Phase stability dependence of deformation mode correlated mechanical properties and elastic properties in Ti-Nb gum metal

The evolution of microstructure and deformation modes in metastable Ti-23Nb-0.7Ta-2Zr-0.80 (at%) alloys with accumulated strain to 0.15 are investigated, where different solution treatments were applied to control both elemental distributions and the bcc beta-phase stability. Recent studies suggest that the occurrence of specific deformation mechanism of the beta-phase is strongly linked with its chemical stability. In the present study, the Bo-Md phase stability diagram was used to evaluate the beta-phase stability and to discuss the deformation modes as function of solution treatment conditions, resulting in different deformed microstructures. Analysis of the deformed microstructure using electron backscatter diffraction and X-ray diffraction revealed that deformation bands formed at the initial stage of strain were composed of not only mechanically induced {332} < 112 > beta and {112} < 111 > beta twinning, but also stress-induced martensite alpha phase. It was observed that the number of deformation bands decreases with increasing homogeneity in the alloy, which is strongly dependent on the phase constitution, and directly impacts its final properties including hardness and elastic modulus. Based on the experimentally observed results, the beta-phase stability dependence of deformation features can explain the possibility of manipulating the mechanical properties without the evident elastic properties variation in Ti-Nb Gum Metal.