Microstructure and evolution of gradient dislocation cells in multi-principal element alloy subjected to cyclic torsion

Cyclic torsion induced dislocation patterns and evolution process of a single-phase Al0.1CoCrFeNi multi-principal element alloy at varying cumulative plastic strain, γcu, from 0.1 to 14.6, were systematically investigated in this study. The results reveal that conventional single-slip individual dislocations dominate plastic deformation at initial straining stage. Whereas, at larger γcu up to 1.2, a large number of dislocation locks formed by mutual dislocation interactions in turn induce the extensive proliferation of multi-slip dislocations within the grain interiors. At γcu > 4, a large number of individual multiple dislocations are gradually organized into massive two-dimensional micrometer-scale multi-slip dislocation wall segments; at γcu > 8, profuse three-dimensional finer equiaxed low-angle dislocation cells are formed. The distinctive structural characteristics of the sample-level hierarchical dislocation cell structure in metals with low stacking fault energies are mainly caused by the gradient distribution of small but large cumulative plastic strain, which are closely related to the enhanced multiple-slip dislocation activities.