Influence of spinodal decomposition structures on the strength of Fe-Cr alloys: A dislocation dynamics study

This paper presents a numerical analysis of the influence of spinodal decomposition on the strength of Fe-Cr alloys using the dislocation dynamics (DD) method. In the DD simulations, the structure of a spinodally decomposed chromium distribution is approximated using a cosine function. Using the equation for internal stress distribution, the interaction between a dislocation and the internal stress distribution is precisely accounted for in the DD simulations. The structure of the spinodally decomposed chromium distribution is parameterized using four variables, including the magnitude of chromium concentration, wave length of chromium distribution, position of the slip plane of dislocation, and the dislocation character (angle between the dislocation line and Burgers vector). Using these variables, the influence of the structure of chromium distribution on the critical resolved shear stress (CRSS) is studied. Furthermore, we focused on two major slip systems of the BCC structure, {110}(111) and {112}(111), and discuss the difference in the influence between the different slip systems. In the {110}(111) slip system, the Delta CRSS appears only for a mixed dislocation with theta = 54.7 degrees, because of the stripe pattern of the resolved shear stress distribution. On the other hand, in the {112}(111) slip system, the dislocations with theta = 39.2 degrees and 90 degrees have a large Delta CRSS. There is a plateau of Delta CRSS in a range of 39.2 degrees < theta < 90 degrees. The slip plane position does not change the Delta CRSS. There is a dependence of Delta CRSS on the wave-length of the chromium distribution. The dependence of Delta CRSS on the wave-length can be found not with a straight dislocation but with a curved dislocation using the DD simulations. The information is a new finding, and is meaningful in understanding the relationship between the material strength and the structure of spinodal decomposition. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.