Giant mechanical energy storage capacity and long-term mechanical cyclability in a fine-grained Heusler-type Co51V33Ga16 shape memory alloy

Shape memory alloys can be exploited for the storage of mechanical energy by utilizing the stress-driven superelasticity. However, the intrinsic hysteresis and non-linear stress-strain response endowed by the first-order martensitic transformation cripple the efficient utilization and controllable release of stored energy. Here, we demonstrate an effective strategy to realize stable linear superelasticity with low hysteresis and giant mechanical energy storage capacity. By utilizing rapid solidification to engineering grain size and crystallographic orientation, a fine-grained Co ₅₁V ₃₃Ga ₁₆ alloy with weakly preferred orientation was synthesized through suction casting. Such microstructure enables large amounts of residual martensite to be trapped by mechanical training, yielding a rate-independent linear superelasticity in a wide temperature range from 290 K to 400 K. Moreover, under a maximum strain of 4.5 %, giant stored energy higher than 20.5 MJ m ⁻³ and small dissipated energy lower than 0.5 MJ m ⁻³ can be retained for more than 200,000 cycles of superelastic deformation, being superior to those in most shape memory alloys reported so far.