosion rate of the latter is 2/5 of the former) in the Kokubo simulated body fluid, lower friction coefficient (0.12 vs. 0.15), higher wear resistance (wear scar width of the latter is 4/5 of the former), and a slightly higher bioactivity (growth rate of Ca-P layer in simulated body fluid about 21.03 vs. 18.40 g/m2). It is believed that the above mentioned improvements were caused by the increase of crystal defects (internal energy) due to ultrafine microstructure.
2013, 42(10):2057-2062.
Abstract:
The uniaxial tensile deformation of Ti-Al nano-rod was studied by molecular dynamics simulation. The influence of strain rate, temperature and Al content on the stress-strain curve and the plastic deformation behavior were analyzed. The Ti-Al nano-rods have the higher yield strength and better ductility than macro material. The slipping of (0001) plane and the formation of {}<> as well as {}<> twinning are the dominant mechanism of the plastic deformation. The lower strain rate and higher deformation temperature decrease the yield strength and then benefit the plastic deformation. The increasing of Al content in Ti-Al reduces the ductility, which results in the earlier necking and cracking.
The uniaxial tensile deformation of Ti-Al nano-rod was studied by molecular dynamics simulation. The influence of strain rate, temperature and Al content on the stress-strain curve and the plastic deformation behavior were analyzed. The Ti-Al nano-rods have the higher yield strength and better ductility than macro material. The slipping of (0001) plane and the formation of {}<> as well as {}<> twinning are the dominant mechanism of the plastic deformation. The lower strain rate and higher deformation temperature decrease the yield strength and then benefit the plastic deformation. The increasing of Al content in Ti-Al reduces the ductility, which results in the earlier necking and cracking.
17 Simulation of Uniaxial Tensile Deformation in Nanocrystalline Material by Phase Field Crystal Method
2013, 42(10):2063-2067.
Abstract:
Uniaxial tensile deformation simulation of nanocrystalline was performed using the phase-field-crystal (PFC) method coupling with strain, including the motion of high-angel boundary and low-angel boundary and the mechanism of grain growth. Simulation results show that in the process of uniaxial tensile deformation, the stress induces grain growth. There exists two mechanisms which are GB migration and grain rotation, and they both influence and interact each other. Since the motion of dislocation of low-angel GB results in grain rotation, grains have merged each other. Curvature-driven high-angle GBs migration shows that high-energy GBs are disappearing and low-energy GBs are growing. Moreover in the process of GBs motion, when the grain size is small enough, it will arouse grain rotation and stimulate grain growth
Uniaxial tensile deformation simulation of nanocrystalline was performed using the phase-field-crystal (PFC) method coupling with strain, including the motion of high-angel boundary and low-angel boundary and the mechanism of grain growth. Simulation results show that in the process of uniaxial tensile deformation, the stress induces grain growth. There exists two mechanisms which are GB migration and grain rotation, and they both influence and interact each other. Since the motion of dislocation of low-angel GB results in grain rotation, grains have merged each other. Curvature-driven high-angle GBs migration shows that high-energy GBs are disappearing and low-energy GBs are growing. Moreover in the process of GBs motion, when the grain size is small enough, it will arouse grain rotation and stimulate grain growth
2013, 42(10):2068-2072.
Abstract:
Combination of high-energy ball milling mechanical alloying and spark plasma sintering was used to fabricate ultrafine-grained stainless steel/TiC composite materials. The corrosion behaviors in a mixture solution of ferric chloride and hydrochloric acid, alkali (NaOH) and formic acid were studied by electrochemical potentiodynamic scanning. SEM and EDS were applied to explore the microstructure characteristics of corrosion products. The results show that compared to ordinary rolled 316 stainless steel, the ultrafine-grained stainless steel/TiC composites have a improved corrosion resistance. The corrosion rate in the mixture solution of ferric chloride and hydrochloric acid is maximum
Combination of high-energy ball milling mechanical alloying and spark plasma sintering was used to fabricate ultrafine-grained stainless steel/TiC composite materials. The corrosion behaviors in a mixture solution of ferric chloride and hydrochloric acid, alkali (NaOH) and formic acid were studied by electrochemical potentiodynamic scanning. SEM and EDS were applied to explore the microstructure characteristics of corrosion products. The results show that compared to ordinary rolled 316 stainless steel, the ultrafine-grained stainless steel/TiC composites have a improved corrosion resistance. The corrosion rate in the mixture solution of ferric chloride and hydrochloric acid is maximum
2013, 42(10):2073-2078.
Abstract:
The influence of Gd concentration on texture and stretch formability of rolled Mg-Zn-Gd alloys were investigated. The result shows that Gd addition in Mg-Zn alloys can effectively modify the basal plane texture. The alloy with 0.2% Gd concentration appears to be low texture intensity, TD-split texture occurs when the position of basal is titled from ND toward TD, and the largest Erichsen value is 6.5 while the elongation rate reaches 29.1% in TD direction. However with Gd concentration increasing, when the Gd concentration is 2.0%, the texture intensity increases slightly, TD-split texture degree decreases dramatically, and Erichsen value is only 3.9. Excessive Gd addition promotes formation of the coarse second phase particles, resulting in the deterioration of stretch formability
The influence of Gd concentration on texture and stretch formability of rolled Mg-Zn-Gd alloys were investigated. The result shows that Gd addition in Mg-Zn alloys can effectively modify the basal plane texture. The alloy with 0.2% Gd concentration appears to be low texture intensity, TD-split texture occurs when the position of basal is titled from ND toward TD, and the largest Erichsen value is 6.5 while the elongation rate reaches 29.1% in TD direction. However with Gd concentration increasing, when the Gd concentration is 2.0%, the texture intensity increases slightly, TD-split texture degree decreases dramatically, and Erichsen value is only 3.9. Excessive Gd addition promotes formation of the coarse second phase particles, resulting in the deterioration of stretch formability
2013, 42(10):2079-2082.
