Ripening of the AlSi9Cu3ZnMg alloy - mechanical and microstructural characterisation

Abstract

Recovered aluminium has poor mechanical properties, to improve them considerably, three main factors have been considered. The first is to add four very low-density elements to the recovered aluminium, including 9% silicon, 3% copper and some traces of zinc and magnesium less than 1% (≤ 1% Zinc, ≤ 1% Mg), which produces the non-standardized casting alloy AlSi9Cu3ZnMg. Then, in order to obtain a fine microstructure, a gravity die-casting is carried out in the as-cast state noted: F. Finally, to further increase the strength of the F-state and essentially obtain high elasticity stresses, high rigidity modulus with low deformations, the AlSi9Cu3ZnMg alloy composed of 60% scrap and 40% new ingots, is subjected to structural hardening by varying the ripening time for 24 hours in increments of 2 hours, thus giving rise to precipitates of various kinds which impede the dislocations sliding. The results thus obtained show that the cured state for 12 hours (M12h) is a good compromise between good strength and maximum ductility.

Keywords

• aluminium alloys, ripening, hardening, microstructure.