Investigation On Preparation,Annealing Process Of Quasicrystal Mg-Zn-Y Alloys

Mg-Zn-Y alloy had good prospect with its high strength and high creep resistance.In this article, using99.9%magnesium ingot、zinc ingot and Mg-30Y as crude materials, by adjusting the content of yttium and zinc,we studied the microstructure and mechanical properties after annealing by optical microscopy,X-ray diffractometer(XRD), scanning electron microscopy(SEM),energy spectrum analysis and transition electron microscopy(TEM).Its results indicated that the atom proportion of zinc and yttrium and the content of Y had obvious influence on the number and shape of the I-Phase.By studying the alloy with different Y content and proportion of zinc and yttrium,we found the alloy in which the atom proportion of magnesium、zinc and yttrium was95.8:3.6:0.6had high content of I-phase.To analyze the second phrase and composition of the alloy which have different content of Zn/Y(at%) and Y throng optical microscope, the Mg95.8Zn3.6Y0.6alloy with higher content of I-Phase was prepared,therefore,was identified as the object of the subsequent heat treatment.by discussing the microstructure and the mechanical properties of the Mg95.8Zn3.6Y0.6alloys annealing at the temperature of300℃、350℃、400℃for12hours, The variation of the grain size and the second phase was obtained, that is, the microstructure of the alloy changed to equiaxed grains from dendrite with the temperature increased; the second phase dispersed inside or between the grains, and the shape changed to rodlike or graininess from reunion organization,.The recrystallization occured when the temperature higher than350℃, epuiaxed grain was obtained and grew with the temperature increased,at the same time the second phase enriched at the grain boundary, got larger size and tend to reunion organization. compared with the as-cast state alloys,The tensile strength achieved to199MPa,improved40%and the elongation is12%with little differences.the changing rules of the grain size and the second phrase have been investigated after the discussion about the microstructure and mechanical properties of the Mg95.8Zn3.6Y0.6alloy. with the time prolonged,matrix dendrites broke gradually and the second phrase became smaller, tending to be dispersed when more than12h, matrix dentrites present a dentrite structure,and the second morophy began toconcentrate again at the grain boundaries,which decreased the mechanical properties of the alloy. while at12h, the tensile strength and the elongation are197mpa and13.4%correspondedingly.by further refinement of the annealing process parameters and the analysis of the microstructure and mechanical propertiesof the alloy at different annealing, the best annealing process parameter is12H at350℃.the grains in the alloy are reletively uniform equiaxed grains and the second phase becomes relatively diffused, making the mechanical properties of the alloy significantly improvedthe grains in the alloy are reletively uniform equiaxed grains and the second phase becomes relatively diffused, making the mechanical properties of the alloy significantly improved the grains in the alloy are reletively uniform equiaxed grains and the second phase becomes relatively diffused, making the mechanical properties of the alloy significantly improved.