Unveiling the mechanical response and deformation mechanism of extruded Mg-2.5Nd-0.5Zn-0.5Zr alloy sheet under high-temperature tensile

Abstract

The microstructure evolution, mechanical response and deformation mechanism of the extruded Mg-2.5Nd-0.5Zn-0.5Zr alloy sheet by high-temperature (423–573 K) tensile were investigated. The results showed that the alloy exhibited excellent high-temperature mechanical properties at 523 K (extrusion direction (ED): ultimate tensile strength (UTS)~191.5 MPa, yield strength (YS)~154.5 MPa, elongation (EL)~30.1%; transverse direction (TD): UTS~190.5 MPa, YS~148.2 MPa, EL~35.2%). The YS of ED and TD of the alloy decreased linearly, and the anisotropy of the alloy decreased gradually (from 0.9261 to 1.009) with the increase of tensile temperature, which was beneficial to the subsequent processing of the alloy. Moreover, the decreased anisotropy was the result of grain size, second phase particles size and texture state. The microstructure showed obvious deformed structures at 423 K and it was gradually replaced by dynamic recrystallization with an average grain size of 3.3–4.2 µm and the texture strength weakened greatly (maximum pole density value reduced from 15.8 to 4.0) as the temperature increased to 573 K. Meanwhile, both the deformation models and the contributions of different deformation mechanisms at different tensile temperatures were roughly estimated. It was found that basal slip was always the main deformation mechanism at different tensile temperatures, but its contribution to deformation decreased with increased tensile temperatures (from 93.0% to 66.6%). With the increase of tensile temperature, the degree of prismatic slip (from 4.1% to 23.2%) and pyramidal slip (from 2.9% to 10.2%) in deformation gradually increased.