Preparation of nanocrystalline high-entropy alloys via cryomilling of cast ingots

The advancement of nanotechnology demands large-scale preparation of nanocrystalline powder of innovative materials. High-entropy alloys (HEAs) exhibit unique properties: mechanical, thermal, magnetic etc., making them potentials candidates for applications in energy, environment and biomaterials etc. Thus, there is a need to develop novel synthesis methods to prepare nanocrystalline high-purity HEAs in large quantity. Conventional mechanical alloying of the multicomponent metallic powder mixture requires larger milling time and it is prone to contaminations and phase transformation. The present investigation reports a unique approach, involving casting followed by cryomilling, leading to formation of nanocrystalline HEAs powder, which are relatively contaminations free with narrow size distribution. Using examples of two FCC and one BCC single-phase HEAs, it has been shown that large-scale nanocrystalline HEAs powder can be prepared after few hours of cryomilling at 123 K. The formation of nanocrystalline HEAs during cryomilling has been discussed using theoretically available approaches.