The Work Softening Behavior of Pure Mg Wire during Cold Drawing

Abstract

We performed multiple-pass cold drawing for pure Mg wire which showed excellent formability (~138% accumulative true strain) at room temperature. Different from the continuous work hardening occurring during cold drawing of Mg alloy wires, for pure Mg, an initially rapid increase in hardness and strength was followed by significant work softening and finally reached a steady-state level, approximately 40~45 HV. The work softening can be attributed to the dynamic recovery and recrystallization of pure Mg at room temperature. Meanwhile, an abrupt change in texture component also was detected with the transition from work hardening to softening in the strain range of 28~34%. During the whole drawing, the strongest texture component gradually transformed from as-extruded basal to <101¯0> fiber (~28% accumulative true strain), and then rapidly returned to the weak basal texture.

Evolution of Recrystallized Grain and Texture of Cold-Drawn Pure Mg Wire and Their Effect on Mechanical Properties

“…The important values of the tensile test and the CV values of specimens at the incomplete recrystallization stage, complete recrystallization stage and grain growth stage are listed in Table 1. The wires exhibited relatively high yield strength after annealing at 200 • C/5 min, while there was no evident improvement of elongation (1.6%), compared with that of the cold-drawn Mg wires (2.1%), which was reported in our previous work [8]. With the development of recrystallization, there was a continuously declining yield strength in the annealed Mg.…”

“…The billets were first hot extruded at 650 K, reaching an extrusion ratio of~20. The as-extruded thick Mg wires with an initial diameter of 3.0 mm were obtained as described in the paper [8]. In the present paper, the constant strain multi-pass drawing was used, namely, keeping the true stain consistent between adjacent drawing dies.…”

“…However, it is widely recognized that Mg and its alloys, with the hexagonal close-packed crystal structure, exhibit poor ductility and formability at room temperature compared with traditional fcc and bcc metals. With the recent development of research in Mg deformation, thin wires of Mg and its alloys were successfully fabricated by cold-drawing along with the subsequent static recrystallization annealing [8][9][10]. In the whole wire preparation procedure, multi-pass cold drawing and annealing treatment are performed repeatedly and the diameter of the wires gradually decreases.…”

“…Moreover, annealing temperature and time determine the subsequent mechanical properties and deformability of Mg wires. Our previous work [8] systematically studied the microstructures, texture and mechanical properties evolution during cold drawing. The excellent cold drawing formability indicates that pure Mg has broad prospects in the preparation of thin wires.…”

Influence of Thermal Processing on Resoloy Wire Microstructure and Properties

“…[21] However, these processes are challenging for magnesium-based materials due to their hexagonal close-packed (HCP) crystal structure that has limited slip systems at room temperature. [22][23][24][25][26][27] In some cases, alloying can increase room-temperature ductility. Fine wires made from an Mg-aluminum (Al) alloy have been widely reported, [28][29][30][31][32][33][34] but accumulations of Al in the body are a concern as they can cause neurological disorders such as Alzheimer's disease and dementia.…”