Influence of nanoscale Cu precipitates in alpha-Fe on dislocation core structure and strengthening

Chen, ZZ (Chen, Zhengzheng); Kioussis, N (Kioussis, Nicholas); Ghoniem, N (Ghoniem, Nasr)

PHYSICAL REVIEW B, 80 (18): Art. No. 184104 NOV 2009

DOI: 10.1103/PhysRevB.80.184104

Atomistic simulations of the interaction of a screw dislocation in alpha-Fe with different size bcc Cu precipitates suggest two plausible strengthening mechanisms. For precipitate diameters in the range 1.5 nm < d < 3.3 nm, the dislocation core structure within the Cu precipitate undergoes a polarized to nonpolarized 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 are in agreement with recent experiments. The structural transition of larger (d >= 3.3 nm) Cu precipitates under high shear stress is responsible for the loss of slip systems and hence for dislocation pinning.

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