Influence of Mg Content on the Microstructure and Solid Solution Chemistry of Al-7%Si-Mg Casting Alloys During Solution Treatment

The heat treatment of Al–Si–Cu–Mg casting alloys

“…e Al-Si-Mg alloy is faster than for the Cu at can be used and the faster diffusivity of -Fe phase transforms into the β-Fe phase and 30°C and the concentration of Mg in the th literature [18,28]. Complete dissolution r the two finest microstructures (Figure 8d-e Si) phase forms during artificial ageing.…”

“…The strength and ductility obtained are affected by factors such as if the Cu and Mg are present as coarse phases after solidification, as atoms in solid solution, as GP zones formed at room temperature, or as precipitates formed during artificial ageing [7]. The coarse phases which may form during solidification are the Al 2 Cu phase and the QAl 5 Mg 8 Si 6 Cu 2 phase in Al-Si-Cu-Mg alloys [16,17], while the π-Al 8 Mg 3 FeSi 6 phase and the Mg 2 Si phase form in Al-Si-Mg alloys [18]. These coarse phases do not contribute to strength and their degree of influence on ductility depends on their distribution and size relative to the Si particles [19].…”

Effects of metallurgical parameters on the decomposition of л-AlFeMgSi phase in AL-SI-MG alloys and its influence on the mechanical properties /

“…In support of the latter suggestion, it was observed that an elevated quality index (Q) can be obtained in Al7Si-Mg alloys with Mg contents of between 0.4 and 0.5 wt % which is less than the solubility limit in Al-matrix, and it was also observed that this is a range where the 7r-phase can decompose to a large extent into /?-phase needles. 10 A gain in the Q may be expected if the 7r-to /?-phase decomposition in Al-7Si-0.6Mg alloys is susceptible to being enhanced by solution heat treatments longer than 8hours. The following sections will thus focus on studying the effects of extended periods of solution treatment time and cooling rate on the decomposition of the 7r-phase in selected non-modified and Sr-modifted Al-7Si-0.55Mg-0.1 Fe alloys in order to understand the phenomenon of the n-to /?-phase decomposition and how it affects the chemistry of the matrix and the mechanical properties.…”

“…10 Since the solution treatment temperature for this type of alloy is restricted to 540° ± 5°C to avoid localized melting at the grain boundaries, 57 ' 103 solution treatment time appears to be the only parameter available for regulating the extent of n-to /?-phase decomposition. 48 hrs, the fragmented jr-phase particle "a" is completely decomposed into small /?-phase needles, while particle "b" is still in the process of decomposition, as may be observed in On the other hand, the results show r that there is no significant difference in the volume fraction of /?-phase particles formed during solidification in the as-cast nonmodified and Sr-modified samples for both low and high cooling rates, as can be seen from shown in Figure 4.19, in order to demonstrate the variation in the n-to /?-phase decomposition rate with respect to solution treatment time.…”

Optimizing the Heat Treatment Process of Cast Aluminium Alloys

“…Various efforts have been made to investigate the effects of solution temperature and time on microstructure and mechanical properties of AlSiMg foundry alloys (Zhang et al, 2002;Rometsch et al, 1999;Pedersen & Arnberg, 2001;Shivkumar et al, 1990a;Dwivedi et al, 2006;Taylor et al, 2000;Langsrud & Brusethaug, 1998;Cáceres et al, 1995;Cáceres & Griffiths, 1996;Wang & Cáceres, 1998). Quenching is usually carried out to room temperature to obtain a supersaturated solid solution of solute atoms and vacancies, in order to achieve an elevated strengthening subsequent ageing (ASM Handbook, 1991;Liščič et al, 1992;Komarova et al, 1973;Totten et al, 1998;Totten & Mackenzie, 2000).…”