Dynamic deformation behavior and ballistic impact properties of Ti-6Al-4V alloy having equiaxed and bimodal microstructures

Effects of microstructural morphology on dynamic deformation behavior and ballistic impact properties of Ti-6Al-4V alloy plates were investigated in this study. Dynamic torsional and ballistic impact tests were conducted on equiaxed and bimodal microstructures, which were processed by different heat treatments, and then the test data were analyzed in relation to microstructures and tensile properties. According to the dynamic torsional test data, maximum shear stress and fracture shear strain of the bimodal microstructure were higher than those of the equiaxed microstructure, and the possibility of the adiabatic shear band formation was more likely in the equiaxed microstructure than in the bimodal microstructure. In the ballistically impacted region of the equiaxed microstructure, a number of adiabatic shear bands and cracks were observed to be formed along plastic flow lines, and delamination occurred because of cracking along the flow lines or shear bands. In the case of the bimodal microstructure, shear bands were found in limited areas near the penetrated surface without occurring delamination, and their number was smaller than that of the equiaxed microstructure. Thus, ballistic performance of the bimodal microstructure was better than that of the equiaxed microstructure, which was consistent with the dynamic torsional test results.