CLUSTER DISLOCATION INTERACTIONS IN DILUTE ALUMINUM-BASED SOLID-SOLUTIONS

The influence of single solute atoms and solute clusters on an extende d edge dislocation dipole in Al was studied by atomistic simulation. S ingle Cu and Ag solute/dislocation interaction energy calculations sho wed that Cu interacts strongly with an Al extended dislocation and pre fers sites in the compressive region, in agreement with elasticity the ory predictions. Single Ag atoms, however, are strongly repelled by an Al extended dislocation, in contrast with elasticity theory predictio ns. Monte Carlo simulations of Al:1% Cu, Al:2% Cu, Al:1% Ag, Al:0.5% C u, 0.5% Ag, and Al:0.75% Cu, 0.25% Ag were carried out in the presence of an extended dislocation dipole at 600 K allowing for solute segreg ation. Cu atoms in the binary alloys were observed to segregate to the compressive regions of the extended dislocation dipole, forming wides pread ''atmospheres'' over the width of both extended dislocations whi ch did not affect the partial dislocation spacing, Ag in the binary al loy formed small Ag zones which also had little influence on the spaci ng between the partials. The ternary systems, however, exhibited highl y localized solute clusters that had a large impact on the extended di slocation dipole structure, increasing the separation between the part ial dislocations. The resulting cluster structures are discussed along with their influence on the apparent stacking fault energy of the all oy systems.