NiAl/TiC改性C/C复合材料的微观结构及力学性能

采用熔渗法对C/C多孔坯体进行预熔渗Ti处理,再用NiAl对预熔渗Ti后的C/C多孔坯体进行金属基体改性,制备出NiAl/TiC金属陶瓷改性C/C复合材料,并初步探讨C/C复合材料中NiAl/TiC金属陶瓷复合结构的形成机理及其对改善复合材料力学性能的作用机理。研究结果表明:预熔渗Ti后,Ti与基体炭反应生成TiC。由于NiAl与TiC润湿性好,生成的TiC可有效改善NiAl在C/C多孔坯体中的熔渗深度。NiAl在C/C多孔坯体中的熔渗深度为3~5 mm,同时,NiAl金属相与TiC陶瓷相在材料中呈镶嵌结构复合生长且分布无规则。经NiAl/TiC金属陶瓷熔渗后,复合材料的密度达到2.39 g/cm3,开孔率为13.44%,抗压强度为85.3 MPa,抗弯强度为67.2 MPa。     

多孔金属材料的制备方法及应用研究

多孔金属材料是一种兼具结构和功能双重性能的材料,因为其具有许多优越的性质,在很多领域得到了广泛的应用.根据当前多孔金属材料的研究进展和发展形势,阐述了制备多孔金属材料的工艺,结合其性能探讨了它的应用现状,并针对当前面临的问题进行了归纳和总结.     

不锈钢粉末与丝网烧结多孔材料高温硫化性能研究

为了考察滤材结构和形貌对材料抗高温硫化性能影响,研究了不锈钢316L、310S粉末与丝网烧结多孔材料在高温硫化氢气氛[350℃,介质:CO2+H2S(0.02％,体积分数)]中的硫化性能以及材料孔结构的稳定性,并利用光学显微镜观察表面形貌,从而评价耐蚀性能.结果表明:经过1 500h试验,316L、310S粉末烧结金属多孔材料在高温硫化氢气氛中耐腐蚀性能明显低于同类丝网材料,粉末与丝网烧结金属多孔材料的耐蚀性能差异主要由滤材结构和其比表面积决定.     

浅谈Fe3Al多孔材料与不锈钢的焊接

文章使用真空焊接工艺,使用Cu-S-Ag混合粉末作为焊接材料,研究铁铝金属间化合物多孔材料和316L不锈钢的焊接性能.结果表明:真空钎焊后焊缝的最大抗拉强度可达86.2MPa,Fe3Al多孔材料和不锈钢的真空焊接机理是液相扩散焊接,母材和焊接材料通过元素的相互扩散和反应进入多孔材料与致密结合部分的界面及部分多孔材料孔道,形成稳固的焊接界面.     

多孔TiAl金属间化合物的抗热盐酸腐蚀性能

以Ti、Al元素粉末为原料,用粉末冶金法制备Al含量为35%(质量分数)的多孔TiAl金属间化合物.通过腐蚀动力学曲线、孔结构参数与表面形貌变化来研究在90 ℃恒温条件下,多孔TiAl在pH为2和3的盐酸溶液中的耐腐蚀性能,并对多孔TiAl与多孔钛、多孔镍以及多孔不锈钢在pH=2时的耐腐蚀性能进行比较.结果表明,当pH值由3减小到2时,多孔TiAl的耐腐蚀性能略有下降,但仍明显优于其他3种多孔材料.分析认为,多孔TiAl的优良耐蚀性能主要归因于钛铝金属间化合物特殊的键合特征以及Ti、Al元素的强钝化能力.     

等离子与火焰喷涂镍铝涂层性能研究

采用等离子和火焰两种方法制备NiAl涂层,对比了NiAl复合粉末在这两种喷涂工艺条件下所得涂层的硬度、结合强度和组织结构。实验结果表明采用等离子法制备的NiAl涂层致密,涂层孔隙率低,与基体的结合强度高,且涂层的硬度较高。     

先驱体浸渍裂解制备多孔C/SiC复合材料及渗透性研究

以聚碳硅烷(PCS)为原料,采用先驱体浸渍裂解(PIP)工艺制备多孔C/SiC复合材料,并研究该材料的孔隙率、孔隙结构及渗透性能.结果表明,所制备的多孔C/SiC复合材料的孔隙主要由纤维束间的开孔组成.经过6次与7次PIP工艺致密化处理后的复合材料,开孔率分别为22.76%和20.51%,绝对渗透率分别为1.17×10-3和9.68×10-4 mm2.水和煤油在该材料中具有良好的渗透性能,渗透表现为线性层流流动,表明多孔C/SiC复合材料在发汗冷却材料中具有很大的应用潜力.     

