The aging precipitation behavior of particle reinforced aluminium matrix composites

It has been well established that the addition of ceramic particles to aluminium matrices results in composites exhibiting different aging kinetics compared to the unreinforced matrix alloys. A range of different weight fraction SiC particle reinforced 6066 aluminium matrix composites and unreinforced alloys have been prepared using spray deposition, and compared to the as-received ingot metallurgy alloy. The materials were processed using extrusion. Results reveal that the activation energies of aging precipitation are much lower for the composites relative to that of the as-received 6066 alloy ingot metallurgy in terms of the calculations using the Kissinger method. This acceleration is attributed to the decreased incubation time required for nucleation and solute diffusivity. Precipitate growth is also facilitated by the high dislocation density in the matrix resulting from the mismatch of the coefficient of thermal expansion and stiffness between the matrix and the ceramic particle. It is also suggested that the grains were refined due to rapid solidification during spray deposition, resulting in reserving much higher accumulated system energy and accelerating heterogeneous nucleation and boosting the kinetics of aging precipitation in the composites.