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Alloying of aluminum with high content of magnesium and silicon (>20 mass-% Mg2Si) offers the possibility of a significant decrease in density (density Mg2Si 2.0 g/cm3) and an increase in stiffness (Young´s modulus Mg2Si 120,000 MPa) at the same time. Due to the high solidification rate a very fine distribution of the Mg2Si-particles can be achieved by spray forming. Twelve aluminum alloys with Mg2Si-contents between 22 and 30 mass-% and additional alloying elements like copper, titanium, vanadium and zirconium were successfully spray formed, extruded and heat treated with different process conditions. A Mg : Si ratio close to the equilibrium mass ratio of Mg2Si (approx. 1.73 : 1) is adjusted for all these alloys. Those new light-weight aluminum alloys have been investigated regarding microstructure, density and mechanical properties. An increase of the Mg2Si-content reduces the density below 2.5 g/cm3 while improving the mechanical properties. Tensile tests at elevated temperatures exhibit a good thermal resistance. Furthermore, a significant dependency of microstructure on mechanical properties was noticed. The microstructural investigations indicate the direct influence of the process parameters on the observed phases respectively properties. Applications of the new light-weight aluminum alloys can be expected where a reduced density together with a high hot yield strength would lead to a more compact design in high temperature environments, e.g. in combustion engines.