梯度多孔金属材料制备及应用的研究进展

梯度多孔金属材料是一种性能优良的新型多孔材料,具有不对称的孔结构,这种结构实现了多孔材料过滤行业的小孔径、大透气这一要求,同时良好的力学性能使得梯度多孔金属材料的应用较陶瓷膜的应用更为广泛.本文综述了梯度多孔金属材料制备工艺和研究应用概况.     

褐铁矿致密化烧结技术试验研究

分析了褐铁矿的烧结特性及成矿机理,根据性能优势互补配矿理论,通过试验将褐铁矿与镜铁矿合理搭配进行烧结.试验结果表明：褐铁矿烧结性能得到强化,烧结矿指标明显改善,主要是镜铁矿液相生成温度高、流动性差,褐铁矿颗粒被镜铁矿包裹,使得褐铁矿颗粒在与液相接触之前得到致密,避免了脆化结构的形成.褐铁矿致密化烧结使得烧结矿的矿物结构发生变化,多孔薄壁结构减少,有利于改善烧结矿高温性能.     

创意材料——泡沫铝

正泡沫铝是一种由铝或铝合金基体与气孔复合而成的新型轻质功能-结构一体化材料。这种特殊结构决定了其轻质性、高孔隙率、高比表面积等特点,由此获得许多致密金属所不具有的优良特性,如很强的能量吸收性、抗冲击性、高比强度、电磁屏蔽、吸声性能、高阻尼性、低热导率、低电导率等。泡沫铝的性能主要取决于孔隙率、孔径、通孔率、孔结构类型、比表面积等孔结构参数及金属基体。     

Physicochemical approaches to designing NiAl-based alloys for high-temperature operation

The structure and properties of new-type materials based on light refractory nickel monoaluminide NiAl as a structural material are analytically reviewed. The choice of various alloying systems and structural-phase states of NiAl-based structural materials, including structural materials, is analyzed, and the choice of the processes of production of the materials is grounded, as applied to their composition.     

Formation of protective coatings on steel Kh12MF by the force of the sequential electric spark treatment by boride and carbon-containing electrodes

Coatings on steel Kh12MF are fabricated by the force of electric-spark treatment by the TiB₂-20% NiAl electrode and carbon-containing materials. Kinetics of their formation, the phase composition, mechanical and tribological properties, roughness, and durability to high-temperature oxidation are investigated. When depositing the coating using the TiB₂-20% NiAl electrode, the effect of a disproportionate increase in the substrate erosion, which is observed with an increase in the energy of a single pulse and leads to lowering the content of boride phases in the coating is discovered. The subsequent electric-spark treatment of the boride coating using an electrode made of fine-grain dense graphite led to a noticeable improvement of tribological properties of the coating having no noticeable effect on its durability to high-temperature oxidation. In the case of applying an electrode made of the silicicated composition material, the coating durability to high-temperature oxidation increased substantially, but no improvement of tribological properties was observed.     

多孔结构对材料吸波性能的影响

总结了当前多孔材料吸波性能的研究现状，指出多孔结构可改善材料的吸波性能，而孔径、相对密度及厚度是影响多孔材料吸波性能的重要因素，对多孔陶瓷材料而言，适当降低孔径、增加相对密度与厚度有利于提高材料的吸波性能．在此基础上对多孔金属材料泡沫铝的吸波性能进行了初步研究，分析了相对密度与微波频率对材料吸波性能的影响，研究表明，降低多孔金属的相对密度可以显著提高材料的吸波性能；随着微波频率的增加，材料的吸波性能也随之增加．     

Potential of Acoustic Methods in Monitoring the Structure and Physicomechanical Properties of Porous Materials

The task of monitoring porous materials is formulated. Principles for developing and using nondestructive acoustic methods for monitoring the structure and physicomechanical properties of porous materials are suggested and discussed. It is noted that the solution of each monitoring problem for porous materials requires an individual, often nontraditional, approach and its success is determined by the possibility of developing theoretical or experimental correlation dependences between the acoustic and material properties sought. It is shown that it is possible from the results of measuring propagation velocity and elastic wave damping factors to determine parameters such as elasticity, inelasticity, porosity, defectiveness, the size of structural elements, anisotropy, and property inhomogeneity.     

