A Novel ‘Bi-Combinatorial’ Tool to Rapidly Probe Phase Stability and Microstructure in Ti-based Alloys

Combinatorial approaches that have enabled the systematic investigation of the influence of composition on the resulting microstructures and mechanical properties were first developed 15 years ago. These methods have relied upon the use of additive manufacturing to deposit compositionally graded specimens that could then be heat-treated, tested, and characterized. These techniques have been extended over the past 5 years to study problems such as oxidation in titanium-based alloys. In 2017, the concept of a high-throughput combinatorial methods were extended by introducing an engineered and controlled thermal gradient orthogonal to the composition using joule heating, allowing for a true assessment of sections of phase diagrams within a single specimen. The details of this new thermal gradient technique will be shown, as will demonstrations on the alloy Timetal 21S. The bi-combinatorial technique has been applied to the Ti-xCr system, and the influence of both composition and temperature on microstructural scale, phase stability (alpha, beta, and TiCr2), and grain size will be shown.