On intergranular interaction and the crystallographic mechanism of plastically deformed polycrystalline metals

Abstract

Taylor principle prevailing currently has been proved to be effective only when grains or grain clusters are deformed in a rigid environment, which disagrees with the reality. Grains realize their plastic deformation in elastoplastic environment, and the equilibrium of intergranular stress and strain need to be reached simultaneously and naturally. The intergranular reaction stress (RS) during deformation can be calculated according to Hooke’s law and the yield stress should be the up-limit of the RS. The combinations of constant external stress and changing RS in RS theory induce alternate activation of deformation systems including slips and twinning with different work hardening rates, while grain orientations and inhomogeneous distribution of external stress have important influence. Some additional deformation systems near the boundaries need to be locally activated when the reduced stress up-limits are reached frequently, to balance the intergranular stress and strain incompatibilities in elastoplastic way. Based on the simpler RS theory, the simulation results of rolling texture on aluminium, low carbon steel, austenite stainless steel, titanium are very close to the reality, indicating that the intergranular elastoplastic interactions and the corresponding crystallographic behaviours of plastic deformation have been reasonably and quantitatively described, therefore, Taylor principle becomes no more necessary.