Ti-6Al-4Zr-2Sn-6Mo is one of the most recent Powder Bed Fusion – Laser Beam (PBF-LB) processed titanium alloys. It could replace the Ti-6Al-4V in automotive and aerospace applications thanks to the higher mechanical properties (about 10% on UTS and YS). In the as-built (AB) condition, the material is characterized by the presence of the soft orthorhombic α’’ martensite. A post-process heat treatment for its decomposition is therefore needed to increase the mechanical properties of the AB alloy. Usually, PBF-LB Ti6246 components undergo an annealing process that transforms the α’’ martensite into an α−β lamellar microstructure [1].

The main goal of the present research was to obtain an ultra-fine bi-lamellar microstructure reinforced by precipitation hardening, developing a Solution Treating and Aging heat treatment (STA) tailored to the peculiar microstructure induced by the additive process. The effect of solution temperature in the α+β field (between 800-900 °C), cooling media (air and water), and aging temperatures were investigated to identify the heat treatment parameters to obtain a suitable bilamellar microstructure. The microstructural characterization was done through optical (OM) and electron microscopy (SEM) analyses, as well as by XRD analyses to evaluate and identify the crystalline phase transformations. Preliminary microhardness tests were performed to assess the effect of different heat treatment parameters on mechanical performance. Tensile tests were performed on samples heat-treated according to the most promising parameters. The comparison of the results of mechanical characterization and literature data highlighted that the optimized STA heat treatment increased the hardness and strength of 35% and 23%, respectively, compared to the annealed alloy, with a reduction of the elongation to failure of 53%. Fracture surface analyses of tensile tests were carried out to study the fracture mechanisms.