Influence of adiabatic shear bands intersection on the ballistic impact of Ti-6Al-4V alloys with three microstructures

The intersection of adiabatic shear band (ASB) and its effect on the ballistic performance of the Ti-6Al-4V plates with equiaxed, bimodal, and lamellar microstructures were studied using transmission electron microscopy (TEM). Focused ion beam (FIB) technology was used to accurately prepare TEM samples at specific locations around the ASB intersections. The effect of different microstructures on the number and morphology of subgrains in ASB intersections was investigated.Multiple ASBs and their interactions were observed in the Ti-6Al-4V plates with equiaxed, bimodal, and lamellar microstructures impacted by armor-piercing projectiles. The ASBs mainly expanded along two directions, which were top-to-down and left-to-right. All the ASBs comprised dynamically recrystallized equiaxed grains and some partial dynamically recrystallized strip subgrains. The arrangement directions of these subgrains were different between the top-to-bottom and left-to-right ASBs. The expansion range of the left-to-right ASBs was the largest in the bimodal microstructure and the smallest in the equiaxed microstructure. The existing subgrains in the previously formed ASBs were elongated and fragmented during the intersection process, and decreased with the expansion of later-formed ASBs. Some of the subgrains were sheared again, which probably inhibited the expansion of the later-formed ASBs. The least amount of fragments and the smallest craters were observed in the Ti-6Al-4V plates with the equiaxed microstructure because of the lowest amount of ASB intersections and cracks, as well as the smallest expansion range of sideward ASBs. More and larger fragments and the largest craters were observed in the bimodal and lamellar microstructures because of more intersections, cracks and the largest expansion range of sideward ASBs.