In-situ investigation of stress-induced martensitic transformation in Ti–Nb binary alloys with low Young's modulus

Microstructure evolution, mechanical behaviors of cold rolled Ti–Nb alloys with different Nb contents subjected to different heat treatments were investigated. Optical microstructure and phase compositions of Ti–Nb alloys were characterized using optical microscopy and X-ray diffractometre, while mechanical behaviors of Ti–Nb alloys were examined by using tension tests. Stress-induced martensitic transformation in a Ti–30 at%Nb binary alloy was in-situ explored by synchrotron-based high-energy X-ray diffraction (HE-XRD). The results obtained suggested that mechanical behavior of Ti–Nb alloys, especially Young's modulus was directly dependent on chemical compositions and heat treatment process. According to the results of HE-XRD, α″-V1 martensite generated prior to the formation of α″-V2 during loading and a partial reversible transformation from α″-V1 to β phase was detected while α″-V2 tranformed to β completely during unloading.