The microstructure and crystallographic texture characteristics of an extruded ZK60 Mg alloy subjected to cyclic extrusion and compression(CEC) up to 8 passes at 503 K were investigated.The local crystallographic text...The microstructure and crystallographic texture characteristics of an extruded ZK60 Mg alloy subjected to cyclic extrusion and compression(CEC) up to 8 passes at 503 K were investigated.The local crystallographic texture,grain size and distribution,and grain boundary character distributions were analyzed using high-resolution electron backscatter diffraction(EBSD).The results indicate that the microstructure is refined significantly by the CEC processing and the distributions of grain size tend to be more uniform with increasing CEC pass number.The fraction of low angle grain boundaries(LAGBs) decreases after CEC deformation,and a high fraction of high angle grain boundaries(HAGBs) is revealed after 8 passes of CEC.Moreover,the initial fiber texture becomes random during CEC processing and develops a new texture.展开更多
Age hardening characteristic and tensile property of Mg-3.5Dy-4.0Gd-3.1Nd-0.4Zr alloy were investigated. The alloy exhibits a considerable age hardening effect up to 250℃. Increasing the aging temperature leads to a ...Age hardening characteristic and tensile property of Mg-3.5Dy-4.0Gd-3.1Nd-0.4Zr alloy were investigated. The alloy exhibits a considerable age hardening effect up to 250℃. Increasing the aging temperature leads to a shorter aging time to reach the peak hardness and a lower peak hardness. The tensile results show that the peak-aged specimens have higher tensile strength at the temperature below 200℃. However, with the increase of temperature further, the tensile strength decreases dramatically and elongation increases drastically. The loss in tensile strength and increase in elongation at high temperature are possibly associated with the instability of secondary precipitates. The fracture mechanism of alloy transfers from intergranular to transgranular with the increase of experimental temperature.展开更多
A large number of scraps are produced in the fabrication process of magnesium alloy products. It is necessary to recycle these scraps for the development and scale application of magnesium alloys. In this research,a m...A large number of scraps are produced in the fabrication process of magnesium alloy products. It is necessary to recycle these scraps for the development and scale application of magnesium alloys. In this research,a method for recycling AZ91D magnesium alloy scraps fabricated by hot-press / extrusion was studied. Mechanical properties and microstructure of the recycled specimens were investigated. Microstructural analyses were performed by using the techniques of optical microscopy and scanning electron microscopy. Microstructural observations reveal that the recycled specimens consisted of fine grains when adopting the extrusion temperature of 400- 450 ℃,the extrusion ratio of( 25- 100) ∶ 1 and the extrusion rate of 0. 10- 0. 20 mm / s. Ultimate tensile strength and elongation to failure increased with the increase of the extrusion temperature,the extrusion ratio and the extrusion rate,respectively. Recycled specimens reached the highest ultimate tensile strength of average 361. 47 MPa and the highest elongation to failure of average 11. 55% when adopting the hot-press,the extrusion temperature of 400± 5 ℃,the extrusion ratio of 100 ∶ 1 and the extrusion rate of 0. 15 mm / s. The shape of bonding interface was tightly relation with the ultimate tensile strength. When the bonding interface formed continuous curves,the ultimate tensile strength decreased almost linearly with increasing the average width of the bonding interface. When the bonding interface formed discontinuous curves,the ultimate tensile strength increased almost linearly with the increase the proportion of the fine bonding length accounting for the measured interface length. Ultimate tensile strength of the recycled specimens could be calculated by using the forecastable equation.展开更多
Mg-10Gd-3Y-0.5Zr alloy was cast in a step-like mould with five different cooling rates. The as-cast microstructures of the different steps were examined with optical microscope(OM) and scanning electron microscope(SEM...Mg-10Gd-3Y-0.5Zr alloy was cast in a step-like mould with five different cooling rates. The as-cast microstructures of the different steps were examined with optical microscope(OM) and scanning electron microscope(SEM). The room temperature mechanical properties were examined by tensile test. The results show that the microstructures are refined and the second phase particles are distributed much uniformly with the increase of cooling rate. The increase of yield strength,ultimate strength and elongation can be ascribed mainly to the strengthening effect of fine grains. The relationship between grain size and yield strength/hardness agrees with the Hall-Petch behavior.展开更多
Microstructure and mechanical properties of AZ31-0.5%Si(mass fraction) alloy processed by ECAP were investigated. Results show that Mg2Si phase formed during solidification can be broken up and be dispersed in matrix ...Microstructure and mechanical properties of AZ31-0.5%Si(mass fraction) alloy processed by ECAP were investigated. Results show that Mg2Si phase formed during solidification can be broken up and be dispersed in matrix by ECAP. With the increase of ECAP passes, Mg2Si phase in microstructure tends to distribute uniformly. The mean grain size is about 4μm, and the mean size of Mg2Si is about 6 Jim. The elongation of AZ31-0.5%Si alloy is significantly increased after ECAP and then changes a little with increasing ECAP passes. The ultimate strength of as-extruded AZ31-0.5%Si alloy reaches 348.9 MPa, while its strength decreases after ECAP.展开更多
