Effects of rapid heat transfer using a fluidized bed on the heat-treating response of Al-Si-Mg alloys (both unmodified and Sr modified) were investigated. Heating rate in fluidized bed (FB) is an order of magnitude greater than in conventional air convective furnaces (CF). On aging using FB, it was observed that the nucleation rate of Mg2Si particles was greater than in CF. Thermal analyses show an endothermic reaction during aging in CF. No such transformation was observed during aging in FB. The endothermic transformation could be due to the dissolution of GP zones or metastable phase(s). The total heat treatment time for T6 temper was reduced to less than 2 h using FB.