Influence of dislocation structure, temperature and grain size on hardening of Cu-Al alloys in low-stability state

Abstract

The paper focuses on the dependence σ = f(ρ^½) between the flow stress and the square root of average scalar dislocation density for the Cu-Al system alloys in a low-stability state with regard to the types of the dislocation structure. This linear dependence σ = f(ρ^½) is obtained in a wide range of strain (at each stage), temperature, and grain size at different content of the second element. It is found that at a given strain stage, a transition from the main dislocation structure to another indicates to a transition to the next stage. In this case, this dependence demonstrates changes in the slope of the curve. It is shown that these changes can be caused by two reasons: the formation of the new type of the dislocation structure and changes in the deformation mechanism associated with the number of microtwin systems and a transition from one slip system to several of them.

Experiments show that in a wide range of strain, content of the solid solution, temperature, and grain size, the relation σ = σ_f + mαGbρ^½ is satisfied. The deviation from the linear dependence σ = f(ρ^½) and changes in the dimensionless factor mα are attributed to the formation of new dislocation structures and another deformation mechanisms. In alloys consisting of the higher content of the alloying element, the substructural hardening is supplemented by the twinning mechanism.