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

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.

An Enhanced Understanding of the Powder Bed Fusion–Laser Beam Processing of Mg-Y3.9wt%-Nd3wt%-Zr0.5wt% (WE43) Alloy through Thermodynamic Modeling and Experimental Characterization

“…There is an accumulation of Mg-RE secondary phases along the melt pool boundaries which to some extent coincides with the grain boundaries. However, in cast material, precipitates are to a large extent found along the grain boundaries [12]. As has been observed in other studies on WE43 processed by PBF, the secondary phases are to a large extent found inside the grains.…”

“…Mg alloys generally have poor corrosion resistance due to the low electrochemical stability of the Mg matrix, the strong cathodic activity of the secondary phases present, refs. [10][11][12], and the limited stability of the MgO surface film in aqueous solutions [13][14][15]. The solid solution of yttrium (Y) decreases the electrochemical activity of the Mg matrix and stabilizes the surface through the formation of Y 2 O 3 [16][17][18].…”

Microstructure, Mechanical, Corrosion, and Ignition Properties of WE43 Alloy Prepared by Different Processes

“…Although not evident in the XRD spectrum, small cubic-shaped particles in microstructure were analyzed as YH x hydrides according to EDS results. A similar observation was confirmed in various publications [25,33,34]. The solid solution (S1) contained 2.1 ± 0.3 wt % Y, 1.0 ± 0.1 wt % Nd, 0.6 ± 0.2 wt % Zr, 0.2 ± 0.1 wt % Dy, 0.2 ± 0.1 wt % Gd.…”

“…Only thermally stable phases remained in the microstructure (Figure 3B,E). Those phases were Mg 24 Y 5 and probably Mg 12 Nd, and YH x hydrides which were not detected by XRD due to their low content and isomorphic behavior (Figure 4) but assigned to according to the EDS analysis [34]. The solid solution was therefore rich in alloying elements (Table 3).…”

Rare Earth Based Magnesium Alloys—A Review on WE Series

“…The microstructures of both WE43 and WE54 have been reported to be rather similar. These alloys consist of the α-Mg matrix, usually with Y and Nd present in solid solution in the matrix, and several types of precipitates distributed along grain boundaries and in the grain interiors Soltan et al, 2019;Kang et al, 2020). Figure 1 shows a typical microstructure of as-cast WE43.…”