On Structural Sensitivity of Young’s Modulus of Ni-Rich Ti-Ni Alloy

Abstract

When developing bone implants, Young’s modulus is one of the primary characteristics of the material that should be considered. This study focuses on regulating the modulus of Ti-50.8 at.% Ni alloy by varying the grain/subgrain size as well as the initial structure using subsequent aging at 430 °C for 10 h. After post-deformation annealing (PDA), the temperature dependence of Young’s modulus exhibits a pronounced V-shaped character with a minimum at the onset temperature of the forward martensitic transformation, Ms, regardless of the structure. The grain/subgrain size of B2-austenite strongly affects the modulus magnitude. This effect is ambiguous for a material with a grain size range of 0.13–3 µm and depends on the test temperature. The effect of aging on the modulus reduction depends on the initial structure; it is most pronounced in an alloy with a relatively coarse grain size of 9 µm and brings a decrease of 3.8 times at a temperature of 37 °C. Aging of the initially recrystallized Ni-rich NiTi alloy makes it possible to obtain a вone-like elastic modulus of E = 12–13 GPa at an operating temperature of 37 °C. An ultrafine-grained substructure exhibits the same Young’s modulus values in the low temperature range from −100 to 25 °C.