Influence of powder on phase transformation in AlCoCrFeNi High Entropy Alloy obtained by SPS

The study focuses on AlCoCrFeNi high entropy alloy, known for its mechanical and high-temperature properties. The influence of mechanical activation, pressure, and high temperature treatments on phase transformations of a pre-alloyed powder was investigated. Both milling and annealing promote the formation of FCC whereas SPS limits the BCC-FCC transformation, favoring intragranular BCC/B2 spinodal decomposition. This was attributed to the pressure when applied at high temperature. Intragranular precipitation of the sigma phase was observed when lowering the cooling rate. Milling of the powder leads to a more homogeneous phase distribution but also to precipitation of the sigma phase.