The Study Of Electronic Theory Of Strengthening Mechanism Of Al-Mg-Si Alloy

As middle-high strength alloy, Al-Mg-Si alloy was attached importance increasingly by virtue of its excellent comprehensive properties, however, precipitation strengthening which was caused by the interaction between dislocation and second-phase article was the leading strengthening mechanism of this kind of alloy. At present, the mechanism of dislocation movement by shearing or circling usually was considered from hardness, dimension and distance of second-phase articles aspects, but had been gone deep into microcosmically electronic level. Concerning Al-Mg-Si based alloy, the microcosmic mechanism of precipitation strengthening had been understood completely so far because of its diverse precipitating-phases and intricate influencing factors, the intrinsically microcosmic causes of the mechanism of dislocation movement by shearing or circling and some properties of alloy were groped by calculating and analyzing respectively valence electron structures as well as atomic bonding represented crystal hardness and interfacial electron-distribution as well as interface energy aiming at all kinds of cells existing in melted solution of alloy and partial precipitation phases according to solid and molecule empirical electronic theory (EET) and interfacial electron structures calculating methods, this laid a foundation for bridging the relation between microcosm and macrocosm. The following contents and conclusions were included in this thesis:1. The valence electron structures of cells including Al-Mg, Al-Si, Al-Mg-Si, and Mg-Si probably existing in the melted solution of alloy containing little Mg and Si in the condition of the ratio Mg /Si>l were calculated. The results show that Mg-Si cell owning the strongest bond-net would become the structural heredity-gene, and contributed to solid solution strengthening to some extent.2. Sliding face bonding-gene H (H = ΣI_αE_α ) based on former study fruits and the microcosmic mechanism of the forming of hardness was proposed, and besides, its superiorities and defects were pointed out as well, this provided a new approach for comparing crystal hardness and valence electron analyzing of precipitation strengthening and dispersion strengthening.3. Valence electron structures and H genes of Al, Mg, GP zone with model Ll₀ , β (Mg₂Si) and β -Si in alloy were calculated. The results show that Mg -Mg bonds were the strongest in GP zones, this made GP zones tend to grow up into sheet; as for H genes,...