Effects of zinc on the properties of Al-Si-Cu die-casting alloys

Abstract

In recent years, the demand for wrough alloys of Al-Zn-Mg system has rapidly developed and the usage of their return scrap or secondary ingot will be a matter of importance. The increase of Zn content in the die-casting aluminum alloys derived from these secondary ingots would be supposed. However, the effects of increased Zn content on the properties of the products have not yet been made clear. The present paper reports the effects of Zn, being present as impurity, in the content equivalent to ADC 10 (aluminum die-casting alloy) on mechanical properties, corrosion resistance, etc.
The results obtained were as follows:
(1) When Zn content was up to 1.48%, tensile strength slightly increased with the increase of Zn, but no effects were observed when the content was over the above limit. When the content was up to 2.88%, yield strength of 0.2% was almost no affected. Moreover, Zn content had little effects on hardness.
(2) Zn content had little effects on elongation, but impact value slightly decreased only when the content was in the range of 1.48-2.0% while it was little changed for over 2.0%.
(3) In salt water (3%) immersion test, weight loss slightly increased with the increase of Zn content. Anode potential (saturated calomel electrode) gave a higher absolute value when Zn content was higher; which proved that Zn content also had effects on corrosion resistance.