1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China; 2. Advance Research Center, Central South University, Changsha 410083, China
Abstract：Two kinds of Al-Zn-Mg-Cu alloys adding Zr, Cr elements and Zr, Cr and Yb clements were prepared by the melting and casting method, respectively. Optical microscopy, transmission electron microscopy, and scanning electron microscopy were used to observe the microstructure of these alloys, and mechanical and corrosion properties were also tested. The results show that AlZnMgCu-Zr-Cr-Yb alloy maintains a fibrous structure dominated by small angular grain boundaries after solid solution treatment, which is attributed to the precipitation of a large number of fine and diffuse (Al,Cr)3(Zr,Yb) phases of 10-20 nm, which can hinder dislocation and grain boundary migration and thus significantly inhibit matrix recrystallisation. The addition of Yb can increase the hardness, strength, elongation, and fracture toughness of the alloy, with the fracture toughness increases from 24.2 MPa·m1/2 to 32.4 MPa·m1/2. The resistances to stress corrosion, intergranular corrosion, and exfoliation corrosion all increase at the same time, with the threshold stress intensity factor for stress corrosion cracking (KISCC) increases from 10.6 MPa·m1/2 to 17.0 MPa·m1/2. The intergranular corrosion depth decreases, the exfoliation susceptibility reduces and the exfoliation grade lowers from EB+ to EA.
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2023, Vol. 28 
