Rapid precipitation in an Al<inf>0.5</inf>CrFeCoNiCu high entropy alloy

The effect of cooling rate on the microstructural evolution of Al0.5CrFeCoNiCu has been studied using differential scanning calorimetry and scanning electron microscopy. As-cast Al0.5CrFeCoNiCu contained three phases; Cr-Fe-Co-Ni solid solution dendrites, Cu-rich interdendritic material and L12 precipitates. During cooling at rates between 10 and 50˚C.min-1 , an additional exothermic event, at ~1010˚C, was observed in the heat flow curves. Microstructural examination after cooling revealed the presence of two distinct populations of intragranular precipitates not present in the as-cast material. Energy dispersive X-ray spectroscopy indicated that Cu-rich precipitates formed within the dendrites, whilst a Cr-Fe-Co rich phase formed in the interdendritic constituent. Precipitation during cooling at rates approaching 1˚C.s-1 indicates that the diffusion kinetics of Al0.5CrFeCoNiCu are not, as previously suggested, sluggish.authors would like to acknowledge support from the EPSRC / Rolls-Royce Strategic Partnership under EP/H500375/1, EP/M005607/1 (NGJ & HJS) and EP/H022309/1 (KAC).This is the final version of the article. It first appeared from Maney via http://dx.doi.org/10.1179/1743284715Y.000000000