Al-Mg alloy
The performance characteristics of Al-Mg aluminum alloy are: good mechanical properties at room temperature; strong corrosion resistance; poor casting properties, large fluctuations in mechanical properties and wall thickness effects; long-term use, the plasticity of the alloy due to aging drop, and even cracking occurs in die castings; the tendency of stress corrosion cracking in die castings is also greater. The disadvantages of Al-Mg alloy partially offset its advantages, making it limited in application.
Al-Zn alloy
Al-Zn aluminum alloy die castings can obtain higher mechanical properties after natural aging. When the mass fraction of zinc is greater than 10%, the strength is significantly improved. The disadvantage of this alloy is poor corrosion resistance, tendency to stress corrosion, and easy hot cracking during die casting. The commonly used Y401 alloy has good fluidity and is easy to fill the cavity. The disadvantage is that it has a large tendency to form pores, and when the content of silicon and iron is low, it is easy to be hot cracked.
Al-Si alloy
Because Al-Si aluminum alloy has the characteristics of small crystallization temperature interval, large solidification latent heat of silicon phase in the alloy, large specific heat capacity, and relatively small linear shrinkage coefficient, its casting performance is generally better than other aluminum alloys. Its filling ability is also good, and the tendency of thermal cracking and shrinkage is relatively small. The Al-Si eutectic contains the least amount of brittle phase (silicon phase), and its mass fraction is only about 10%, so its plasticity is better than that of other aluminum alloy eutectic, and the remaining brittle phase can be further treated by modification. Improve plasticity. The test also shows that the Al-Si eutectic still maintains good plasticity at the temperature near its freezing point, which is not found in other aluminum alloys. There is often a considerable amount of eutectic in the cast alloy structure to ensure its good casting performance; the increase in the number of eutectic will make the alloy brittle and reduce the mechanical properties, there is a certain contradiction between the two. However, due to the good plasticity of Al-Si eutectic, it can better take into account the requirements of both mechanical properties and casting properties, so Al-Si alloy is currently the most widely used die-casting aluminum alloy.
