Structure and properties of quenched and aged Cu-2Be after deformation to large strains

Samples of a Cu-2Be alloy in the solution treated and quenched, lightly aged, and overaged conditions have been cold rolled up to 98% reduction. Structural changes have been determined by optical and electron microscopy, the texture by X-ray diffraction, and the mechanical properties by conducting tensile tests on specimens cut from the rolled strips. Inhomogeneous modes of deformation have been found, with shear banding becoming predominant at the larger strains. The zones produced by aging are completely disrupted by shear and slip banding at large strains. In the overaged material the initial orientation relationship between the γ' -precipitates and the matrix was broken down after large strains. In all the conditions of heat treatment the rate of development of texture with increasing strain was low and this could be related to the microstructural change. The relationship between the structure and properties is discussed in relation to results reported previously from similar experiments on an AI-4Cu alloy, and it is concluded that the differences can be associated with differences in stacking fault energy precipitate morphology and the homologous temperature. The results suggest that shear banding is a stress-induced deformation mode, like twinning, and does not depend upon achieving a suitable deformation texture.