Dynamic precipitation in a Mg-Gd-Y-Zr alloy during hot compression

Dynamic precipitation of a Mg-8.3Gd-2.6Y-0.4Zr (wt.%) alloy during hot compression was systematically investigated in the present work. For this purpose, the compression tests were conducted at temperatures ranging from 300 °C to 500 °C and strain rates varying from 0.001 s−1 to 1 s−1. Results revealed that the dynamic precipitation of equilibrium β phase, i.e., Mg5(Gd,Y) phase, was sensitive to the deformation temperature rather than the strain rate. The precipitation took place during compression in the temperature range of 300-400 °C, whereas it did not occur when temperature exceeded 450 °C. The dynamically precipitated β phase showed an irregular shape and did not possess any specific crystallographic orientation relationship with the matrix. The precipitates distributing at the dynamically recrystallized (DRXed) grain boundaries could severely suppress the growth of DRXed grains due to pinning effect, which therefore formed ultra-fine DRXed grains with sizes of ~200-400 nm.