Elastic constants of Ti50Ni30Cu20 alloy prior to martensitic transformation

Elastic constants of Ti50Ni30Cu20 alloy prior to the martensitic transforma tion B2 --> B19 was measured for the first time by using the rectangular pa rallelepiped resonance method. The softening in both shear modulus c' and c (44) was found with approaching transformation temperature. As a result of soft c(44), the anisotropy factor shows a low value of 2.8 in the vicinity of the transformation temperature. c(11), c(12), and bulk modulus were foun d to show little temperature dependence in the vicinity of the transformati on temperature. Compared with the binary Ti50Ni50 alloy, Ti50Ni30Cu20 alloy exhibits a 40% higher and increasing anisotropy with approaching transform ation temperature. Based on the experimental results, we explained why Ti50 Ni30Cu20 transforms into B19 martensite, while Ti50Ni50 transforms into a s trange monoclinic B19' martensite.