Superplasticity and microstructure in Mg–Gd–Y–Zr alloy prepared by extrusion

Superplastic mechanism and microstructure of Mg–Gd–Y–Zr alloy extruded rod with an initial grain size of 10 μm were investigated. For the purposes, tensile tests at various temperatures and strain rates were conducted. The tests revealed that the material showed a maximum elongation of 410% at 450 °C and 2 × 10−4 s−1. The high ductility was attributed to grain boundary sliding accommodated by dislocation motion assisted by lattice diffusion. It is suggested from microstructural analysis results that second phases, cuboidal Mg3Gd and irregular-shaped β, exhibited significant effect of pinning grain boundaries, and that the irregular-shaped β was deformable and the strain was partly transferred from the matrix to β phases.