The strengthening effect of nanosized Cu precipitates in body-centered cubic Fe was studied by performing molecular dynamics simulations of the interaction between a screw dislocation and a coherent body-centered cubic Cu precipitate of 1 to 4nm diameter in body-centered cubic Fe. The dislocation detachment mechanism changes from shear at a precipitate diameter of 4 and 2.5nm in the twinning and anti-twinning directions, respectively, due to the coherency loss caused by the screw dislocation assisted martensitic transformation of the precipitate. The screw dislocation detachment mechanism with the larger, transformed precipitates involves annihilation-and-renucleation, or Orowan looping in the twinning vs. anti-twinning direction, respectively. The critical resolved shear stress of the screw dislocation-precipitate interaction increases with increasing precipitate size, and was strongly dependent on the precipitate structure and detachment mechanism. The critical resolved shear stress was much larger in the anti-twinning direction.

Strengthening of Nanosized BCC Cu Precipitate in BCC Fe - a Molecular Dynamics Study. J.H.Shim, D.I.Kim, W.S.Jung, Y.W.Cho, B.D.Wirth: Materials Transactions, 2009, 50[9], 2229-34