Rheology and microstructural development of a Al-4wt%Cu alloy in the semi-solid state

Rheological and microstructural studies were performed on a Al-4wt%Cu alloy in the semi-solid state employing two different experimental techniques: t he indentation test and the simple compression test. Results showed that re crystallized microstructures exhibit lower viscosities than dendritic micro structures and that the theological behavior can be described by the Power Law. The viscosity values were analyzed in terms of solid volume fraction a nd deformation rate and the pseudoplasticity of the Al-4wt%Cu alloy was thu s ascertained. As for the solid particle size and shape evolution within th e semi-solid temperature range, the experimental growth kinetics obeyed the classic D-3 = K(c)t relation, which indicates a Ostwald Ripening type of g rowth, but the particles size distribution was wider than the one predicted by the LSW theory. Also, comparison of the experimental and the theoretica l growth rate constants suggested that coarsening due to hard impingement o f the solid particles was the main growth mechanism. (C) 1999 Elsevier Scie nce S.A. All rights reserved.