Microstructure and mechanical properties of squeeze-cast Al−5.0Mg−3.0Zn−1.0Cu alloys in solution-treated and aged conditions

固溶态和时效态挤压铸造Al−5.0Mg−3.0Zn−1.0Cu合金的显微组织及力学性能

The microstructure and mechanical properties at different depths of squeeze-cast,solution-treated and aged Al−5.0Mg−3.0Zn−1.0Cu alloy were investigated.For squeeze-cast alloy,from casting surface to interior,the grain size ofα(Al)matrix and width of T-Mg32(AlZnCu)49 phase increase significantly,while the volume fraction of T phase decreases.The related mechanical properties including ultimate tensile strength(UTS)and elongation decrease from 243.7 MPa and 2.3%to 217.9 MPa and 1.4%,respectively.After solution treatment at 470℃ for 36 h,T phase is dissolved into matrix,and the grain size increases so that the UTS and elongation from surface to interior are respectively reduced from 387.8 MPa and 18.6%to 348.9 MPa and 13.9%.After further peak-aging at 120℃ for 24 h,numerous G.P.II zone andη′phase precipitate in matrix.Consequently,UTS values of the surface and interior increase to 449.5 and 421.4 MPa,while elongation values decrease to 12.5%and 8.1%,respectively.

研究Al−5.0Mg−3.0Zn−1.0Cu合金挤压铸造态、固溶态和时效态显微组织及力学性能随截面深度的变化规律。对于挤压铸造态合金,从表层到心部,α(Al)的晶粒尺寸和T-Mg32(AlZnCu)49相的宽度显著增加,而T-Mg32(AlZnCu)49相的体积分数显著下降,这些变化导致挤压铸造态合金抗拉强度从243.7 MPa降低到217.9 MPa,伸长率从2.3%降低到1.4%。在470℃下固溶处理36 h后,大部分第二相溶解于α(Al)基体中,并且表面和心部的晶粒尺寸均较挤压铸造态的增大,从表层到心部,合金的伸长率从18.6%降低到13.9%,抗拉强度从387.8 MPa降低到348.9 MPa。在120℃下进一步时效24 h后,在基体中析出G.P.II区和η'相,合金表层和心部的抗拉强度分别增加到449.5 MPa和421.4 MPa,而伸长率则降至12.5%和8.1%。