| Abstract Scope |
Refractory medium entropy alloys (RMEA) are promising candidates for ultra-high temperature applications. The laser powder bed fusion (LPBF) additive manufacturing of TiTaNb RMEA from its elemental powders remains largely unexplored. This study investigates whether a second laser pass, representative of re-scanning in LPBF, changes the microstructure of TiTaNb alloy formed during the first pass. CALPHAD equilibrium calculations, Scheil-Gulliver solidification modeling, and molecular dynamics simulations are combined to analyze TiTaNb during two consecutive laser passes. CALPHAD predicts BCC and HCP coexistence at room temperature, whereas Scheil modeling indicates rapid solidification into single-phase BCC. Molecular dynamics tracks thermal history, cooling rate, grain structure, and dislocation evolution after each pass. The second pass strongly remelts the first-pass structure, but the final microstructure changes only slightly, indicating stable BCC formation under repeated thermal cycling in LPBF fabricated TiTaNb. |