Microstructural features and functional properties of NiCuTiZrAl high entropy shape memory alloys

In the present study, the Ni 25 Cu 25 Ti 35-X Zr 15 Al X (X = 5, 7.5, 10, 12.5) high-entropy shape memory alloys (HESMAs) with the lower costs were designed and optimized. The results revealed that the pronounced segregation behavior existed in the as-casted NiCuTiZrAl high-entropy shape memory alloys, which resulted in the generation of dendrite-interdendrite structure. Among, the dendrite region was mainly comprised of B2 TiNi type matrix phase, while the NiAl-rich phase with BCC structure and a AlCu 2 Zr phase with FCC structure can be observed in interdendrite region. With Al content increasing, the volume fraction of B2 phase increased firstly and then decreased. In proportion, the mechanical properties of the as-casted Ni 25 Cu 25 Ti 32 Zr 15 Al X HESMAs firstly increased and then decreased with the increase of Al content. In contrast, the as-casted Ni 25 Cu 25 Ti 25 Zr 15 Al 10 HESMAs exhibited a superior combination of higher compressive strength and microhardness as well as the excellent superelasticity with the recoverable strain of 5 % and the excellent cyclic stability, which can be the solution strengthening of multiple principle elements and precipitation strengthening of higher density of nano-scale precipitates.