Solidification and Homogenization Modeling of High Entropy Alloys

High entropy alloys (HEA) are an exciting new class of alloys, which are composed of several metallic elements with equiatomic or near-equiatomic composition to maximize configurational entropy, leading to desirable properties. However, during solidification, as in casting or welding, elements can segregate, creating local regions of distinct composition. A homogenization heat treatment is therefore needed to remove this segregation effect. To determine the conditions of the heat treatment needed, the solidification behavior of two HEA compositions, CoCrFeNi and AlCoCrCuFeNi, are first modeled using the Scheil module within Thermo-Calc along with the TCHEA2 database. Energy dispersive spectroscopy is performed across the dendrite arms of as-cast HEA to compare with the Scheil simulations.  The resulting segregation profile is then given a series of simulated heat treatments using DICTRA to determine the optimum conditions to homogenize the material. Select heat treatments are given to the as-cast samples to compare with the simulated results.