Abstract:
The porosity formation mechanism of the laser spot microwelded joints between Pt-Ir alloy and 316L stainless steel wires was investigated by characterizing the weld geometry, morphology and distribution of porosity in cross sections. The porosity is believed to be a result of preferential vaporization of stainless steel alloying elements spread into weld pool. Porosity is also attributed to low solubility of stainless steel alloying elements in weld pool due to its high temperature. In addition, the solidification process is speeded up by high heat conductivity of Pt-Ir alloy as well as characteristics of laser microwelding, and the porosity is formed
The porosity formation mechanism of the laser spot microwelded joints between Pt-Ir alloy and 316L stainless steel wires was investigated by characterizing the weld geometry, morphology and distribution of porosity in cross sections. The porosity is believed to be a result of preferential vaporization of stainless steel alloying elements spread into weld pool. Porosity is also attributed to low solubility of stainless steel alloying elements in weld pool due to its high temperature. In addition, the solidification process is speeded up by high heat conductivity of Pt-Ir alloy as well as characteristics of laser microwelding, and the porosity is formed
2013, 42(10):2083-2087.
Abstract:
Vanadium-doped microarc oxidation (MAO) films were prepared on a magnesium substrate by adding a small quantity of ammonium metavanadate into MAO solutions to control the electrochemical and optical properties of the films. The results indicate that the doping content of vanadium in the film is about 8.5at%, and some of vanadium forms V2O3. The porous structures of doped and undoped films are notably different, but similar thickness and hardness are demonstrated. The polarization curve test reveals that the corrosion potential of the doped film obviously rises, but the corrosion current remarkably decreases, whose values change from –1.208 V and 0.825×10-3 A/cm2 without doping to –0.037 V and 0.3837×10-4?A/cm2 with doping, respectively. The UV-Vis spectra indicate that vanadium-doping can weaken the reflectance, and a significant decrease is especially observed in the range of visible light
Vanadium-doped microarc oxidation (MAO) films were prepared on a magnesium substrate by adding a small quantity of ammonium metavanadate into MAO solutions to control the electrochemical and optical properties of the films. The results indicate that the doping content of vanadium in the film is about 8.5at%, and some of vanadium forms V2O3. The porous structures of doped and undoped films are notably different, but similar thickness and hardness are demonstrated. The polarization curve test reveals that the corrosion potential of the doped film obviously rises, but the corrosion current remarkably decreases, whose values change from –1.208 V and 0.825×10-3 A/cm2 without doping to –0.037 V and 0.3837×10-4?A/cm2 with doping, respectively. The UV-Vis spectra indicate that vanadium-doping can weaken the reflectance, and a significant decrease is especially observed in the range of visible light
2013, 42(10):2088-2092.
Abstract:
With the help of isothermal compression tests and high-speed camera, the critical fracture reduction was determined and the fracture mode was verified in hot compression of Ti40 alloy in the deformation temperature range of 850~1100 oC, strain rate range of 0.01~10 s-1 and at the reduction of 70%. And the fracture mechanisms were investigated. It is found that the high-speed photography can shoot accurately the crack initiation and propagation, and observe the different fracture modes such as 45o shear cracking, V-type and longitudinal cracking to high-speed photography. Optical microscope and SEM were employed to observe the fracture morphologies. The results show that at high strain rate, it is mixed type brittle fracture in low-temperature region, whereas intergranular cracking with small dimple in middle-temperature region, and ductile fracture with a large number of dimple in high-temperature region. Moreover, the effect of deformation temperature and strain rate on fracture patterns and crack growth rate is significant. Fracture modes change from 45o shear cracking to V-type and longitudinal cracking and critical fracture reduction increases with the increase of temperature, while crack growth rate increases and critical fracture reduction decreases with the increasing of strain rate. It is suggested that high-speed photography is effective for research on the fracture initiation and crack propagation of Ti40 titanium alloy. Meanwhile, the exploration to the fracture mechanisms in hot compression of Ti40 alloy is of great significance for the study of deformation mechanism, optimization of processing parameters and process-microstructure-property in hot working of Ti40 alloy
With the help of isothermal compression tests and high-speed camera, the critical fracture reduction was determined and the fracture mode was verified in hot compression of Ti40 alloy in the deformation temperature range of 850~1100 oC, strain rate range of 0.01~10 s-1 and at the reduction of 70%. And the fracture mechanisms were investigated. It is found that the high-speed photography can shoot accurately the crack initiation and propagation, and observe the different fracture modes such as 45o shear cracking, V-type and longitudinal cracking to high-speed photography. Optical microscope and SEM were employed to observe the fracture morphologies. The results show that at high strain rate, it is mixed type brittle fracture in low-temperature region, whereas intergranular cracking with small dimple in middle-temperature region, and ductile fracture with a large number of dimple in high-temperature region. Moreover, the effect of deformation temperature and strain rate on fracture patterns and crack growth rate is significant. Fracture modes change from 45o shear cracking to V-type and longitudinal cracking and critical fracture reduction increases with the increase of temperature, while crack growth rate increases and critical fracture reduction decreases with the increasing of strain rate. It is suggested that high-speed photography is effective for research on the fracture initiation and crack propagation of Ti40 titanium alloy. Meanwhile, the exploration to the fracture mechanisms in hot compression of Ti40 alloy is of great significance for the study of deformation mechanism, optimization of processing parameters and process-microstructure-property in hot working of Ti40 alloy
2013, 42(10):2093-2096.
Abstract:
Microstructure and micro-area chemical composition of surface bleeding segregations of magnesium alloy strips processed via twin-roll casting were investigated by OM, SEM and WDS. The results indicate that surface bleeds are composed of solute-rich intermetalics of Al and Zn element, the percentage composition of Mn element in surface bleeds is similar to that of the matrix alloy. The structure of surface bleeds changes into equiaxed grain with fine grain size. Stop-samples were achieved by abruptly interrupting casting for analyzing the solidification and deformation characters in the set-back of magnesium alloys strips, and the formation mechanism of surface bleeds were discussed. Furthermore, the characteristics of solute elements distribution in surface bleedings including Al, Zn and Mn elements were discussed
Microstructure and micro-area chemical composition of surface bleeding segregations of magnesium alloy strips processed via twin-roll casting were investigated by OM, SEM and WDS. The results indicate that surface bleeds are composed of solute-rich intermetalics of Al and Zn element, the percentage composition of Mn element in surface bleeds is similar to that of the matrix alloy. The structure of surface bleeds changes into equiaxed grain with fine grain size. Stop-samples were achieved by abruptly interrupting casting for analyzing the solidification and deformation characters in the set-back of magnesium alloys strips, and the formation mechanism of surface bleeds were discussed. Furthermore, the characteristics of solute elements distribution in surface bleedings including Al, Zn and Mn elements were discussed
2013, 42(10):2097-2100.
