Crystallographic anisotropy of the superelastic and mechanical properties of the Ti-20Zr-3Mo-3Sn alloy evidenced by nanoindentation at the grain scale

Abstract : Nanoindentation was combined with electron backscatter diffraction (EBSD) to investigate the crystallographic anisotropy of indentation responses of individual grains in the superelastic Ti2033 alloy. The high statistic of measurements from grains oriented over a large range of crystallographic directions facilitated a fundamental study covering the entire stereographic triangle of the beta phase. For a highlighted visual effect, results were presented as inverse pole figure distribution maps of depth recovery, work recovery, indentation modulus and hardness. Results showed that the pronounced anisotropy behaviors of indentation modulus, depth and work recovery ratios resulted from the anisotropy in Young's modulus and in compressive lattice distortion between the bcc structure of beta phase and the orthorhombic structure of the stress-induced alpha" martensite phase, respectively. However, orientation dependence was gone when plasticity occurred. The orientation-independency in indentation hardness was due to the various slip systems that might be activated within bcc crystals.