Substructure parameters in deformed Cu – Mn alloys with a FCC lattice

Abstract

Development and successes of the physical science of strength and durability allow us to formulate the main aspects of dislocation physics. In this paper, the current state of this issue is considered within the framework of a multilevel approach – patterns of dislocations accumulation in the material after deformation with various degrees. The main mechanism of hardening of a metallic polycrystal is the dislocations accumulation in its grains, and the main parameter of hardening is the average scalar density of dislocations. The scalar dislocation density is divided into components: the density of statistically stored (ρS ) and the density of geometrically necessary (ρG ) dislocations. Transmission diffraction electron microscopy (TEM) is used to study the stages of development of types of dislocation substructure (DSS) in Cu – Mn alloys depending on concentration of the alloying element during active plastic deformation. Polycrystalline alloys were studied in a wide concentration range: from 0.4 to 25 % Mn (at.). A number of dislocation substructure parameters were measured using the images obtained on an electron microscope: the average scalar density of dislocations <p>, the density of statistically stored (ρS ) and geometrically necessary (ρG ) dislocations, the curvature-torsion of the crystal lattice (χ), the density of microstrips (Рstrips ), the density of ragged sub-boundaries (Мrag.bound. ). The authors established the effect of the sequence of DSS types transformations with an increase in the degree of deformation and the second element quantity on formation of the type of substructure and its parameters. Influence of concentration of the second element and the grain size on the average scalar density of dislocations and its components was experimentally determined. The presence of disorientations in the substructure during deformation is based on the measurement of these parameters by the TEM method.