Interaction between a ½<111>{110} edge dislocation and voids or coherent body-centered cubic Cu precipitates (diameter D = 2 or 4nm) in Fe with their centre displaced by ±Δz from the dislocation glide plane was investigated by computer simulation at 0 to 450K. Voids provide the highest critical stress, τc, when Δz = 0. The dislocation climbs up on release when Δz ≥ 0, but down when Δz < 0. Void-surface facets influence the sense of climb. There was no correspondence between τc and the sense or magnitude of climb. 2nm precipitates gave the highest τc when Δz < 0 and lowest when Δz > 0, due to a combination of the modulus difference and size misfit between body-centered cubic Cu and Fe. 4nm precipitates were partially transformed to face-centered cubic structure by the dislocation when T ≤ 300K and Δz ≥ 0. Surprisingly, the transformed fraction of Cu at low T was highest for Δz = D/2, due to the compressive field of the dislocation. The geometries that produce large transformed fractions result in the lowest τc, in contrast to expectation from previous studies.

The Influence of Interaction Geometry on the Obstacle Strength of Voids and Copper Precipitates in Iron. P.Grammatikopoulos, D.J.Bacon, Y.N.Osetsky: Modelling and Simulation in Materials Science and Engineering, 2011, 19[1], 015004