Effect of precipitates on plastic anisotropy for polycrystalline aluminum alloys

The effects of crystallographic texture and precipitate distribution on mac roscopic anisotropy in aluminum alloys were investigated. In order to simul taneously consider the effects of crystallographic texture and precipitate distribution on macroscopic anisotropy, predictions of plastic properties w ere carried out using an anisotropic yield function based on the material t exture and a combined isotropic-kinematic hardening rule. The input to the model was a single stress-strain curve, the crystallographic texture, and t he precipitate volume fraction, shape, and habit planes. It was shown that the kinematic hardening rule, which expresses a translation of the yield su rface in stress space, was a function of all the parameters describing the precipitate distribution. The model was applied to the case of an extruded and recrystallized binary Al-3 wt pct Cu alloy deformed in uniaxial compres sion in different directions. Excellent agreement was observed between the experimental and predicted yield stress anisotropy and the specimen cross s ection shape anisotropy. Gaussian distributions of grain orientations aroun d ideal texture components typical of aluminum alloys were generated using computer simulations. These textures were combined with the isotropic-kinem atic hardening rule determined for the Al-3 wt pet Cu binary alloy to theor etically assess the influence of precipitates on the r-value (the width-to- thickness plastic strain ratio in uniaxial tension) and yield stress anisot ropy for aluminum sheets. It was shown that, for these textures, the precip itate distribution had the effect of reducing plastic anisotropy, in agreem ent with the trends generally observed in practice.