Effects of the volume fraction and the size of crystallized alumina silicate short fibers as well as heat treatment processes on micro-yield strength(MYS) of Al2O3-SiO2(sf)/Al-Si metal matrix composite(MMC) that was f...Effects of the volume fraction and the size of crystallized alumina silicate short fibers as well as heat treatment processes on micro-yield strength(MYS) of Al2O3-SiO2(sf)/Al-Si metal matrix composite(MMC) that was fabricated by squeezing cast, were investigated by using continuous loading method on an Instron 5569 tester with a special extensometer with an accuracy of 10?7. The results show that MYS of MMC decreases with the increase of volume fraction and length of the alumina silicate short fibers in the metal matrix composite, respectively. MYS of quenched Al2O3-SiO2(sf)/Al-Si MMC is the lowest, MYS of the MMC through peak-aging treatment is higher than that through other heat treatment methods. And before the peak-aging, MYS of MMC aging treated gradually increases with the increase of the aging time. Aging treatment after solution treatment is a preferred way that enhances micro and macro-yield strength of Al2O3-SiO2(sf)/Al-Si MMC.展开更多
Microstructures and properties of three Nb micro-alloyed steels were studied through hot rolling experiment. The result indicates that the ferrite grain size （dF ） decreases with increasing Nb content （Nb）, and th...Microstructures and properties of three Nb micro-alloyed steels were studied through hot rolling experiment. The result indicates that the ferrite grain size （dF ） decreases with increasing Nb content （Nb）, and the bainite fraction （fB） increases with increasing Nb content （Nb）. The effect of ferrite grain size （dF） on yield strength （δy） is related to Nb content （Nb）, and the effect of bainite fraction （fB） on yield strength （δy） is unrelated to Nb content （Nb）. Modelling of yield strength （δy） for Nb micro-alloyed steels with high accuracy has been built up with Nb content （Nb） and bainite fraction （fB） taken into account as new parameters, and formulas for ferrite grain size （dF ） and bainite fraction （fB） vs Nb content （Nb） have also been established under the experiment conditions. The research results could provide instructions for industrial productions.展开更多
Dimensional stability properties of hot extruded 2024 Al alloy bar in T4 and T6 aging states and dif- ferent extruded directions were investigated by testing micro-yield strength (MYS), stress relaxation resistance (S...Dimensional stability properties of hot extruded 2024 Al alloy bar in T4 and T6 aging states and dif- ferent extruded directions were investigated by testing micro-yield strength (MYS), stress relaxation resistance (SRR), and dimensional change in thermal cycling and unloading conditions.The results show that micro-plastic deformation resistance in longitudinal(parallel to the axis of the extruded bar) direction is higher than that in transverse(perpendicular to the axis of the extruded bar) direction. Testing in short-term loading condition MYS value corresponding to micro-plastic strain of 1 *10m^(-5)in longitudinal direction is 1.4 times than that in transverse.Compared with the results of MYS and dimensional change in thermal cycling and unloading conditions, the values in T6 state are higher than that in T4 state. Using TEM the microstructures before micro-plastic deformation were observed.The analyses confirm that stability of thermodynamics condition and dislocation results in dimensional stability of the alloy.展开更多
基金Project(19972021)supported by the National Natural Science Foundation of China
文摘Effects of the volume fraction and the size of crystallized alumina silicate short fibers as well as heat treatment processes on micro-yield strength(MYS) of Al2O3-SiO2(sf)/Al-Si metal matrix composite(MMC) that was fabricated by squeezing cast, were investigated by using continuous loading method on an Instron 5569 tester with a special extensometer with an accuracy of 10?7. The results show that MYS of MMC decreases with the increase of volume fraction and length of the alumina silicate short fibers in the metal matrix composite, respectively. MYS of quenched Al2O3-SiO2(sf)/Al-Si MMC is the lowest, MYS of the MMC through peak-aging treatment is higher than that through other heat treatment methods. And before the peak-aging, MYS of MMC aging treated gradually increases with the increase of the aging time. Aging treatment after solution treatment is a preferred way that enhances micro and macro-yield strength of Al2O3-SiO2(sf)/Al-Si MMC.
文摘Microstructures and properties of three Nb micro-alloyed steels were studied through hot rolling experiment. The result indicates that the ferrite grain size （dF ） decreases with increasing Nb content （Nb）, and the bainite fraction （fB） increases with increasing Nb content （Nb）. The effect of ferrite grain size （dF） on yield strength （δy） is related to Nb content （Nb）, and the effect of bainite fraction （fB） on yield strength （δy） is unrelated to Nb content （Nb）. Modelling of yield strength （δy） for Nb micro-alloyed steels with high accuracy has been built up with Nb content （Nb） and bainite fraction （fB） taken into account as new parameters, and formulas for ferrite grain size （dF ） and bainite fraction （fB） vs Nb content （Nb） have also been established under the experiment conditions. The research results could provide instructions for industrial productions.
文摘Dimensional stability properties of hot extruded 2024 Al alloy bar in T4 and T6 aging states and dif- ferent extruded directions were investigated by testing micro-yield strength (MYS), stress relaxation resistance (SRR), and dimensional change in thermal cycling and unloading conditions.The results show that micro-plastic deformation resistance in longitudinal(parallel to the axis of the extruded bar) direction is higher than that in transverse(perpendicular to the axis of the extruded bar) direction. Testing in short-term loading condition MYS value corresponding to micro-plastic strain of 1 *10m^(-5)in longitudinal direction is 1.4 times than that in transverse.Compared with the results of MYS and dimensional change in thermal cycling and unloading conditions, the values in T6 state are higher than that in T4 state. Using TEM the microstructures before micro-plastic deformation were observed.The analyses confirm that stability of thermodynamics condition and dislocation results in dimensional stability of the alloy.
