Excellent Ductility in the Extruded AZ61 Magnesium Alloy Tube Induced by Electropulsing Treatment during Tension

Bo Jiang,Zhanyi Cao,Xiaohong Yang,Hong Xu,Dongdong Zhang,Yongbing Liu

doi:10.3390/met11050813

Abstract

In this work, we reported the high ductility of an extruded AZ61 magnesium alloy tube achieved by electropulsing current-assisted tension. The elongation of the alloy reached up to about 45%, which is largely superior to the majority of AZ61 wrought Mg alloys. We found that the hardening capacity of the alloy seemed to slightly increase as the electropulsing frequency increased. Furthermore, electropulsing can arouse the serrated flow phenomenon. Here we proposed an equation describing the correlation between the average amplitude and frequency: Aa = C − 6 × 10−3f, where Aa is the average amplitude, f is the frequency, and C is the constant. In addition, introducing electropulsing current pronouncedly reduced the tendency of twinning, but the twinning fraction seemed to fail depending on the electropulsing frequency. Based on microstructure analysis, we concluded that the outstanding ductility of the studied alloy was mainly due to the combined role of the thermal effects from Joule heating, the athermal effects from electron wind, and the magnetic effects from the electropulsing current. The serrated flow phenomenon occurred along stress–strain curves after electropulsing treatment, and the underlying reasons also were uncovered.

Highlights

Magnesium alloys are of low density, high specific rigidity, and high specific strength, having a wide range of applications and development potential in military, automotive, consumer electronics, and other fields
We investigated the underlying reasons of improved ductility in an AZ61 magnesium alloy tube due to a pulse current based on microstructure observation
We investigated microstructure and tensile properties of extruded AZ61 magnesium alloy tubes during tension by electropulsing treatment

Summary

Introduction

Magnesium alloys are of low density, high specific rigidity, and high specific strength, having a wide range of applications and development potential in military, automotive, consumer electronics, and other fields. The electroplasticity is of increasing interest because the energy consumption by pulsed current is usually less than that necessary to heat the material to a temperature that provides comparable ductility [5]. The thermal effect of pulsed current from Joule heating was believed to generate thermal softening, resulting in the improvement of ductility [6]. Electroplasticity is usually demonstrated by dramatic increases in elongation during deformation under electric current without a significant elevation in temperature due to Joule heating. Various works have shown that the thermal effect alone is insufficient to explain this phenomenon, and other hypotheses of athermal effects of pulsed currents have been proposed, such as electron wind [9], magnetic effect [10], and pinch effect [11].

Methods

Results

Discussion

Conclusion