Effects of Cu addition on microstructure and mechanical properties of as-cast Mg-6Zn magnesium alloy

Abstract

F or decades, magnesium alloys have wide applications in the aerospace, transportation and mobile electronics industries due to their advantages such as extremely low density and good damping capacity, high specific strength and stiffness, excellent machinability and good castability [1][2][3][4] . However, commercial magnesium alloys provide limited mechanical properties, which hinder their widespread applications [5] . More particularly, to the best of our knowledge, the Mg-Zn binary alloys possess coarse dendritic microstructures, extensive hot cracking tendency, critical shrinkage cavities and porosities. These drawbacks will significantly worsen the mechanical properties of the alloy [6] . The improvement of mechanical properties is a severe and urgent challenge in magnesium alloys research fields. He et al. [7] found that the mechanical properties of magnesium alloys can be significantly improved via appropriate microalloying due Abstract:The application of Mg-Zn binary alloys is restricted due to their developed dendritic microstructure and poor mechanical properties. In this study, an alloying method was used to improve the mechanical properties of Mg-Zn alloy. The Mg-6Zn magnesium alloys microalloyed with varying Cu content (0, 0.8, 1.5, 2.0 and 2.5wt.%) were fabricated by permanent mould casting, and the effects of Cu content on the microstructure and mechanical properties of as-cast Mg-6Zn alloys were studied using OM, SEM, XRD and tensile tests at room temperature.The obtained results show that the addition of Cu not only can refine the grains effectively, but also can modify the eutectic morphology and improve the mechanical properties of the alloys. The main phases of the studied alloys include α-Mg, MgZn 2 , Mg 2 Cu and CuMgZn. When the content of Cu exceeds 0.8wt.%, Mg 2 Cu phase appears. Meanwhile, the eutectic morphology is modified into dendritic shape or lamellar structure, which has an adverse effect on the tensile properties. Furthermore, among the investigated alloys, the alloy containing 0.8% Cu shows an optimal ultimate tensile strength of 196 MPa, while the alloy with 1.5wt.% Cu obtains an excellent elongation of 7.22%. The experimental alloys under different Cu contents show distinguishing fracture behaviors: the fracture of the alloy with 0.8wt.% Cu reveals a mixed mode of inter-granular and quasi-cleavage, while in other investigated alloys, the fracture behaviors are dominated by cleavage fracture. to grain refinement and microstructure modification in the as-cast condition. In order to improve the microstructure and mechanical properties of Mg-Zn binary alloys, many attempts have been devoted to the research and development of high-performance new Mg-Zn based alloys. For example, Mg-Zn-Zr, Mg-Zn-RE, Mg-Zn-Cu and Mg-Zn-Al-Mn alloy systems have been developed and widely applied for some industrial products. There are some minor alloying element investigations in Mg-Zn binary alloys, for instance, adding Ag, Zr, rare earth (RE) or Cu to the Mg-Zn alloy system [8] . It is noteworthy th...

Dynamic compressive behaviour and microstructural evolution of extrusion-shear Mg–6Zn–1Cu–1Y–0.6Zr alloy

“…Among commercially available magnesium alloys, Mg–Zn-based alloys are of particular interest because of their good age-hardening effects. However, they have coarse dendritic microstructures, tend to exhibit extensive hot cracking, and have critical shrinkage cavities and porosities; these characteristics deteriorate the mechanical properties [13]. Previous studies have shown that Cu significantly enhances the aging strength and improves the mechanical properties of magnesium alloys [13–16].…”

“…However, they have coarse dendritic microstructures, tend to exhibit extensive hot cracking, and have critical shrinkage cavities and porosities; these characteristics deteriorate the mechanical properties [13]. Previous studies have shown that Cu significantly enhances the aging strength and improves the mechanical properties of magnesium alloys [13–16]. According to reports by Zhu et al and Wang et al Mg–6Zn– x Cu–0.6Zr alloys have better yield strength, ultimate tensile strength, and elongation, when the added Cu is 0.5–1.0 wt-% [16,17].…”

Microstructure and mechanical properties of AZ31-Ce prepared by multipass solid-phase synthesis

“…The Al 4 Ce phase has some advantages such as high melting point, high stability and insolubility in α-Mg matrix. At the same time, the formation of Al 4 Ce reduces the β-Mg 17 Al 12 content, and then the Al content in the matrix decreases [21]. Al element has a certain initiative in the whole process of forming the Al 4 Ce layer.…”

Dynamic compressive behaviour and microstructural evolution of extrusion-shear deformed ZC61 alloy

“…However, Wang et al [12] demonstrated that ZK60 alloy has a rough dendritic microstructure that makes it prone to hot cracking, which degrades the mechanical properties. Moreover, Zhang et al [13] reported that the copper (Cu) element aided in significant increase in the age–strength and improvement in the mechanical properties of magnesium alloys. Zhu et al and Chen et al reported that the Mg–Zn–Cu alloys exhibited the best age-hardening phenomenon and tensile properties at room temperature when Cu was added in the range of 0.5–1.0 wt-% during the isothermal ageing process at 180°C [14,15].…”