Effect of Grain Size and Temperature on Scalar Dislocation Density and Curvature–Torsion of the Crystal Lattice in Copper–Manganese Alloys during Plastic Deformation

The dependences of the flow stress at different temperatures of homogeneous solid solutions based on Cu–Mn alloys with an fcc crystal lattice are obtained depending on the composition. It has been established that the difference between the flow-stress curves at different temperatures increases with an increase in the Mn content in the alloy. The results of the study of the evolution of the dislocation structure in Cu–Mn alloys with manganese content of 1, 2, 4, and 6 at % in the grain size range of 20–240 µm at deformation temperatures from 293 to 673 К by the methods of diffraction electron microscopy are presented. The dependences of the scalar dislocation density on the grain size and test temperature in Cu–Mn alloys have been established. It has been established that, with an increase in the degree of deformation, a significant increase in the average scalar density of dislocations occurs. At a fixed degree of deformation in all the alloys studied, an increase in the deformation temperature leads to a decrease in the dislocation density. In the grain size range from 10 to 100 μm, at all test temperatures, an intense decrease in the average scalar dislocation density is observed. For grain sizes above 100 μm, this value of the dislocation density does not change. The numerical values of the curvature–torsion of the crystal lattice were measured from the micrographs obtained in an electron microscope along the width of the bending extinction deformation contours. It has been established that the magnitude of the curvature–torsion of the crystal lattice increases with deformation in a nonlinear manner in all the investigated alloys. The value of curvature–torsion of the crystal lattice at a fixed degree of deformation in alloys with a grain size of ~10 μm is greater than in alloys with higher grain sizes of ~200 μm.