Promoting hybrid twins structure to reduce yield asymmetry of rolled AZ31 plates by combining side-rolling and torsion

In this work,an as-rolled AZ31 square bar with c-axis//ND(normal direction)texture was used.Side-rolling and reciprocating torsion were performed to treat the bar.Microstructure evolution and tensile-compressive properties were investigated in detail.Initial rolled AZ31 bar exhibits a large yield asymmetry along the rolling direction(RD).Reciprocating torsion can generate extension twins to introduce twin boundaries and twin-texture.The twin structure can reduce yield asymmetry.However,only limited regions in the rolled AZ31 bar can be twinned during torsion.Pre-side-rolling along the transverse direction(TD)can generate two texture components(c-axis//TD texture and c-axis//ND texture)by introducing profuse{10–12}twins.Such dual texture components help increase the regions which are favorable for twinning during torsion.Finally,combining side-rolling and reciprocating torsion generates hybrid{10–12}twins structure on the entire cross-section,resulting in a remarkably low yield asymmetry.The relevant mechanisms were discussed in detail.

Effect of free-end torsion on microstructure and mechanical properties of AZ31 bars with square section

In this study,a rolled AZ31 bar with square section was used.The reciprocating torsion was performed to maintain the shape of the sample.The microstructure evolution of AZ31 bar during torsion and its influence on compressive anisotropy were investigated in detail.Results showed that reciprocating torsion can simultaneously enhance yield strength in three compressive directions,and reduce compressive anisotropy.Reciprocating torsion generated profuse dislocations and{10–12}twin boundaries to harden the micro-hardness and yield strength.Reciprocating torsion can also generate new texture component which is mainly from the orientation of newly generated{10–12}twins.The new twin-structures will be responsible for the reduction in compressive anisotropy.Moreover,uneven deformation features in twisted sample were systematically investigated.