Wide-temperature-range superelasticity in a lightweight Mg-Sc-Gd shape memory alloy

Recently, Mg-based shape memory alloys (SMAs) have emerged as the most promising candidate for developing lightweight SMAs. However, challenges such as limited temperature window for superelasticity (SE) persist, prompting the investigation of new lightweight SMAs suitable for application scenarios with significant temperature fluctuations. In this work, a novel Mg-17.8Sc-1.3Gd ternary alloy exhibiting heterogeneous grains from 40 to 710 μm with random texture were prepared by deformation and cyclic heat treatment (CHT). The polycrystalline alloy showed the maximum superelastic strain ( ε _SE) of 2.6 % obtained at 153 K. Besides, the alloy possessed narrow stress hysteresis ( σ _hys) of approximately 80 MPa at 153 K. It is worth noting that the SE over a wide temperature range from 153 K to 323 K coupled with a small superelastic stress variation of 0.34 MPa K⁻¹ was achieved in the Mg-17.8Sc-1.3Gd alloy. Furthermore, the Mg-17.8Sc-1.3Gd alloy shows excellent cyclic stability of SE, with a stable recoverable strain ε _R of approximately 3.8 % over 30 loading-unloading cycles at 253 K. Also, a ε _R of approximately 3.1 % was retained even after 30 cycles at a relatively high temperature of 323 K. Such excellent wide-temperature-range-SE in Mg-17.8Sc-1.3Gd alloy was attributed to the solid-solution strengthening and fine-grained strengthening effects induced by Gd doping. This work may guide further optimization of lightweight Mg-based SMAs with high-performance SE.