Effect of stacking-fault energy on the accumulation of dislocations during plastic deformation of copper-based polycrystalline alloys

N. Koneva, L. Trishkina, T. Cherkasova


Storage of dislocations at plastic deformation of polycrystalline FCC alloys of Cu-Al and Cu-Mn is studied. It is determined that storage of dislocation  (<ρ>) at plastic deformation depends from stacking fault energy (γ sf).The transmission electron microscopy was used to investigate the dislocation structure and accumulation of dislocations during the plastic deformation in Cu-Al and Cu-Mn polycrystalline FCC solid solutions. Al content in Cu-Al alloys varied from 0.5 to 14 at.%, and Mn content in Cu-Mn alloys varied from 0.4 to 25 аt.%. The alloy samples with the grain size ranging from 20 to 240 μm were studied., They were subjected to tensile deformation at the strain rate of 2 · 10–2 s–1 at temperatures 293 – 673 K. Observations of the structure on thin foils were carried out on electron microscopes at 125 kV accelerating voltage. For different strains, the scalar dislocation density and other parameters of the defect structure such as the size of the dislocation cells, density of microtwins etc. were measured. The results show that the increased content of Mn and Al in alloys is accompanied by an increase in the dislocation density. In Cu-Al alloys the dislocation density depends on the stacking fault energy. With its decrease, the density of dislocations increases. An explanation of this behavior is given. In Cu-Mn alloys the increased Mn content does not modify the stacking fault energy, while in Cu-Al alloys the dislocation density increases with the increase in the deformation temperature due to the temperature effect on the stacking fault energy. In Cu-Mn alloys, the temperature reduces the dislocation density. The resistance to deformation both in Cu-Al and Cu-Mn alloys decreases with the temperature increase. Physical causes of the absence of the temperature anomaly of mechanical properties in Cu-Al alloys are discussed.

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