Abstract:
A simple green synthesis method of Ag nanoparticles was proposed. The silver nanoparticles were formed with the protection of starch using a water-bath heating method. The Ag+ from AgNO3 solution was reduced to Ag by glucose reduction. The product was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The nanocomposite with a silver core and starch shell was obtained. UV-Vis absorption spectrum shows that the absorbance of the colloidal silver nanoparticles increases with the radiation time, and it keeps stable when the radiation time is more than 4 h. TEM test shows that silver nanoparticles are of spherical shape, single dispersion and about 20 nm in particle size. The silver nanoparticles exhibit good antibacterial activity against S.aureus and E.coli, measured by the inhibition ring test
A simple green synthesis method of Ag nanoparticles was proposed. The silver nanoparticles were formed with the protection of starch using a water-bath heating method. The Ag+ from AgNO3 solution was reduced to Ag by glucose reduction. The product was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The nanocomposite with a silver core and starch shell was obtained. UV-Vis absorption spectrum shows that the absorbance of the colloidal silver nanoparticles increases with the radiation time, and it keeps stable when the radiation time is more than 4 h. TEM test shows that silver nanoparticles are of spherical shape, single dispersion and about 20 nm in particle size. The silver nanoparticles exhibit good antibacterial activity against S.aureus and E.coli, measured by the inhibition ring test
2013, 42(10):2101-2106.
Abstract:
Only-Palladium catalysts modified with BaO as a promoter was prepared by an impregnation method. Specific surface area measurements (BET), X-ray diffraction (XRD), CO-chemisorption, H2-temperature-programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the effect of BaO on the physicochemical properties of the catalysts. Their catalytic activities towards methanol, CO and C3H8 conversions were evaluated. The results show that the addition of BaO makes palladium highly dispersed, enhances the amount of active oxygen and promotes the reductive ability. The electron effects between Pd and support is improved. It is favorable for maintaining Pd in a higher oxidized state and transiting Ce4+ to Ce3+, thus accelerating the activated oxygen migration between Pd and the support and consequently increasing the catalytic activities for methanol and CO oxidation at low temperature. The light-off temperature of T50 is lowered by 26 and 21 oC to methanol and CO, respectively compared with unmodified only-Palladium catalysts. Whereas the conversion of C3H8 falls directly because of the higher oxidized Pd2+ and the amount and intensity of the acid sites decreasing obviously
Only-Palladium catalysts modified with BaO as a promoter was prepared by an impregnation method. Specific surface area measurements (BET), X-ray diffraction (XRD), CO-chemisorption, H2-temperature-programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the effect of BaO on the physicochemical properties of the catalysts. Their catalytic activities towards methanol, CO and C3H8 conversions were evaluated. The results show that the addition of BaO makes palladium highly dispersed, enhances the amount of active oxygen and promotes the reductive ability. The electron effects between Pd and support is improved. It is favorable for maintaining Pd in a higher oxidized state and transiting Ce4+ to Ce3+, thus accelerating the activated oxygen migration between Pd and the support and consequently increasing the catalytic activities for methanol and CO oxidation at low temperature. The light-off temperature of T50 is lowered by 26 and 21 oC to methanol and CO, respectively compared with unmodified only-Palladium catalysts. Whereas the conversion of C3H8 falls directly because of the higher oxidized Pd2+ and the amount and intensity of the acid sites decreasing obviously
2013, 42(10):2107-2111.
Abstract:
Molybdenum (Mo) bilayer thin films were deposited on soda-lime glass using DC magnetron sputtering process. The structure, morphology, and electrical properties of Mo films have been studied by XRD, SEM, four-probe tester, etc. The results show that all bilayer films exhibit a body-centered cubic structure. The buffer layer with rough surface and many defects is initially made on the substrate, whose R-T relationship reflects the characteristics of the semiconductor. The resistivity of the thin film decreases with the top layer’s deposition time increasing. In addition, the R-T relationship of these films shows a metal feature. Compared with the monolayer film, bilayer films have lower resistivity and shorter sputtering time, so it greatly satisfies the requirement of CIGS solar cell back electrode.
Molybdenum (Mo) bilayer thin films were deposited on soda-lime glass using DC magnetron sputtering process. The structure, morphology, and electrical properties of Mo films have been studied by XRD, SEM, four-probe tester, etc. The results show that all bilayer films exhibit a body-centered cubic structure. The buffer layer with rough surface and many defects is initially made on the substrate, whose R-T relationship reflects the characteristics of the semiconductor. The resistivity of the thin film decreases with the top layer’s deposition time increasing. In addition, the R-T relationship of these films shows a metal feature. Compared with the monolayer film, bilayer films have lower resistivity and shorter sputtering time, so it greatly satisfies the requirement of CIGS solar cell back electrode.
2013, 42(10):2112-2116.
Abstract:
Butt joints of 3.0 mm thick sheets of 5A90 Al-Li alloys have been produced using Nd:YAG laser welding. Grain shapes and grain orientations in the horizontal and transversal welds were studied using electron back scattered diffraction (EBSD). The results show that a narrow band of non-dendritic equiaxed grain zone (EQZ) is formed along the fusion boundary. The weld metals exhibit equiaxed dendritic microstructures with random orientations. The non-epitaxial growth mode occurs in the weld metal grains, which does not follow special orientation relationships with the base metal grains due to the presence of the EQZ. The equiaxed dendritic grains are resulted from heterogeneous nucleation aided by equilibrium A13Zr phases as well as the high degree of constitutional supercooling occurring in the advancing solidification front of welding pool during the solidification. A combination of the chemical compositions of 5A90 Al-Li alloys and Nd:YAG laser welding processes accelerate heterogeneous nucleation
Butt joints of 3.0 mm thick sheets of 5A90 Al-Li alloys have been produced using Nd:YAG laser welding. Grain shapes and grain orientations in the horizontal and transversal welds were studied using electron back scattered diffraction (EBSD). The results show that a narrow band of non-dendritic equiaxed grain zone (EQZ) is formed along the fusion boundary. The weld metals exhibit equiaxed dendritic microstructures with random orientations. The non-epitaxial growth mode occurs in the weld metal grains, which does not follow special orientation relationships with the base metal grains due to the presence of the EQZ. The equiaxed dendritic grains are resulted from heterogeneous nucleation aided by equilibrium A13Zr phases as well as the high degree of constitutional supercooling occurring in the advancing solidification front of welding pool during the solidification. A combination of the chemical compositions of 5A90 Al-Li alloys and Nd:YAG laser welding processes accelerate heterogeneous nucleation
2013, 42(10):2117-2122.
