Huicong Chen

Reducing tension–compression yield asymmetry by free end torsion in extruded Mg alloy

Free end torsion was carried out on extruded Mg alloy AZ31. Subsequently, tension or compression was implemented on pretorsion specimens. The microstructures of samples with 100 and 200° of pretorsion reveal that no obvious change has occurred; however, samples with 300 and 400° of pretorsion show that there are extensive twins. Compressive yield stress of pretorsion samples increases with increasing pretorsion angle. However, their tensile yield stress exhibits practically the same value with extruded samples. Consequently, yield asymmetry ratio increases from 0.55 of extruded sample to 0.84 of sample with 400° of pretorsion. Both textures rotated around the radial axis by free end torsion, and different deformation mechanisms of compression and tension deformation result in decrease in yield asymmetry.

Effects of prior compression on ductility and yielding behaviour in extruded magnesium alloy AZ31

Abstract In the present paper, the effects of precompression along extrusion direction (ED) on subsequent compression perpendicular to ED were investigated in an extruded magnesium alloy AZ31. The results showed that the yield stress under compression perpendicular to ED increased if there was precompression along ED. The evolution of deformation mechanism was responsible for increase in yield stress because plastic deformation was dominated by both basal slip and {10–12} twinning under compression perpendicular to ED in samples without prestrain, but basal slip was difficult to be activated and {10–12} twinning dominated deformation in samples with precompression. However, because basal slip had no obvious contribution to plastic deformation, the ductility decreased if there was precompression along ED.

Roles of detwinning in strain hardening and ultimate elongation in extruded Mg–3Al–1Zn alloy

Abstract For extruded magnesium alloy, prior compression along extrusion direction has great influences in the flow stress during subsequent tension. Detwinning plays an important role for these influences. In the present study, the effects of different prestrains on strain hardening behaviour during subsequent tension were examined in an extruded magnesium alloy AZ31. The results showed that the existence of detwinning decreased the tensile yield stress. Samples with different prestrains exhibited different strain hardening behaviour during subsequent tension. The reorientation due to detwinning had a great effect on strain hardening during tension. In addition, the effect of detwinning on ultimate elongation was investigated. The results showed that the sample with higher prestrain always has higher ultimate elongation due to the contribution of detwinning on macroscopic strain.