Abstract
Quasicrystal alloys have a wide application prospect because of excellent performances and characteristics; meanwhile, magnesium alloys are known as green engineering materials because of their high specific strength and light weight. Therefore, the study of Mg-Zn-Gd quasicrystal alloys is of great significance for the development of new materials. In this paper, Mg(70-x)Zn30Gdx(x=3,4,5) alloys were prepared by a conventional casting method and the morphologies and properties of these alloys were studied. There was a new symmetrical rod phase found in the Mg66Zn30Gd4 alloy and the symmetrical rod phase was identified as a ternary phase by mapping scanning and energy dispersive spectroscopy (EDS) analysis. The Zn/Gd ratio of the symmetrical rod phase was found to be 4.8 and the TEM images obtained were different from the typical diffraction spots patterns of quasicrystalline, which means it is unlikely to be quasicrystalline. With different melt holding time, the symmetrical rod phase evolved gradually over time from a lamellar eutectic structure; differential scanning calorimetry (DSC), heat treatment, and microhardness tests showed that the melting temperature of the rod phase was 453 °C and that its thermal stability and microhardness are better than quasicrystalline. Hence, the symmetrical rod phase is a new kind of complex metallic alloy phase whose composition and properties are close to those of quasicrystals but is not quasicrystalline.
Highlights
As the lightest green engineering structural material, magnesium alloy has many advantages, including high specific strength and stiffness, good shock and noise reduction performance, electromagnetic shielding, and easy processing and forming, etc
The microhardness microhardness of of the the main quasicrystalline and symmetrical rod phases before and after heat treatment were studied; the results quasicrystalline and symmetrical rod phases before and after heat treatment were studied; the results show that that the the microhardness microhardness of of the the symmetrical symmetrical rod rod phase phase did did not not decrease decrease obviously obviously but but that that that that show of the the quasicrystalline quasicrystalline phase phase decreased decreased aa lot
The symmetrical rod phase was found in the Mg66 Zn30 Gg4 alloy but not in the other two alloys considered, which indicates that the formation of the phase is related to the content of
Summary
As the lightest green engineering structural material, magnesium alloy has many advantages, including high specific strength and stiffness, good shock and noise reduction performance, electromagnetic shielding, and easy processing and forming, etc It has broad application prospects in transportation, aerospace, and military industries [1]. Quasicrystals have special symmetry of five or more times [3,4,5,6]. This structural particularity makes them have high hardness and strength, as well as low friction coefficients, strong thermal stability, and corrosion resistance [7,8,9].
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