Age-hardening of high pressure die casting AlMg alloys with Zn and combined Zn and Cu additions

Abstract

This study investigates the age-hardening of AlMg alloys with Zn and combined Zn and Cu additions. Two AlMg5Mn1 alloys modified with Zn and Cu were processed by high pressure die casting (HPDC) and different heat treatment strategies. Single step artificial aging, artificial aging with pre-aging and the effect of the quenching rate were studied via hardness measurements and transmission electron microscopy (TEM). Single-step artificial aging resulted in an increase in hardness of 58% in peak aged condition for the Zn-only modified alloy and of 56% for the Zn- and Cu-containing alloy. Pre-aging treatments either reduce the necessary aging time or increase the hardness, depending on the parameters used. Microstructural investigations indicate a significant change in the S- or T-phase precursors, and in precipitation density with pre-aging. The alloys have high potential for use as complex structural HPDC components in lightweight transport applications, but are also of general interest for components which require high strength and formability. Keywords: Aluminum alloys, AlMg, Alloy design, Hardening behavior, Precipitation, High pressure die casting