Abstract
In this study, the effect of Ce additions on microstructure evolution of Mg–7Gd–3.5Y–0.3Zn (wt %) alloys during the casting, homogenization, aging and extrusion processing are investigated, and novel mechanical properties are also obtained. The results show that Ce addition promotes the formation of long period stacking ordered (LPSO) phases in the as-cast Mg–Gd–Y–Zn–Ce alloys. A high content of Ce addition would reduce the maximum solubility of Gd and Y in the Mg matrix, which leads to the higher density of Mg12Ce phases in the as-homogenized alloys. The major second phases observed in the as-extruded alloys are micron-sized bulk LPSO phases, nano-sized stripe LPSO phases, and broken Mg12Ce and Mg5RE phases. Recrystallized grain size of the as-extruded 0.2Ce, 0.5Ce and 1.0Ce alloys can be refined to ~4.3 μm, ~1.0 μm and ~8.4 μm, respectively, which is caused by the synthesized effect of both micron phases and nano phases. The strength and ductility of as-extruded samples firstly increase and then decrease with increasing Ce content. As-extruded 0.5Ce alloy exhibits optimal mechanical properties, with ultimate strength of 365 MPa and ductility of ~15% simultaneously.
Highlights
In recent years, the demand for environment-friendly structural materials with light weight and novel mechanical properties has become urgent owing to strict emission limitations in the international community and the rapid depletion of fossil fuels [1,2]
Phases increase, and the fraction of long period stacking ordered structure (LPSO) phases increases gradually, which means that Ce addition can promote the formation of LPSO phases in the as-cast Mg–Gd–Y–Zn alloys
It can clearly be seen that Ce addition would decrease the maximum solubility of the Gd elements, and induce formation of the new Mg12 Ce phase
Summary
The demand for environment-friendly structural materials with light weight and novel mechanical properties has become urgent owing to strict emission limitations in the international community and the rapid depletion of fossil fuels [1,2]. As the lightest metallic structural material, possesses some obvious advantages such as low density, high specific strength, notable shock absorption and noise reduction, excellent electromagnetic shielding performance, good machine ability, and recyclability [3,4]. In this sense, Mg alloy has become a promising candidate for use in various fields such as aircraft, automotives, 3D products and so on [5,6,7]. Mg alloys containing the LPSO phases mainly involve ternary
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