Computer Simulation of the Elementary Process of Solid Solution Hardening in Copper Alloys

The elementary process of solid solution hardening is the dislocation motion overcoming solute atoms in a crystal. The motion of an extended dislocation in Cu-Au solid solution alloy has been investigated by molecular dynamics simulation using Morse-type potential. Firstly, the equilibrium core structure of an extended dislocation is constructed in a pure Cu crystal. The spacing of partial dislocations is 5.2 nm for the edge dislocation and 1.8 nm for the screw dislocation. These results are consistent with experimental observations. The Peierls stress is 12×10−4 G for the edge dislocation and 20×10−4 G for the screw dislocation, where G is the shear modulus. Substitutional solute Au atoms are inserted into the region adjacent to the slip plane in front of the extended dislocation, and shear stress is applied to the crystal. The stress required to make the dislocation pass over Au atoms is 123−146×10−4 G for the edge dislocation and 112−126×10−4 G for the screw dislocation. The stress to move the screw dislocation is comparable to that to move the edge dislocation on condition of the same solute content. Thus, not only the edge dislocations but also the screw dislocations contribute to the initial stage of slip deformation in Cu-Au solid solution alloys.