The properties of Al Mg aluminum alloy are as follows: good mechanical properties at room temperature; strong corrosion resistance; poor casting performance, large fluctuation of mechanical properties wall thickness effect; long-term use, the plasticity of the alloy decreases due to aging effect, even the cracking phenomenon of die-casting parts; the tendency of stress corrosion cracking of die-casting parts is also large. The disadvantages of Al Mg alloy partially offset its advantages, which limits its application.
The mechanical properties of Al Zn aluminum alloy die casting can be improved after natural aging. When the mass fraction of zinc is more than 10%, the strength of die casting can be improved significantly. The disadvantages of this alloy are poor corrosion resistance, tendency of stress corrosion easy to hot crack during die casting. The common y401 alloy has good fluidity is easy to fill the cavity. The disadvantage is that it has a large tendency to form pores, it is easy to hot crack when the silicon iron content are small.
As Al Si aluminum alloy has the characteristics of small crystallization temperature interval, large solidification latent heat, large specific heat capacity small linear shrinkage coefficient, its casting performance is generally better than other aluminum alloys, its filling capacity is better, its hot cracking shrinkage porosity inclination are also smaller. The amount of brittle phase (silicon phase) in Al Si eutectic is small, its mass fraction is only about 10%. Therefore, its plasticity is better than that of other aluminum alloys. The only brittle phase can be further improved by modification. The experiment also shows that Al Si eutectic has good plasticity near its solidification point, which is found in other aluminum alloys. In order to ensure the good casting properties, a considerable amount of eutectic is often needed in the structure of casting alloy. The increase of the amount of eutectic will make the alloy brittle reduce the mechanical properties. There is a certain contradiction between the two. However, due to the good plasticity of Al Si eutectic, which can meet the requirements of both mechanical properties casting properties, Al Si alloy is a widely used die-casting aluminum alloy.