Precipitation pathways in Refractory Metal High Entropy Superalloys

Refractory metal high entropy superalloys (RSA) look set to offer a step change in temperature capability over existing high temperature alloys. However, the transformation sequences that lead to their two-phase A2-B2 microstructures are yet to be fully understood, preventing process optimisation. Current hypotheses are based on a spinodal decomposition but ordering must also occur given the formation of the B2 phase. Direct characterisation of these transformation sequences, along with identification of the key transformation temperatures is imperative to this field. Here, in a follow up to MA4490, we propose to use high energy monochromatic diffraction to conclusively establish the evolution of the microstructure of a systematic study of four RSA for the first time.