Improving ductility and functional properties of (TiZrHf)50Ni25Co10Cu15 high entropy shape memory by melt-spinning technique

Abstract

This study utilized the melt-spinning technique to suppress the formation of coarse Ti₂Ni-type second phases. The amorphous as-spun ribbon was treated at 1000 °C for 3 min and fully crystallized with B2 matrix and nano-scale Ti₂Ni-type second phase. The Ti₂Ni-type second phase was evenly dispersed in the B2 matrix, with its diameter limited to below 325 nm. By reducing the size of the Ti₂Ni-type second phase from micro-scale to nano-scale, the crystallized ribbon showed excellent ductility under tensile deformation. The ribbon exhibited superelasticity at a wide temperature range between 20 and 200 °C with a maximum recoverable strain of 4 %. Furthermore, the ribbon delivered a promising shape memory effect with a recoverable strain of 5.3 %. The melt-spinning technique conquered the brittleness problem of TiNi-based high entropy shape memory alloys, enabling TiNi-based high entropy shape memory alloys to be designed and applied for versatile applications.