Abstract:
High-temperature deformation behavior of a new type of Niobium-based superalloy Nb10Zr was investigated by the Gleeble-1500 thermo-mechanical simulator compression test at deformation temperatures of 1273~1373 K and strain rates of 0.01~1 s-1. The Arrhenius constitutive equation with the strain compensation was established based on the experiment data. The relationship between peak stress, strain rate and deformation temperature was also established. Furthermore, the law of activation energy and material constants with the variation of true strain is obtained in consideration of the strain influence. The results show that the constitutive model could accurately predict the deformation behavior at low temperature, but the bad predicting ability occurs with increasing deformation temperature. However, the new improved constitutive model could meet the engineering need in the range of strain rate and deformation temperature in this study and the average relative error of 4.3% is relatively low
High-temperature deformation behavior of a new type of Niobium-based superalloy Nb10Zr was investigated by the Gleeble-1500 thermo-mechanical simulator compression test at deformation temperatures of 1273~1373 K and strain rates of 0.01~1 s-1. The Arrhenius constitutive equation with the strain compensation was established based on the experiment data. The relationship between peak stress, strain rate and deformation temperature was also established. Furthermore, the law of activation energy and material constants with the variation of true strain is obtained in consideration of the strain influence. The results show that the constitutive model could accurately predict the deformation behavior at low temperature, but the bad predicting ability occurs with increasing deformation temperature. However, the new improved constitutive model could meet the engineering need in the range of strain rate and deformation temperature in this study and the average relative error of 4.3% is relatively low
2013, 42(10):2123-2126.
Abstract:
Ti-containing diamond-like carbon (Ti-DLC) films were deposited on Ti6Al4V substrate by a hybrid deposition system of MEVVA ion source and magnetron sputtering. The influence of Ti contents on the hydrophobic property of DLC films was investigated. The composition, bonding structure and surface morphology of the films were characterized by EDS, XPS and AFM, respectively. The wettability of the films was examined by the contact angle measurement. The surface energy including the dispersive and polar components was evaluated using two types of liquid with different polarity. The results show that the hydrophobicity of Ti-doped DLC films is obviously improved, whose water-contact angle increases to 105° from 68.5°. The main reason for the hydrophobicity improving may be that the surface energy of the Ti-doped DLC film is decreased by higher sp2-bonded carbon configuration and the formation of Ti-O bond
Ti-containing diamond-like carbon (Ti-DLC) films were deposited on Ti6Al4V substrate by a hybrid deposition system of MEVVA ion source and magnetron sputtering. The influence of Ti contents on the hydrophobic property of DLC films was investigated. The composition, bonding structure and surface morphology of the films were characterized by EDS, XPS and AFM, respectively. The wettability of the films was examined by the contact angle measurement. The surface energy including the dispersive and polar components was evaluated using two types of liquid with different polarity. The results show that the hydrophobicity of Ti-doped DLC films is obviously improved, whose water-contact angle increases to 105° from 68.5°. The main reason for the hydrophobicity improving may be that the surface energy of the Ti-doped DLC film is decreased by higher sp2-bonded carbon configuration and the formation of Ti-O bond
2013, 42(10):2127-2130.
Abstract:
Ti35Zr30Be24Cu7.5Co3.5 bulk amorphous alloy was prepared by a copper mold casting method. The structure and thermal stability of the bulk amorphous alloy was investigated by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and differential scanning calorimetry (DSC). Its corrosion resistance was evaluated by conducting electrochemical corrosion test and variable temperature weightless corrosion test. Results show that the as-prepared Ti35Zr30Be24Cu7.5Co3.5 alloy exhibits an amorphous structure with at least 12 mm diameter, and has a high glass forming ability and a good thermal stability. The corrosion behaviors of Ti35Zr30Be24Cu7.5Co3.5 bulk amorphous alloy and the 304 stainless steel were investigated by an electrochemical method in 0.6 mol/L NaC1 solution and by variable temperature weightless corrosion in 313 K and 333 K 1mol/L HCL solution. Compared with the 304 stainless steel, the Ti35Zr30Be24Cu7.5Co3.5 bulk amorphous alloy has a better corrosion resistance
Ti35Zr30Be24Cu7.5Co3.5 bulk amorphous alloy was prepared by a copper mold casting method. The structure and thermal stability of the bulk amorphous alloy was investigated by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and differential scanning calorimetry (DSC). Its corrosion resistance was evaluated by conducting electrochemical corrosion test and variable temperature weightless corrosion test. Results show that the as-prepared Ti35Zr30Be24Cu7.5Co3.5 alloy exhibits an amorphous structure with at least 12 mm diameter, and has a high glass forming ability and a good thermal stability. The corrosion behaviors of Ti35Zr30Be24Cu7.5Co3.5 bulk amorphous alloy and the 304 stainless steel were investigated by an electrochemical method in 0.6 mol/L NaC1 solution and by variable temperature weightless corrosion in 313 K and 333 K 1mol/L HCL solution. Compared with the 304 stainless steel, the Ti35Zr30Be24Cu7.5Co3.5 bulk amorphous alloy has a better corrosion resistance
2013, 42(10):2131-3135.
