The first investigation of the Orowan strengthening mechanism in the thermal plastic regime of body-centered cubic materials was made here using dislocation dynamics simulations. In body-centered cubic crystals, the mobility of dislocations strongly depends upon temperature and dislocation line characters. Unlike the classical picture of the Orowan mechanism, simulations show that the difference in mobility between screw and non-screw characters was the key parameter. Simulations at different temperatures and with different precipitate microstructures illustrate the contribution of two mechanisms to Orowan strengthening: a thermally activated mechanism induced by the length dependency of the screw dislocation mobility and an athermal mechanism associated with dislocation line tension. The influence of the particle distribution was studied with a comparison between regular and random particle arrangements. In most cases, distribution effect could be accounted for by calculating effective particle spacing in the screw dislocation directions.

Orowan Strengthening at Low Temperatures in BCC Materials Studied by Dislocation Dynamics Simulations. G.Monnet, S.Naamane, B.Devincre: Acta Materialia, 2011, 59[2], 451-61