Microstructural evolution of the LENS manufactured TiAl structure

Abstract

The advent of additive manufacturing presented the new-era where complex structures can be prototype and rapidly manufactured from a computer aided device file. Robust industries such as the aerospace and medicinal require 3D printed complex components which can be reproduced and are without defects. The laser engineered net-shaping (LENS) system is an additive manufacturing machines and can be used for industrial research and prototyping. In this paper, the Optomec LENS; a 1 kW maximum power output system, was used to fabricate a cubic structure of titanium aluminides from elemental titanium (Ti) and aluminium (Al) by in-situ alloying. This is a novel approach since the traditional methods used in the production of TiAl structures focus primarily on powder metallurgy and electron beam melting (EBM) process where pre-alloyed powders instead are used. These pre-alloyed powders are superior since they already have oxidation promoting and ductility stabilisers element. The resulting microstructure of the in-situ alloyed Ti and Al powders were evaluated, bottom-up, on the produced structure. The SEM images concluded a lamellar rich microstructure at the top, middle and the bottom. The HAZ showed a hexagonal structure. The EDS map of the different regions concluded Ti:Al ratio of 3:1 which could mean the overall composition was Ti3Al.