Abstract:
The microstructure, phase transformation and shape memory properties of Ti69Zr30Fe1 high-temperature shape memory alloy were investigated by optical microscopy (OM), X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and compressive tests. The results show that Ti69Zr30Fe1 alloy is composed of single needle-like a￠￠ martensite with orthorhombic structure at room temperature. During heating process, nano scale ω phases precipitate within the grains at 584 oC, and then reverse martensitic transformation from α￠￠ phase to β phase occurs at 615~633 oC. When cooling, martensitic transformation occurs from 584 to 529 oC. The critical stress of Ti69Zr30Fe1 alloy is about 550 MPa and the maximum shape memory effect (SME) is 2.1%
The microstructure, phase transformation and shape memory properties of Ti69Zr30Fe1 high-temperature shape memory alloy were investigated by optical microscopy (OM), X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and compressive tests. The results show that Ti69Zr30Fe1 alloy is composed of single needle-like a￠￠ martensite with orthorhombic structure at room temperature. During heating process, nano scale ω phases precipitate within the grains at 584 oC, and then reverse martensitic transformation from α￠￠ phase to β phase occurs at 615~633 oC. When cooling, martensitic transformation occurs from 584 to 529 oC. The critical stress of Ti69Zr30Fe1 alloy is about 550 MPa and the maximum shape memory effect (SME) is 2.1%
2013, 42(10):2136-2138.
Abstract:
The hydrogen absorption-desorption thermodynamics of the magnetic refrigeration material LaFe11.6Si1.4 alloy at 25 oC and its hydrogen absorption kinetics under different hydrogen pressures (2.0×106, 2.5×106 and 3.0×106 Pa) have been investigated. The results show that about 2×105 Pa hysteresis occurs in the process of hydrogen absorption and hydrogen desorption of LaFe11.6Si1.4 alloy at room temperature; there is an incubation period sensible to the hydrogen pressure in the process of hydrogen absorption. Increasing hydrogen pressure conduces to saturated alloy hydride rapidly, whereas it slightly influences the hydrogen absorption capacity. It is difficult to prepare LaFe11.6Si1.4 magnetic refrigeration material with accurate hydrogen content, i.e. variable Curie temperature, via changing the hydrogen pressure at room temperature
The hydrogen absorption-desorption thermodynamics of the magnetic refrigeration material LaFe11.6Si1.4 alloy at 25 oC and its hydrogen absorption kinetics under different hydrogen pressures (2.0×106, 2.5×106 and 3.0×106 Pa) have been investigated. The results show that about 2×105 Pa hysteresis occurs in the process of hydrogen absorption and hydrogen desorption of LaFe11.6Si1.4 alloy at room temperature; there is an incubation period sensible to the hydrogen pressure in the process of hydrogen absorption. Increasing hydrogen pressure conduces to saturated alloy hydride rapidly, whereas it slightly influences the hydrogen absorption capacity. It is difficult to prepare LaFe11.6Si1.4 magnetic refrigeration material with accurate hydrogen content, i.e. variable Curie temperature, via changing the hydrogen pressure at room temperature
2013, 42(10):2139-2143.
Abstract:
The microstructure and magnetostriction of Fe83Ga17Tby (y=0, 0.2, 0.4, 0.6, 0.8) alloys were investigated. Results show that the cast alloys are mainly composed of A2 phase with a little L12, DO3 and DO19 phase. L12 phase and DO3 increase with the increasing of Tb content in Fe83Ga17Tby alloys; ternary additions of Tb element have conduced to the formation of (200) texture from the binary Fe-Ga alloy; equiaxed grains change into columnar grains and Tb grain boundary enrichment are observed by backscattering electron images and point analysis in the ternary alloys of Tb addition. Magnetostriction is strengthened by accession of Tb. The most felicitous Tb addition is 0.2at%, and Fe83Ga17Tb0.2 can produce magnetostrictive strain of 1.5×10-4 in low field. Spin-orbit coupling is affected by outer shell electron which might result in magnetostriction enhancement
The microstructure and magnetostriction of Fe83Ga17Tby (y=0, 0.2, 0.4, 0.6, 0.8) alloys were investigated. Results show that the cast alloys are mainly composed of A2 phase with a little L12, DO3 and DO19 phase. L12 phase and DO3 increase with the increasing of Tb content in Fe83Ga17Tby alloys; ternary additions of Tb element have conduced to the formation of (200) texture from the binary Fe-Ga alloy; equiaxed grains change into columnar grains and Tb grain boundary enrichment are observed by backscattering electron images and point analysis in the ternary alloys of Tb addition. Magnetostriction is strengthened by accession of Tb. The most felicitous Tb addition is 0.2at%, and Fe83Ga17Tb0.2 can produce magnetostrictive strain of 1.5×10-4 in low field. Spin-orbit coupling is affected by outer shell electron which might result in magnetostriction enhancement
2013, 42(10):2144-2148.
Abstract:
Mo-Zr alloys were fabricated via a powder metallurgy method. The effects of Zr on sintering densification behavior, microstructure and property of Mo-Zr alloy were studied. The results indicate that the alloy with Zr addition approach full density after sintering, and the solid phase sintering between Mo particles is the main cause for the densification of the alloy. The tensile strength at room temperature of the alloy is effectively enhanced after adding Zr, and continues to rise with the increasing of Zr content. Enhancing the pressing pressure leads to a better density but not to the tensile strength, while increasing sintering temperature will do harm to the property of the alloy. The microstructure analysis reveals that a little part of Zr solves into Mo matrix, which enhances the tensile strength of the alloys signally, while other part of Zr form oxide second phase particles dispersing throughout grain boundary and inner grain and making the grains to be significantly refined
Mo-Zr alloys were fabricated via a powder metallurgy method. The effects of Zr on sintering densification behavior, microstructure and property of Mo-Zr alloy were studied. The results indicate that the alloy with Zr addition approach full density after sintering, and the solid phase sintering between Mo particles is the main cause for the densification of the alloy. The tensile strength at room temperature of the alloy is effectively enhanced after adding Zr, and continues to rise with the increasing of Zr content. Enhancing the pressing pressure leads to a better density but not to the tensile strength, while increasing sintering temperature will do harm to the property of the alloy. The microstructure analysis reveals that a little part of Zr solves into Mo matrix, which enhances the tensile strength of the alloys signally, while other part of Zr form oxide second phase particles dispersing throughout grain boundary and inner grain and making the grains to be significantly refined
2013, 42(10):2149-2152.
