Investigation into the dynamic mechanical properties of selective laser melted Ti-6Al-4V alloy at high strain rate tensile loading

Abstract

In general, mechanical properties of most materials under dynamic loading are completely different from those under static/quasi-static loading. In this paper, a comparative study between the selective laser melted Ti-6Al-4V alloy and its heat-treated counterpart was carried out. After heat treatment, the microstructure transformed from full fine acicular α' into basket-weave morphology with coarsened α + β lamella, grain boundaries α tended to globularization, and the volume fractions of β phase and LAGBs increased due to the α′→α + β transformation and increasing of dislocation density respectively. During high strain rate tension, strain was dispersive in the elastic deformation region, then it began to concentrate at the centre of samples and increased until fractured as loading time increased. As expected, evident reduction in the UTS and σy and increase in the ε were caused by heat treatment, however both of them increased as the strain rate increased due to the twinning deformation occurred in the α/β interface phase, thus contributed to improving the strength and plasticity of SLMed TC4 alloy under high strain rate loading simultaneously. This work provided a relationship between microstructure and dynamic responses of SLMed TC4 alloy, which contributes to exploiting the performance potential of SLMed alloy.