Controlling factors of microstructural evolution and corresponding deformation behaviour of Al–4Cu alloy in semisolid state

Abstract

The present work describes the microstructural evolution of an Al–4Cu alloy and its deformation response, as measured by the parallel plates technique. Specimens were heat treated to obtain a variety of Al₂Cu dispersions, and deformed by extrusion (1:16 ratio). Results indicated that microstructural coarsening took place initially by particle coalescence, but after 10 min soaking time Ostwald ripening became the controlling mechanism. It was also shown that texture accelerated particle growth rate by increasing the likelihood that chance encounters produced grain boundaries, and hence coalescence events. The mechanism of action of particle stimulated nucleation of recrystallisation was suggested, by observing that the particle growth kinetics of deformed specimens was much higher than that of non-deformed specimens with their larger initial particle size and slower initial growth rate. Finally, rheological experiments showed that deformation behaviour was mainly controlled by particle shape, and to a lesser extent by particle size.