High strain rate deformation behavior, texture and microstructural evolution, characterization of adiabatic shear bands, and constitutive models in electron beam melted Ti-6Al-4V under dynamic compression loadings

Abstract

The results of an investigation on the influence of strain rate on the microstructural and texture evolution, adiabatic shear band characterization, and deformation mechanism of electron beam melted Ti-6Al-4V vertically built cylindrical rods are presented and discussed in this paper. Typical initial microstructure includes a mixture of α (aluminum-rich) and β phases (vanadium-rich) and grain boundary α along with the columnar prior β-grain boundaries. High strain rate compressive loadings were applied using a Split-Hopkinson pressure bar at the strain rates of 700 s−1 and 1650 s−1 at room temperature. By increasing the strain rate from 700 s−1 to 1650 s−1, the maximum stress and total strain in the alloy increased by 510 MPa and 141%, respectively. The higher dislocation density in the more severely deformed sample led to a more considerable amount of dislocation cells and consequent subgrains, high-angle grains, and piled-up dislocations. Intense shear strain localization leading to the adiabatic shear bands formation that occurred at higher strain rates. Texture investigations of the ASB region proposed that α→β phase transformation occurred within the ASB. Flow behavior prediction and experimental data revealed reasonable accordance, using the Gao-Zhang-Yan and the Chang-Asaro model.

Keywords

• Electron beam melting (EBM)
• Ti-6Al-4V
• Dynamic deformation
• Deformation mechanism
• Adiabatic shear bands (ASBs)
• Constitutive modeling