Rheological behaviour and deformation characteristics of a commercial and a laboratory-cast Al-4%Cu alloy in the semi-solid state

A commercial AA2024 and a Al-4%Cu alloy in the semi-solid state (high solid volume fraction) were studied with regard to both theological and mechanic al behaviour during simple compression. From stress-strain curves and power law exponents analysis two deformation regimes were identified. The deform ation response was adequately described by the Ngyuen, Favier and Suery the oretical model. Comparison of stress-strain curves of the two materials sho wed that the 2024 alloy has higher intrinsic resistance. Interrupted and ju mp compression tests, plus different dwelling time experiments gave informa tion on both thixotropy and microstructural evolution of the alloys. Micros tructural observation showed that deformation is highly inhomogeneous and t akes place by the formation of liquid,filled channels surrounding particle aggregates. Correlations between liquid phase segregation, particle size di stribution and process parameters are discussed. (C) 2001 Acta Materialia I nc. Published by Elsevier Science Ltd All rights reserved.