Forging induces changes in the formability and microstructure of extruded Mg96Zn2Y2 alloy with a long-period stacking order phase

We examined the effects of the processing temperature and the grain size on the ductility and flow stress of extruded Mg96Zn2Y2 (atom%) alloy by upsettability testing at various forging temperatures and for various grain sizes of the α-Mg phase. The extruded Mg96Zn2Y2 alloy showed a forging limit as a reduction in height of 65% at forging temperatures of 573-673 K and an initial strain rate of 3.5×10−1 s−1. The formability of LPSO-type Mg alloys can be improved by the production of an α-Mg phase with small grains and a LPSO phase with kink bands with a large-angle tilt. The hard LPSO phase has a bending angle of about 100° at the grain boundaries and has a large deformability. Forging of about 10% is necessary for the formation of kink bands in the LPSO phase, and these kink bands deform continuously with increasing plastic deformation.