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

An embedded atom (EAM) potential was employed to examine the lattice resist ance to dislocation motion in pure aluminum under pressure. The sign and th e magnitude of the pressure effect on glide (Peierls) stress in Al are obta ined by direct atomistic calculation (molecular statics technique) in agree ment 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 associa ted with the activated state of dislocation motion. The latter result suppo rts the conclusion reached in Richmond and Spitzig (Pressure Dependence and Dilatancy of. Plastic Flow. Int. Union of Theoretical and Applied Mechanic s, 1980) and Spitzig and Richmond (Acta metall., 1984, 32, 457) that pressu re-dependent slip in metals is due to the interaction of a transient activa tion dilatancy of the moving dislocations with external pressure. Although in pure aluminum the tension-compression yield strength differential (SD) i s only about 0.3%, the effect is significant for quantitative modeling of t he performance of high strength aluminum alloys in tension and compression. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rig hts reserved.