Influence of silicon content and heat treatment parameters on mechanical properties of cast Al–Si–Mg alloys

Abstract

The influence of silicon content and solution and aging temperature on microstructure and mechanical properties, and mode of fracture of cast Al-(4-20)Si-0 . 3Mg alloys is reported. Alloys were prepared by controlled melting, casting and heat treatment. Increasing solution temperature from 450 to 550uC and aging temperature from 150 to 230uC increased the tensile strength of all the Al-Si-Mg alloys. High solution temperatures produce greater refinement and distribution of eutectic silicon grains than low temperatures. Scanning electron microscopy of tensile fracture surfaces showed that the fracture surface of specimens treated at higher solution and aging temperatures is characterised by finer, equaixed dimples than that of specimens heat treated at lower temperatures.a Al-4Si-0 . 3Mg; b Al-8Si-0 . 3Mg; c Al-12Si-0 . 3Mg; d Al-16Si-0 . 3Mg; e Al-20Si-0 . 3Mg 1 Optical micrographs of as cast alloys Dwivedi et al. Influence of silicon content and heat treatment parameters on properties of Al-Si-Mg alloys

Influence of Si and cooling rate on microstructure and mechanical properties of Al–Si–Mg cast alloys

“…A similar influence of Si content on mechanical properties has also been reported by other studies. [9][10][11] Increasing the Si level in the materials increased the fraction of hard and brittle eutectic phases while decreased the soft and ductile Al phases. Also, the microstructure was affected by increasing the Si concentration; the Al phase was refined, and the dendrite boundary, which is the eutectic phase, was well structured.…”

“…[8] The influence of Si content and its morphology on mechanical properties of Al-Si alloys has been investigated. [1,7,[9][10][11][12][13] Si additions can reduce the density and coefficient of thermal expansion, and improve the mechanical properties, which include the modulus, strength, hardness and wear resistance of Al alloys; however, the ductility decreases with an increase of Si level. [9][10][11] The mechanical properties of Al-Si alloys are also determined by the morphology of the Si particle.…”

Effect of Solution Heat Treatments on the Microstructure and Mechanical Properties of a Die-Cast AlSi7MgMn Alloy

“…[14,42] The reason for the increase in strength is primarily due to the precipitation of metastable b¢-Mg 2 Si precipitates from the supersaturated solid solution, which obstructs the movement of dislocations. Generally, from the AQ condition, in which the mechanical properties are principally controlled by supersaturated solid solution, the average YS and UTS increase by more than 70 and 20 pct, respectively, in fully T6 heat-treated specimens.…”

“…[10][11][12][13][14][15][16] It was established that the magnesium and silicon contents in a-Al phase reach the maximum equilibrium level according to the alloy composition, and that the distribution of magnesium and silicon becomes homogeneous within less than 1 hour of solution heat treatment. The mathematical model proposed by Rometsch et al also provides evidence that the dissolution of the primary Mg 2 Si particles and the homogenization of the a-Al solid solution are strongly influenced by the scale of the microstructure.…”

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).…”