Al2O3/BaZrO3双陶瓷界面微观组织演化及机理

以Al₂O₃为背层(硅溶胶为粘结剂), 电熔BaZrO₃作为面层材料(钇溶胶为粘结剂), 1550℃烧结后制成50 mm×25 mm×5 mm的Al₂O₃/BaZrO₃双陶瓷试样。通过光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)和EDS等手段观察了BaZrO₃层和Al₂O₃/BaZrO₃界面的显微结构, 研究了BaZrO₃与Al₂O₃的界面反应。结果表明, 面层由BaZrO₃基体和分布其上的大小10 μm左右的Y稳定的ZrO₂晶粒组成; Al₂O₃/BaZrO₃界面发生反应形成厚约300 μm的过渡层, 界面反应生成物有BaOAl₂O₃、ZrO₂和BaO·Al₂O₃·2SiO₂。界面从单纯的BaZrO₃/Al₂O₃双陶瓷结构演变为BaZrO₃、ZrO₂、BaO·Al₂O₃、BaO·Al₂O₃·2SiO₂和Al₂O₃等多种物相组成的复杂结构。反应过程中Al元素基本不迁移扩散, BaZrO₃中Ba元素向Al₂O₃所在的位置扩散形成BaO·Al₂O₃, 残留物形成一层条状ZrO₂, 而BaO·Al₂O₃·2SiO₂围绕着EC95(Al₂O₃+5%SiO₂)粉体颗粒周围生成。     

Improvements in mechanical properties of TiB2 ceramics tool materials by the dispersion of Al2O3 particles

TiB₂–Al₂O₃ composites with Ni–Mo as sintering aid have been fabricated by a hot-press technique at a lower temperature of 1530 °C for 1 h, and the mechanical properties and microstructure were investigated. The microstructure consists of dispersed Al₂O₃ particles in a fine-grained TiB₂ matrix. The addition of Al₂O₃ increases the fracture toughness up to 6.02 MPa m^1/2 at an amount of 40 vol.% Al₂O₃ and the flexural strength up to 913.86 MPa at an amount of 10 vol.% Al₂O₃. The improved flexural strength of the composites is a result of higher density than that of monolithic TiB₂. The increase of fracture toughness is a result of crack bridging by the metal grains on the boundaries, and crack deflection by weak grain boundaries due to the bad wetting characters between Ni–Mo and Al₂O₃.     

特高压气体绝缘金属封闭开关设备用Al2O3/环氧树脂复合材料的非等温固化动力学及蠕变性能

针对特高压气体绝缘金属封闭开关设备（GIS）用Al₂O₃/环氧树脂（EP）复合材料,采用非等温差示扫描量热（DSC）法研究了Al₂O₃/EP复合材料的固化行为,对其DSC曲线进行分峰处理,利用等转化率方法求得不同反应阶段的表观活化能。根据Málek判据得到Al₂O₃/EP复合材料的固化行为符合的模型类型,并求得不同反应阶段的各个动力学参数及固化动力学方程。利用SEM观察Al₂O₃/EP复合材料的微观形貌,通过动态热力学分析仪（DMA）分析其动态热力学性能和高温蠕变性能,利用时温等效预测了Al₂O₃/EP复合材料的长时蠕变行为。结果表明,DSC热流曲线表现为双峰分布;Al₂O₃/EP复合材料的两个反应阶段的表观活化能分别为35.3 kJ/mol及48.1 kJ/mol,Sestak-Berggren自催化模型能够很好地描述Al₂O₃/EP复合材料体系在不同固化阶段的固化行为。Al₂O₃颗粒均匀分散于树脂基体中,填料的加入使裂纹发生偏转。Al₂O₃/EP复合材料的储能模量（E'）随温度的升高而降低,损耗因子（tanδ）峰值对应的玻璃化转变温度（T_g）为120.03℃。Al₂O₃/EP复合材料的抗蠕变性能随着拉伸应力和温度的增加而减弱,随着时间的延长,其蠕变速率减小。      

