Thanks to the advantages of light weight, high strength and favorable heat resistance, Mg-Gd alloys owns a wide application prospect in the field of aerospace. Nevertheless, simple Mg-Gd binary alloys often bears a high content of heavy rare earth and unsatisfactory comprehensive mechanical properties, which cannot match the novel magnesium alloy design concept of light weight, high strength and low cost. Up to now, great efforts have been put into the research on further improving the properties of the Mg-Gd alloys. The main improving scheme focus on proper heat treatment process, necessary deformation processing technology, and reasonable composition optimization design. Among them, creating a novel alloy with excellent properties by constant optimization of the composition ratio through alloying is the fundamental method for promoting the performance of Mg-Gd alloy. In view of the fact that the chemical composition is an important factor affecting the microstructure and mechanical properties of the alloy, this paper reviews the effects of alloying elements Ag, Al, Zn, Ca, Si, Mn and diverse rare earth elements (RE) on the microstructure and properties of Mg-Gd alloys, and looks forward to the development direction of alloying. For example, the addition of elements like Zn, Cu, Ni, etc. can contribute to form a new long-cycled ordered stacking structure phase in the structure, while the original nano-precipitated phases in the Mg-Gd-based alloy can still be preserved, thereby achieving the purpose of multi-phase synergistic strengthening of the alloy. Besides, because rare earth elements are expensive and difficult to obtain, if common elements like Al, Mn, and Si can be used as alternatives for rare earth elements to form a new strengthening phase, the alloy performance will be effectively improved and the cost will be reduced. In addition, the effect of single element on the composition of the alloy composition is limited, and compound addition is an important development direction for Mg-Gd alloying study. Whereas special attention should be paid to the fact that interactions between certain elements in the diversified design process may cause the failure of reaction. For example, Al should not be added into Mg-Gd alloys containing Zr generally, because Al element will not only react with Zr to generate Al3Zr phase to deteriorate the alloy structure, but also consume a large amount of rare earth in the matrix alloy, thus redu-cing the utilization ratio of rare earth elements. To sum up, two major problems must be solved in the alloying design process. Ⅰ. Innovative alloy series should be created through the rational combination of the alloying elements. Ⅱ.The optimal content ratio of various elements in the series of alloys should be determined, so as to further optimize their performance. This article analyzes and summarizes the research progress of alloying in Mg-Gd alloys. The effect of LPSO forming elements, non-LPSO forming elements, rare earth metal elements, and non-metallic elements on Mg-Gd alloys is discussed separately. The research status of various elements in this alloy series is presented and their application prospects are proposed, which is expected to provide reference for the future alloying design of magnesium alloy. © 2018, Materials Review Magazine. All right reserved.
