Dynamic deformation behavior and ballistic performance of Ti-6Al-4V alloy containing fine alpha_2 (Ti_3Al) precipitates

摘要

Equiaxed and bimodal microstructures containing very fine alpha_2 (Ti_2Al) particles were produced by over-aging of a Ti-6Al-4V alloy, and effects of alpha_2 precipitation on dynamic deformation behavior and ballistic performance were investigated in comparison with unaged microstructures. According to the dynamic torsional test data, maximum shear stress and fracture shear strain were higher in the aged bimodal microstructure than in aged equiaxed microstructure, and the possibility of the adiabatic shear band formation was less likely in the former than in the latter. In the ballistically impacted region of the aged equiaxed microstructure, a number of adiabatic shear bands and cracks were observed to be formed along plastic flow lines. In the case of the aged bimodal microstructure, shear bands were found in limited areas near the perforated surface, and their number was smaller than that of the aged equiaxed microstructure. Thus, the ballistic performance of the aged bimodal microstructure was better than that of the equiaxed microstructure, which was consistent with the dynamic torsional-test results. Also, the ballistic performance of the aged microstructures was slightly increased over the unaged microstructures. This was explained by the improvement of dynamic torsional properties and by the lower possibility of adiabatic shear band formation.