Strength anisotropy in extruded copper-alumina bars

Abstract

Copper-alumina bars were made by hot extrusion of precompacted blends of powders. They have a [100] fibre texture in the core and a (100)[001] cyclical fibre texture in the outer layers. The sharpness of these textures is mainly determined by the size of the powders and by the volumetric concentration of alumina. Because of these particularly preferred orientations, a texture softening occurs under tensile loading but a pronounced texture strengthening is found in shear loading. Ratios of shear to tensile flow stress were measured and compared with estimations on the basis of pole figures. A good agreement was found. A maximal experimental value of ρ/ σ = 0.87 was measured in a 0.5 vol.% alumina bar in comparison with 0.54 for an isotropic material It is also shown how the presence of a (100) [001] cyclical fibre texture is responsible for unusually large elongations measured in free end torsion testing.