ZrB2陶瓷的制备和烧结

采用自蔓延高温合成(Self-propagating high-temperature synthesis,SHS)技术和热压烧结(Hot pressing,HP)方法分别研究了Zr-B2O3-Mg和ZrO2-B4C-C体系反应原料的粒度和配比以及烧结温度对产物的影响规律,并烧结得到ZrB2陶瓷.采用X射线衍射和化学分析方法分析了材料的相组成,利用SEM和TEM观察了显微结构;并用阿基米德排水法测定了相对密度.结果表明:在Zr-B2O3-Mg体系中,50μm Zr粉和Mg过量15%(摩尔分数)的体系是最理想的SHS反应体系;SHS产物粒径、酸洗产物粒径和烧结体粒径分别为2～5μm、0.5～2.0 μm和2～10μm;酸洗产物组成为94.59%ZrB2、3.87%ZrO2和1.54%H3BO3(质量分数);烧结体为单相ZrB2陶瓷,相对密度为95.4%.在ZrO2-B4C-C体系中,B4C过量15%和C过量10%(摩尔分数)的体系是最理想的反应体系;烧结体相对密度为94%;烧结体组成为95.44%ZrB2、3.87%ZrO2、0.32?C和0.37%C(质量分数).     

机械化学反应合成Fe3Al-Al2O3复合粉体

以Fe3O4粉和Al粉为原料,采用机械球磨诱发化学反应制备了Fe3Al-Al2O3纳米晶复合粉体。利用X射线衍射仪(XRD)和附带能量色散谱仪(EDS)的扫描电子显微镜(SEM)对复合粉体球磨过程中的固态反应过程、表面形貌进行表征。结果表明,球磨过程中,30 min后混合粉末中开始出现少量的Al2O3颗粒,1 h后大部分Fe3O4被还原,形成α-Al2O3、θ-Al2O3、Fe(Al)固溶体和FeO,另有Al剩余。球磨3 h后,大部分的θ-Al2O3转变为α-Al2O3,Fe(Al)固溶体、FeO和剩余的Al粉在机械力的作用下反应形成FeAl化合物和Fe.911O。继续球磨至5 h后,FeAl化合物和Fe.911O相互反应而完全消耗,得到Fe3Al-Al2O3复合粉体。机械力诱发的Fe3O4和Al之间的反应属于突发型反应,诱发反应的临界球磨时间约为50 min。     

采用自蔓延高温合成技术连接TiAl合金

采用自蔓延高温合成技术实现了TiAl合金的连接。在连接过程中采用了具有很高放热量的Ti-Al-C中间层以及外加电磁场辅助连接。连接接头包括3个典型的反应区域,靠近TiAl母材界面处发现了深灰色的TiAl,反应层,在中间层内观察到了TiC颗粒以及Ti-Al系化合物。直接连接时由于产物和反应物之间的比热差,杂质的气化和孔隙中束缚气体的释放而导致孔隙无法避免。为了提高致密度,在粉末压坯和TiAl母材之间添加了Ag-Cu钎料箔。在SHS反应过程中熔化的钎料改善了中间层对TiAl母材的润湿同时填充到了中间层反应产物的孔隙中,采用这种方法能够提高反应产物的致密度和连接质量。     

中间层成分对TiAl/TiB2金属陶瓷SHS连接的影响

采用自蔓延高温合成(SHS)连接技术对TiB2金属陶瓷与TiAl进行连接试验,并研究工艺参数对SHS连接接头界面结构的影响.结果表明,不同成分的中间层发生SHS反应的放热量不同,从而会导致连接界面处的界面结构发生明显的变化.TiAl侧界面处出现的TiAl3反应层厚度与TiB2金属陶瓷侧出现的贫Cu层的厚度均随放热量的增加而明显增加,中间层环状结构的层数及尺寸也发生相应的变化.     

Microstrucmre and mechanical properties of Al2O3/TiAl composite

Al2O3/TiAl composites were fabricated by PAXD （pressure-assisted exothermic dispersion） method. The effects of Nb205 content on the microstructure and mechanical properties of the composites were investigated. The results show that the ultimate phases of the composite consist of TiAl, Ti3Al, Al2O3 and a small amount of NbA13. SEM reveals that a submicron γ＋（α2/γ） dual phases structure can be presented after sintered at 1 200 ℃, Furthermore, with the increase of Nb205 content, the ratio of TiAl to Ti3Al phase decreases correspondingly, the grains of the corflposites are remarkably refined, and the produced Al2O3 particles are uniformly dispersed. When 6% Nb205 is added, the composite has the best comprehensive properties. It exhibits a Vickers hardness of 4.77 GPa and a bending strength of 642 MPa. Grain-refinement and dispersion-strengthening are the main strengthening mechanisms.     

