Phase Equilibria of the Al-Ti-Nb-Zr-Ta System

TL;DR

This study investigates phase equilibria in the Al-Ti-Nb-Zr-Ta alloy system using high throughput experiments, revealing microstructural details and comparing results with CALPHAD predictions.

Contribution

It introduces a high throughput experimental approach to map phase stability and microstructures in complex multicomponent alloys, providing new insights and validation for CALPHAD models.

Findings

Identified equilibrium microstructures mainly of BCC, B2, and secondary phases.

Observed nanoscale precipitates in Zr and Ta rich regions.

Compared experimental phase compositions with CALPHAD predictions, noting agreements and deviations.

Abstract

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 {\deg}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.