Unravelling precipitation behavior and mechanical properties of Al-Zn-Mg-Cu alloy

We investigate the effect of aging temperature on precipitation behavior and mechanical properties of an Al-7.6Zn-2.7Mg-2.0Cu-0.1Zr-0.07Ti (wt.%) alloy by evaluating the matrix's microhardness, electrical resistivity, and tensile properties: additionally, employing X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and atom-probe tomography (APT) to characterize this alloy. The nanoprecipitates forming under peak-aging conditions vary with aging temperature, forming coherent GPI zones at 80 degrees C, GPII zones with minor eta ' at 120-150 degrees C, and eta '/ eta with minor GP zones at 180-220 degrees C. GPI and GPII zones forming at 80-150 degrees C contain similar concentrations of solute atoms (11Zn-9Mg-( < 1.0)Cu (at.%)), whereas the eta '/ eta nanoprecipitates forming at 180 degrees C contain larger concentrations of solute atoms (28Zn-24Mg-3.4Cu (at.%)). The strength of the peak-aged alloy decreases with increasing aging temperature owing to the increasing size and decreasing number density of the nanoprecipitates. Under peak-aging conditions, precipitation strengthening originates mainly from dislocation shearing at 80-150 degrees C and from Orowan bypassing at temperatures above 180 degrees C. The shearable to non-shearable transition of the nanoprecipitates at 180 degrees C reduces the strain hardening rate, thereby decreasing the alloy's ductility. (c) 2024 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.