EFFECT OF 2ND-PHASE PRECIPITATES ON RECOVERY AND RECRYSTALLIZATION BEHAVIOR OF COLD-WORKED AL2024-SICP COMPOSITES

The restoration behaviour of SiC particle reinforced 2024-aluminium co mposite has been studied under conditions where recrystallization-grai n growth and precipitation occur concurrently. An emphasis has been gi ven to understanding the recrystallization-precipitation interaction, in the presence of SiCp, during annealing. The composite was fabricate d by a casting route followed by hot extrusion. Samples were cold defo rmed to a reduction in height of either 30 or 42 per cent following a heat treatment. The kinetics of recrystallization has been studied in the temperature range 100-485 degrees C. Recrystallization has been mo nitored by optical microscopy, coupled with hardness measurements. It has been observed that the composite has a lower recrystallization tem perature compared to that of an unreinforced alloy under identical ann ealing conditions. Following recrystallization, grain growth has been noticed in the composite. Although the degree of cold deformation show ed some effect on the recrystallization temperature of the composite, it was found to be a weak controlling factor for average recrystallize d grain size. Results showed that, in spite of the hardness reduction due to recrystallization-grain growth, the hardness of a composite can be partially restored by concurrent solid solution hardening (dissolu tion of precipitates) and also by the generation of dislocations durin g quenching to a low temperature.