Spherical shape of γ-Mg17Al12 precipitates in AZ91 magnesium alloy processed by equal-channel angular pressing

The microstructure investigations of the AZ91 alloy after equal-channel angular pressing (ECAP) were presented. Solution annealed billets were processed at a 0.16 mm s−1 pressing rate and temperatures of 623 and 553 K. The average grain size was reduced from 150 μm initially to a final value of 10 μm. The microstructure analyses revealed γ-Mg17Al12 precipitates with a spherical morphology located particularly inside the equiaxal grains of an α-solid solution. Additionally, different shapes of γ precipitates, plate-like or rod-like (typical for heat treatment processes) were not observed. The spherical shape of γ precipitates was obtained due to correlate magnesium matrix alloy deformation during pressing with precipitation process.