Synergistic precipitation reactions in a novel high-temperature Ti-alloy

There is a pressing need for the development of new Ti-alloys tailored to wire-based directed energy deposition (waDED), to enable the wider uptake of this additive manufacturing process by the aerospace and energy industries. Here we present a novel high-temperature Ti-alloy for waDED. Our alloy design aims to exploit phase transformations and precipitation to achieve fine and homogeneous microstructures during processing and to provide improved high-temperature mechanical properties. Our new alloy design features combined additions of Si, Cu, Nb, and Y. We study its microstructural evolution during a simulated waDED solidification route and after various heat-treatments replicating the waDED thermal history in a deposited layer. Our alloy shows significant potential for the formation of fine and equiaxed β grains during waDED. Atom probe and transmission electron microscopy reveal the formation of nm-sized Ti2Cu, (Ti, Zr)6Si3 and sandwich-like Y-Cu dispersoids that are known to improve high-temperature properties in Ti-alloys.