A Ti-Zr-Hf-Ni-Nb high-entropy shape memory alloy with an exceptional strength-ductility synergy for high-temperature application

A novel Ti35.16Zr5.86Hf5.86Ni46.87Nb6.25 (at. %) high-entropy shape memory alloy (HESMA) is developed for applications in high-stress, high-temperature environments. This alloy consists of B19’ martensitic laths with minor β-Nb and Ti2Ni particles along grain boundaries. It demonstrates an exceptional strength-ductility synergy, a relatively-high martensitic transformation start temperature (Ms = 392 K), and outstanding shape memory property with maximum recoverable strain (ϵmre = 1.94%) under 550 MPa. This combination of characteristics successfully overcomes the traditional trade-off among Ms, strength-ductility, and shape memory effect. Moreover, the thermal-induced transformation behavior is systematically investigated. This work establishes a paradigm for developing high-performance high-temperature HESMAs.