Phase equilibria of the Al–Ti–Nb–Zr–Ta system

Phase equilibria in the Al–Ti–Nb–Zr–Ta refractory complex concentrated alloy system were investigated using a high-throughput experimental approach. A pseudo-ternary section of the quinary compositional space was prepared by a honeycomb type powder metallurgy design, consolidated by spark plasma sintering and subsequently homogenized at 1400 °C for 168 h. Phase constitution and chemical partitioning were characterized by SEM/EDS, XRD, EBSD, and TEM, supported by a custom EDS phase clustering workflow. Equilibrium microstructures consisting primarily of BCC, B2, and secondary phases were identified across the sampled compositions, with nanoscale precipitates forming in Zr- and Ta-rich regions. Measured phase compositions were compared with CALPHAD predictions, revealing both agreements and systematic deviations linked to CALPHAD database limitations. The results provide new experimental insight into phase stability and microstructural trends in Al–Ti–Nb–Zr–Ta alloys and demonstrate the effectiveness of high-throughput combinatorial approaches for mapping complex multicomponent systems.