**5. Conclusions**

In this work, the Mg(70-x)Zn30Gdx(x=3,4,5) alloys with di fferent content of Gd were prepared and the morphologies and properties of these alloys were studied: (1) the main phases were found to be a pentapetaloid phase for the Mg67Zn30Gd3, a symmetrical rod phase for the Mg66Zn30Gd4 alloy, and an irregularly shaped phase for the Mg65Zn30Gd5 alloy; (2) the symmetrical rod phase was found to consists of three elements (Mg, Zn, and Gd), its Zn/Gd ratio was obtained as 4.8 (which is close to but not in conformity with the requirements of quasicrystals) and its electron di ffraction spots were complex and had no obvious quasicrystal phase characteristics; (3) this phase was found to evolve gradually over time from the lamellar eutectic structure and to be able to exist in alloy melt for a long time. The melting temperature of the symmetrical rod phase was 453 ◦C, and its thermal stability and microhardness were found to be better than those of quasicrystal phase; (4) the composition and phase transition temperature of the symmetrical rod phase were found to be close to those of a quasicrystal phase, but its electron di ffraction pattern was seen to have no characteristics of a quasicrystal phase, so it may be a new kind of complex metal alloy phase, and needs further study.

**Author Contributions:** Conceptualization, J.Y.; data curation, Y.F.; formal analysis, J.Y.; methodology, Y.F.; software, H.W.; validation, G.Z., M.Z., and J.L.; writing—original draft, J.Y.; writing—review and editing, X.T.

**Funding:** This research was funded by the National Natural Science Foundation of China (grant nos. 51571102, 51701081, and 51871111), the Young-Aged Talents Lifting Project of the Shandong Association for Science and Technology (grant no. 301-1505001, recorded by the University of Jinan), and the Shandong Provincial Natural Science Foundation (grant no. ZR2017BEM001).

**Acknowledgments:** Thank you to my instructor, the teachers and students of the project group for their help, and also to the fundings.

**Conflicts of Interest:** The authors declare no conflict of interest.
