Achieving high-efficiency and stable refrigeration performance through composition modulation inducing non-twinned martensite

The development of high-efficiency, eco-friendly, and compact refrigeration systems requires materials that achieve the ideal elastocaloric effect with minimal driving forces. However, existing shape memory alloys for refrigeration have difficulties in overcoming the trade-off between strain-dissipation work and driving force-COPmat (coefficient of performance). Here, we report a Cu-18Zn-8Al-0.3V-0.3Si single-crystal alloy with a recoverable strain of 13% and a low stress hysteresis of 8 MPa under a minimal driving force of 251.1 MPa. Moreover, the alloy exhibits a high COPmat value of 17.4, with a stability over 800 cycles. The high performance is attributed to the unique microstructure of ordered domains and distortion regions induced by composition modulation, which enables simultaneous achievement of low driving force and energy dissipation during phase transformation. Additionally, the formation of non-twinned martensite contributes to maintaining long-term performance stability. This microstructure regulation strategy synergistically optimizes energy efficiency and durability, offering an innovative solution for new-generation refrigeration systems.