Influence of Zr content on microstructure and mechanical properties of As-cast Al-Zn-Mg-Cu alloy

摘要

Al-Zn-Mg-Cu alloy, as an important lightweight structural material in the aerospace field, has ushered in a broader application space and proposed higher performance requirements. This paper presents the experimental investigation of the effect of Zr content on the microstructure refinement and performance improvement of cast Al-5.8Zn-2.3Mg-1.7Cu alloy, aiming to optimize the additional amount of Zr, refine the alloy grains, and improve the microstructure uniformity and mechanical properties. The chemical component, phase, and microstructure were observed by inductively coupled plasma, X-ray diffraction, optical microscope and scanning electron microscope; the hardness and mechanical properties were measured by Brinell hardness tester and tensile testing machine. The addition of different contents of Zr into the alloy can form fine dispersed or primary coarse Al3Zr phase, which has a significant effect on the microstructure and mechanical properties of the alloy. The results indicate that the addition of 0.05 wt% Zr does not significantly improve the grain refinement and mechanical properties, but the Brinell hardness reaches the maximum. As the Zr content rises, the grain refinement effect becomes more obvious, while the mechanical properties first increase and then decrease. The addition amount reaches 0.20 wt%, the second dendrite arm spacing is the smallest, the ultimate tensile strength, yield strength and elongation at room temperature reach the maximum of 296.74 MPa, 249.41 MPa and 8.26%, respectively. When the amount of Zr added exceeds 0.20 wt%, the existence of coarse and brittle primary Al3Zr phase reduces the mechanical properties, and the fracture morphology changes from ductile to brittle intergranular fracture. (C) 2021 Elsevier B.V. All rights reserved.