抄録
It has been experimentally clarified that the shear fracture in tension tests of Al-4%Cu-0.5%Mn-0.5%Mg alloy arises from two different origins: the one is the negative strain rate sensitivity of flow stress and the other is the formation of sharp ⟨111⟩ fiber texture. The shear fracture due to the former is observed in the solution treated specimen stretched at ambient temperature, but that due to the latter occurs in the aged specimen stretched not only at ambient temperature but at 77 K. In the aged specimen having nearly random texture the shear fracture does not occur. The texture-induced shear fracture has been analyzed based on the Bishop-Hill theory. The analysis shows that the difference between the stress necessary for the shear deformation and that for the axisymmetrical deformation is less in the specimen with the sharp ⟨111⟩ texture than in that with the random one. Furthermore the geometric softening due to the crystal rotation occurs in the shear deformation zone of the ⟨111⟩ textured specimen. These results can explain that the formation of sharp ⟨111⟩ texture is a requisite for the occurrence of shear fracture in the aged specimen.
