Microstructure and texture evolution during compression-extrusion process for tension/compression symmetrical ZK61 magnesium alloy rod

Tension/compression symmetrical ZK61 magnesium alloy rod with fine grain and weak texture was achieved by compression-extrusion process. The formation mechanism of fine grain and weak texture was analyzed by investigating the microstructure and texture evolution during compression-extrusion process. In compression stage, {10–12} twinning deformation was activated greatly, which brought about significant grain refinement and formation of <0002>∥ED texture. As extrusion process going on, twinning gradually decreased and basal slip dominated the following deformation. Texture oriented into single annular shape by subsequent twinning in early extrusion and the annulation rotated toward ED gradually then merged into fiber texture by basal slip in late extrusion. Besides, texture was weakened by grain boundary slip and non-basal slip. With DRXed grain orientations similar to that of the deformed parent grains, Discontinuous dynamic recrystallization played a dominant role in grain refinement during extrusion stage, but the refinement was relatively minor compared to twining refinement in compression stage. Finally, magnesium alloy with fine grain and weak texture was achieved. The benefit of this microstructure and texture characteristic upon mechanical properties was the great enhancement of compressive yield strength, from the suppression of twinning when compressed. Therefore, tension/compression asymmetry was greatly improved by compression-extrusion process.