Al_2O_3/TiAl 复合材料的原位合成、结构与性能研究(英文)

以 Ti, Al, TiO2和 Nb2O5混合粉为原料,采用热压反应合成技术制备了 Al2O3/TiAl 复合材料。对复合材料的微观组织与力学性能进行了研究。结果表明:产物由γ-TiAl, α2-Ti3Al, Al2O3和 NbAl3相组成。原位反应形成的细小 Al2O3粒子主要分布在基体晶界处。随着 Nb2O5含量的增加,晶粒明显细化,Al2O3粒子呈弥散分布在基体中。最终形成了由γ和γ α2构成的特殊组织。随着 Nb2O5含量的增大,复合材料的硬度逐渐增大,抗弯强度和断裂韧性在 Nb2O5含量为 6 wt%时达到最大,分别为 398.5 MPa 和 6.99 MPa·m1/2。     

原位反应合成Nb掺杂Al2O3/TiAl复合材料的显微结构分析

利用Al-Ti-TiO2体系原位反应合成了Nb掺杂Al2O3／TiAl复合材料。借助XRD和SEM研究了Nb掺杂Al2O3／TiAl的显微结构以及Nb引入量对复合材料显微结构的影响。结果表明，复合材料由TiAl、Ti3Al、Al2O3、Nb和NbAl3相构成，细小Al2O3颗粒分布于基体晶粒交界处，存在一定的团聚；Nb元素引入量的高低，可调节产物中TiAl和Ti3Al的相对含量，随Nb含量的增大，TiAl含量逐渐减少，Ti3Al则逐渐增大；同时，基体晶粒和Al2O3颗粒均有所细化，且分布逐渐均匀，材料的均匀性得到改善。     

采用XD工艺合成TiAl合金及TiC／TiAl复合材料的研究

研究了用ＸＤ（热爆）工艺合成ＴｉＡｌ合金及ＴｉＣ／ＴｉＡｌ复合材料,井探讨了其合成反应机制。结果表明,可在Ａｌ的熔点附近用ＸＤ工艺制备ＴｉＡｌ合金及其ＴｉＣ颗粒增强的ＴｉＣ／ＴｉＡｌ复合材料,Ｔｉ－Ａｌ粉末间的放热反应促进了ＴｉＣ的合成。ＴｉＡｌ合金由ＴｉＡｌ＋Ｔｉ３Ａｌ相组成,而ＴｉＣ／ＴｉＡｌ复合材料由ＴｉＣ＋ＴｉＡｌ＋Ｔｉ３Ａｌ相组成。     

Impermeability of Y3Al5O12 ceramic against molten glassy calcium-magnesium-alumina-silicate

Degradation of thermal barrier coatings (TBCs) caused by calcium-magnesium-alumina-silica (CMAS) glassy penetration is becoming an urgent issue for TBCs industrial applications. In this work, yttrium aluminum garnet (Y₃Al₅O₁₂, YAG) nano-powders were synthesized through a chemical co-precipitation route. The resistance of YAG ceramic to glassy CMAS infiltration at 1250?°C was evaluated. YAG ceramic bulk sintered at 1700?°C for 10?h was comprised of a single garnet-type Y₃Al₅O₁₂ phase. The molten CMAS glass was suppressed on the surface of the YAG ceramic at 1250?°C. A chemical reaction between YAG and the molten CMAS glass did not occur at 1250?°C for 24?h, suggesting that YAG could act as an impermeable material against glassy CMAS deposits in the TBC field.     

Combustion mechanism of fluorinated organic compound-modified nano-aluminum composite particles: Towards experimental and theoretical investigations

Fluorinated Organic Compounds (FOCs) are commonly used as modifiers for Aluminum (Al) powder to improve its ignition, combustion, and agglomeration characteristics. However, the effects of FOCs on combustion and inhibition mechanisms of agglomeration of Al powder are not well understood. In this paper, based on the experimental study of Fluorinated Graphite (FG)-modified Al matrix composite particles, the combustion and aggregation inhibition mechanisms of FOCs on Al particles were studied by the quantum chemical calculation at B3LYP/6-311+G(d,P) and G3//B3LYP/6-311+G(d,p) levels. The flame behavior and single particle burning behavior of FG-modified samples were compared through ignition experiments, and the characteristic spectra of Al related oxides of different samples in the initial ignition stage were captured. It is found that FG increases the burning intensity of Al composite samples significantly, while it decreases the emission intensity of Al secondary oxides. Quantum chemical calculation results show that the thermal decomposition intermediates of FOCs, namely C₂F₄, can react with AlO and Al₂O, which weakens the characteristic emission intensity of AlO and Al₂O in the sample, and thus inhibits the formation of Al₂O₃ in the combustion process. These results contribute to enriching the combustion dynamics model of Al-FOCs reaction system.     

