Stress evolution in Fe laths undergoing plastic deformation was investigated using three-dimensional dislocation dynamics simulations adapted to body centred cubic crystals, in the ductile to brittle transition temperature range. The selected boundary conditions, applied stress tensor and initial dislocation structures account for the realistic microstructure observed in bainitic steels. The effective stress field projected in the three different {100} cleavage planes was calculated for two different temperatures (50 and 200K) and presented quantitatively, in the form of stress/frequency diagrams. It was shown that plastic activity tends to relax the stress acting in certain cleavage planes (the (010) and (001) planes) while, at the same time, amplifying the stress acting in other cleavage planes (the (100) planes). The selective stress amplification in the latter planes depends on the applied load direction, in combination with the limited set of available slip systems and the lath geometry. In the examined configuration, this selection effect was more pronounced with decreasing temperature, emphasizing the role of thermally activated plasticity on deformation-induced stress concentrations.

Internal Stress Evolution in Fe Laths Deformed at Low Temperature Analysed by Dislocation Dynamics Simulations. J.Chaussidon, C.Robertson, M.Fivel, B.Marini: Modelling and Simulation in Materials Science and Engineering, 2010, 18[2], 025003