低压液相浸渗制造高强度C/A1复合材料

本文提出非润湿性涂层框架浸渗模型,适当设计涂层形态,于低压力下可以实现金属液对涂覆非润湿性涂层纤维的完全浸渗。在1.5MPa浸渗压力下采用Al-Si-Mg合金浸渗涂覆SiC涂层碳纤维实验,结果表明该模型正确可行。所获得的C/Al复合材料试样抗拉强度达900MPa(纤维体积分数V_f=35％)。论文讨论了三种涂层状态下的浸渗结果。     

铸造碳化钨颗粒／中锰钢表面复合材料制作新工艺及其理论研究

开发了铸造碳化颗粒／中锰钢表面复合材料的制作新工艺，进行了金属液浸渗颗粒层过程动力学分析，结果表明，采用普通粘土干砂型或ＣＯ２硬化砂型及铬铁加稀土合金改善浸渗性技术，可以制成质量良好的表面复合材料，建立了金属液浸渗深度物理模型对有较好的指导作用。     

铸造碳化钨颗粒／中锰钢表面复合材料制作新工艺及其理论研究

开发了铸造碳化钨颗粒／中锰钢表面复合材料的制作新工艺，进行了金属液浸渗颗粒层过程动力学分析。结果表明，采用普通粘土干砂型或ＣＯ２硬化砂型及铬铁加稀土合金改善浸渗性技术，可以制成质量良好的表面复合材料。建立的金属液浸渗深度物理模型对实验有较好的指导作用     

混杂Cf／SiCp／Al复合材料的低压浸渗

提出了混杂低压浸渗模型，理论计算表明：在0.45MPa压力下可实现对非润湿体系浸杂Cf/Al复合材料的完全浸渗。采用超声混杂法制出了SiCp分布均匀的混杂预制型Cf/SiCp，探讨了混杂预制型的均匀性，采用气压浸渗法在1MPa压力下制出了纤维分布均匀的混杂复合材料Cf/SiCp/Al，分析了纤维分布与混杂预制型中SiCp分布的关系。     

熔体在连续纤维预制型中的浸渗动力学

从理论和实验上研究了熔体沿连续纤维纵向和横向的浸渗动力学。提出了熔体沿连续纤维纵向和横向的漫渗模型，依据达西定律推导出相应的纵向和横向浸渗系数，测定了铝液在碳纤维／碳化硅颗粒混杂预制型中的纵向和横向浸渗速度。结果表明：当熔体浸渗同样距离时，沿垂直于纤维轴向的浸渗速度约是沿平行于纤维轴向浸渗速度的2．0～2．5倍。     

低压浸渗Preform制备Al_2O_3/Zn合金复合材料

利用液态浸渗技术制备了Al_2O_3/Zn合金复合材料。研究结果表明,在低压下使液态金属浸渗Preform制备金属基复合材料是可行的,浸渗压力低于10MPa;在浸渗过程中,液态金属的温度对浸渗压力有较大影响。所制备的复合材料具有均匀的显微组织,纤维与基体中的活性元素的相互作用有利于Zn合金的共晶组织生核和长大。     

一种纳米石墨镀铜均匀性定量表征方法

建立了纳米级石墨化学镀铜的均匀性表征方法,为提高石墨镀铜颗粒的导电性和润滑性提供数据参考。采用化学镀铜的方法对石墨颗粒进行镀铜处理,并用XRD和TEM对纳米级石墨镀铜的结构和形貌进行了表征;通过对石墨化学纳米镀层TEM图像的分析,给出了一种适合于纳米级石墨镀铜TEM的二值化方法,结合数学形态学,定位出铜颗粒。提出了一种结合颗粒面积比和颗粒数量分布的均匀性表征方法。对不同纳米级石墨镀铜TEM图像进行了铜颗粒定位和均匀性分析。结果表明,铜颗粒定位准确,均匀性表征方法有效。同时,验证了对于纳米级石墨镀铜材料,石墨的颗粒越小,石墨镀铜中铜颗粒的分布越均匀。     

多孔陶瓷铜复合材料的显微组织

针对电机上电刷等部件服役寿命短的实际问题,采用有机泡沫浸渍法制备了多孔陶瓷;以多孔陶瓷为基体,采用熔渗法制备出铜 陶瓷复合材料.利用SEM对多孔陶瓷以及铜 陶瓷复合材料进行了显微组织结构分析.发现多孔陶瓷的孔径均匀,孔洞在三维空间上相互连通,基本上接近圆形,且陶瓷骨架的宏观结构表面较粗糙、有微孔,这样的结构有利于熔渗铜;同时发现加入硅灰石和方解石的多孔陶瓷,在熔渗铜的过程中发生粉化现象,而加入堇青石的多孔陶瓷耐高温性能良好,与铜能够形成结合牢固的界面.因此作为导电耐磨材料的多孔陶瓷,其添加剂应选择堇青石.     

