Quasi-static and dynamic deformation behavior of Ti–6Al–4V alloy containing fine α2-Ti3Al precipitates

Widmanstätten and equiaxed microstructures containing very fine α2 particles were obtained by aging a Ti–6Al–4V alloy, and their quasi-static and dynamic deformation behavior was investigated in comparison to that of unaged microstructures. Quasi-static and dynamic torsional tests were conducted on them using a torsional Kolsky bar, and torsionally deformed areas beneath fracture surfaces were observed to investigate various microstructural factors determining the deformation behavior and effects of α2 precipitation. The dynamic torsional test results indicated that maximum shear stress and fracture shear strain of the aged Widmanstätten and equiaxed microstructures were higher than those of the unaged microstructures. The number of voids initiated in the aged Widmanstätten and equiaxed microstructures was five times greater than those in unaged microstructures because of the α2 precipitation. This indicated that the aging treatment had a homogenizing effect, i.e., less likelihood of developing a region of concentrated strain that preceded the adiabatic shear band formation, thereby reducing the possibility of the adiabatic shear band formation. Fine α2 precipitation by aging was effective in the improvement of quasi-static and dynamic torsional properties and in the reduction of the adiabatic shear banding, which provided a new idea to improve ballistic performance of Ti alloy armor plates.