Effects of microstructural morphology on quasi-static and dynamic deformation behavior of Ti-6Al-4V alloy

The effects of microstructural morphology on quasi-static and dynamic defor mation behavior of a Ti-6Al-4V alloy were investigated in this study. Quasi -static and dynamic torsional tests were conducted using a torsional Kolsky bar for Widmanstatten, equiaxed, and bimodal microstructures, which were p rocessed by different heat treatments, and then, the test data were analyze d in relation to microstructures, tensile properties, and fracture mode. Qu asi-static torsional properties showed a tendency similar to tensile proper ties and ductile fracture occurred in all three microstructures, Under dyna mic torsional loading, maximum shear stress of the three microstructures wa s higher and fracture shear strain was lower than those under quasi-static loading, but the overall tendency was similar. In the Widmanstatten and equ iaxed microstructures, adiabatic shear bands were found in the deformed reg ion of the fractured specimens. The possibility of the adiabatic shear band formation under dynamic loading was quantitatively analyzed, depending on how plastic deformation energy was distributed to either void initiation or adiabatic shear banding. It was found to be most likely in the equiaxed mi crostructure, whereas it was least likely in the bimodal microstructure.