The effects of Cu and Sn additions on the precipitation hardening of Al-Mg-Si alloys were systematically studied by performance testing and microscopic characterisation. Sn addition can retard the onset of natural aging (NA), while after long-term NA, the NA hardening is enhanced. Although Cu and Sn can promote the NA hardening, the Cu and Sn combination addition results in NA hardness lower than the individual Cu addition. Compared with Sn, Cu addition is more efficient in promoting the artificial aging hardening of these alloys. Both of the Sn and Cu atoms can incorporate in the interior of the β′′ phase and produce disordered structure. The results are expected to provide new insight for designing new aluminium alloys for automotive application.
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