Composition Gradient and Particle Deformed Zone: An Emerging Correlation

Compressive ductility of the as-cast AA7075 was nearly doubled by hot compression and by appropriate homogenization treatment. The latter dissolved the 2nd phase, and introduced compositional gradients around the ‘surviving’ precipitates. Direct observations, through split channel die compression, revealed a correlation between particle deformed zone (PDZ: deformed aluminum matrix surrounding coarse 2nd phase particle), the composition gradient and the working temperature. Local misorientation in the PDZ reduced, remarkably, with the introduction of composition gradient and higher working temperature. The generation of PDZ, especially the influence of the composition gradient and the working temperature, was modeled successfully with discrete dislocation dynamics (DDD). More importantly, tailoring the composition gradients around the second phase brought out clear technological possibility of improving the as-cast compressive ductility without sacrificing the particle content and the compressive strength.