Cu-Be合金鋳物の応力負荷時効による変形

抄録

  Cu-Be alloy castings revealed an anomalous phenomenon of spontaneous deformation by aging under stress and restoration of the deformation by solution treatment. Three kinds of Cu-Be cast alloys containing beryllium of 1.5 mass %, 2.0 mass % and 2.5 mass % respectively were prepared. The alloy containing beryllium of 1.5 % is mainly composed of the α phase and the alloys containing beryllium of 2.0 % and 2.5 % are composed of the α and β phases. The cast alloys were cut into plate-like specimens of 2.5 mm thickness. The plate was fixed to a cantilever jig and loaded at the free end of the cantilever up to the elastic limit of the alloy. The loaded specimen was aged to measure deflection following spontaneous deformation. The Cu-1.5 % Be alloy composed of uniform α phase exhibited the highest warping deflection and the longest incubation time to start the spontaneous warping among the alloys. The spontaneous warping has a close correlation to the hardening and contraction behaviors during aging and therefore to the precipitation of the metastable γ” and γ’ phases in the α phase of Cu-Be alloy. These experimental results indicate that the warping deflection and the incubation time are dependent upon the volume fraction and beryllium content of the α phase, respectively. Homogenizing treatment was found to be effective in enhancing the warping deflection and shortening the incubation time even in cast alloy with higher beryllium content due to the dissolution of β phase.