A method for designing spatially varying alloy composition gradients that finds a feasible isothermal path between two alloys by querying CALPHAD equilibrium calculations on the fly inside a rapidly-exploring random tree, instead of pre-building a surrogate model whose sampling cost grows exponentially with the number of elements. Its key device is the Bad Phase Purge transformation, a conjectured corollary of the lever rule that pointwise reprojects a path allowed to cross undesirable ('bad') phase regions onto one containing only good phases using only the phase information already computed. This makes gradient path planning tractable for systems of more than four elements, where surrogate modeling becomes untenable.
Functional gradients have recently experienced an explosion in activity due to advances in manufacturing, where compositions can now be spatially varied on-the-fly during fabrication. In addition, mo…