Molecular dynamics simulations of the interaction between a screw dislocation and a coherent body-centered cubic Cu precipitate in body-centered cubic Fe indicated that the screw dislocation stress field assisted a martensitic transformation into a close-packed structure for precipitate diameters larger than 1.8nm; resulting in a stronger obstacle to dislocation glide. The observed martensitic transformation mechanism agreed with the Nishiyama-Kajiwara model. For coherent body-centered cubic Cu precipitates with diameters larger than 2.5nm, the screw dislocation by-pass mechanism became Orowan looping due to the coherency loss of the precipitates during the transformation.

Screw Dislocation Assisted Martensitic Transformation of a BCC Cu Precipitate in BCC Fe. J.H.Shim, Y.W.Cho, S.C.Kwon, W.W.Kim, B.D.Wirth: Applied Physics Letters, 2007, 90[2], 021906 (3pp)