木制品真空浸蜡实验研究

主要对在真空的条件下用液蜡作浸溃液、做木块被浸溃物的真空浸溃实验过程作了详细的介绍,分别介绍实验前的准备,实验中的现象及注意事项,试验结论等。然后说明在真空条件下的浸渍质量优于常规浸渍的质量,并得到一些浸渍质量与真空度和浸渍时间的定量关系,从而给出研究高质量浸渍结果的实验方法。     

纯铜热喷涂扩散渗铝层的显微组织

铜铝合金具有很好的抗高温氧化性能.在纯铜表面分别电 弧喷涂15mm和25mm厚的铝涂层,经900?℃保温4?h的扩散处理后获得19mm和36mm厚的铜铝合金渗层.主要针对渗层显微组织、渗层内的成分分布以及渗层的物相构成进行观察与测定.分析结果表明：渗层由表面层和内层两部分组成,层间结合良好.在加热处理过程中,铝涂层发生熔化,基体中的铜原子进入铝熔体形成表面渗层,表面渗层中遗留了原涂层的氧化物和孔洞.铝原子向铜基体的扩散形成组织紧密的内扩散层.内、外渗层都由金属间化合物Cu₉Al₄与αCu固溶体二相结构组成.在同样的扩散处理条件下,试件喷涂的铝涂层越厚,形成的渗层厚度越大,渗层中平均     

Preparation and arc erosion resistance of Cf/Cu composite by vacuum melting infiltration

Cf/Cu composite was prepared by vacuum melting infiltration. Ti and Cr were doped to the Cu alloy to improve the wettability between Cu and carbon. The microstrueture was investigated by XRD, SEM and EDS. The arc erosion rate of Cf/Cu composite was investigated in vacuum. The results showed that the Ti and Cr could improve the wettability between Cu and C/C preform and the infiltration ability of Cu into C/ C preform greatly. A TiC interface formed between the fibers and matrix. The good bonding between the fiber and matrix guaranteed that part of the Cu matrix can still be bonded on the fibers even when the material was exposed to the plasma. Consequently, the carbon fibers were protected from the erosion. In comparison, Cu was completely consumed by the arc erosion. Hence, the graphite was eroded and presented a cauliflower-like morphology. Therefore, the prepared C/Cu bad better ability to resist the arc erosion, compared with common Cu-C material.     

稀土元素镧和锶对镍基钎焊料焊接性能的影响

碳化钨(WC)复合涂层是一种高温下使用的有效耐磨蚀保护涂层.在BNi-2钎料粉末中添加稀土粉末,用机械合金化技术制备了改进的BNi-2钎料粉末,并在Q235钢基体上制备了碳化钨复合涂层;采用SEM观察了涂层显微组织,分析了稀土元素La和Ce对钎料焊接性能的影响规律.结果表明,在BNi-2合金中分别加入0.1 Wt.%稀土元素La,0.05 Wt.%稀土元素Ce,并采用机械合金化制备的粉状镍基焊料,与母材润湿性良好,焊接性能有所提高.采用此焊料及渗透钎焊技术可以制备出界面结合良好的WC复合涂层.     

Microstructure and thermal properties of SiCp/Cu composites with Mo coating on SiC particles

SiCp/Cu composites with a compact microstructure were successfully fabricated by vacuum hot-pressing method. In order to suppress the detrimental interfacial reactions and ameliorate the interfacial bonding between copper and silicon carbide, molybdenum coating was deposited on the surface of silicon carbide by magnetron sputtering method and crystallized heat-treatment. The effects of the interfacial design on the thermo-physical properties of Si Cp/Cu composites were studied in detail. Thermal conductivity and expansion test results showed that silicon carbide particles coated with uniform and compact molybdenum coating have improved the comprehensive thermal properties of the Si Cp/Cu composites. Furthermore, the adhesion of the interface between silicon carbide and copper was significantly strengthened after molybdenum coating. Si Cp/Cu composites with a maximum thermal conductivity of 274.056 W/(m·K) and a coefficient of thermal expansion of 9 ppm/K were successfully prepared when the volume of silicon carbide was about 50%, and these Si Cp/Cu composites have potential applications for the electronic packageing of the high integration electronic devices.     

Research on Percolation Network and Physical Properties of Graphite/Antimony Composites

The microstructure, friction and wear behaviour of graphite preform and graphite/antimony composites are analysed based on the percolation theory of hydrodynamics to investigate the relationship between the percolation network and physical properties of graphite/antimony composites. The result shows that there are two important factors to enhance friction and wear behaviour of graphite/antimony composites at high temperature： 1） the formation of the pore network in the preform, which is called the first percolation and 2） the optimization of infiltration method in the process of infiltrating antimony, which is called the second percolation. By adding some pyrolysate and controlling the roasting process, perfect net pores and sub-micron percolation microstructure may be formed in the graphite preform. By con- trolling the infiltration process, the saturation of molten antimony infiltrating into perfect pores can be optimized.     