Abstract:
The oxidation of a quaternary two-phase Cu-40Ni-12Cr-2.5Al alloy formed by the 2.5at% Al addition to Cu-Ni-Cr alloy were investigated at 700~800 oC in 0.1 MPa pure oxygen, and the effect of adding the forth component Al on the oxidation of Cu-Ni-Cr alloy was also discussed. Results show that kinetic curves of the present alloy deviate considerably from the parabolic rate law and the mass gain at 700 oC is higher than that at 800 oC. Moreover, the mass gain of the Cu-40Ni-12Cr-2.5Al alloy is lower than that of the Cu-40Ni-20Cr alloy evidently. The Cu-40Ni-12Cr-2.5Al alloy form uncontinuous external CuO scales followed by the mixed scales composed of Cu, Ni and Cr oxides. Finally, the alloys form a very thin and continuous Cr2O3 scales in contact with the alloy. Obviously, adding the forth component Al to Cu-Ni-Cr alloy is able to decrease the critical content to form Cr oxide and facilitates the formation of continuous Cr2O3 scales under much lower Cr content in spite of the simultaneous presence of two phase in the alloy.
The oxidation of a quaternary two-phase Cu-40Ni-12Cr-2.5Al alloy formed by the 2.5at% Al addition to Cu-Ni-Cr alloy were investigated at 700~800 oC in 0.1 MPa pure oxygen, and the effect of adding the forth component Al on the oxidation of Cu-Ni-Cr alloy was also discussed. Results show that kinetic curves of the present alloy deviate considerably from the parabolic rate law and the mass gain at 700 oC is higher than that at 800 oC. Moreover, the mass gain of the Cu-40Ni-12Cr-2.5Al alloy is lower than that of the Cu-40Ni-20Cr alloy evidently. The Cu-40Ni-12Cr-2.5Al alloy form uncontinuous external CuO scales followed by the mixed scales composed of Cu, Ni and Cr oxides. Finally, the alloys form a very thin and continuous Cr2O3 scales in contact with the alloy. Obviously, adding the forth component Al to Cu-Ni-Cr alloy is able to decrease the critical content to form Cr oxide and facilitates the formation of continuous Cr2O3 scales under much lower Cr content in spite of the simultaneous presence of two phase in the alloy.
2013, 42(10):2153-2156.
Abstract:
After solution treatment, Ti-10Mo-8V-1Fe-3.5Al (TB3) alloy was aged at 500 oC under a compressive stress. TEM results show that several α variants are observed in conventionally aged samples. However, in the stress-aged TB3 samples, most α plates are parallel to each other in one β grain, which indicates a variant selection effect. Two kinds of TB3 samples were selected for low cycle fatigue tests, which had been heat treated to the same strength level. The one was conventionally aged at 500 oC for 9 h, and the other was aged at 500 oC for 6 h with about 200 MPa compressive stress. Low cycle fatigue (LCF) test results show that the stress-aged TB3 samples exhibit a longer LCF lifetime than the conventionally aged ones
After solution treatment, Ti-10Mo-8V-1Fe-3.5Al (TB3) alloy was aged at 500 oC under a compressive stress. TEM results show that several α variants are observed in conventionally aged samples. However, in the stress-aged TB3 samples, most α plates are parallel to each other in one β grain, which indicates a variant selection effect. Two kinds of TB3 samples were selected for low cycle fatigue tests, which had been heat treated to the same strength level. The one was conventionally aged at 500 oC for 9 h, and the other was aged at 500 oC for 6 h with about 200 MPa compressive stress. Low cycle fatigue (LCF) test results show that the stress-aged TB3 samples exhibit a longer LCF lifetime than the conventionally aged ones
2013, 42(10):2157-2162.
Abstract:
The high purity silver was leaching-out and prepared using a nitric acid dissolution method from waste photosensitive film. The grain size controllable spherical ultrafine silver was prepared with ascorbic acid as reducing agent, macromolecules (PVP) and surfactant (TEA) as dispersant. The results show that the leaching effect is good, and high-purity 99.5% silver of higher content can be obtained when the concentration of nitric acid is 1.6 mol·L-1, the leaching temperature is 50 oC, and the leaching is 10 min and 3 times. Superfine silver powder of uniform size 0.15 μm, regular shape and good dispersion can be prepared when the reaction temperature is 20 oC, pH value of silver nitrate solution is 8, the concentration of silver nitrate is 0.02 mol·L-1, the m(PVP)/m(AgNO3)>4.5 and m(TEA)/m(AgNO3)=1
The high purity silver was leaching-out and prepared using a nitric acid dissolution method from waste photosensitive film. The grain size controllable spherical ultrafine silver was prepared with ascorbic acid as reducing agent, macromolecules (PVP) and surfactant (TEA) as dispersant. The results show that the leaching effect is good, and high-purity 99.5% silver of higher content can be obtained when the concentration of nitric acid is 1.6 mol·L-1, the leaching temperature is 50 oC, and the leaching is 10 min and 3 times. Superfine silver powder of uniform size 0.15 μm, regular shape and good dispersion can be prepared when the reaction temperature is 20 oC, pH value of silver nitrate solution is 8, the concentration of silver nitrate is 0.02 mol·L-1, the m(PVP)/m(AgNO3)>4.5 and m(TEA)/m(AgNO3)=1
38 Effects of Aging Treatments on Tensile Properties and Fracture Toughness of AA6156 Aluminum Alloy
2013, 42(10):2163-2168.
