Microstructure and mechanical properties of Al-6.02Zn-1.94Mg alloy at higher solution treatment temperature

Abstract

The effects of solution treatment temperature and holding time on the microstructure and mechanical properties of extruded Al-6.02 wt.%Zn-1.94 wt.%Mg alloy were investigated by differential scanning calorimetry (DSC), optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and tensile test. The results showed that the optimum solution treatment process for the alloy was 470 °C, 2 h. The tensile strength, yield strength, and elongation of the samples after the aging treatment at 120 ° C for 24 h were 486 MPa, 431 MPa, and 14.8%, respectively. The alloy produced more copious recrystallization with the augment of solution temperature and the extension of holding time. While the second phase of η (MgZn₂), and T (AlZnMgCu) in the matrix was not fully re-dissolved under the treatment condition of lower temperature or shorter holding time. Interestingly, the Zr aggregation was observed in the samples treated at 510 ° C for 2 h, which led to the growth of the second phase particles and the increase of their area fraction.

Keywords

microstructure / solution treatment / second phase / recrystallization / aggregation

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