Experiments show that special processing techniques such as asymmetrical rolling （ASR）, equal channel angular pressing （ECAP） and equal channel angular rolling （ECAR） can weaken the basal texture of the magnesiu...Experiments show that special processing techniques such as asymmetrical rolling （ASR）, equal channel angular pressing （ECAP） and equal channel angular rolling （ECAR） can weaken the basal texture of the magnesium alloys and therefore improve their plasticity. However, the deformation mechanisms related are different. In this paper, we determine the deformation mechanisms activated during ASR, ECAP and ECAR by calculation of orientation factors. Analysis shows that during ASR the shear stress σ13 on the rolling plane of the samples obviously weakens the basal slip and tension twinning that all produce basal texture and improve plasticity due to the promotion of tilt basal texture. During ECAP the shear stress σs on the intersecting plane of two channels promotes tension twinning in the basal oriented grains, whereas under ECAR the shear stress σ13 induced by roller friction on the rolling plane produces the shear stress as on the intersection plane of the two channels that also promotes tension twinning. Although the shear strain is lower in ECAR than in ECAP, the channel clearance in ECAR facilitates tension twinning.展开更多
The hot ductility of 6061 aluminum alloy,which was subjected to two different severe plastic deformations（SPD）,was studied at different temperatures and strain rates.The tensile tests were carried out at the tempera...The hot ductility of 6061 aluminum alloy,which was subjected to two different severe plastic deformations（SPD）,was studied at different temperatures and strain rates.The tensile tests were carried out at the temperature range of 300-500 ℃ and at the strain rates of 0.0005-0.01 s^（-1）.The microstructure evolution was characterized using optical microscopy,transmission electron microscopy and X-ray diffraction technique.The influences of the microstructure after SPD,thermomechanical parameters（temperature and strain rate） and specimen size on the hot formability of this alloy were then analyzed.The results show that a decrease in grains/subgrains exhibited significant effect on the hot ductility of SPDed samples.The constitutive equations were then developed to model the hot formability of the studied alloy.The developed model can be represented by Zener-Hollomon parameter in a hyperbolic sinusoidal equation form.Both the changes of elongation to failure and Zener-Hollomon parameter indicate that the hot ductility of the alloy is more sensitive to the temperature rather than to the strain rate.The uniform elongation is independent of the specimen size,but the postnecking elongation increases dramatically as the ratio of l/A^（1/2） decreases.展开更多
基金support from the National Natural Science Foundation of China(Nos50571009 and 50771019)
文摘Experiments show that special processing techniques such as asymmetrical rolling （ASR）, equal channel angular pressing （ECAP） and equal channel angular rolling （ECAR） can weaken the basal texture of the magnesium alloys and therefore improve their plasticity. However, the deformation mechanisms related are different. In this paper, we determine the deformation mechanisms activated during ASR, ECAP and ECAR by calculation of orientation factors. Analysis shows that during ASR the shear stress σ13 on the rolling plane of the samples obviously weakens the basal slip and tension twinning that all produce basal texture and improve plasticity due to the promotion of tilt basal texture. During ECAP the shear stress σs on the intersecting plane of two channels promotes tension twinning in the basal oriented grains, whereas under ECAR the shear stress σ13 induced by roller friction on the rolling plane produces the shear stress as on the intersection plane of the two channels that also promotes tension twinning. Although the shear strain is lower in ECAR than in ECAP, the channel clearance in ECAR facilitates tension twinning.
文摘The hot ductility of 6061 aluminum alloy,which was subjected to two different severe plastic deformations（SPD）,was studied at different temperatures and strain rates.The tensile tests were carried out at the temperature range of 300-500 ℃ and at the strain rates of 0.0005-0.01 s^（-1）.The microstructure evolution was characterized using optical microscopy,transmission electron microscopy and X-ray diffraction technique.The influences of the microstructure after SPD,thermomechanical parameters（temperature and strain rate） and specimen size on the hot formability of this alloy were then analyzed.The results show that a decrease in grains/subgrains exhibited significant effect on the hot ductility of SPDed samples.The constitutive equations were then developed to model the hot formability of the studied alloy.The developed model can be represented by Zener-Hollomon parameter in a hyperbolic sinusoidal equation form.Both the changes of elongation to failure and Zener-Hollomon parameter indicate that the hot ductility of the alloy is more sensitive to the temperature rather than to the strain rate.The uniform elongation is independent of the specimen size,but the postnecking elongation increases dramatically as the ratio of l/A^（1/2） decreases.
