Uncovering all possible dislocation locks in face-centered cubic materials

Abstract

• Eight locks form from all possible dislocation reactions in the FCC structure. • More locks form when incoming reactant dislocations are obtusely oriented. • Number of locks limited to obtuse and acute cases is 5 and 1, with 1 common lock. • All lock planes are positioned in a distinctive “fan-shaped” sector convergently. • Lock immobility is re-defined by considering lock planes vs. slip planes. Dislocation reactions and locks play an important role in the plastic deformation and mechanical behavior of crystalline materials. Various types of dislocation locks in face-centered cubic (FCC) materials have been reported in the literature pertaining to material-specific molecular-dynamic simulations and high-resolution transmission electron microscopy observations. However, it is unknown how many dislocation locks are possible, and how immobile all the dislocation locks are, with respect to each other. Here we present a discrete mathematics-based approach to reveal all possible dislocation locks in the FCC crystal structure. Totally eight types of dislocation locks are uncovered, resulting from all possible reactions of mobile/glissile (namely, perfect and Shockley partial) dislocations with (a) non-coplanar Burgers vectors which reside on two slip planes intersecting at both obtuse and acute angles and (b) coplanar Burgers vectors. We redefine the degree of dislocation lock immobility based on misorientations between non-close-packed lock planes and close-packed {111} slip planes. The subsequently derived sequences for the dislocation lock immobility and formation tendency are rationalized by the reported experimental and dislocation-dynamics simulation results.