Nanostructuring of Multi-Principal Element Alloys by Severe Plastic Deformation: from Fundamentals to an Improved Functionality

Multi-principal element alloys (MPEAs) are in the forefront of materials science since their compositions can be found in the undiscovered central parts of phase diagrams. These materials contain 3-6 elements with similar fractions, i.e., the constituents do not play the classical solvent and solute roles in the alloys. This class of materials includes high entropy alloys (HEAs). Novel MPEA compositions often have unique and superior properties compared to conventional materials. It has been shown that the features of MPEAs can be further improved by nanostructuring using severe plastic deformation (SPD) techniques. In this study, the evolution of the microstructure in MPEAs during SPDprocessing (defect formation, grain refinement and phase transformation) is overviewed on the basis of the literature. The corresponding changes of the mechanical and physical properties, such as the strength, corrosion resistance and hydrogen diffusivity are discussed. In addition, the potential applications of SPD-processed MPEAs are presented.