Abstract
The microstructure evolution of a Mg–Gd–Y alloy was studied using uniaxial tension combined with an electron backscatter diffraction technique. The results show that large amounts of slip transfer phenomena can be observed around the grain–boundary area after tension, and the activation of these slips depends largely on the misorientation of grain boundaries. The Mg–Gd–Y alloy shows almost randomized grain–boundary misorientation, but transferred slip traces were preferred at boundaries with misorientation around the [0001] axis between 0–30°. Theoretically, materials with a higher fraction of slip transfer at the grain–boundary area would improve the ductility. Upon comparing the two groups of magnesium alloy with different grain–boundary misorientation distributions, the one with more grain boundaries favored for slip transfer achieved higher elongation during a tension test. Therefore, in addition to weakening the texture, adjusting the misorientation of the grain boundaries appears to be a new method to improve the ductility of magnesium alloys.
Highlights
Alloy shows almost randomized grain–boundary misorientation, but transferred slip traces were preferred at boundaries with misorientation around the [0001] axis between 0–30◦
The application of wrought magnesium alloys is restricted by its poor formability at room temperature, caused by the strong basal texture developed during processing and the lack of available deformation modes [3]
Jonas [9] and Barnett [10] suggested that the strain accommodation required by the neighboring grains might affect the variant selection of twins in magnesium alloys
Summary
The alloy used in this paper, with a nominal composition of Mg–8.0Gd–3.0Y–0.5Zr (wt%) (GW83), was prepared by semi–continuous casting. The observation planes of tension samples were polished before the tensile test using a sequence of ethanol–based diamond suspensions of 6, 3, and 1 μm, respectively. This was followed by fine–polishing using colloidal silica suspension (OPS), and a final 2–4 s etching using a solution of 5% HNO3 , 15% acetic acid, 20% H2 O and 60% ethanol before SEM and EBSD observations. Misorientation distribution function (MDF) [14,15], calculated using the symmetrized hyperspherical harmonic formulation, was applied to quantify misorientation statistics for the magnesium samples in this paper. 36 misorientation relationships were calculated (same misorientation angle, but different axis). The MDF was normalized to the random distribution of misorientation and are plotted in this paper
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