热处理工艺对Al65Cu20Cr15准晶颗粒/Al基复合材料组织与性能的影响

采用热压方法制备了Al65Cu20Cr15准晶颗粒／Al基复合材料，对热处理前后复合材料的显微组织及硬度进行分析，结果表明：在500％高温退火过程中，准晶颗粒中的Cu和Cr原子向纯铝基体中扩散，基体中的Al原子向颗粒中扩散，从而使二十面体准晶相颗粒转变为十次准晶及其类似相，硬度有所降低；基体中，退火过程高温过饱和的Cu以Al2Cu的形式析出，而淬火过程高温过饱和的Cu来不及充分析出，产生固溶强化效应，使淬火后基体的硬度显著增加。     

Precipitation of Icosahedral Quasicrystalline Phase, R-phase and Laves Phase in Ferritic Alloys

Ferritic heat resistant steels involving precipitation of intermetallic phases have drawn a growing interest for the enhancement of creep strength, while the brittleness of the intermetallic phases may lower the toughness of the alloy.Therefore, it is necessary to optimize the dispersion characteristics of the intermetallics phase through microstructural control to minimize the trade-off between the strength and toughness. The effects of α-Fe matrix substructures on the precipitation sequence, morphology, dispersion characteristics, and the stability of the intermetallic phases are investigated in Fe-Cr-W-Co-Si system. The precipitates of the Si-free Fe-10Cr-I.4W-4.5Co (at%) alloy aged at 873K are the R-phase but those of the Si-added Fe-10Cr-1.4W-4.5Co-0.3Si (at%) alloy are the icosahedral quasicrystalline phase. The precipitates in both the Si-free and Si-added alloys aged at 973K are the Laves phase. Matrix of the alloys is controlled by heat treatments as to provide three types of matrix substructures; ferrite, ferrite/martensite mixture and martensite. The hardening behavior of the alloys depends on the matrix substructures and is independent of the kinds of precipitates. In the alloys with ferrite matrix, the peak of hardness during aging at 873K shifts to longer aging time in comparison with that in the alloys with lath martensite matrix which contain numbers of nucleation sites.     

准晶合金形成规律的探讨

利用Miedema参数△φ*和△nws^-1/3构成坐标系统，探讨了准晶合金形成规律。对已有实验结果的31个二元、48个三元准晶合金进行了系统的分析，同时与利用化学镀及电镀方法制备的二元合金系中的47个非晶、32个晶态；三元合金系的54个非晶J2个晶态合金进行了比较。结果表明：在给定的准晶合金形成区内，区分二元准晶、非晶以及晶态合金形成的准确率分别为93．5％、87．2％和72．7％；区分三元合金形成的准确率分别为97．9％、87．0％和75．0％。该判据对于定性地研究及寻找新型准晶合金开辟了一条新的途径，在材料研究领域具有一定的理论指导意义。     

Ag42In42Ca16二十面体准晶与2/1立方近似相Ag42In45Ca13的稳定性研究

Ag3In3Ca中的主要合金相是简单立方Ag42In45Ca13(空间群为Pa3↑-，α=2．496nm)，它是Ag42In42Ca16二十面体稳定准晶的2／1立方近似相．选区电子衍射(SAED)实验表明，2／1立方近似相与二十面体准晶有相似的局部结构．X射线能谱(EDS)、电子能量损失谱(EELS)和X射线粉晶衍射分析表明，Ag3In3Ca合金中的立方相Ag42In45Ca13不稳定．薄膜电镜样品在空气中易发生化学反应，产物中主要是Ca和O，还有少量C．块状合金在空气中放置14d后，其中的立方相Ag42In45Ca13分解，二元合金相AgIn2和In4Ag9的含量明显增加．在550℃保温55h后，立方近似相Ag42In45Ca13的含量显著减少．在相同条件下，二十面体准晶Ag42In42Ca16保持不变，具有高的结构和化学稳定性。     

等离子喷涂Al65CU23Fe12涂层的组织与性能研究

采用等离子喷涂方法在AZ31镁合金表面制备一层Al65Cu23Fe12涂层以改善其表面性能。通过OM、XRD及EDS等分析方法,分析了涂层热处理前后的组织及性能。结果表明:等离子喷涂Al65Cu23Fe12涂层组织由Al65Cu20Fe15准晶相和Al(Cu,Fe)相两相组成;经过T4和T6处理后,相组成没有发生变化,T6处理使准晶相含量明显增加,由喷涂态的31.3%(原子分数)提高到40.4%(原子分数);Al65Cu23Fe12涂层的硬度与其准晶含量呈正比,T6态下的准晶含量最多,硬度最大,达到752.8HV0.1,比喷涂态提高了22.2%,远远大于AZ31基体的硬度;涂层的耐腐蚀性(自腐蚀电位=-1.22～-0.79V,自腐蚀电流密度=21.5～58.7A/m2)远高于基体的耐腐蚀性(自腐蚀电位=-1.6V,自腐蚀电流密度=135.8～242.7A/m2)。热处理使涂层和基体的耐蚀性能降低。     

