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The effect of T5 heat treatment on microstructure and mechanical properties of A356 alloy was observed. The as-cast A356 alloy exhibited coarse dendrites and long Si needles. RSF process changed the dendritic α-Al phase to globular morphology which helps in improving the mechanical properties of the alloy. The addition of 0.6wt-% Al–5Ti–1B grain refiner refined the average grain size of primary α-Al phase. T5 heat treatment at 170 °C for 20 h in different processing conditions was given to A356 alloy. T5 heat treatment led to further refinement of α-Al phase and Si needles, precipitation hardening due to Mg2Si phase and reduction in the porosity level (%). The Quality Index for A356 alloy in different processing conditions was also measured. Results showed that RSF process with the use of baffles, addition of grain refiner and T5 heat treatment had improved the mechanical properties over other processing conditions. [ABSTRACT FROM PUBLISHER]

Al-Cu alloys of compositions near eutectic point [hypoeutectic (Al-19Cu), eutectic (Al-33Cu) and hypereutectic (Al-35·5Cu) and (Al-36Cu)] were chemically modified by adding 0·6 wt-%Al-Ti5-B1 master alloy. In addition, the specimens of unmodified and chemically modified eutectic alloy were heat treated at 500°C for different holding times (4, 24, 48 and 72 h for the unmodified and 4 and 29 h for the modified ones) followed by water quenching. The structure of chemically treated alloy was changed from large dendrites to fine rosette shaped α-Al grains inside fine eutectic matrix. For these alloys, the liquid-solid transformation temperature was shifted to a higher value. The addition of Al-Ti5-B1 master alloy to the eutectic (Al-33Cu) alloy transforms it into hypoeutectic one of fine lamellar eutectic structure. The chemically treated hypereutectic alloy (Al-35%5Cu) was changed into full eutectic alloy. [ABSTRACT FROM AUTHOR]