Improved age-hardening response and altered precipitation behavior of Al-5.2Mg-0.45Cu-2.0Zn (wt%) alloy with pre-aging treatment

In this research, pre-aging treatment has been performed on our newly developed Al-5.2Mg-0.45Cu-2.0Zn alloy. Results show that the age-hardening response of the alloy has been significantly improved with pre-aging treatment due to a modified precipitation microstructure. Without pre-aging treatment, the microstructure in peak aged condition consists of coarse lath-like T-Mg32(Al, Zn)49 phase and needle-like S-Al2MgCu phase. However, the microstructure of the alloy in peak aged condition with pre-aging treatment only consists of high density of finer and equiaxed T phase with the S phase disappeared. Though both kinds of T phases have the same body-centred cubic (BCC) Mg-32( Al, Zn)(49)-type structure (Im3, a = 1.422 nm), they have big difference in composition. Schematic illustration of the precipitation behaviors in the alloy during aging at 180 degrees C with or without pre-aging treatment is made according to the analysis results. (C) 2016 Elsevier B.V. All rights reserved.