Abstract:
The tensile properties and plane-stress fracture toughness of AA6156 aluminum alloy with different aging treatments were studied. The results show that the natural aged AA6156 alloy obtains perfect fracture toughness, while a lower strength. The AA6156 alloy in single peak aging at 175 oC and in 175 oC/6 h+190 oC/13 h duplex over aging can both offer preferable strength, while lower fracture toughness. The property of the alloy can achieve the superior combination of the strength and toughness under 175 oC/2 h+200 oC/0.5 h aging conditions. Microstructure observations indicate that pre-aged treatment can increase the quantity of GP-zones, thus promoting homogeneous precipitation of β″ phase in the following aging treatments. The effect of aging treatments on fracture toughness of AA6156 alloy mainly depends on the strengthening phase β″ in the matrix, whereas grain boundary microstructures have less effect on it
The tensile properties and plane-stress fracture toughness of AA6156 aluminum alloy with different aging treatments were studied. The results show that the natural aged AA6156 alloy obtains perfect fracture toughness, while a lower strength. The AA6156 alloy in single peak aging at 175 oC and in 175 oC/6 h+190 oC/13 h duplex over aging can both offer preferable strength, while lower fracture toughness. The property of the alloy can achieve the superior combination of the strength and toughness under 175 oC/2 h+200 oC/0.5 h aging conditions. Microstructure observations indicate that pre-aged treatment can increase the quantity of GP-zones, thus promoting homogeneous precipitation of β″ phase in the following aging treatments. The effect of aging treatments on fracture toughness of AA6156 alloy mainly depends on the strengthening phase β″ in the matrix, whereas grain boundary microstructures have less effect on it
2013, 42(10):2169-2173.
Abstract:
Magnetic composite nanoparticles Fe3O4/Ag were prepared by adding silver acetate into (3-aminopropyl)triethoxysilane (APTES)-coated Fe3O4 nanoparticles solution, silver ions were absorbed on the surface and formed a coordination compound with amino groups, and finally the complexed silver ions were reduced by sodium formate to generate magnetic Fe3O4/Ag composite nanoparticles. The morphology, microstructure, composition and magnetic properties of the Fe3O4/Ag nanoparticles were characterized by ultraviolet-visible spectroscopy (UV-Vis), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID) magnetometry. And the antibacterial activities of the composites were investigated by E. coli and S. aureus as test bacterial spawn. The results show that as-obtained magnetic silver-containing nanoparticles possess a saturation magnetization (Ms) of about 2.0 (A·m2)/kg, and their average diameter is about 30 nm; meanwhile, the antibacterial tests show the composites demonstrate great antibacterial activity for restraining these two bacteria. Under controlled experiments, the number of these two bacteria id both under 0.11×103 (CFU) after 24 h test. Further test by adding more nanocomposites could sterilize nearly 100% of the E. coli. The magnetic and antibacterial nanocomposite fabrication process provides a good example for preparing novel biological antibacterial material, which is sensitively responded to external field (such as magnetic field
Magnetic composite nanoparticles Fe3O4/Ag were prepared by adding silver acetate into (3-aminopropyl)triethoxysilane (APTES)-coated Fe3O4 nanoparticles solution, silver ions were absorbed on the surface and formed a coordination compound with amino groups, and finally the complexed silver ions were reduced by sodium formate to generate magnetic Fe3O4/Ag composite nanoparticles. The morphology, microstructure, composition and magnetic properties of the Fe3O4/Ag nanoparticles were characterized by ultraviolet-visible spectroscopy (UV-Vis), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID) magnetometry. And the antibacterial activities of the composites were investigated by E. coli and S. aureus as test bacterial spawn. The results show that as-obtained magnetic silver-containing nanoparticles possess a saturation magnetization (Ms) of about 2.0 (A·m2)/kg, and their average diameter is about 30 nm; meanwhile, the antibacterial tests show the composites demonstrate great antibacterial activity for restraining these two bacteria. Under controlled experiments, the number of these two bacteria id both under 0.11×103 (CFU) after 24 h test. Further test by adding more nanocomposites could sterilize nearly 100% of the E. coli. The magnetic and antibacterial nanocomposite fabrication process provides a good example for preparing novel biological antibacterial material, which is sensitively responded to external field (such as magnetic field
2013, 42(10):2174-2178.
Abstract:
Properties of Ni47Ti44Nb9 alloy cold drawn wires and hot drawn wires were studied by means of the differential scanning calorimetry measurement and the tensile test. With increasing annealing temperature, the tensile strength and the yield strength decrease, while the elongation, the martensite transformation temperature and the transformation heat increase. The recovery strain keeps decreasing, and the transformation temperature, the transformation intervals increase with the increment of annealing temperature. Proper heat-mechanical treatment can promote the shape memory effect, and the recovery strain of 40% cold drawn wire is better than that of the hot drawn wires
Properties of Ni47Ti44Nb9 alloy cold drawn wires and hot drawn wires were studied by means of the differential scanning calorimetry measurement and the tensile test. With increasing annealing temperature, the tensile strength and the yield strength decrease, while the elongation, the martensite transformation temperature and the transformation heat increase. The recovery strain keeps decreasing, and the transformation temperature, the transformation intervals increase with the increment of annealing temperature. Proper heat-mechanical treatment can promote the shape memory effect, and the recovery strain of 40% cold drawn wire is better than that of the hot drawn wires
2013, 42(10):2179-2182.
Abstract:
The SHS agglomerate power was made by grinding Al, Ni and Co powers with vesicant and adhesive. The Ni-Al-Co composite hollow microspheres were prepared by a self-propagating synthesis flame spraying quenching method. The microstructure and crystal structure of the hollow sphere power were studied by SEM, EDS and XRD. The results show that the spheres have hollow structure. At the high temperature of the oxyacetylene flame, the SHS reaction of the agglomerate is ignited. So the synthesized product becomes droplets. At the same time some gas is generated from vesicant so that the droplets become bubbles. The hollow droplets are injected into cold water and solidified to hollow microspheres. The permittivity and permeability were analyzed by a vector network analyzer. The microwave absorbing properties of the microspheres are good at band 6 GHz.
The SHS agglomerate power was made by grinding Al, Ni and Co powers with vesicant and adhesive. The Ni-Al-Co composite hollow microspheres were prepared by a self-propagating synthesis flame spraying quenching method. The microstructure and crystal structure of the hollow sphere power were studied by SEM, EDS and XRD. The results show that the spheres have hollow structure. At the high temperature of the oxyacetylene flame, the SHS reaction of the agglomerate is ignited. So the synthesized product becomes droplets. At the same time some gas is generated from vesicant so that the droplets become bubbles. The hollow droplets are injected into cold water and solidified to hollow microspheres. The permittivity and permeability were analyzed by a vector network analyzer. The microwave absorbing properties of the microspheres are good at band 6 GHz.
