Fine-grained structure and recrystallization at ambient temperature for pure magnesium subjected to large cold plastic deformation

The cold drawing of magnesium wires has constantly been an obstacle in industrial manufacture due to the lack of sufficient independent slip system at ambient temperature and the frequent intermediate annealing gives rise to regrettably low production efficiency. Aiming at the technique challenge, a feasible and effective method of multi-pass cumulative cold drawing with small deformation per pass was utilized in this study and a wire of 0.625 mm in diameter was obtained out of primitive Φ2.0 mm material with the accomplishment of about 2.3 in cumulative strain (90% in area reduction), the efficiency of which was dramatically improved. The microstructure, texture and mechanical properties with the variation of cumulative area reduction were investigated. It can be apparently observed that continuous dynamic recrystallization had occurred during cold drawing. The outcomes are displayed as follows: the transition emerged from low angle grain boundary to high angle grain boundary; the increased fraction of undeformed/recrystallized structure first descended then ascended; the deformed structure initially appeared yet disappeared quickly. All of above owned an almost same critical point at around 23% cumulative area reduction. One of the most remarkable consequences of the deformation was the degeneration of the average grain size steadily from 11.8 to 3.1 µm. 〈10-10〉//DD fiber component was gradually transformed from the primitive {0002}//DD fiber texture and this deformation texture was continuously strengthened. The enhanced mechanical properties achieved uncommonly high strength of 214.5 MPa in yield strength and 256.9 MPa in ultimate tensile strength due to grain refinement arising from continuous dynamic recrystallization and intense fiber texture strengthening introduced during cold drawing.