Al2O3/环氧树脂-氰酸酯复合材料反应动力学及力学性能

以双酚A型环氧树脂(E51)和双酚A型氰酸酯(BCE)为原料,研究E51改性BCE共固化反应机制。同时,以E51-BCE为基体树脂,溶胶-凝胶法(Sol-Gel)自制Al2O3为增强体,制备Al2O3改性E51-BCE (Al2O3/E51-BCE)复合材料。通过非等温DSC确定了E51-BCE体系的固化工艺及固化反应动力学,并根据Kissinger法和Ozawa法求得体系的表观活化能分别为66.13 kJ/mol和69.46 kJ/mol。利用红外光谱跟踪固化体系在起始固化温度为160℃、 180℃时的反应历程,结果表明:起始固化温度在160℃时,以E51与BCE直接反应为主;起始固化温度在180℃时, BCE反应活性提高,以BCE自聚反应为主,生成三嗪环的速率加快,少量的BCE直接与E51反应生成恶唑啉结构。对Sol-Gel法自制Al2O3进行FTIR和TEM表征,结果表明:Al2O3为短纤维状的晶体,表面含有少量羟基。SEM结果显示:Al2O3为分散相,与基体间界面模糊, Al2O3/E51-BCE复合材料的脆断面裂纹不规则,为典型的韧性断裂;当Al2O3掺杂量为3wt%时, Al2O3在基体中分散均匀, Al2O3/E51-BCE复合材料的冲击强度和弯曲模量分别为24.2 kJ/m2和2.54 GPa,比基体树脂的冲击强度和弯曲模量分别提高53.65%和22.12%,力学性能得到明显改善。     

原位自生纳米Al2O3/Al-Zn-Cu复合材料的力学性能

将纳米ZnO粉末和Al粉球磨后冷压成Al-ZnO预制块,然后将其加到Al-Zn-Cu熔体中进行Al-ZnO原位反应,制备出纳米Al₂O₃颗粒增强Al-Zn-Cu基复合材料。能谱面扫描分析和透射电镜观察结果表明,复合材料由纳米Al₂O₃颗粒和Al₂Cu析出相两种颗粒/析出相组成。纳米Al₂O₃颗粒通过异质形核和晶界钉扎,细化了Al-Zn-Cu合金晶粒组织和Al₂Cu析出相。原位纳米Al₂O₃颗粒的生成提高了基体合金的拉伸性能,轧制+热处理使Al₂O₃/Al-Zn-Cu复合材料的拉伸强度比相同处理的基体合金提高约100%,总伸长率提高约98%。     

Bi2O3助熔剂对CaO-B2O3-SiO2/Al2O3玻璃陶瓷复合材料性能的影响

以CaO-B₂O₃-SiO₂(CBS)玻璃粉体和Al₂O₃陶瓷粉体为原料,通过在CBS与Al₂O₃的质量比固定为50:50的玻璃-陶瓷复合材料中添加适量的Bi₂O₃作为烧结助熔剂,探讨了Bi₂O₃助熔剂对CBS/Al₂O₃复合材料的烧结性能、介电性能、抗弯强度和热膨胀系数的影响规律.研究表明:Bi₂O₃助熔剂能通过降低CBS玻璃的转变温度和黏度促进CBS/Al₂O₃复合材料的致密化进程,于880 ℃下烧结即能获得结构较致密、气孔较少的CBS/Al₂O₃复合材料.然而,过量添加Bi₂O₃将使玻璃的黏度过低,从而恶化CBS/Al₂O₃复合材料的烧结性能、介电性能及抗弯强度.当Bi₂O₃的添加量为CBS/Al₂O₃复合材料的1.5wt%时,于880 ℃下烧结即能获得最为致密的CBS/Al₂O₃复合材料,密度为2.82 g·cm^-3,这一材料具有良好的介电性能(介电常数为7.21,介电损耗为1.06×10^-3),抗弯强度为190.34 MPa,0~300 ℃的热膨胀系数为3.52×10^-6 K^-1.     