硬脂酸/膨胀石墨复合相变储热的动力学研究

采用真空吸附法制备硬脂酸(SA)/膨胀石墨(EG)复合相变储热材料,利用差示量热扫描法(DSC)研究SA及SA/EG复合材料的非等温熔化和结晶过程动力学。运用Kissinger和Ozawa两种动力学数据处理方法对样品的非等温熔化DSC曲线进行处理,应用Mo法分析各样品的非等温结晶动力学特性。结果表明:SA/EG复合材料具有储热密度大、导热系数高且相变过程中无液相物质泄漏的优点;EG多孔结构的物理吸附作用会阻碍SA分子链段的扩散,使其熔化过程中的表观活化能升高;但EG的异相成核和传热强化作用能促进SA的相变,有利于降低其过冷度,提高其相变速率。     

Surface composites fabricated by vacuum infiltration casting technique

Alumina （Al2O3） particles reinforced copper matrix surface composites were fabricated on the bronze substrate using the vacuum infiltration casting technique. Three cases were obtained in the vacuum infiltration casting technique： no infiltration, partial infiltration and full infiltration （the thickness of preforms do not exceed 3.5mm）. The reason of no infiltration is that the vacuum degree is not enough so that the force acting on the liquid metal is lower than the resistance due to the surface tension. Partial infiltration is because of somewhat lower vacuum degree and pouring temperature. Full desired infiltration is on account of suitable infiltration casting conditions, such as vacuum degree, pouring temperature, grain size and preheating temperature of the preform. The most important factor of affecting formation of surface composites is the vacuum degree, then pouring temperature and particle size. The infiltration mechanism was discussed on the bases of different processing conditions. The surface composite up to 3.5 mm in thickness with uniformly distributed Al2O3 particles could be fabricated via the vacuum infiltration casting technique.     

In-Situ Synthesis and Characteristics of TiC-Fe Cermet Graded Composite Coating on a Steel Substrate

1　IntroductionOneofthemajorcoatingfamiliesisthecermet,whichgenerallyconsistsofceramicparticlesandametalbinder.Relativelyspeaking ,TiC Fecermetpossesseslow ercostbesidesitsextremelyhighhardnessandgoodresis tancestoabrasion ,hightemperatureandcorrosiveatmo sphere .Meanwhile ,thiscermetcanbeannealedsoastobeworkedbynormalmachiningtechniques ,andcanalsobehardenedbysubsequentheattreatments[1,2 ] .There fore ,whenTiC Fecermetcoatingisdepositedonasteelsubstrate ,anumberofsurfacepropertiesofthepart…     

Ag-Cu-Ti钎料在石墨表面的润湿

针对石墨钎焊过程中如何提高钎料在石墨表面的润湿问题，采用真空钎焊，在两组不同的工艺参数条件下，分别取Ti的质量分数W Ti不同的Ag-Cu-Ti钎料，做钎料在石墨表面的润湿性实验。结果表明，W Ti及工艺参数对钎料的润湿性有重要的影响；发现用这种钎料润湿石墨，由于二者热膨胀系数相差悬殊，产生的热应力使石墨产生开裂现象；通过分析对比实验结果，优选了钎料成分及钎焊工艺参数。     

<Emphasis Type="Italic">In-situ</Emphasis> synthesis and characteristics of TiC−Fe cermet graded composite coating on a steel substrate

By means of an inherent elevated-temperature of poured liquid steel, a Ti-C-30 wt% Fe preform, which was pre-placed in a mould cavity, was directly ignited and a combustion synthesis reaction took place. As a result, a TiC−Fe cermet coating with a thickness of about 10 mm was simutaneously synthesized on the solidified steel matrix. The synthesized coating exhibits a feature of graded composite structure, in which both the amount and size of TiC particles decrease gradually with an increasing distance from the furface of the coating. Moreover, by a proper casting technique, the pores formed during the combustion synthesis of the preform could be centrally distributed in 2–3 mm in outer layer of the coating. When this outer porous layer was worn off, the rest coating with a thickness of about 8 mm possesses a dense structure and a high abrasive wear resistance. YAN You-wei Born in 1965 Financially supported by the National Natural Science Foundation of China (No. 50276023)     

SiC颗粒增强Al基复合材料的热膨胀性能

采用气压浸渗方法制备了SiCp/Al(SiC颗粒增强铝基复合材料),由于浸渗程度的不同导致了复合材料密度的不同,研究了复合材料的工程CTE和物理CTE随密度的变化关系.实验结果表明,对于给定的SiC颗粒增强Al基复合材料,随着密度的增加工程CTE会出现3个不同斜率近似线性的增长,同时密度的增加会导致工程CTE下降,物理CTE突变点的温度升高,但是物理CTE突变点的值却不受密度的影响.