The effect of single solute atoms and solute clusters upon an extended edge dislocation dipole was studied by means of atomistic simulations. Single Cu and Ag solute plus dislocation interaction energy calculations showed that Cu interacted strongly with an extended dislocation in Al, and preferred to occupy sites in the compressive region. This was in agreement with the predictions of elasticity theory. On the other hand, single Ag atoms were strongly repelled by such a dislocation. This contrasted with the predictions of elasticity theory. Monte Carlo simulations of Al-1Cu, Al-2Cu, Al-1Ag, Al-0.5Cu-0.5Ag and Al-0.75Cu-0.25%Ag alloys containing an extended dislocation dipole were carried out at 600K. Allowance was made for solute segregation effects. It was observed that Cu atoms in the binary alloys segregated to the compressive regions of the dislocation dipole and formed diffuse atmospheres, over the width of both extended dislocations, which did not affect the partial dislocation spacing. The Ag in the binary alloys formed small Ag zones which also had little effect upon the spacing between partials. However, the ternary systems exhibited highly localized solute clusters that had a marked effect upon the extended dislocation dipole structure by increasing the separation of the partial dislocations.

C.L.Rohrer: Journal of Materials Research, 1995, 10[3], 578-90