The roles of stress state and pre-straining on Swift effect for an extruded AZ31 Mg alloy

The Swift effect of Mg alloy is sensitive to initial texture. However, dislocation slip is the main deformation mechanism during torsion of Mg alloy. The underlying relation of Swift effect and dislocation slip is still not clarified. The effect of stress state and pre-straining on Swift effect was studied experimentally during free-end torsion for an extruded AZ31 alloy. The free-end torsion was performed with axial tension and compression stress which is lower than yield stress. It is found that the transition of axial deformation from contraction to elongation occurs when the axial stress changes from negative to positive. The pre-dislocations introduced by pre-tension promote axial shortening during torsion. While the pre-twins introduced by pre-compression are inhibition of axial shortening. The change of axial deformation is attributed to competition between twinning and prismatic slip. The axial shortening of extruded Mg alloy is generated by tensile twinning leading to c -axis strain. In contrast, the axial elongation can be generated by the activation of prismatic slip. The magnitude of axial strain generated by twinning is larger than that by prismatic slip. Moreover, the occurrence of detwinning results in axial elongation at low shear strain. & COPY; 2021 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University

Automated summary

The Swift effect of Mg alloy is influenced by initial texture, and dislocation slip is the main deformation mechanism during torsion. The relationship between Swift effect and dislocation slip is still unclear. Experimental study on the effect of stress state and pre-straining during free-end torsion was conducted on an AZ31 alloy. It was found that the axial deformation changes from contraction to elongation when the axial stress changes from negative to positive. Pre-dislocations from pre-tension promote axial shortening, while pre-twins from pre-compression inhibit axial shortening. The change in axial deformation is attributed to the competition between twinning and prismatic slip.