An atomistic dislocation mechanism of pressure-dependent plastic flow in aluminum

An embedded atom (EAM) potential was employed to examine the lattice resistance to dislocation motion in pure aluminum under pressure. The sign and the magnitude of the pressure effect on glide (Peierls) stress in Al are obtained by direct atomistic calculation (molecular statics technique) in agreement with experimental data (Richmond and Spitzig, Pressure Dependence and Dilatancy of Plastic Flow. Int. Union of Theoretical and Applied Mechanics, 1980). Additionally, a significant transient dilatancy is observed associated with the activated state of dislocation motion. The latter result supports the conclusion reached in Richmond and Spitzig (Pressure Dependence and Dilatancy of. Plastic Flow. Int. Union of Theoretical and Applied Mechanics, 1980) and Spitzig and Richmond (Acta metall., 1984, 32, 457) that pressure-dependent slip in metals is due to the interaction of a transient activation dilatancy of the moving dislocations with external pressure. Although in pure aluminum the tension-compression yield strength differential (SD) is only about 0.3%, the effect is significant for quantitative modeling of the performance of high strength aluminum alloys in tension and compression. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.