Microstructure evolution in adiabatic shear band in fine-grain-sized Ti–3Al–5Mo–4.5V alloy

Dynamic testing of Ti–3Al–5Mo–4.5V (TC16) alloy was carried out in a hat-shaped specimen by a split Hopkinson pressure bar (SHPB) at ambient temperature. The microstructure and phase transformation in adiabatic shear band (ASB) produced in TC16 alloy were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). ASB in TC16 alloy is a “white” band of width about 13 μm. The elongated cell structures of width about 0.2–0.5 μm with thick dislocation exist in the boundary of the shear band. Results suggest that the fine equiaxed grains with α-phase and α″-phase coexist in the shear band. The “white” band is a transformation band. Calculation indicates that the maximum temperature within ASB is about 1069 K. The phase transformation and the microstructure evolution within ASB in TC16 alloy are explained.