| Magnesium is the lightest structural materials with high specific strength and highspecific stiffness and excellent damping properties, which draws broadly attention both athome and abroad in recent years. However, its poor mechanical properties, especially at theelevated temperature limit its broader applications.Y and Zn elements can be added inmagnesium alloys to improve the room temperature strength, high temperature strength andcreep resistance, so it has good prospects in the aviation, aerospace and civilian transport andother manufacturing fields. Adding Zn to the Mg-Y alloy can produce several phases(Mg-Y-Zn compounds, quasicrystalline phase and LPSO phase). Both of the LPSO phaseand quasicrystalline phase have a special crystal structure, which can play a special role as itpresents in the matrix as a secondary phase. This paper researches the microstructure of theMg-Y-Zn alloy containing special crystal structural phase with or without heat treatment;furthermore, strength, hardness, friction and wear resistance, corrosion resistance anddamping properties of the alloy were also studied.The main conclusions are as follows:(1) For Mg93ZnxY7-x(x=2.33,2.8,3,3.5,6) alloys, Zn/Y (at.%) ratio has a significantinfluence on the phase component of the alloy. When Zn/Y is1:2, the main phse componentof the alloy is-Mg, LPSO(Mg12ZnY) and W(Mg3Zn2Y3) phase; while the Zn/Y,respectively2:3,3:4and1:1, the main phase component of the alloys is-Mg andLPSO(Mg12ZnY) phases; when the Zn/Y is6:1, the main phase component of the alloy is-Mg alloy and I(Mg3Zn6Y) phase. Hardness, strength, wear resistance and corrosionresistance of the alloy varies with Zn/Y ratio. By comparison, when Zn/Y ratio is1:2,thehardness, wear resistance, ductility and corrosion resistance of the alloy shows the best.(2) For Mg97Zn1Y2alloy, heat treatment has an influence on the microstructure andproperties. The microstructure of the alloy takes a great change with the solid solution timeincrease,-Mg dendrite gradually fuses. In the process of solid solution heat treatment, LPSOphase is not dissolved but grown. The hardness, mechanical properties, corrosion resistanceand damping properties shows a certain level of improvement with the heat treatment timeincreasing.(3) For Mg93Zn6Y alloy containing I phase, heat treatment has an impact on themicrostructure and properties of the alloy. There are more small precipitation particlesappeared in the-Mg phase of the alloy after T6treatment, which like hexagonal or block. ByEDS analysis, these particles are subject to I phase. Furthermore, the particles exist in themicrostructure of the alloy tends to increase with the aging time increasing. (4) Quasicrystal (I) and long period structure (LPSO) phase coexists in a Mg-Y-Zn alloys,which was rarely reported in the previous literature. The chemical composition of the alloy isMg80Y4Zn16(at.%). During continuously heating Mg-Y-Zn alloy in DTA, the initialendothermic peak is located at350℃, corresponding to dissolution of the Mg12YZn phaseand the eutectic melting; endothermic peak appears with426℃,corresponding to dissolutionof the Mg3Zn6Y1phase; endothermic peak appears with an onset temperature of498℃,corresponding to melting of the-Mg phase. The average damping values of the alloyis0.03, which indicates a high damping alloy. The hardness and corrosion resistance of thealloy is firstly increased and then reduced with the soild solution treatment time increasing. |
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