Clarifying the deformation modes and strengthening mechanisms of Mg-11Gd-5Y-2Zn-0.7Zr with outstanding high-temperature mechanical properties.

The mechanical properties of as-extruded Mg-11Gd-5Y-2Zn-0.7Zr (GWZ1152) alloy were systematically studied with respect to their microstructures at room and high temperatures. It exhibited excellent ultimate tensile strength (UTS) of 365 MPa at room temperature (RT), while it maintained relatively high UTS as the temperatures increased to 250 °C (342 MPa), 300 °C (337 MPa) and 350 °C (278 MPa) with a strain rate of 1.85 × 10−3 s−1. The microstructural characterizations revealed that such outstanding heat resistance is mainly attributed to (i) the fine dynamic recrystallized (DRXed) grains and strongly textured un-DRXed grains, (ii) the block-shaped LPSO phase and the nano-scale β precipitates, (iii) the nano-spaced basal LPSO/SFs. Compared to other heat-resistant Mg alloys, our intrinsic chemistry properties contribute to the superior high-temperature mechanical properties of GWZ1152 alloy. For the deformation modes at RT, the dislocations were mainly generated and accumulated on the block-shaped LPSO, followed by cracking and propagation. At 250 °C and 300 °C, non-basal slip inside the coarse un-DRXed was generated, the cracks and fractures were initiated along the slip trace. The main deformation mechanism of GWZ1152 alloy at 350 °C was grain boundary sliding, cracks usually occurred at grain boundaries. • Mg-11Gd-5Y-2Zn-0.7Zr alloy exhibited excellent ultimate tensile strength at 25 °C, 250 °C, 300 °C and 350 °C. • The deformation modes of the alloys were systematically studied at different temperatures. • The relationship between the deformation modes and mechanical properties were discussed at room and high temperatures. [ABSTRACT FROM AUTHOR]