Al含量对空心阴极等离子烧结Ti/Ni等原子比TiNiAl合金组织和力学性能的影响

 采用空心阴极等离子烧结工艺制备了Ti/Ni等原子比的Ti_50-x/2Ni_50-x/2Al_x(x=0,3,6,9)合金,研究了Al含量对合金微观组织以及力学性能的影响。结果表明:未添加铝的合金微观组织主要由NiTi基体、强化相Ti₂Ni、Ni₃Ti及孔隙组成;随着Al含量的提高,合金中Ti₂Ni(Al)数量不断增多,孔隙数量和孔径不断增加,Ni₃Ti(Al)数量不断减少,在Ti_45.5Ni_45.5Al₉中还生成了少量Ni₂TiAl相;合金的抗弯强度随Al含量的提高而增加,并在Al含量为6%时达到最大值296.3 MPa;合金的硬度随铝含量的提高而增加,Ti_45.5Ni_45.5Al₉的硬度值为295.6 HV。     

Ho_2O_3掺杂对原位合成HoAl-Al_2O_3/TiAl复合材料显微组织及性能的影响

采用固态置换反应原位合成工艺,利用Al—Ti—TiO2-Ho2O3体系的放热反应合成了HoAl-Al2O3／TiAl复合材料。利用XRD和SEM分析了Ho2O3掺：枭对原位合成HoAl,Al2O3颗粒强化钛铝基复合材料显微组织的影响,探讨了稀土氧化物（Ho2O3）的细化机制。测试了力学性能。结果表明：Al—Ti—TiO2-Ho2O3系原位合成的HoAl-Al2O3／TiAl复合材料由TiAl,Ti3Al,Al2O3以及HoAl相组成;HoAl金属间化合物弥散分布于基体晶粒和Al2O3颗粒交界处,限制颗粒长大,细化基体晶粒与Al2O3,颗粒,同时提高了HoAl,Al2O3颗粒在基体中的分散度;Ho2O3的引入改善了复合材料的力学性能。     

Influence of TiB2 particles on machinability and machining parameter optimization of TiB2/Al MMCs

In situ formed TiB₂ particle reinforced aluminum matrix composites (TiB₂/Al MMCs) have some extraordinary properties which make them be a promising material for high performance aero-engine blade. Due to the influence of TiB₂ particles, the machinability is still a problem which restricts the application of TiB₂/Al MMCs. In order to meet the industrial requirements, the influence of TiB₂ particles on the machinability of TiB₂/Al MMCs was investigated experimentally. Moreover, the optimal machining conditions for this kind of MMCs were investigated in this study. The major conclusions are: (1) the machining force of TiB₂/Al MMCs is bigger than that of non-reinforced alloy and mainly controlled by feed rate; (2) the residual stress of TiB₂/Al MMCs is compressive while that of non-reinforced alloy is nearly neutral; (3) the surface roughness of TiB₂/Al MMCs is smaller than that of non-reinforced alloy under the same cutting speed, but reverse result was observed when the feed rate increased; (4) a multi-objective optimization model for surface roughness and material removal rate (MRR) was established, and a set of optimal parameter combinations of the machining was obtained. The results show a great difference from SiC particle reinforced MMCs and provide a useful guide for a better control of machining process of this material.     

Preparation and Characterization of Fe3O4/T-ZnOw Composites

Fe3O4/T-ZnOw composites are fabricated by depositing a layer of Fe3O4 film on the surface of tetrapod-shaped ZnO whisker (T-ZnOw) by ferrite plating method. The morphology, structure and magnetic properties of the composites are characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and vibrating-sample magnetometer (VSM), respectively. The effects of temperature and pH value of ferrite plating on the Fe3O4/T-ZnOw composites and the magnetic properties of composites are studied. It is shown that the chemical environment with pH value at 7.5 is most favorable for the ferrite plating processes by analyzing the main peaks intensity of Fe3O4 in the XRD patterns and the average diameters of the Fe3O4 crystalline. The increase of the ferrite plating temperature with pH value around 7.5 benefits the whole encapsulation of T-ZnOw by the Fe3O4 magnetic films. The composites exhibit ferromagnetic properties and show much lower magnetization intensity than bulk samples at the same magnetic field intensity.     

