Quasicrystal And It's Formation Mechanism In As-Cast Mg-Zn-Y Alloy

The formation and distribution of quasicrystal in as-cast Mg-Zn-Y alloy are investigated. On this base, the thoughtfulness to prepare quasicrystal reinforced and super-high magnesium alloy is also provided. The microstructure of the as-cast Mg-Zn-Y alloys are analyzed by optical microscope and SEM, composition and phases are checked by EDS, the constituent phases are identified by XRD and quasicrystal structure is identified by TEM. Analyzing results show:1. The I-phases directly nucleate and grow from melt of cooling Mg-Zn-Y ternary alloys. The micromorphology of the alloy appears in five-petal shape or in small pentagonal grains and firstly founds the six-petal shape, is uniformly dispersed on the matrix with less than 50(im grain size.2. The different component of alloys leads to different solidification microstructure. Mg(69-x)Zn(3o+X)Yi, Mg64Zn34Y2, Mg7oZn2gY2, Mg7iZn27Y2, Mg35Zn57Y8 alloys , the microstructures of conventional solidified consist of a-Mg, MgZn and Zn60Mg3oYIO ; Mg72.52Zn25.48Y2, Mg74Zn24Y2, Mg76Zn22Y2, Mg66Zn3iY3, Mg6gZn28Y4 alloys , the microstructures of conventional solidification consist of a-Mg, MgZn ,Zn6oMg30Y|0 and eutectic.3. The different component of alloys leads quasicrystals that have differentIIIAbstractmicromorphologies, amounts and distributing. The rule is that with the increasing of yttrium's contents, the granularity, the circular-degree and the distributing-leveling \of the quasicrystals are improved. Otherwise, I-phases appear the trait of various shapes. 4. Ternary phase diagram Mg-Zn-Y with primary solidification area of the i-phase is redemarcated. This can establish base of searching and analyzing of quasicrystals.