Thermodynamic analysis of combusion synthesis and reaction hot pressing of Al2O3/B4C composite

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纳米掺杂Al2O3/ZrO2等离子喷涂涂层的组织及性能

利用自行研制的纳米掺杂AZ-20热喷涂粉末，采用大气等离子喷涂技术，在35号钢基体上制备A12O3／ZrO2复合材料热障涂层，对涂层的组织结构及性能进行分析。结果表明：制备的涂层是由四方结构的t＇=ZrO2与六方结构的α-A12O3构成的，具有纳米晶与微米晶混晶组织；涂层孔隙率为11．2％，孔隙尺度较均匀：涂层硬度HV100为702，抗磨损能力较常规AZ-20涂层高约25％：涂层具有良好的隔热性能。     

Porous NiTi fabricated by self-propagating high-temperature synthesis of elemental powders

Porous NiTi shape memory alloy has been an active area of research for medical application due to their similar microstructure to human bone. In this study, porous product was obtained by self-propagating high-temperature synthesis (SHS) of compacts prepared from elemental nickel and titanium powders and the effects of the green porosity and preheating temperature were examined. The porosity in the synthesised products was in the range of 45–59 vol.%, with the green porosity being the primary source of final porosity. NiTi was present as the dominant phase in the porous product with other secondary intermetallic compounds and element powders. The effect of green porosity and preheating temperature was found to have an effect on the pore morphology and microstructure.     

ZrB2-Al2O3复合粉体的制备及应用综述

以ZrO2（或ZrOCl2·8H2O）、B2O3（或H3BO3）和工业Al粉为原料,在氩（氮）气气氛中合成了ZrB2-Al2O3复合粉体,较佳的摩尔配比为ZrO2（ZrOCl2·8H2O）：H3BO3：Al=3：6：20。自蔓延高温合成法、微波法以及高能球磨法合成的复合粉体晶粒细小,具有良好的成型性和烧结性。ZrB2-Al2O3复合粉体可用来制备高性能陶瓷以及作为含碳耐火材料的添加剂来提高材料的抗氧化性和抗侵蚀性,此复合粉体在磨料磨具工业也有广阔的应用前景。     

Effect of inner oxidant on self-propagating high-temperature synthesis of MnZn-ferrite powder

Using KClO3 as an inner oxidant, MnZn-ferrite powder was synthesized by a self-propagating high-temperature synthesis (SHS) process in normal air atmosphere. The effects of the inner oxidant on combustion temperature, combustion velocity, microstructure and the phase of the product were investigated by XRD and SEM,respectively. The results show that a highly ferritized powder can be obtained as well as the highest combustion temperature and the highest combustion velocity when the inner oxidant content m equals 5/4( k -1/6).     

Al2O3p/2024Al基复合材料的界面结构

利用TEM、HRTEM等分析测试手段,对挤压铸造法制备的Al2O3颗粒增强2024Al基复合材料的界面组织结构进行了观察与分析。结果表明：Al2O3p/2024Al基复合材料的界面结合良好,未发现界面反应物,铝基体与Al2O3颗粒以共格关系结合,界面属直接结合型,且Al2O3颗粒与Al基体存在如下的位向关系：Al2O3（1^-1^-21^-）//Al（1^-1^-1^-）;Al2O3〈3^-41^-1^-〉//Al〈110〉。     

Effects of laser processing parameters on solidification microstructures of ternary Al2O3/YAG/ZrO2 eutectic in situ composite and its thermal property

Rapid surface resolidification with a high powered CO₂-laser was performed in preparing directionally solidified Al₂O₃/YAG/ZrO₂ ternary eutectic ceramic in situ composite. The effects of laser processing parameters on the solidification microstructure characteristics and thermal properties were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD) and synthetically thermal analysis (STA). Detailed investigations of the influence of laser power and scanning rate on the preparation and microstructural parameters of the ternary eutectic were presented. Moreover, the eutectic phase separation rule at high temperature was discussed. The results indicate that solidification microstructure of the ternary eutectic composite is greatly influenced by the laser processing parameters. The synthetically thermal analysis shows that the eutectic temperature of ternary Al₂O₃/YAG/ZrO₂ composite is 1 738 °C, well matching the phase diagram of Al₂O₃-Y₂O₃-ZrO₂.     

