Effect of Sn on Microstructures and Transformation Temperatures of (TiZrHf)50Ni25Co10Cu14 Multi-Component High Entropy Shape Memory Alloys

Multi-component (TiZrHf)50Ni24.5Co10Cu14.5Sn1, (TiZrHf)50Ni24Co10Cu14Sn2, and (TiZrHf)50Ni23.5Co10Cu13.5Sn3 high entropy shape memory alloys (HESMAs) were prepared in this study, and the microstructures, transformation temperatures (TTs), and superelasticity were investigated through scanning electron microscopy, differential scanning calorimetry, and dynamic mechanical analysis in the tensile mode, respectively. The microstructure of the solution-treated TiZrHfNiCoCuSn HESMA specimens consisted of the matrix, (TiZrHf)2(NiCoCuSn)-type and (TiZrHf)5(NiCoCuSn)3-type second phases. The TTs of the solution-treated specimens increased with the addition of a 1 at.% of Sn content and then decreased with an additional increase in the Sn content. The (TiZrHf)50Ni24Co10Cu14Sn2 HESMAs exhibited clear superelasticity, and their total recovery strain was 2.2%.