Comparative investigation of phase formation in Ti–Zr–Cu alloying processes via laser powder-bed fusion and plasma arc melting

This study presents a comparative analysis of phase formation in a Ti 38 Zr 27 Cu 35 alloy produced via Laser Powder-Bed Fusion (L-PBF) and Plasma Arc Melting (PAM). The investigation evaluates phase constituents, microstructure, elemental distribution, phase formation, and hardness using L-PBF specimens fabricated from in-situ elemental powders and PAM specimens as a reference for the conventional process. Analysis was conducted through FESEM for microstructure, XRD for phase identification, EPMA for chemical quantification, including chemical composition in identified phases, and Vickers testing for hardness. Results indicate that rapid solidification of L-PBF suppressed the predicted primary β -Ti phase, yielding a two-phase microstructure consisting of (Ti, Zr) 2 Cu dendrite and TiZrCu 2 intermetallic phase at the interdendritic. This non-equilibrium state demonstrated reduced lattice parameters and fine-grained structure. In contrast, the slower cooling rate in PAM, at approximately 2–3 orders of magnitude of that of L-PBF, allowed the formation of β phase (Ti-enriched equiaxed dendrites), resulting in β + (Ti, Zr) 2 Cu + TiZrCu 2 three-phase structure consistent with Scheil calculations. Consequently, the L-PBF specimens exhibited higher hardness than PAM. While both methods achieved elemental homogenization, their distinct alloying characteristic and cooling rates resulted in divergent morphological features, phase composition, and mechanical properties, fundamentally influencing the manufacturing.