Formation of MgAl2O4 in Al2O3-(Al-4wt.%Mg) composites

The Al₂O₃ particles are introduced into the Al-4wt.%Mg melt by the “vortex” method. After being cast, Al₂O₃-(Al-4wt.%Mg) composites are remelted at 700, 750, 800 and 850°C for different residence times to investigate the formation of MgAl₂O₄ (spinel).

The results show that MgAl₂O₄ is the unique interface of the Al₂O₃-(Al---Mg) composites held at 700–850°C. Fine MgAl₂O₄ crystals grow on the surface of the Al₂O₃ particle but, as the holding temperature and the residence time increase, some spinels will form themselves into pyramidal shape. The MgAl₂O₄ grows not only at the matrix-particle interface but also on the surface of the composite specimens. The formation reactions of interfacial MgAl₂O₄ are as follows: Mg(1) + 2Al(1) + 2O₂(g) = MgAl₂O₄(s)3Mg(1) + 4Al₂O₃(s) = 3MgAl₂O₄(s) + 2Al(1) Both of them are equally important.     

Processing, microstructure and properties of C40 Mo(Si,Al)2/Al2O3 composites

The C40 Mo(Si_0.75Al_0.25)₂/Al₂O₃ composites were prepared by spark plasma sintering (SPS) of mechanically alloyed (MA) powders. The Mo(Si_0.75Al_0.25)₂/0–20 vol.% Al₂O₃ materials, showing micron and submicron composite structure, possess a hardness of 13.9–14.6 GPa but a poor toughness of 1.78–1.80 MPa m^1/2. The addition of 30 vol.% Al₂O₃ leads to the formation of the micron C40 Mo(Si_0.75Al_0.25)₂/Al₂O₃ composite with an intergranular distribution of Al₂O₃, that results in a drop of the hardness to 10.2 GPa and an improvement of the toughness to 3.67 MPa m^1/2. The transition of the cleavage facets to the intergranular fracture with the addition of Al₂O₃ is assumed as the main toughening mechanism.     

片状纳米Al2O3/环氧树脂复合材料的制备及性能

采用水热法制备片状纳米Al₂O₃,经过偶联剂改性后与环氧树脂复合,通过溶液混合法制备了不同填充量的片状纳米Al₂O₃/环氧树脂复合材料,研究了片状纳米Al₂O₃用量对片状纳米Al₂O₃/环氧树脂复合材料介电性能和热性能的影响,利用SEM对复合材料的断口形貌进行了表征。结果表明: 片状纳米Al₂O₃在环氧树脂基体中分散良好;随着片状纳米Al₂O₃填充量的增加,复合材料的起始热分解温度升高、介电强度增大,当片状纳米Al₂O₃的填充量为7wt%时,复合材料的介电强度为 29.58 kV/mm,比纯环氧树脂的介电强度提高了30%;复合材料的介电常数(3.8~4.5)和介电损耗(0.015)比纯环氧树脂稍有增大,但仍维持在较好的介电性能范围内。     

ZrO2增韧Al2O3颗粒增强Fe45复合材料拉伸断裂的有限元-离散元耦合方法仿真ZrO2增韧Al2O3颗粒增强Fe45复合材料拉伸断裂的有限元-离散元耦合方法仿真

采用有限元-离散元耦合方法（FEM-DEM方法）,进行了氧化锆增韧氧化铝颗粒增强Fe45复合材料（ZrO₂-Al₂O₃/Fe45）轴对称代表体元模型的拉伸断裂仿真分析。分析了FEM-DEM模型对单元尺寸的敏感性,结果表明采用,二阶实体单元加双零厚度内聚力单元的FEM-DEM模型降低了计算结果对单元尺寸的敏感性。ZrO₂-Al₂O₃/Fe45复合材料拉伸断裂的模拟结果表明,颗粒形状对裂纹的扩展会产生较大影响,复合材料的开裂首先在垂直于拉力方向的界面处发生,界面裂纹扩展至基体应力集中处之后基体发生开裂,裂纹由开裂的界面和基体裂纹共同组成。      

