Influence of Zn Addition on Microstructures and Martensitic Transformation in CuZr-based Alloys

Compositional dependences on microstructures and martensitic transformation behaviors in (Cu0.5 Zr0.5)100–x Znx (x = 1.5, 2.5, 4, 5, 7.0, 10.0, and 14.0 at. %) alloys were investigated. It was found that CuZr martensites were present in the present alloys. With increasing Zn content, the volume fractions of CuZr martensitic crystals and B2 CuZr phase gradually decrease and increase, respectively. With the addition of high Zn contents (i.e., 7.0, 10.0, and 14.0 at. %), the matrix proves to be eutectic. Thermal analysis results show that the initial martensitic transformation temperature (Ms) decreases from (412±5) K to (329±5) K as the Zn content increases from 1.5 at. % to 14.0 at, %. The values of Ms of Cu-Zr-Zn shape memory alloys are inversely proportional to the number and concentrations of valence electrons (i.e., ev/a and cv), respectively, implying that the martensitic transformation in CuZr-Zn alloys could be of electronic nature.