Atomistic simulations of the interaction of a screw dislocation in α-Fe with different-sized body-centered cubic Cu precipitates suggested two plausible strengthening mechanisms. For precipitate diameters in the range 1.5nm ≤ d ≤ 3.3nm, the dislocation core structure within the Cu precipitate undergoes a polarized to non-polarized transformation, leading to the dislocation pinning at the precipitate-matrix interface and the bowing out of the dislocation line. The calculated bow-out angle and resolved shear stress required to detach the dislocation from the precipitate were in agreement with recent experiments. The structural transition of larger (d≥3.3 nm) Cu precipitates under high shear stress was responsible for the loss of slip systems and hence for dislocation pinning

Influence of Nanoscale Cu Precipitates in α-Fe on Dislocation Core Structure and Strengthening. Z.Chen, N.Kioussis, N.Ghoniem: Physical Review B, 2009, 80[18], 184104