Al2O3-TiC/Al2O3-TiC-CaF2复合叠层陶瓷材料摩擦磨损性能

将Al₂O₃-TiC陶瓷材料与具有固体润滑特性的Al₂O₃-TiC-CaF₂陶瓷材料进行叠层, 通过真空热压烧结制备Al₂O₃-TiC/Al₂O₃-TiC-CaF₂复合叠层陶瓷材料。在环盘式摩擦磨损试验机上进行摩擦磨损实验, 研究该材料在不同载荷、 转速条件下的摩擦系数和磨损率, 分别用SEM及EDS观察材料磨损前后的微观形貌和分析其成分组成, 研究其磨损机制。结果表明: 在相同载荷条件下, Al₂O₃-TiC/Al₂O₃-TiC-CaF₂复合叠层陶瓷材料的摩擦系数和磨损率随着转速的升高而下降, 在相同转速条件下, 其摩擦系数和磨损率随着载荷的增加而下降; Al₂O₃-TiC/Al₂O₃-TiC-CaF₂复合叠层陶瓷材料的磨损机制主要是磨粒磨损和黏着磨损。     

Fe/Al2O3复合材料的制备和性能

用石墨埋烧方法制备Fe/Al₂O₃复合材料,对其力学性能和微观结构进行了分析。结果表明:Fe/Al₂O₃复合材料的弯曲强度与断裂韧性均随Al₂O₃含量的升高先升高后降低,当Al₂O₃含量（质量分数）为70%时,其弯曲强度与断裂韧性分别达到602.49 MPa和9.33 MPa·m¹/2,其硬度随Al₂O₃含量先降低后升高。在烧结过程中在Fe颗粒周围形成一种成分为FeO与FeAl₂O₄的壳体,在壳体与Fe颗粒之间存在微裂纹缺陷。壳体的形成和壳体与金属颗粒间的微裂纹钝化了外部应力,从而提高了复合材料的韧性。     

纤维预热温度对连续Al2O3f/Al复合材料力学性能的影响

选用Nextel610型Al₂O₃纤维为增强体、ZL210A连续氧化铝合金为基体,采用真空压力浸渗法制备纤维增强铝基复合材料(Al₂O_3f/Al),纤维的体积分数为40%,预热温度分别为500、530、560和600℃,研究了纤维预热温度对Al₂O_3f/Al复合材料的微观组织、纤维损伤和力学性能的影响。结果表明：随着纤维预热温度的提高复合材料的致密度随之提高,最大达到99.2%,材料的组织缺陷最少,纤维的分布均匀;随着纤维预热温度的提高从复合材料中萃取出来的Al₂O₃纤维的拉伸强度不断降低,纤维预热温度为600℃的复合材料中Al₂O₃纤维的拉伸强度仅为1150 MPa,纤维表面粗糙,有大尺寸附着物。纤维的预热温度对Al₂O_3f/Al复合材料的拉伸强度有显著的影响。预热温度为500、530、560和600℃的复合材料其拉伸强度分别对应于298、465、498和452 MPa。组织缺陷、纤维损伤和界面结合强度,是影响连续Al₂O_3f/Al复合材料强度的主要因素。     

Crystal morphology and growth mechanism of reinforcements synthesized by direct melt reaction in the system Al–Zr–O

