The Effect of Decomposed Microstructure on Mechanical Properties of Additively Manufactured Ti-6Al-4V Alloy

This study investigated the effect of microstructural decomposition on the mechanical properties of additively manufactured Ti-6Al-4V by directed energy deposition. The formation of α’ martensite and α massive phase (αm) was observed in the deposited layers. The α’ and αm in the lastly deposited layer appeared as a needle-shaped and a sub-lamellar structure, respectively. However, the morphology of α’ and αm was decomposed in the lower layers due to the intrinsic heat treatment. Moreover, The heat conduction rate calculation showed that the lower powder feed rate generates more heat conduction. Therefore, the microstructure was further decomposed for the specimen with a lower powder feed rate. These phenomena consequently affected the mechanical properties and fracture behavior of the Ti-6Al-4V alloy.