The microstructure and mechanical properties of AZ31 Mg alloy processed by high ratio extrusion (HRE) were investigated. General extrusion with extrusion ratio of 7 and high ratio extrusion with extrusion ratio 100 we...The microstructure and mechanical properties of AZ31 Mg alloy processed by high ratio extrusion (HRE) were investigated. General extrusion with extrusion ratio of 7 and high ratio extrusion with extrusion ratio 100 were contrastively conducted at 250,300 and 350℃. The results show that HRE process may be applied successfully to AZ31 Mg alloy at temperatures of 250, 300 and 350℃and this leads to obvious grain refinement during HRE process. The strength of HRE process is improved obviously compared with that of general extrusion. The grain refining mechanism of HRE process was also discussed. The current results imply that the simple high ratio extrusion method might be a feasible and effective processing means for refining the microstructure and improving the mechanical properties of AZ31 Mg alloy.展开更多
The cyclic extrusion compression （CEC） was applied to severely deform the as-extruded GW102K （Mg- 10.0Gd-2.0Y-0.5Zr, wt%） alloy at 350, 400, and 450 ℃, respectively. The microstructure, texture, and grain boundar...The cyclic extrusion compression （CEC） was applied to severely deform the as-extruded GW102K （Mg- 10.0Gd-2.0Y-0.5Zr, wt%） alloy at 350, 400, and 450 ℃, respectively. The microstructure, texture, and grain boundary character distribution of the CECed alloy were investigated in the present work. The mechan- ical properties were measured by uniaxial tension at room temperature. The crack initiation on the longitudinal section near the tensile fracture-surface was investigated by high-resolution scanning elec- tron microscopy （SEM）. The result shows that the microstructure was dramatically refined by dynamic recrystallization （DRX）. The initial fiber texture was disintegrated and obviously weakened. The 8-passes/ 350 ℃ CECed alloy exhibited yield strength of 318 MPa with an elongation-to-fracture of 16.8%, increased by 41.3% and 162.5%, respectively. Moreover, the elongation-to-fracture of the 8-passes/450 ℃ CECed alloy significantly increased more than 3 times than that of the received alloy. The cracks were mainly initi- ated at twin boundaries and second phase/matrix interfaces during tensile deformation. The microstructure refinement was considered to result in the dramatically enhanced of the strength and ductility. In ad- dition, the texture randomization during CEC is beneficial for enhancing ductility. The standard positive Hall-Petch relationships have been obtained for the CECed GW102K alloy.展开更多
基金Projects(50674067,51074106) supported by the National Natural Science Foundation of ChinaProject(09JC1408200) supported by the Science and Technology Commission of Shanghai Municipality,China
文摘The microstructure and crystallographic texture characteristics of an extruded ZK60 Mg alloy subjected to cyclic extrusion and compression(CEC) up to 8 passes at 503 K were investigated.The local crystallographic texture,grain size and distribution,and grain boundary character distributions were analyzed using high-resolution electron backscatter diffraction(EBSD).The results indicate that the microstructure is refined significantly by the CEC processing and the distributions of grain size tend to be more uniform with increasing CEC pass number.The fraction of low angle grain boundaries(LAGBs) decreases after CEC deformation,and a high fraction of high angle grain boundaries(HAGBs) is revealed after 8 passes of CEC.Moreover,the initial fiber texture becomes random during CEC processing and develops a new texture.
文摘Age hardening characteristic and tensile property of Mg-3.5Dy-4.0Gd-3.1Nd-0.4Zr alloy were investigated. The alloy exhibits a considerable age hardening effect up to 250℃. Increasing the aging temperature leads to a shorter aging time to reach the peak hardness and a lower peak hardness. The tensile results show that the peak-aged specimens have higher tensile strength at the temperature below 200℃. However, with the increase of temperature further, the tensile strength decreases dramatically and elongation increases drastically. The loss in tensile strength and increase in elongation at high temperature are possibly associated with the instability of secondary precipitates. The fracture mechanism of alloy transfers from intergranular to transgranular with the increase of experimental temperature.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50974048)the Doctoral Fund of Ministry of Education of China(Grant No.200802140004)+1 种基金the Foundation of Heilongjiang Educational Committee(Grant No.12531116)the Harbin Special Funds for Creative Talents in Science and Technology(Grant No.2013RFQXJ102)
文摘A large number of scraps are produced in the fabrication process of magnesium alloy products. It is necessary to recycle these scraps for the development and scale application of magnesium alloys. In this research,a method for recycling AZ91D magnesium alloy scraps fabricated by hot-press / extrusion was studied. Mechanical properties and microstructure of the recycled specimens were investigated. Microstructural analyses were performed by using the techniques of optical microscopy and scanning electron microscopy. Microstructural observations reveal that the recycled specimens consisted of fine grains when adopting the extrusion temperature of 400- 450 ℃,the extrusion ratio of( 25- 100) ∶ 1 and the extrusion rate of 0. 10- 0. 20 mm / s. Ultimate tensile strength and elongation to failure increased with the increase of the extrusion temperature,the extrusion ratio and the extrusion rate,respectively. Recycled specimens reached the highest ultimate tensile strength of average 361. 47 MPa and the highest elongation to failure of average 11. 55% when adopting the hot-press,the extrusion temperature of 400± 5 ℃,the extrusion ratio of 100 ∶ 1 and the extrusion rate of 0. 15 mm / s. The shape of bonding interface was tightly relation with the ultimate tensile strength. When the bonding interface formed continuous curves,the ultimate tensile strength decreased almost linearly with increasing the average width of the bonding interface. When the bonding interface formed discontinuous curves,the ultimate tensile strength increased almost linearly with the increase the proportion of the fine bonding length accounting for the measured interface length. Ultimate tensile strength of the recycled specimens could be calculated by using the forecastable equation.
