Assessment of Phase Evolution in Titanium-Niobium-Based Alloys During Rapid Solidification

In this work, microstructural evolution in β-Ti alloys during solidification is studied as the cooling rate increases, approaching the cooling rates found in additive manufacturing processes. Using suction casting of thin rods, high cooling rates can be studied and compared, to find a trend in how these phases evolve under a broad range of solidification conditions. The effect of varying cooling rates is studied on the microstructural evolution of Titanium-Niobium (Ti-Nb)-based alloys with Tantalum (Ta) additions. A combined simulation and experimental approach is used to investigate the predictability of differences in microstructural evolution during rapid-solidification casting. Rods of binary Ti–25Nb and ternary Ti–20Nb–10Ta (wt% and hereafter) alloys were synthesized in diameters of 3, 5, and 10 mm using suction casting into copper moulds. Finite element (FE) and thermodynamic modelling was used to calculate the cooling rates and temperature gradients of the alloys. The microstructural and mechanical differences were determined via XRD, SEM/EDS, and mechanical testing.