Effect of heat treatment on dynamic recrystallization behaviors and mechanical properties of Mg-2.7Nd-0.5Zn-0.8Zr alloy

The fine-grained structure development and the resultant mechanical properties during/after hot deformation were investigated in a Mg-2.7Nd-0.5Zn-0.8Zr alloy pretreated in solution and subsequently full aging. The true stress-true strain flow curves show a two-step work hardening during hot compression due to the interactions between dislocations and Mg-Nd precipitates as well as Zn-Zr intermetallics. In as-aging (AA) sample containing statically precipitated particles (SPPs), deformation bands (DBs) are easily developed at low strains and then ultrafine grains (UFGs) are evolved at along the boundaries of DBs and original grains at medium strains and rapidly approaches to a full development of final stable UFGs as the strain goes higher. In as-solution (AS) sample, by contrast, equiaxial UFGs are partially developed even in high strain and the grain sizes are smaller attributed to dynamic precipitated particles (DPPs). Tensile tests were carried out at ambient temperature for both types of sample, the results show that the tensile elongation to fracture of the hot deformed AA sample is higher than that of the AS one, because the former has a higher volume fraction and a weaker texture of UFGs developed. Besides, the AA sample contains a higher 5% proof strength compared with the AS one at low deformation temperature, however, such trend is reversed at high temperature, which may be resulted from the effect of SPPs and DPPs, respectively.