Investigation of the dynamic mechanical properties of additive manufactured Ti-6Al-4V alloys: the effect of impact orientation and heat treatment

Ti-6Al-4V is a high-strength alloy widely used in various industries due to its exceptional mechanical properties. This study focuses on the dynamic mechanical behavior of Ti-6Al-4V alloys manufactured through additive manufacturing techniques, specifically selective laser melting (SLM), which enables the production of complex structures with high precision. The microstructure of Ti-6Al-4V is influenced by the thermal conditions during solidification, resulting in variations in grain size, morphology, and crystallographic texture. We investigate the effects of impact direction and heat treatment processes on the dynamic mechanical properties of SLM Ti-6Al-4V alloys through one-dimensional plate impact loading experiments. Our microscopic characterizations reveal two types of spall damage mechanisms in the SLM samples, influenced by the impact directions and velocities. Interestingly, the strength of SLM samples exhibits minimal anisotropy, indicating little difference in spall strength between different impact directions. Moreover, we found that the Hugoniot elastic limit of SLM samples shows greater sensitivity to impact velocity than the traditionally wrought samples. Wrought Ti-6Al-4V demonstrates superior dynamic tensile strength compared to SLM counterparts. Furthermore, we analyze the impact of heat treatment on the SLM Ti-6Al-4V samples. The phase composition and texture undergo changes during recrystallization, with the non-equilibrium acicular α′ martensite transforming into an equilibrium (α+β) microstructure. This recrystallization process leads to a decline in the dynamic tensile properties of the SLM samples. Our findings contribute to a better understanding of the dynamic behavior and spallation damage mechanisms of SLM Ti-6Al-4V alloys.