A Review on Additive Manufacturing of Titanium Alloys for Aerospace Applications: Directed Energy Deposition and Beyond Ti-6Al-4V

Abstract

Titanium alloys are expensive and difficult to process into large complex components for aerospace applications. Directed energy deposition (DED), one of the additive manufacturing (AM) technologies, offers a high deposition rate, being suitable for fabricating large metallic components. So far, most review articles on the AM of titanium discuss the popular powder bed fusion method with the emphasis on the “workhorse” titanium alloy—Ti-6Al-4V. There have been few review articles on the DED process of a broad range of titanium alloys—near-α, β, and other α + β alloys beyond Ti-6Al-4V. This article focuses on the processing–microstructure–property relationships in the DED-processed titanium alloys (Ti-6Al-4V and beyond) with the following aspects: (1) microstructure evolution induced by solidification, thermal cycles, and post-processing heat treatment; (2) tensile properties of as-deposited and heat-treated titanium alloys; (3) defects, residual stresses, and fatigue properties; and (4) micro/nanomechanical properties. The article concludes with perspectives about future directions in this field.