Microstructure and deformation behavior of the wire-arc directed energy deposited high-performance near-β Ti-10V-2Fe-3Al alloy

Abstract

The near-β titanium alloy Ti-10V-2Fe-3Al is a high-performance alloy in use in highly loaded, safety relevant applications such as landing gears. The conventional manufacturing route employs several forging and heat treatment steps. Here, we investigate an alternative route via wire-based directed energy deposition (waDED) offering advantages regarding energy consumption, time, and resource efficiency. The deposited and heat-treated material is characterized in terms of microstructure using optical light microscopy, scanning electron microscopy including electron back-scatter diffraction and high-energy X-ray diffraction. The mechanical properties are assessed using microhardness and tensile testing. The microstructure consists of large primary β grains with embedded α laths. Upon aging, the retained β-phase decomposes forming a bimodal microstructure. In the final solution heat-treated and aged condition, yield strength values reach above 960 MPa and ultimate tensile strength values above 1030 MPa with fracture strains of about 3 % and only weak anisotropy. The performed analyses suggest that plastic deformation is assisted by stress-induced martensite formation. This transformation was substantiated by atomistic simulations. A comprehensive understanding of the material characteristics of the Ti-10V-2Fe-3Al alloy processed by waDED and subsequent heat treatments is provided – a contribution to implementing advanced titanium alloys processed via alternative routes.