Dynamic compressive properties and underlying failure mechanisms of selective laser melted Ti-6Al-4V alloy under high temperature and strain rate conditions

Abstract

In this study, high speed impacting tests are systematically conducted on a split Hopkinson pressure bar device to investigate the strain rate and temperature dependence of dynamic compressive properties of Ti-6Al-4 V (TC4) fabricated by selective laser melting (SLM), the ranges of strain rate and temperature are 2000–6000/s and 25–650 ℃, respectively. The results reveal that the yield strength and ultimate compressive strength of the SLM-TC4 alloy increase with the increasing strain rate and the decreasing temperature, showing obvious strain rate and temperature sensitivities. The high speed impacting load intensifies the texture of the SLM-TC4 alloy significantly. Adiabatic shear band (ASB) is more likely to evolve at higher temperatures and strain rates, submicron equiaxed grains formed in the ASB and the surrounding area are mainly ascribed to the combination of dynamic recrystallization, deformation-induced twinning and transverse α-lath splitting. Within the ASB, grains with {0001} pole orientation are rotated by approximately 45° with respect to the shear direction, indicating that the recrystallized grains are able to reorient themselves to accommodate to the shear deformation. The findings in this work provide a theoretical basis to understand the deformation behavior and mechanism of SLM-TC4 alloy under impacting loads, thus is helpful to widen the application of SLM technique and products. • SLMed TC4 alloy has significant temperature and strain rate sensitivities. • Strain hardening and thermal softening cause instable plastic deformation of SLMed TC4. • Ultrafine grains within ASBs mainly due to the deformation twinning, α -lath splitting and DRX. • Dynamic impact loading enhances the texture intensity of the deformed samples. • Recrystallized grains within ASBs can reorient themselves to accommodate to the shear deformation.