Improvement of microstructure and microhardness of AZ31 Mg alloy sheet by cross-forging-bending repeated deformation with sharply increasing temperature

Abstract

In this study, AZ31 Mg alloy sheets were processed by a severe plastic deformation (SPD) technique called forging-bending repeated deformation (FBRD). The effect on the microstructure and microhardness of AZ31 Mg alloy through FBRD was investigated with increasing temperature treatment and a 90° cross route. The results reveal that the effective strain increases with the number of passes. The flow uniformity is effectively enhanced due to alterations in shear deformation direction. After four passes of deformation, the average grain size is refined by 79.3% compared to the initial specimen. The grain refinement mechanism predominantly originates from the synergistic effects of discontinuous dynamic recrystallization (DDRX), continuous dynamic recrystallization (CDRX), and twinning-induced recrystallization (TDRX). The formation of

\{10\overline{1}2\}

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extension twins (ET) significantly contributes to coarse grain subdivision and plastic deformation coordinated. Furthermore, pyramidal <c+a> slip activation effectively enhances the plasticity of Mg alloys. By post four-pass processing, the alloy exhibits a microhardness of 81.9HV, primarily governed by fine grain strengthening and dislocation strengthening mechanisms.

Keywords

AZ31 Mg alloy sheet / forging-bending repeated deformation / microstructure / microhardness

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