Alloying metals with other elements is often done to improve the material strength or hardness. A key microscopic mechanism is precipitation hardening, where precipitates impede dislocation motion, but the role of such obstacles in determining the nature of collective dislocation dynamics remains to be understood. In this paper, together with researchers from Aalto University, we present results from extensive three-dimensional discrete dislocation dynamics (DDD) simulations with precipitates. These show that the quenched disorder field due to precipitates, if strong enough compared to dislocation-dislocation interactions, induces a depinning phase transition of the dislocation assembly at a critical external stress value. We show how this transition is manifested in the properties of the deformation dynamics when applying constant or quasistatically increasing external stresses. We also discuss the connection of our results with the Bacon-Kocks-Scattergood relation, a well-known result in materials science linking precipitate density and yield stress.
H. Salmenjoki, A. Lehtinen, L. Laurson, and M. J. Alava, Plastic yielding and deformation bursts in the presence of disorder from coherent precipitates, Phys. Rev. Materials 4, 083602 (2020).