Effect of SiC volume fraction on the age-hardening behavior in SiC particulate-reinforced 6061 aluminum alloy composites

The age-hardening behavior in the SiC particulate-reinforced 6061 aluminum alloy composites (SiCp/6061 Al alloy composites) was investigated using hardness measurement, calorimetric technique and transmission electron microscopy. The aging time for the peak hardness in 10%SiCp/6061 Al and 20%SiCp/6061 Al alloy composites was shorter than that of the unreinforced 6061 Al alloy, and the age-hardening was most accelerated in the 20%SiCp/6061 Al alloy composite. It is induced from the high density of dislocations in SiCp/6061 Al alloy composites which act as heterogeneous nucleation sites of precipitates and as a high diffusivity path of alloy elements. The precipitation sequence and the aspect of precipitates in the 6061 Al alloy cannot be affected considerably by the presence of SiC particulate and the volume fraction of SiC particulate. The activation energies for the formation of the intermediate β' phase in the unreinforced 6061 Al alloy, 10%SiCp/6061 Al and 20%SiCp/6061 Al alloy composite were 142.6 kJ/mol, 127.3 kJ/mol, 106.1 kJ/mol, respectively.