Effect of mushy state rolling on age-hardening and tensile behavior of Al–4.5Cu alloy and in situ Al–4.5Cu–5TiB2 composite

▶ Mushy state rolling of composites reduces peak-aging times to ≈7.5–10% of that of as-cast alloy. ▶ Uniform Cu atom distribution achieved in matrices by mushy state rolling enhances aging kinetics. ▶ Uniform precipitate distribution obtained by mushy state rolling leads to higher microhardness. ▶ Peak-age tensile strength and strain hardening rates are found to increase on mushy state rolling. The effect of mushy state rolling on aging kinetics of stir-cast Al–4.5Cu alloy and in situ Al–4.5Cu–5TiB2 composite and their tensile behavior in solution-treated (495°C) or differently aged (170°C) conditions, has been investigated. As-cast or pre-hot rolled alloy and composite samples were subjected to single or multiple mushy state roll passes to 5% thickness reduction at temperatures for 20% liquid content. Peak-aging times of mushy state rolled composite matrices have been found as ≈7.5–10% of that of as-cast alloy. Such enhancement in aging kinetics is attributed to homogeneity in Cu atom distribution as well as increase in matrix dislocation density due to thermal expansion coefficient mismatch between Al and TiB2, matrix grain refinement and particle redistribution, achieved by mushy state rolling. Uniform precipitate distribution in mushy state rolled composite matrices leads to greater peak-age microhardness with higher yield and ultimate tensile strengths than those in as-cast alloy and composite.