DSC study of ageing sequence in 6061 aluminium alloy - SiC whiskers composite

Results of a Differential Scanning Calorimetry (DSC) investigation on precipitation hardening in solubilized 6061 aluminum alloy and its composites reinforced with SiC whiskers are reported. The exothermic and endothermic effects in DSC traces of these materials (in the solubilized state) have been attributed to phase formation and reversion on the base of the 6061 AA ageing sequence described in previous TEM studies. Apparent activation energies have been calculated according to the Ozawa method in non-isothermal conditions. The ageing sequence in composites is analogous to that of 6061 AA. It was found that the SiC whiskers reinforcement accelerates many steps of the ageing sequence. G.P. zone reversion and β' and β phase precipitations happen at lower temperatures in composite materials than in 6061 AA. The apparent activation energy for β' formation calculated for aluminum alloy and its composite gave rather similar results. The handbook solubilization method reported for 6061 alloy could not allow a complete dissolution of alloying elements for the composite.