42 Preparation and Tribological Properties Research of NbSe2 Nanowires as Additive in Lubricating Oil
2013, 42(10):2183-2186.
Abstract:
One dimensional nanostructure NbSe2 was synthesized by a solid-phase reaction method. And the micrographite was characterized by XRD and TEM. Adding different mass fraction ratios of NbSe2 to the lubricant, their tribological properties were evaluated using UMT-2 micro-tribometer. The worn surface morphologies were observed by SEM. And the lubricant tribological mechanism with NbSe2 adding was explored. The results show that lubricants containing the NbSe2 additives can effectively reduce the friction coefficient, especially under high load and high speed conditions. As NbSe2 increases, the friction coefficient decreases, the wear decreases and the carrying capacity of lubricating oil is improved. It is found that the effects are mainly produced by the unique closed structure, the lubricant film formation and nano-materials self-repair together.
One dimensional nanostructure NbSe2 was synthesized by a solid-phase reaction method. And the micrographite was characterized by XRD and TEM. Adding different mass fraction ratios of NbSe2 to the lubricant, their tribological properties were evaluated using UMT-2 micro-tribometer. The worn surface morphologies were observed by SEM. And the lubricant tribological mechanism with NbSe2 adding was explored. The results show that lubricants containing the NbSe2 additives can effectively reduce the friction coefficient, especially under high load and high speed conditions. As NbSe2 increases, the friction coefficient decreases, the wear decreases and the carrying capacity of lubricating oil is improved. It is found that the effects are mainly produced by the unique closed structure, the lubricant film formation and nano-materials self-repair together.
2013, 42(10):2187-2191.
Abstract:
High stability and dispersibility colloidal silver nanoparticles in pure inorganic system were prepared by wet chemical reduction of AgNO3 with NaBH4 and with sodium hexametapnosphate as dispersant through optimizing the sodium hexametapnosphate concentrations and the molar ratios of NaBH4 and AgNO3. Feature absorptions of the colloids obtained from UV-vis analysis appears at below 400 nm. TEM shows that colloidal silver nanoparticles have narrow particle size distribution, and a mean particle size below 10 nm with single spherical-like shape. The colloidal silver nanoparticles prepared in traditional organic systems are easily adsorbed by surface active agents or ionic polymers which could not be easily removed and thus the residues would directly influence the physical and chemical properties of the colloidal silver nanoparticles. The dispersant of sodium hexametapnosphate adsorbed on the colloidal silver nanoparticles prepared in pure inorganic system is a water loving reagent which could be removed easily for preparing pure colloidal silver nanoparticles. This method is simple and effective for preparing colloidal silver nanoparticles without any control of pH, temperature, ultrasound, etc
High stability and dispersibility colloidal silver nanoparticles in pure inorganic system were prepared by wet chemical reduction of AgNO3 with NaBH4 and with sodium hexametapnosphate as dispersant through optimizing the sodium hexametapnosphate concentrations and the molar ratios of NaBH4 and AgNO3. Feature absorptions of the colloids obtained from UV-vis analysis appears at below 400 nm. TEM shows that colloidal silver nanoparticles have narrow particle size distribution, and a mean particle size below 10 nm with single spherical-like shape. The colloidal silver nanoparticles prepared in traditional organic systems are easily adsorbed by surface active agents or ionic polymers which could not be easily removed and thus the residues would directly influence the physical and chemical properties of the colloidal silver nanoparticles. The dispersant of sodium hexametapnosphate adsorbed on the colloidal silver nanoparticles prepared in pure inorganic system is a water loving reagent which could be removed easily for preparing pure colloidal silver nanoparticles. This method is simple and effective for preparing colloidal silver nanoparticles without any control of pH, temperature, ultrasound, etc
2013, 42(10):2192-2196.
Abstract:
The thixoformability of Ti14 was evaluated by upsetting and die forging tests, and the microstructure and mechanical properties of the forgings were also investigated. The results show that low upsetting force and excellent upsettability with the upsetting reduction in height of 70%~85% could be obtained in semi-solid state ranging from 1000 to 1100 °C. Die forging tests also show the excellent workability with a forging ratio of 75% in the temperature range of 1000 to 1050 °C. It is found that the existence of liquid on grain boundary may serve to relax the stress concentrations caused by solid deformation, causes low deformation resistance and finally improves forgeability of the alloy. The microstructure of samples reveals that dynamic recrystallization might occur during thixoforging and the grain refinement is attained, which also benefit in the improvement of the semi-solid formability and mechanical properties of forgings
The thixoformability of Ti14 was evaluated by upsetting and die forging tests, and the microstructure and mechanical properties of the forgings were also investigated. The results show that low upsetting force and excellent upsettability with the upsetting reduction in height of 70%~85% could be obtained in semi-solid state ranging from 1000 to 1100 °C. Die forging tests also show the excellent workability with a forging ratio of 75% in the temperature range of 1000 to 1050 °C. It is found that the existence of liquid on grain boundary may serve to relax the stress concentrations caused by solid deformation, causes low deformation resistance and finally improves forgeability of the alloy. The microstructure of samples reveals that dynamic recrystallization might occur during thixoforging and the grain refinement is attained, which also benefit in the improvement of the semi-solid formability and mechanical properties of forgings
2013, 42(10):2197-2200.
Abstract:
Nanoporous Ti alloy foam was prepared by dealloying from Ti-6Al-4V with low Al content in NaOH solution. The dealloying behavior for these systems was characterized using both dynamic polarization and potential hold measurements. The results indicate that the critical potential values for these system is 0.6 V. Potentials hold within the vicinity of the critical potential displays rapid decaying currents. With potential hold at 2.1 V, current intensities rapidly reach the peak and then show a constant. It is ascribe to Al sustain dissolution
Nanoporous Ti alloy foam was prepared by dealloying from Ti-6Al-4V with low Al content in NaOH solution. The dealloying behavior for these systems was characterized using both dynamic polarization and potential hold measurements. The results indicate that the critical potential values for these system is 0.6 V. Potentials hold within the vicinity of the critical potential displays rapid decaying currents. With potential hold at 2.1 V, current intensities rapidly reach the peak and then show a constant. It is ascribe to Al sustain dissolution
