Study on distribution of long-period stacking ordered phase in Mg–Gd–Y–Zn–Zr alloy using friction stir processing

Friction stir processing (FSP) was applied to Mg–Gd–Y–Zn–Zr casting at various process parameters to study the influence of heat and deformation conditions on the distribution of long-period stacking ordered (LPSO) phase. FSP resulted in grain refinement, fundamental elimination of β-Mg3RE eutectics and formation of LPSO phase. Various distributions of LPSO phase, including no LPSO phase, LPSO phase both at the grain boundaries and within the grains and LPSO phase only within the grains could be obtained after FSP at the investigated process parameters. Based on the microstructure analyses and formation mechanism of LPSO phase, this varied distribution is believed to be caused by the combined influence of temperature, plastic strain and cooling rate. Detailed influence of these factors on the distribution of LPSO phase was discussed.