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Ageing Processes in Al-Mg-Si Alloys during Continuous Heating

“…The hardness of the excess Si alloy was much higher than that of the quasi-binary alloy aged ate temperatures below PH2 but the hardness increment was much reduced in the over-aged condition. In the present study, although the hardness of the excess Mg alloy decreased in comparison with that of the quasi-binary alloy, Suzuki et al 23) reported that the excess Mg alloy quenched after complete solutionising induces hardness higher than that of the quasi-binary alloy. Such difference may arise from the incomplete solution-treatment, 23) because the chemical composition of this alloy was in rather critical region.…”

“…In the present study, although the hardness of the excess Mg alloy decreased in comparison with that of the quasi-binary alloy, Suzuki et al 23) reported that the excess Mg alloy quenched after complete solutionising induces hardness higher than that of the quasi-binary alloy. Such difference may arise from the incomplete solution-treatment, 23) because the chemical composition of this alloy was in rather critical region. The peak temperature of PH2 was lowered considerably with increasing excess Si content.…”

Influence of Excess Si on the Morphology and Thermal Stability of Metastable Precipitates Formed in an Al–Mg–Si Alloy

“…Figure 7(s) shows the HRTEM image of the microstructure of the S3 specimens aged at 483 K for 0.06 ks. Figure 7(1), (2) and (3) were taken with the specimens heated up to the exothermic peak temperatures of peak top, 450 K, 495 K and 530 K, respectively, at a heating rate of 0.17 K/s in the DSC apparatus after isothermally ageing for 0.06 ks at 483 K. Two small type-1 precipitates are observed, as indicated by arrows (T1) in Fig. 6(s).…”

“…We used the DSC curves of the specimen isothermally aged for 0.06 ks as the reference, DSC 530K Fig. 8 The density of the precipitates of each type for the S3 specimen heated at 0.17 K/s to each exothermic peak temperature in the DSC scan after isothermally ageing for 0.06 ks at 483 K. 2 ; heat corresponding to precipitates amount formed and reversed during DSC measurement, respectively…”

“…Some previous studies examined the density of the precipitates for an Al-Mg-Si alloy containing several excess Si concentrations at the peak hardness by bright-field TEM observations, electrical resistivity measurements and specific heat measurements. [1][2][3] In recent years, a HRTEM study investigated an Al-Mg-Si alloy containing excess 0.4 mass% Si and reported the morphology and structures of the precipitates formed during isothermal ageing. 4) There remain, however, a number of ambiguities in the features of the stability of metastable phases, the evolution of precipitates and the influence of excess Si on the hardness, and so on.…”