| Magnesium alloy as a new structural materials has a series of advantages such as smalldensity, high specific stiffness and strength, strong electromagnetic shielding performance,superior damping capacity and damping performance, the dimension stability, richresources,and which has been known as “the most promising structure material in21stcentury”. By far,the AZ91is the most widely used magnesium alloy for its superiorcomprehensive performance. However, the the grain of as-cast magnesium is bulky, even morethe comprehensive mechanical performance and wear-resisting performance are poor, whichlead to substantially limite the using ranges of magnesium alloy. Compound aggrandizement isone of the most effective ways to improve the performance of magnesium alloys. but thewettability between plus particle used at present and magnesium matrix is very bad, moreoverthe preparation process is Magnesium matrix quasicrystals as a new magnesium basedmaterials possess a series of advantages such as high hardness, low surface energy and goodwettability with magnesium matrix. Therefore, magnesium matrix quasicrystals fits theenhancement of magnesium.In normal casting condition,the high density MZY （Mg-Zn-Y）quasicrystal matrix alloyhas been prepared. MZY quasicrystal–particle-reinforced-AZ91magnesium alloys wereobtained by MZY quasicrystal master alloy into AZ91magnesium alloy melt.In the paper,theeffects of Zn/Y atom ratio on the microstructure of MZY quasicrystal matrix alloy and thedistribution of element in decahedron and icosahedron Mg3Zn6Y quasicrystal phase have beenstudied detailedly by scanning electron microscope, energy spectrum analysis and X-rayscattering; the microstructure、mechanical properties and wear resistance of AZ91alloys withthe different addition of MZY quasicrystal matrix alloy have been centred on.It is found that in MZY quasicrystal matrix alloy of the same zinc content,the content ofyttrium atom decide to the type, morphology, quantity and distribution of MZY quasicrystal.The quantity of MZY quasicrystal phase gradually increase; the morphology of MZYquasicrystal phase change from polygon-shaped、 petaliform icosahedron to rhabditiformdecanedron with increased content of yttrium in MZY quasicrystal matrix alloy.Thepolygon-shaped、petaliform icosahedron and rhabditiform decanedron quasicrystal phase have existed some degree microsegregation.However,the microsegregation phenomenon inrhabditiform decanedron quasicrystal phase is harder than which in icosahedron quasicrystalphase.Because of MZY quasicrystal phase’s low surface energy and high thermal stabilityAZ91magnesium alloys with homogeneously distributed quasicrystal particles were obtainedby method of particle additionnal.The results showed that after adding MZY quasicrystalmaster alloy, the microstructure of the AZ91alloys is improved greatly. Morphology of β-Mg17Al12phase changes from continuous nets to discontinuous nets or even to particles and thequantity of β-Mg17Al12phase is obviously reduced. The Mg3Zn6Y quasicrystal phase with highmelting point and fine high-temperature stability diffusively distributes on the matrix and grainboundary. The results show that holding time could obviously effect the microstructures ofMZY quasicrystal particle in AZ91alloy strengthened by quasicrystals alloy. When holdingtime is within2min,the five petals-like quasicrystals could leave well in AZ91matrix alloy;holding time for4min,the smooth petal’s top of Mg3Zn6Y quasicrystal particle become sharpand its petals change for polygons;as holding time for6-8min, the petals of Mg3Zn6Yquasicrystals particle begin to desquamate, the phenomena of groomed fracture would beappeared in a single petals; holding time for10min and more,the petals of Mg3Zn6Yquasicrystal particle was not obvious and the petals with stamen form the oval quasicrystalparticles.For Mg3Zn6Y quasicrystal particle can promote fine grain size and pin grainboundary,Mg3Zn6Y quasicrystal master alloy significantly improves the room temperaturemechanical properties of the AZ91. With up to6wt%of addition of Mg30Zn60Y10quasicrystalmaster alloy, hardness of the alloys increases by35%. The tensile strength and elongationincreases by33%and150%, respectively.Under the different load condition，the friction coefficient of the alloy adding6%MZYquasicrystal alloy decrease from0.68to0.26, In100N load its quality wear is only46.2%of thematrix alloy’s under30min dry friction. The wear properties are obviously improved, thefriction mechanism changes from conglutination abrasion to grain abrasion with increasing ofMZY quasicrtstal alloy. |
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