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In contrast to isothermal aging, few reports document the non-isothermal aging of deformed Al–Mg–Si alloys. The knowledge of non-isothermal aging of pre-deformed Al–Mg–Si alloys is of primary importance to understand the thermal stability as well as to control the microstructure of the final product during industrial processing. Therefore, the present work has been focused to understand the microstructure evolution during the continuous heating of a cold rolled Al–Mg–Si alloy. This has been followed using dilatometry, Differential Scanning Calorimetry, X-Ray Diffraction and microhardness measurement. Based on the results obtained, it is shown that dilatometry is a powerful tool to study phase transformations in deformed Al-Mg-Si alloys, moreover, the microstructural evolution, of the cold rolled sample, can be described as follows: at the earlier stages of the non-isothermal aging, formation and then the reversion of fully coherent GP zones take place. This is followed by the simultaneous occurrence of β” and β’ precipitation and recovery reaction. By continuing aging, the next reactions which will take place are β” and β’ dissolution and recrystallization. Finally, one can observe the formation and then the dissolution of the equilibrium phase β.

Despite the large number of papers dealing with the Al -Mg-Si system, the decomposition of the supersaturated solid solutions during the different aging treatments and therefore, the related hardening is still under debate. In the present work, by the use of simple techniques such as the Differential Scanning Calorimetry (DSC), Microhardness measurements and X-Ray Diffraction (XRD) analysis the precipitation behaviour and the impact of prior natural aging after homogenization on the subsequent microstructural and mechanical evolutions during artificial heat treatment at 160℃, of nuclear aluminium alloy Al-1.32% Mg-0.53% Si (% wt.) alloy, were identified. Through DSC, lattice parameter and microhardness measurements, the precipitation sequence were indirectly identified to be as follows: supersaturated solid solution (S.S.S.) → atomic clusters and GP zones →β” →β’ →β. The evolution of the mechanical properties during natural aging has been explained to be due to GP zones and atomic clusters formation. Storage at RT was found to have an important effect on the mechanical properties of the studied alloy. Under the light of the DSC results, this effect was explained by a slower precipitation kinetics of the β” phase; the atomic clusters and GP zones, which formed during storage at RT and the low concentration of the quenched-in vacancies in the stored samples have a delaying effect upon the nucleation of β” phase. Consequently, the final microstructure developed in these samples is coarse; hence lower mechanical properties are obtained

The effects of cold deformation and low temperature aging on the microstructural stability of a peak aged (PA) Al 6061 alloy were investigated by means of DSC and microhardness measurements. During aging at a relatively low temperature (100 °C) of the PA material, a small increasing of the mechanical properties was detected, which was explained by the formation of atomic clusters, GP zones and β phase. The response to the aging treatment of the cold deformed materials depends on both the level of the cold deformation and the aging temperature. During aging at relatively low temperature (100 °C), in contrast to the 75 % deformed material that shows a small variation in their mechanical properties, the mechanical properties, of the 30 % deformed material, are almost constant. This was attributed to the higher driving force of the recovery reaction in the heavily deformed material. In the other hand, aging at relatively higher temperature (140 °C) of the heavily deformed material, leads to a fast softening due to an increasing of the recovery kinetics.

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The precipitation phenomena and the related hardening in an Al-Cu-Mg-Si alloy were studied by calorimetry, X-ray diffraction analysis and microhardness measurements. The main calorimetric peaks were identified to be due to β ′′ , θ ′ and Q ′ phases precipitation. The hardening during aging at room temperature and 160 • C, was respectively, explained by atomic clusters and GP zones formation and by GP zones and β ′′ /θ ′ phases coprecipitation. Although the mechanical properties variation during aging at 200 • C is simple, the corresponding microstructural evolution is complex: on the basis of the DSC results, the increasing of microhardness values, is mainly due to the coprecipitation of GP zones and β ′′ /θ ′ phases, however, the maximum hardening is explained by the coexistence of β ′′ /θ ′ and θ ′′ phases. Another important conclusion is that during aging at 160 • C and 200 • C, the θ ′ phase is essentially developed from GP zones.