【作者】 史菲；

【导师】 郭学锋；

【作者基本信息】 西安理工大学 ， 材料物理与化学， 2003， 硕士

【摘要】 本文采用普通凝固技术制备高镁、低锌和低钇的Mg-Zn-Y系合金稳定准晶相。在此基础上研究合金中准晶的形成机理和分布特征。为后续研究和制备准晶增强自生复合材料和超高强度镁合金提供思路。用金相显微镜和SEM分析低Zn和低Y含量普通凝固镁合金组织形貌；SEM和EDS分析合金和凝固组织中各相的成分；XRD分析凝固组织的相组成；TEM确定准晶的结构。研究结果表明： 1．Mg-Zn-Y三元合金熔体在室温冷却过程中，准晶相直接从液相形核、长大。准晶的微观形貌呈现出没有完全长大的五边形、完整五瓣以及首次发现的六瓣花瓣。准晶晶粒尺寸小于50μm。 2．合金成分不同导致凝固组织不同。Mg_（69-x）Zn_（30+x）Y₁、Mg₆₄Zn₃₄Y₂、Mg₇₀Zn₂₈Y₂、Mg₇₁Zn₂₇Y₂及Mg₃₅Zn₅₇Y₈合金，试验产生的凝固组织为MgZn基体相+析出的α-Mg相+Mg₃₀Zn₆₀Y₁₀二十面体准晶相；Mg_72.52Zn_25.48Y₂、Mg₇₄Zn₂₄Y₂、Mg₇₆Zn₂₂Y₂、Mg₆₆Zn₃₁Y₃及Mg₆₈Zn₂₈Y₄合金，试验产生的凝固组织为MgZn+α-Mg+Mg₃₀Zn₆₀Y₁₀二十面体准晶相+共晶团。 3．由于合金成分不同，导致准晶相存在形貌、数量、大小和分布的差异。其规律为，伴随Y含量的增加，准晶体的晶粒度、圆整度和分布均匀化程度均有提高。此外，准晶体展现了形貌多样性的特点。 4．重新圈出了Mg-Zn-Y三元合金相图中能够获得二十面体准晶的凝固区域，标出可能获得理想准晶的范围。为今后进一步寻找准晶及准晶的定性分析奠定了基础。更多还原

【Abstract】 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.更多还原