Microstructural response of beta-stabilized Ti-6Al-4V manufactured by direct energy deposition

Abstract

The present study describes the influence of beta stabilizers (namely Fe and Cr) on the microstructural evolution and mechanical behavior of Ti-6Al-4V alloy fabricated by direct energy deposition. As the beta stabilizer content increases from 1 to 4 wt%, the coarse columnar-grained morphology typical of additively manufactured Ti-6Al-4V is significantly refined, with a columnar-to-equiaxed transition. Furthermore, reheating of the deposited layers by the deposition of overlaying layers during fabrication induces an element partitioning effect, resulting in the formation of fine-grained alpha and isothermal omega. Hence, the heat profile during direct energy deposition resembles conventional solution and aging treatments. In addition, increasing the amount of beta stabilizer steadily increases the room temperature strength of the Ti-6Al-4V alloy. The alloy with 4 wt% Fe showed the maximum strength, of similar to 1.5 GPa. (C) 2019 Elsevier B.V. All rights reserved.