In-situ Al₃Zr and Al₂O₃ particulates reinforced aluminum matrix composites were fabricated by the direct melt reaction (DMR) technique in the system Al–Zr–O. Microstructures of the composites and crystal morphology of in-situ formed Al₃Zr and Al₂O₃ particulates were analyzed by scanning-electron microscope (SEM) and transmission electron microscope (TEM). Results indicated that in-situ formed Al₃Zr and Al₂O₃ particles were finer and well distributed in aluminum matrix. Al₃Zr particulates with a tetragonal structure are mainly in the shape of polyhedron. A few of them are rectangular. The length/width ratio of the rectangular Al₃Zr is less than 2.0 and the maximum size is 4 μm. In addition, submicro Al₂O₃ particles with a hexagonal structure were also found in this system. Furthermore, it is found that twin may appear in the Al₃Zr crystal. The twin plane is (1 ). The twinning direction is [2 1].     

Al2O3掺杂BaTi0.85Sn0.15O3陶瓷的制备及性能表征

通过传统固相二次烧结法来制备x wt% Al₂O₃（x=0、1.0、1.5）/BaTi_0.85Sn_0.15O₃（BTS）陶瓷。研究了掺杂不同含量Al₂O₃对BTS陶瓷的微观结构、介电性能及挠曲电性能的影响。结果表明,掺杂Al₂O₃的BTS陶瓷不改变陶瓷的晶体结构,仍为标准钙钛矿结构晶型;Al₂O₃的掺入能够有效降低晶粒尺寸,具有明显的细晶作用。随着Al₂O₃含量的增大,Al₂O₃/BTS陶瓷的介电常数减小,介电损耗得到明显改善,居里峰逐渐宽化且向温度高的方向偏移。Al₂O₃/BTS陶瓷的挠曲电系数随着Al₂O₃含量的增加和测试环境温度的升高均减小。此外,Al₂O₃/BTS陶瓷的挠曲电系数和介电常数之间存在一种近线性关系,但当温度非常接近于居里温度时,这种线性关系减弱。     

The effect of second principal stress on the fatigue propagation of mode I surface crack in Al2O3/Al alloy composites

Using a plate made of A2017-T6 metal matrix composites reinforced with 10 volume % and 20 volume % Al₂O₃ particles and Al alloy possesses the same composition as matrix alloy, the crack propagation rate da/dN of a mode I surface crack by the simultaneous action of plane bending and cyclic torsion are studied. And the effects of crack tip opening stress σ_top, crack opening displacement COD, biaxial stress ratio C (=second principal stress/first principal stress) and the surface roughness of crack section are examined. When stress intensity factor range ΔK is lower than the specific level, da/dN decreases with the increase of volume fraction of Al₂O₃ in C=0 and C=−0.55. But, da/dN of Al alloy becomes minimum in C=−1 and the effect of Al₂O₃ particles disappears. σ_top rises with the increase of volume fraction of Al₂O₃ particles and the decline of C. On the other hand, COD doesn’t always rise with the decline of C. These phenomena can be explained by the residual compressive stress formed at the surface layer of the specimen by the fatigue test and the surface roughness of crack section.     

三维网络结构Al2O3陶瓷/高铬铸铁复合材料干摩擦磨损性能

采用往复式滑动摩擦磨损（SRV）试验机研究了高铬铸铁及三维网络结构Al₂O₃陶瓷增强高铬铸铁复合材料的干摩擦磨损性能,测量了高铬铸铁和Al₂O₃陶瓷/高铬铸铁复合材料在不同摩擦频率及载荷下的摩擦系数和磨损率;用扫描电镜观察磨损表面形貌,并分析了三维网络Al₂O₃陶瓷对复合材料磨损机制的影响。结果表明：陶瓷Al₂O₃与高铬铸铁基体之间具有良好的界面结合,复合材料的摩擦系数随摩擦频率和载荷的变化保持稳定,耐磨性远优于高铬铸铁,而且随着摩擦频率和载荷的增加,Al₂O₃陶瓷/高铬铸铁复合材料的抗磨损性能明显提高,这是由于复合材料中Al₂O₃与高铬铸铁相之间三维空间结构和良好的界面结合有利于摩擦载荷的传递;三维Al₂O₃陶瓷骨架在磨损表面形成硬的网络突体并起承载作用,能有效保护金属基体;磨损机制为氧化磨损及磨粒磨损共同作用。     

