Michimasa Miyanaga

Superplasticity in a Chip-Consolidated Mg 97 Zn 1 Y 2 Alloy with LPSO Phase

Novel Mg97Zn1Y2 alloy of equiaxed fine grains with long-period stacking ordered (LPSO) phase was prepared by consolidation of chips machined from a twin-roll-cast alloy. The chip-consolidated Mg97Zn1Y2 alloy exhibited superplasticity at a wide initial strain-rate ranging from 1 × 10−3 to 3 × 10−1 s−1 at temperatures of 623 and 673 K. The maximum elongation was approximately 560% at 3 × 10−2 s−1 at 673 K. The strain rate sensitivity index (m-values) was shown to be greater than 0.3 in this study; this value seems to be large enough to ensure uniform elongation during superplastic deformation. SEM/EBSD measurements revealed that the chip-consolidated Mg97Zn1Y2 alloy was composed of mixed equiaxed fine-grains of α-Mg and LPSO phases of a mean size of ~1 μm. The grain boundary sliding in the equiaxed fine-grains appears to account for most of the mechanism of superplastic deformation in this alloy.