航空航天用多功能SiC/Al复合材料研究进展(英文)

Multi-functional Al-matrix composites with high volume fraction （55%-57%） of SiC particles are produced with the new pressureless infiltration fabrication technology. X-ray detection and microscopic observation display the composites which are macroscopically homogeneous without porosity. The investigation further reveals that the SiC/Al composites possess low density （2.94 g/cm^3）, high elastic modulus （220 GPa）, prominent thermal management function as a result of low coefficient of thermal expansion （8 × 10^4 K^-1） and high thermal conductivity （235 W/（m.K）） as well as unique preventability of resonance vibration. By adopting a series of developed techniques, the multi-functional SiC/Al composites have managed to be made into near-net-shape parts. Many kinds of precision components of space-based optomechanical structures and airborne optoelectronic platform have been turned out. Of them, several typical products are being under test in practices.     

Al2O3/ZrO2(n)微纳米复合陶瓷超声振动精密磨削表面微观特征试验研究

 基于Al₂O₃/ZrO₂（n）微纳米复合陶瓷的“晶内型”微观结构，应用原子力显微镜(AFM)重点分析了微 纳米复合陶瓷二维超声振动磨削表面微观形貌。结合磨削表面X射线衍射定性分析与定量计算，研究了“晶内型”微纳米复合陶瓷材料超精密振动磨削表面变质层结构。X射线衍射分析表明：二维振动磨削和普通磨削表面均以α-Al₂O₃和四方相ZrO₂为主，存在少量单斜相ZrO₂，磨削表面无非晶相产生；磨削表层和基体之间的过渡层的X射线衍射峰具有半峰宽化现象。AFM分析结果表明：细粒度金刚石砂轮普通磨削和振动磨削表面均无微裂纹和断裂破碎，磨削表面粗糙度是由不同幅值的多种波形叠加的结果；AFM轮廓特征分析表明：二维超声振动磨削表面峰谷较均匀，磨削表面均匀一致性优于普通磨削表面；材料晶化过程中产生的固有缺陷是限制硬脆材料近纳米表面形成的重要因素。     

Effects of Alloying Elements Ti, Cr, Al, and Hf on β-Nb5Si3 from First-principles Calculations

The energy, lattice parameters, electronic structures, and elastic constants of the intermetallic compound β-Nb₅Si₃ alloyed by Ti, Cr, Al, and Hf elements are investigated using first-principles methods based on plane-wave pseudopotential theory. From the impurity formation energy calculated, it is found that Ti, Cr, and Hf prefer to occupy the Nb_I, Nb_I, and Nb_II site, respectively, and that Al decreases the stability of β-Nb₅Si₃. Ti and Cr atoms reduce the c/a ratio of crystal lattices and Hf atom transforms the crystal lattice of β-Nb₅Si₃ from the tetragonal system to the orthorhombic system. The total state density of pure β-Nb₅Si₃ system and Ti, Cr, and Hf doped systems shows that Ti, Cr, and Hf improve the conductibility of β-Nb₅Si₃ system. The bulk modulus, shear modulus, and elastic modulus are obtained using Voight approximation equation. Ti and Cr increase the hardness and reduce the ductility of β-Nb₅Si₃. In contrast, Hf decreases the hardness and improves the ductility.     

SiCp/Al复合材料加工损伤及刀具优选研究进展

SiC_p/Al复合材料中增强相SiC颗粒的存在降低了该材料的加工性能,使得其切削加工时产生一系列加工损伤。本文综述了SiC_p/Al复合材料的加工缺陷类型、缺陷形成机理、缺陷控制策略和切削刀具的磨损机理与优选策略,并对今后SiC_p/Al复合材料加工损伤研究进行了展望。     

镍掺杂对α-Al2O3烧结过程、微观结构及力学性能的影响

 首先采用非均相沉淀包裹法制备金属镍包裹α-Al₂O₃复合微球粉体,然后采用热压烧结制备了Al₂O₃/Ni金属陶瓷。通过X射线衍射仪（XRD）、扫描电子显微镜（SEM）、能谱仪（EDS）对复合粉体及热压烧结产物的成分和结构进行了表征,利用阿基米德法测量了复合陶瓷的密度,分别通过三点弯曲法和单边切口横梁法对陶瓷试条的抗弯强度和断裂韧性进行评估。研究发现：金属镍的引入活化了α-Al₂O₃的烧结,镍粒子均匀地分布在氧化铝的晶界上,增加了弱界面,提高了氧化铝的断裂韧性,最高可达7.62 MPa·m^1/2。     

