Precise measurement of strain accommodation in a Mg-Gd-Y-Zn alloy using cross-correlation-based high resolution EBSD

Abstract

Mg-RE alloys show improved ductility compared to other classical magnesium alloys at room temperature. The present study focused on the strain accommodation mechanism in a wrought Mg-5.4Gd-1.8Y-1.5Zn alloy at the microstructural scale. For this purpose, a tensile specimen was uniaxially strained in-situ in tension up to 6%, and the lattice rotation tensor and geometrically necessary dislocation (GND) density were measured using cross-correlation-based high angular resolution electron backscatter diffraction (HR-EBSD) technique. The strain incompatibility within the Mg-Gd-Y-Zn alloy was accommodated by basal slip together with pyramidal dislocation. The GND measurements via HR-EBSD showed a high occurrence of pyramidal <c + a> dislocation even in well-aligned grains. The orientation dependence of basal <a> and pyramidal <c + a> dislocation was also investigated. It was found that the soft oriented grains had a higher basal <a> density, whereas the average GND density of <c + a> slip appeared to decrease with the Schmid factor of pyramidal dislocation. In addition, slip transfer process of the basal-basal and basal-pyramidal type was observed with high m' factors in this study.