Al_(65)Cu_(20)Cr_(15)准晶颗粒/铝基复合材料中二十面体准晶的扩散相变

用JCXA—733型电子探针、H—800型透射电镜、D／max-IIIA型X射线衍射仪等研究了Al65Cu20Cr15准晶颗粒／铝基复合材料中的准晶颗粒在热压过程中的扩散相变结果表明,在热压温度为600,650和700℃的工艺条件下,准晶颗粒的转变产物分别为FIQC,（DQC＋DA）＋θ和θ相.SIQC相在与纯铝的扩散相变过程中经过过渡相FIQC,DQC,DA最终转变为θ相而达到平衡态     

挤压铸造准晶增强AZ91D镁基复合材料组织与性能

为了改善AZ91D镁合金的性能,采用挤压铸造法制备了Mg-Zn-Y准晶中间合金增强AZ91D镁基复合材料,研究了准晶中间合金含量对复合材料组织和性能的影响。结果表明挤压铸造工艺可以有效细化晶粒,复合材料的显微组织主要由α-Mg基体、晶界上分布的β-Mg17Al12相以及Mg3Zn6Y准晶颗粒组成,准晶颗粒和α-Mg基体之间形成稳定结合。当准晶中间合金含量为5%时,抗拉强度和断后伸长率达到最大值,分别为194.3MPa和9.2%。复合材料的强化机制为细晶强化和准晶颗粒强化。     

Hydrogen absorption in Ti45Zr38-xNi17+x quasicrystals and measurements of the equilibrium vapor pressure

To evaluate their technological usefulness and to probe the local structure of the quasicrystal, p-c-T curves were measured for as-quenched Ti₄₅Zr₃₈Ni₁₇ and Ti₄₅Zr₃₀Ni₂₅ quasicrystal ribbons at 350°C with a computer-controlled apparatus. For both quasicrystals, the p-c-T curves do not exhibit a clear pressure plateau. Instead, the equilibrium vapor pressure remains low (<5 torr) below H/M ≈1; it increases sharply for increasing H/M. Such p-c-T curves may reflect structural features of the quasicrystal. Due to the formation of the crystal hydride phase during the p-c-T measurements, however, the site energy distribution in the quasicrystals could not be obtained. Instead, qualitative conclusions are presented. For Ti₄₅Zr₃₈Ni₁₇ quasicrystals, estimates of the site energy distribution for hydrogen suggest a prominent site located between -0.2 eV and -0.15 eV with a possible broad, weakly binding second peak at higher energy. The site energy locations for hydrogen for Ti₄₅Zr₃₀Ni₂₅ quasicrystals are similar. The Ti₄₅Zr₃₈Ni₁₇ quasicrystals desorb most of the absorbed hydrogen at 650°C in one hour by continuous pumping without phase transformation, and do not become powder after three cycles.     

Al基三元准晶相图的电子浓度特征

准晶是一种电子型金属间化合物，其形成及结构稳定性主要由电子浓度因素控制。三元准晶相图的电子浓度特征表明，三元准晶与其晶体学类似相一起位于一等电子浓度线附近，称为准晶等电子浓度线现象。同时，三元准晶与二元准晶的存在密切联系，它们同第三组元一起落在同一变电子浓度线上，称为准晶变电子浓度线现象，三元准晶的理想成分位于准晶等电子浓度线和准晶变电子浓度线的交点上，据此特征，区分了两种类型的Al-Ni-Fe三元十次准晶，它们的典型成分分别为：D-Al72.5Fe14.5Ni13(Al-Fe型）和D′-Al70.5Fe12Ni17.5(Al-Ni型）。     

十次二维准晶材料的接触问题

准晶作为一种新的固态物质结构给传统的凝聚态物理学带来了深刻的变革 ,其弹性基本方程比传统晶体的弹性基本方程要复杂得多 .通过引入位移函数和应用Fourier分析与对偶积分方程理论圆满解决了在一个平底冲头作用下十次二维准晶材料的接触问题 ,得到了此材料接触问题应力与位移的解析表达式 .结果表明 ,如果接触位移在接触区域内为一常数 ,则垂直接触应力在接触边缘具有 - 1/ 2阶奇异性 ,这为准晶材料的接触变形提供了重要的力学量 .