Microstructure evolution of a hypereutectic Nb–Ti–Si–Cr–Al–Hf alloy processed by directional solidification

In this work, the Nb–14Si–24Ti–10Cr–2Al–2Hf–0.1Y alloy(at.%) was processed by the liquid–metal-cooled directional solidification(DS) at 1750 C with withdrawal rates of 1.2, 6,18 mm/min and post heat treatment(HT) at 1450 C for 10 h. The microstructures of the directionally solidified and heat treated samples were investigated. The results show that the microstructure of directionally solidified alloy mainly consists of petaloid Nbss+ Nb5Si3eutectics and Ti-rich Nbss+ Nb5Si3+ Cr2Nb eutectics. With the increase of withdrawal rate, the primary Nb5Si3is eliminated, Nbss+ Nb5Si3eutectic cells turn round and connected with the microstructure refinement and Nbss+ Nb5Si3+ Cr2Nb eutectics turn to a river-like morphology. After heat treatment,Nbss+ Nb5Si3+ Cr2Nb eutectics disappeared and petaloid Nbss+ Nb5Si3eutectics turn to a specific fiber-mesh structure gradually, which is promoted by higher withdrawal rates. Furthermore,both the volume fraction of Cr2Nb and the content of Cr in Nbssof Nbss+ Nb5Si3eutectics change regularly with the increase of withdrawal rate and heat treatment at 1450 C for 10 h.     

以Ti/V/Cu、V/Cu为中间层的TiAl合金

用真空扩散连接方法对TiAl/Ti/V/Cu/40Cr钢及TiAl/V/Cu/40Cr钢进行了研究。结果表明,以Ti/V/Cu作中间层的接头拉伸强度高于以V/Cu作中间层的接头强度。界面分析显示,Ti/V、V/Cu、Cu/40Cr钢的各个结合界面处未形成金属间化合物,而TiAl/Ti的结合界面上有Ti3Al产生;在TiAl/V的界面上有Ti3Al、Al3V两种金属间化合物产生;界面上脆性金属间化合物的产生是接头发生断裂的原因。     

共熔法制备超高温陶瓷基复合材料

首次采用共熔法制备超高温陶瓷基复合材料,三个样品初始组分分别为ZrB_2与鳞片石墨,ZrB_2、TaB_2、SiC及鳞片石墨,ZrB_2、MoSi_2与鳞片石墨。研究结果表明,共熔法制备的复合材料中各相分散均匀,产物中的石墨高度有序,石墨层间距分别为0.335 4、0.335 9与0.337 7 nm,且三者的微晶厚度分别为63.4、51.5及68.7 nm,拉曼光谱结果表明硼已经掺杂进入了石墨的网格结构。所制得的超高温陶瓷基复合材料样品中均存在一定的孔隙率,且制备的超高温陶瓷基复合材料的热导率较低。该方法为一种新型、快速、一步法制备超高温陶瓷基复合材料工艺。     

Improving tensile-shear properties of friction stir lap welded dissimilar Al/Mg joints by eliminating hook defect and controlling interfacial reaction

To improve tensile-shear properties of fiction stir lap welded(FSLW) dissimilar Al/Mg joints, pin-tip profiles were innovatively designed and welding speed was optimized, and effects of them on formation, interface microstructure and mechanical properties of different FSLW joints were investigated. With increasing the welding speed, the tensile-shear load of FSLW joints produced by three pins presents an increasing firstly and then decreasing trend. Compared with Rpin, the hook and hole defect i...     

航空用原位颗粒增强铝基复合材料研制与发展

与外加颗粒法相比,原位自生法制备的颗粒尺寸小、表面干净且与基体界面结合强度高,使得铝基复合材料具有高比强度、高比模量以及良好的强塑性匹配等优势。因此,原位自生铝基复合材料是航空航天结构件轻量化设计的理想材料之一。从原位自生TiB₂颗粒增强铝基复合材料制备、组元配比优化设计、性能与强韧化机制等三个方面总结其研究现状,同时梳理了原位自生TiB₂颗粒增强铝基复合材料存在问题与未来发展方向,以期望促进原位自生铝基复合材料在民航客机等航空高端领域快速发展。     

催化剂对HMX/AP/HTPB推进剂热分解特性的影响

热分析实验是使用国产CDR-1型差动热分析仪。热分解活化能用Ozawa法和Kissinger法计算[1],其它动力学参数均用Kissinger法求得。全部热分析实验均在氮气气氛中进行。推进剂燃速用靶线法燃速仪测定。HMX和各种催化剂在使用前均经过烘干处理。催化剂过100目筛。