基金Project(5133001B) supported by the National Basic Research Program (973 Program) of China
文摘Mg-10Gd-3Y-0.5Zr alloy was cast in a step-like mould with five different cooling rates. The as-cast microstructures of the different steps were examined with optical microscope(OM) and scanning electron microscope(SEM). The room temperature mechanical properties were examined by tensile test. The results show that the microstructures are refined and the second phase particles are distributed much uniformly with the increase of cooling rate. The increase of yield strength,ultimate strength and elongation can be ascribed mainly to the strengthening effect of fine grains. The relationship between grain size and yield strength/hardness agrees with the Hall-Petch behavior.
基金Project(50674067) supported by the National Natural Science Foundation of China
文摘Microstructure and mechanical properties of AZ31-0.5%Si(mass fraction) alloy processed by ECAP were investigated. Results show that Mg2Si phase formed during solidification can be broken up and be dispersed in matrix by ECAP. With the increase of ECAP passes, Mg2Si phase in microstructure tends to distribute uniformly. The mean grain size is about 4μm, and the mean size of Mg2Si is about 6 Jim. The elongation of AZ31-0.5%Si alloy is significantly increased after ECAP and then changes a little with increasing ECAP passes. The ultimate strength of as-extruded AZ31-0.5%Si alloy reaches 348.9 MPa, while its strength decreases after ECAP.
基金Project (50674067) supported by the National Natural Science Foundation of China
文摘The microstructure and mechanical properties of AZ31 Mg alloy processed by high ratio extrusion (HRE) were investigated. General extrusion with extrusion ratio of 7 and high ratio extrusion with extrusion ratio 100 were contrastively conducted at 250,300 and 350℃. The results show that HRE process may be applied successfully to AZ31 Mg alloy at temperatures of 250, 300 and 350℃and this leads to obvious grain refinement during HRE process. The strength of HRE process is improved obviously compared with that of general extrusion. The grain refining mechanism of HRE process was also discussed. The current results imply that the simple high ratio extrusion method might be a feasible and effective processing means for refining the microstructure and improving the mechanical properties of AZ31 Mg alloy.
基金supported by the National Natural Science Foundation of China (No. 51204117)Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxithe Natural Science Foundation of Shanxi province (No. 2015021017)
文摘The cyclic extrusion compression （CEC） was applied to severely deform the as-extruded GW102K （Mg- 10.0Gd-2.0Y-0.5Zr, wt%） alloy at 350, 400, and 450 ℃, respectively. The microstructure, texture, and grain boundary character distribution of the CECed alloy were investigated in the present work. The mechan- ical properties were measured by uniaxial tension at room temperature. The crack initiation on the longitudinal section near the tensile fracture-surface was investigated by high-resolution scanning elec- tron microscopy （SEM）. The result shows that the microstructure was dramatically refined by dynamic recrystallization （DRX）. The initial fiber texture was disintegrated and obviously weakened. The 8-passes/ 350 ℃ CECed alloy exhibited yield strength of 318 MPa with an elongation-to-fracture of 16.8%, increased by 41.3% and 162.5%, respectively. Moreover, the elongation-to-fracture of the 8-passes/450 ℃ CECed alloy significantly increased more than 3 times than that of the received alloy. The cracks were mainly initi- ated at twin boundaries and second phase/matrix interfaces during tensile deformation. The microstructure refinement was considered to result in the dramatically enhanced of the strength and ductility. In ad- dition, the texture randomization during CEC is beneficial for enhancing ductility. The standard positive Hall-Petch relationships have been obtained for the CECed GW102K alloy.
基金supported by the National Natural Science Foundation of China(Nos.11272173 and 11572170)the Foundation of Traction Power State Key Laboratory of Southwest Jiaotong University(No.TPL1503),China
