Evolution of the Initial Precipitation and Strengthening Mechanism of Al-Mg-Si alloys

The evolution of the initial precipitation and strengthening mechanism of Al-Mg-Si alloys during non-isothermal aging were investigated. The results indicated that, during heating, two corresponding strength peaks appear, which were attributed to the precipitation of clusters and β″ precipitates. The strong coherency strain field attributed to β″ conferred maximum strengthening effects on Al-Mg-Si alloys. Three variants of clusters were identified, and the sequence of evolution was as follows: the spherical morphology of cluster 1 evolved into an elongated morphology, first located on the tight surface {111}Al plane and growing along the \( \left\langle {111} \right\rangle \)Al direction (cluster 2). When cluster 2 exceeded a certain size, it oriented itself on the {100}Al plane and along the \( \left\langle {100} \right\rangle \)Al direction as cluster 3, which was then transformed into the β″ phase. The strengthening contributions of the various initial precipitates of the alloy were ultimately evaluated.