低Si量Cu-Si合金単結晶の容易辷り領域の初期段階

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Single crystals of Cu-Si alloy oriented for single slip were subjected to tensile deformation. It was confirmed that the initial stage of easy glide (stage I) in crystals with small amounts of Si had very little hardening (stage IA) for a few per cent elongation. The extent of stage IA increased with decreasing temperature from 295 to 77°K and with increasing Si content from 1.5 to 2.4 at%. On the other hand, the density and distribution of dislocations in stage IA in Cu-1.5 at%Si crystals were studied by the etching method. The dislocation distribution was very inhomogeneous; the dislocation density was distinctly high along band-like slipped regions parallel to the trace of the primary glide plane. In slipped regions, the dislocation density was of the order of 107 cm−2, and dislocation multiplication was not detected in secondary slip systems. The deformation during stage IA was characterized by the growth of slipped regions in width and the formation of new slipped regions between old ones formed earlier. When the specimen surface was all covered with slipped regions, stage IA ended and followed by stage I hardening. The deformation in stage IA was apparently similar to “Lüders deformation” in single crystals of copper alloys with high concentrations of alloying elements. However, as the density and distribution of dislocations in stage IA are considerably different from those in Lüders deformation, stage IA is thought to be different from Lüders deformation.