Rate and temperature dependent deformation behavior of as-cast WE43 magnesium-rare earth alloy manufactured by direct-chill casting

Abstract

In this work, we study the deformation behavior of a direct chill cast WE43 Mg alloy. This material initially has equiaxed grains approximately 40µm in diameter and a random texture. The room temperature, quasi-static response exhibits little plastic anisotropy when evaluated parallel to and normal to the solidification direction and no initial yield tension-compression asymmetry. The deformation at room temperature is accompanied by significant basal texture development and formation of three types of deformation twins: {101̅2}〈1̅011〉, {101̅1}〈1012̅〉, and {112̅1}〈1̅1̅26〉 as well as double twins {101̅1}〈1012̅〉-{101̅2}〈1̅011〉, although each in small amounts < 10% up to failure. We find that in the elevated 250°C ± 20°C regime, the material exhibits a negative strain rate sensitivity, with a decreasing flow stress as the strain rate increases. In most of the high-temperature, 250°C to 350°C, and high-strain-rate, 0.01/s to 10/s, tests, the material failed at moderate compression strains, 0.35–0.45. Subsequent fracture analyses find that the material fractures transgranularly by a typical shear fracture, often with the presence of additional arrested cracks. At elevated temperatures and under strain rates sufficiently low (i.e., 275°C and 0.01/s, 300°C and 0.1/s, 350°C and 1/s, 375°C and 10/s) or at a temperature of 400°C deformation conditions, the material exhibited pseudo-super plastic behavior, experiencing relatively high deformation strains (> 1.0 true strain) without fracturing.