Al2O3对电沉积Ni-Co／AlO3复合镀层性能的影响

应用直流复合电沉积技术制备Ni—Co／Al2O3复合镀层，并研究了Al2O3对电沉积Ni—Co／Al2O3复合镀层性能的影响。结果表明：在本试验范围内，镀层的硬度和耐磨性随着Al2O3含量的增加而提高。     

Al2O3/Mo纳米粉末模压成形烧结及其动力学

对Mo和Al 2 O 3/Mo纳米粉末进行模压成形,研究纯Mo和Al 2 O 3/Mo压坯在1700~2000℃温度范围内的等温烧结过程,并结合烧结模型分析材料烧结过程中的动力学;利用SEM和TEM分析复合材料的显微组织。结果表明：压坯密度与Al2O3的加入量有关,高温烧结时Al2O3/Mo复合材料的致密度高于纯Mo的致密度;在Al2O3/Mo复合材料烧结过程中,烧结机制既有体积扩散又有晶界扩散,且随着Al2O3含量的增加,晶界扩散趋势明显;纯Mo和Al 2 O 3体积分数为5%、10%和15%Al 2 O 3/Mo复合材料的烧结激活能分别为254.24、234.04、221.40和164.37 kJ/mol;Al 2 O 3的加入可促进晶粒的均匀化和组织的细化。     

Microstructure of nanometer Al2O3 dispersion strengthened Ni-based high-temperature protective coatings by laser cladding

The nanometer Al2O3 dispersion strengthened NiCoCrAlY high-temperature protective coatings by crosscurrent CO2 laser on Ni-based superalloy GH4033 were produced. Microscopic morphologies, phase constitutions of cladding coatings and distribution of nano-Al2O3 particles were examined using SEM and XRD. The results show that the interface grains, after adding proper nano-Al2O3, grow from epitaxial to non-epitaxial shape gradually, and the columnar dendrites become thinner and denser with cellular shape. Cracks in the substrate close to the interface are eliminated. Moreover, dispersive nano-Al2O3 particles mainly distribute around cellular substructure and on grain-boundaries, which prevents the diffusion of alloying elements and restrains the formation of new phase. There is a critical value of nano-Al2O3 addition, and the most suitable content of nano-Al2O3 is 1% (mass fraction) in this experimental conditions. The "nanometer effect" of nano-Al2O3 particles plays an important role in the improvement of coating microstructure.     

Al2O3/ZrO2(Y2O3)复合材料断裂过程中的相变及力学性能

用真空烧结方法制备了Al2O3/ZrO2(Y2O3)复合材料,分析了ZrO2(3Y)和ZrO2(2Y)含量对Al2O3基陶瓷抗弯强度、断裂韧性的影响.用XRD定量分析了含摩尔分数2%与3%Y2O3的ZrO2(2Y)与ZrO2(BY)在断裂过程中四方相转变成单斜相的相变量,用以阐明增韧机制.结果表明,在ZrO2含量为15%(体积分数)时,Al2O3/ZrO2(3Y)和Al2O3/ZrO2(2Y)复合材料的抗弯强度、断裂韧性分别达到825MPa,7.8MPa·m1/2和738MPa,6.7MPa·m1/2,两者的性能差异主要来自不同的增韧机制.     

真空烧结法制备ZrO2(Y2O3)/Al2O3复合材料

用真空烧结工艺制备了ZrO2（Y2O3）／Al2O3复合材料,分析了ZrO2（3Y）和ZrO2（2Y）含量对Al2O3基陶瓷烧结相对密度、显微结构及相变行为的影响．结果表明：Zro2（Y2O3）的含量对t-ZrO2→m-ZrO2相变量有影响,ZrO2（3Y）和ZrO2（2Y）含量（体积分数）分别为15％和20％时,烧结试样相对密度分别为99．6％和98．5％,ZrO2的晶粒平均尺寸分别为1．1μm和1．8μm,样品断裂前后的最大相变量（体积分数）分别是Vt→m=44％和Vt→m=18％．     

Synthesis of ZrO2-SiC composite powder and effect of its addition on properties of Al2O3-C refractories

ZrO2-SiC composite powder was synthesized by carbothermal reduction of zircon in argon atmosphere, and it was used as the additive to prepare Al2O3-C refractories. The effects of heating temperature on the synthesis process and the addition of the synthesized composite powder on the properties of the Al2O3-C refractories were investigated. The results show that the synthesized composite powder can be easily obtained by heating the mixture of zircon and carbon black at 1 873 K for 4 h in argon atmosphere, and the relative contents of ZrO2 and SiC in sample reach about 83.7% and 16.3%, respectively. The bulk density, crushing strength and thermal shock resistance of the Al2O3-C refractories can be improved obviously by the addition of the synthesized ZrO2-SiC composite powder.     

热挤压变形对亚微米Al2O3p/Al复合材料组织性能的影响

利用金相显微镜、扫描电镜、透射电镜和万能拉伸试验机等手段考察了粒度为0.3μm的Al2O3颗粒(体积分数为26%)增强6061Al复合材料在热挤压前后的显微组织及室温拉伸性能。结果表明:以10∶1的挤压比热挤压后复合材料组织的均匀性得到了明显改善,显微组织变化上呈现位错由压铸态的近无位错转变为位错有明显增殖特征,并促进了时效析出;复合材料挤压材的抗拉强度、屈服强度和延伸率较压铸材普遍提高;热挤压没有改变复合材料的断裂机制,由于挤压后颗粒分布均匀等原因,使复合材料的塑性得到改善。