A High Throughput CALPHAD Approach to Design B2 + bcc Microstructures Using Spinodal-Assisted Transformation Pathways and Experimental Validation: Al10Mo10Nb10Ta10Ti30Zr30

Abstract In this work, we implement high throughput CALPHAD calculations to systematically scan the Al–Mo–Nb–Ta–Ti–Zr elemental space and design HEA compositions which exhibit only nanoscale B2 + bcc microstructures. From this down-selection, experimental observations of a particular alloy composition are reported. Specific heat treatment strategies were employed to probe the accuracy of thermodynamic predictions and to investigate the nature of the decomposition products. Solutionizing followed by water quenching indicates that phase separation cannot be suppressed. Solutionizing followed by a step-quench to, and aging treatment at, 750 °C produces a three-phase microstructure consisting of a matrix phase with the B2 structure. The nanoscale, disordered bcc precipitates have a uniform spatial distribution, suggesting a spinodal-assisted phase transformation pathway. An Al–Zr rich phase, with an hexagonal structure, is present with low phase fractions.