Damage mechanisms of a metastable β-titanium alloy with bimodal microstructure revealed by void growth models using synchrotron X-ray microtomography

In order to investigate the damage tolerance of a metastable Ti-5Al-3V-3Mo-2Cr-2Zr-1Nb-1Fe (Ti5321) alloy with bimodal microstructure using void growth quantification and micromechanical modeling, in situ tensile testing was performed during X-ray microtomography experiments. Compared with investigations of surface voids by traditional two-dimensional (2D) methods involving post-mortem characterization, three-dimensional (3D) information on void evolution inside optically opaque samples obtained through X-ray microtomography is essential. The Rice and Tracey model and Huang model were applied to predict void growth and show good agreement with experimental data using calibration of the damage parameter α. The void growth kinetics of Ti5321 with bimodal microstructure was analyzed by comparing the α value with that of Ti64 for different microstructure morphologies. The damage mechanism of ductile fracture of Ti5321 with bimodal microstructure is discussed. It was found that the size of the voids apparently increases with the triaxiality of stress. Post-mortem scanning electron microscopy (SEM) was also used to demonstrate this damage mechanism of ductile fracture of Ti5321.

Graphical abstract