The development of low-temperature heat-treatable high pressure die-cast Al-Mg-Fe-Mn alloys with Zn levels

Abstract

© The Author(s) 2021. In the present work, a novel low-temperature heat-treatable recycled die-cast Al–Mg alloy was developed by adding Zn into non-heat-treatable Al–5Mg– 1.5Fe–0.5Mn alloy. The results showed that Zn additions resulted in the for- mation of equilibrium phase T-Mg32(Al, Zn)49 under as-cast condition, which can be dissolved into the a-Al matrix at a relatively low solution temperature (430 °C) and thus set the base for the low-temperature heat treatment. The mechanical test results indicated that Zn additions had a smooth liner improvement in the strength of all as-cast alloys and T6-state alloys with 1% and 2% Zn as its concentration increased but resulted in a sharp improvement on the strength of T6-state alloy when Zn concentration increased from 2 to 3%. TEM analysis revealed that the precipitate in T6-state Al–5Mg–1.5Fe–0.5Mn–3Zn alloy is g0 phase, rather than the widely reported T00 or T0 phase in other Al–Mg– Zn alloys with approximately same Mg and Zn concentrations. After the opti- mized low-temperature T6 heat treatment (solution at 430 °C for 60 min and ageing at 120 °C for 16 h), the Al–5Mg–1.5Fe–0.5Mn–3Zn alloy exhibits the yield strength of 321 MPa, ultimate tensile strength of 445 MPa and elongation of 6.2%.