Development of a technology of compaction of increased-density parts using gas drainage methods. IV. Compaction of powder materials without plasticizer

A new compaction method uses a porous female die made of powdered materials without plasticizer. Powders alloyed with carbon, nickel, chromium, molybdenum, and microtalc were used to produce the porous die. The powder was compacted by a special device, in which the operating surface of the matrix was lubricated through the open pores of the powdered material. Compaction of materials into a porous die ensures highly efficient drainage of gases from the press mold. As a result the density of iron-based compacts increases to 7.4–7.7 g/cm³ and in regard to mechanical properties the sintered materials can compete with those obtained by hot forging.     

Preliminary studies on NiAl/Nb2Be17 reaction and effectiveness of BeO as an interfacial reaction barrier

Alloys based on the ordered B2 NiAl phase are being considered as potential high-temperature structural materials. One drawback for this material is its lack of high-temperature strength,[1] which can be overcome by reinforcing the alloy with high-strength fibers. Like any other composite system, a suitable reinforcement material must have a matching coefficient of thermal expansion (CTE) with the matrix in addition to high-temperature strength and be chemically compatible with the matrix. Although there are many high-melting ceramic materials which are thermodynamicalry stable in the NiAl matrix, [2] the high CTE of NiAl,[3] 16 X 10⁻⁶ K⁻¹ at 1200 K, makes it difficult to find a suitable ceramic reinforcement material with a matching CTE. Thus, there is a need to develop high CTE fibers for the NiAl matrix. One group of materials with matching CTE[3] to NiAl are the Be-rich intermetallic compounds called beryllides (CTEs in the range of 16 to 18 × 10⁻⁶ K₋₁ at 1200 K) of formula M₂Be₁₇, M₂Be₁₃, or M₂Be₁₂ (where M = Ta, Nb, Ti, Zr, Hf, or Y). Matching CTEs with the NiAl matrix along with their good high-temperature strength[4] and low densities[4] make Be-rich intermetallic compounds attractive as candidate reinforcement materials for the NiAl matrix.     

High Temperature Materials Based on the Intermetallic Compound NiAl Reinforced by Refractory Metals for Advanced Energy Conversion Technologies

Advanced NiAl‐based high temperature materials are developed and characterized for structural applications in energy conversion systems. The intermetallic compound NiAl with B2 superlattice structure exhibits superior physical and high temperature mechanical properties, and excellent oxidation resistance. Disadvantages of polycrystalline pure NiAl are the lack in plasticity and fracture toughness at room temperature and insufficient high temperature strength at temperatures above 800 °C. The refractory metals Cr, Mo, and Re form with NiAl quasi‐binary eutectic systems which enable to produce metal fibres reinforced NiAl‐based alloys in the as‐cast condition and by performing directional solidification. These in‐situ composites show fine‐grained and thermally stable microstructures possessing high temperature strength, superior creep resistance and sufficient room temperature ductility.     

自蔓燃高温合成碳化物陶瓷

介绍了自蔓延高温合成（SHS）制备碳化物粉体。单晶、多孔材料和致密材料。重点讨论了通过控制反应参数,控制合成材料的组织结构和性能的一些措施。以催化剂载体、泡沫陶瓷过滤器、粗TiC磨料以及Si-SiC复合材料为例,介绍了SHS在材料合成中的应用和控制方法。参考Ti3SiC2陶瓷的合成,讨论了多元SHS体系中产物相的控制问题。另外,文中还介绍了提高烧结助剂BxC在SiC中的分散性,从而提高SHSSiC烧结性的实例。     

Effect of porosity on the size of surface microirregularities in the finish lathe-turning and smoothing of sintered materials

Conclusions The greatest influence on surface roughness in the lathe-turning of P/M materials is exerted by the ductility properties of the materials. The effect of this factor in lathe-machining is greater with P/M than with similar dense materials. The mechanism of the influence of porosity on the surface roughness and service properties of parts made of P/M materials is very complex, and should, in the author's opinion, be the subject of a special investigation. Smoothing not only strengthens the surface layer of a part made of a P/M material, but also consolidates it, i.e, increases its density, and this in turn improves the operating characteristics of the part. In finish lathe-turning and smoothing, to each class of P/M material there corresponds a certain tool material which enables the best-quality machined surface to be obtained.Translated from Poroshkovaya Metallurgiya, No. 9(213), pp. 94–99, September, 1980.     

镜铁矿烧结性能试验研究

镜铁矿因成球性和可烧性较差,使得该矿在烧结料中的应用受到了极大限制。本文通过试验对镜铁矿制粒性能、烧结特性及冶金性能的研究,采取优化原料结构技术措施,探索出镜铁矿在烧结中合理使用新途径,为提高其在生产中的配比和改善烧结性能提供指导。