三维网络Al2O3增强球墨铸铁基复合材料摩擦磨损性能

采用SRV摩擦磨损试验机研究了球墨铸铁及三维网络Al₂O₃增强球墨铸铁基复合材料的干摩擦磨损性能, 测量了球墨铸铁和复合材料在不同摩擦频率及载荷下的摩擦系数和磨损率; 用扫描电镜观察磨损表面形貌, 并分析了三维网络Al₂O₃对复合材料磨损机制的影响。结果表明: 陶瓷与金属基体之间具有良好界面结合的三维网络Al₂O₃/球墨鋳铁复合材料, 其摩擦系数随载荷和摩擦频率的变化保持稳定; 复合材料的耐磨性能远优于球墨铸铁, 而且随着摩擦频率和载荷的增加, 复合材料的抗磨损性能明显提高。这是由于复合材料中陶瓷与金属相之间三维空间结构和良好的界面结合有利于摩擦载荷的传递; 金属基体中的石墨减摩作用保持摩擦系数的稳定; 三维陶瓷骨架在磨损表面形成硬的微突体并起承载作用, 制约了基体的塑性变形和高温软化, 有利于磨损表面氧化膜的留存。     

Microstructure and tensile properties of in situ synthesized (TiB+Y2O3)/Ti composites at elevated temperature

A novel titanium matrix composites reinforced with TiB and rare earth oxides (Y₂O₃) were prepared by a non-consumable arc-melting technology. Microstructures of the composites were observed by means of optical microscope (OM) and transmission electron microscope (TEM). X-ray diffraction (XRD) was used to identify the phases in the composites. There are three phases: TiB, Y₂O₃ and titanium matrix alloy. TiB grows in needle shape, whereas Y₂O₃ grows from near-equiaxed shape to dendritic shape with increase of yttrium content in the composite. The interfaces between reinforcements and titanium matrix are very clear. There is no interfacial reaction. Tensile properties of the composites were tested at 773, 823 and 873 K. Both the fracture surfaces and longitudinal sections of the fractured tensile specimens were comprehensively examined by scanning electron microscope (SEM). The fracture mode and fracture process at different temperatures were analyzed and explained. The results show that the tensile strength of the composites has a significant improvement at elevated temperatures. The predominant fracture mode of composites is cleavaged at 773 and 823 K. Fracture occurs by ductile failure at 873 K.     

Al2O3基多孔隔热材料表面Al2O3/MoSi2涂层的制备及其性能

采用刷涂法在Al₂O₃基多孔隔热材料表面制备Al₂O₃/MoSi₂涂层,涂层以硅溶胶作为粘结剂,纳米Al₂O₃与Al₂O₃纤维作为耐高温组分,MoSi₂为高发射率组分。通过SEM、XRD对Al₂O₃/MoSi₂涂层微观表面结构、物相组成进行分析。研究纳米Al₂O₃与Al₂O₃纤维的质量比和MoSi₂含量对Al₂O₃/MoSi₂涂层耐温性能的影响,并对Al₂O₃/MoSi₂涂层的抗热震性能、发射率进行表征。结果表明,当纳米Al₂O₃与Al₂O₃纤维的质量比小于1∶1时,热考核后Al₂O₃/MoSi₂涂层表面无裂纹产生;当纳米Al₂O₃与Al₂O₃纤维的质量比在1∶2~1∶4之间时,Al₂O₃/MoSi₂涂层中的纤维网络较完整。MoSi₂的含量为20%时,Al₂O₃/MoSi₂涂层抗热震实验循环25次后表面保持完好,热考核后在2.5~25 μm波段的平均发射率在0.85左右,具有较高的发射率。