STRAIN LOCALIZATION AND FORMATION OF HETEROGENEOUS DISTRIBUTION OF SHEARABLE ORDERED PRECIPITATES - APPLICATION TO AN AL-10AT.PERCENT-LI SINGLE-CRYSTAL

A model is established for plastic deformation of crystals containing shearable ordered precipitates. The precipitate structure undergoes an evolution caused by enhanced growth and redissolution of precipitates due to their shearing by dislocations. Opposing the strain hardening of the matrix and the spatial coupling effect between adjacent materia l elements, such a thermodynamic evolution, in addition to the geometr ical effect of the shearing, finally causes strain softening and hence leads to a plastic instability-strain localization with the formation of precipitate-deficit channels. A numerical simulation is earned out taking as an illustrative example the case of an Al-10at.%Li single c rystal. The results are compared with some known observations concerni ng post-yield properties, especially of the plastic instability and th e corresponding microstructure. (C) 1998 Acta Metallurgica Inc.