Comparative Study of Hot Deformation Behavior and Microstructure Evolution of As-Cast and Extruded WE43 Magnesium Alloy

Yuehua Kang,Chunlei Gan,Jing Zhang,Zhenghua Huang,Nan Zhou,Hu Zhao,Kaihong Zheng,Shuncheng Wang,J.C Huang,Fusheng Pan

doi:10.3390/met10040429

Abstract

Under compressive testing at 400 °C and a strain rate range of 0.05–5 s−1, the hot deformation behavior and microstructure evolution of an as-cast (AC), as-extruded (with a bimodal grain structure (named as Ex-1) or a relatively uniform fine grain structure (Ex-2)) WE43 alloy have been investigated and compared. The results indicate that the AC sample exhibits the highest peak stress, while the Ex-2 sample has the lowest value. Within the AC material, fine grains were firstly formed along the pancake-like deformed grains (as a necklace structure). The necklace structure was also formed within the Ex-1 and Ex-2 materials at high strain rates of 0.5 and 5 s−1. However, a lamellar structure that the coarse elongated grains divided by parallel boundaries was formed within the Ex-1 material. A relatively more homogeneous fine grain structure is achieved after a true strain of 1.0 within the Ex-2 material at a low strain rate of 0.05 s−1. In addition, a discontinuous dynamic recrystallization mechanism by grain boundary bulging is found to occur. After a true strain of 1.2, a (0001) fiber texture, a typical rare earth (RE) texture, and a relatively random texture are formed within the AC, Ex-1, and Ex-2 WE43 alloy material, respectively.

Highlights

WE43 magnesium alloy offers an excellent performance of a good casting ability, high strength-to-weight ratio, creep resistance, ignition resistance and superior damping characteristics, which has been widely used in the automotive and aircraft industries [1,2,3,4]
The initial microstructures of the WE43 alloy in as-cast (AC), as-extruded Ex-1 and Ex-2 conditions are shown in Figures 1–3, respectively
The as-cast (AC) microstructure has an equiaxed grain structure and the average grain diameter is 63 ± 4.8 μm (Figure 1a). It mainly consists of α-Mg matrix and an eutectic phase, which is distributed around the grain boundaries (Figure 1a–b)

Summary

Introduction

WE43 magnesium alloy offers an excellent performance of a good casting ability, high strength-to-weight ratio, creep resistance, ignition resistance and superior damping characteristics, which has been widely used in the automotive and aircraft industries [1,2,3,4]. In order to identify the processing conditions (namely temperature-strain rate window) for hot working, the processing-map (PM) technique has been widely used [17]. It helps in avoiding the regimes of flow instabilities (e.g., adiabatic shear bands or flow localization), which could lead to a material fracture. It is indicated that a homogenization treatment of as-cast AZ31 alloy or a hot extrusion of as-cast TX31 alloy is beneficial in improving their hot workability [18,19]

Methods

Results

Conclusion