铸渗法制备颗粒增强钢基复合材料的研究

通过对负压铸渗理论的分析，得出了影响负压铸渗深度的因素及其影响规律（见式（９））；用碳化钨、镍包氧化铝及不同粒度氧化铝为陶瓷颗粒、耐热钢为基体进行了负压铸渗实验，得到了颗粒分布均匀的复合材料，揭示和证实了颗粒与金属液间的湿润特性及颗粒粒度对铸渗的影响规律。     

Al2O3颗粒/耐热钢复合材料的制备及高温磨料磨损性能

氧化铝与耐热钢在高温下都具有优异的特殊性能,氧化铝硬度高、热稳定性好、耐热钢的抗氧化性与热强性高,因此氧化铝颗粒增强耐热钢基复合材料可望获得好的抗高温磨料磨损性能。在154~200 μm的氧化铝颗粒表面通过化学气相沉积技术获得Ni涂层后,通过在氧化铝颗粒中加入耐热钢颗粒的方法与负压铸渗技术,获得了氧化铝颗粒体积分数在18 %~52 %的氧化铝颗粒/耐热钢基复合材料,并考察了其在900℃的磨料磨损工况下的耐磨性。结果表明:所有复合材料的耐磨性均比耐热钢的好,耐磨性最好的复合材料是氧化铝颗粒体积分数为39 %的复合材料,其耐磨性是耐热钢的3.27倍。通过扫描电镜分析了复合材料的磨损机理及不同氧化铝颗粒体积分数复合材料的磨损行为。      

用CVD 法在陶瓷颗粒表面获得TiN 涂层与应用

研制了适合陶瓷颗粒表面涂层处理的化学气相沉积装置, 并探索了在氧化铝颗粒表面获得TiN 涂层的工艺; 所获得的TiN 涂层能提高耐热钢在氧化铝颗粒间的铸渗深度, 并使颗粒得到基体的牢固支撑。氧化铝颗粒体积分数在23%～ 57% 可调。      

消失模铸渗法制备复合材料的研究

研究了消失模铸渗法中合金颗粒粒度，粘结剂含量、复合熔剂含量和浇注温度等因素对铸渗工艺的影响，给出了合适的铸渗涂层涂料配比，制备了铸铁HT200表面渗铬复合材料，分析了铸渗层的组织和性能，结果表明合金化涂料配比比较优方案为Cr-Fe粉末粒度为0．127－0．181mm，水溶性酚醛树脂含量为2％（质量分数），复合熔剂为7．5％（质量分数）以及适量水和微量添加剂，浇注温度的适宜范围为1400－1500摄氏度。影响消失模铸渗工艺的各因素主次顺序依次为浇注温度，合金粉末粒度，粘结剂含量和复合熔剂含量，铸渗层由外向里可分为3个区，碳化物类型由M7C3向M3C转变，且硬度逐渐降低，表面合金化层的耐磨性为正火45＃钢的2．8倍。     

铸渗法制备铜基表面复合材料

利用铸渗法对铜合金表面进行改性, 用Fe 基合金粉末作为渗剂在负压条件下进行浇注制备铜基表面复合材料。实验结果表明: 在本实验工艺条件下, 在铜合金铸件的特定表面获得了致密的组织结构不同于基体的渗层———表面复合材料层。经SEM 观察, 发现渗剂颗粒与基体的界面结合良好, 证实了铸渗法制备铜基表面复合材料的可行性。     

氧化铝和氢氧化铝颗粒分析方法

简述了激光衍射法测量氧化铝和氢氧化铝颗粒粒度的原理和方法，以及其分析方法的优缺点，通过在砂状氧化铝试验过程中对大量的氧化铝和氢氧化铝颗粒粒度测量和分析，总结了影响颗粒粒度分析的共性因素。提出消除影响因素的措施和改进氧化铝和氢氧化铝颗粒粒度的分析方法。     

分散剂聚合度对纳米氧化铝粉体特性的影响

以不同聚合度的聚乙二醇(PEG)为分散剂,采用沉淀法制备氢氧化铝胶体,胶体经 800~1100℃高温煅烧得到纳米氧化铝粉体。对粉体进行了颗粒分布、XRD谱、HRTEM形貌及电子衍射等分析。结果表明分散剂(PEG)的聚合度对纳米氧化铝的粒度分布有着重要的影响。当用 PEG2000 作分散剂时制备出的粉体颗粒细而均匀,平均粒径为 25nm,无明显团聚与颗粒长大现象;经 1000℃/2h煅烧已完全转化为α Al2O3。文章对不同聚合度的分散剂的分散机理进行了讨论。     

碳素钢粉末法渗铬的研究

本文报导粉末法渗铬工艺试验和性能研究的部分结果,目的在于阐明渗铬工艺的特点及渗铬层的优良的综合性能,以利于工业生产中进一步采用。一、渗铬工艺1.试验方法(1)渗铬试样,采用工业纯铁,10号钢、20号钢、50号钢及 T12钢等。渗铬剂的组成为50%铬粉(含98.5%Cr,0.037%C)、48%氧化铝和2%氯化铵。铬粉和氧化铝的粒度为100～200目,氧化铝先在1000℃焙烧脱水。(2)操作过程及仪器设备:渗铬是在碳硅棒高温炉中进行的,用铂铑—铂热电偶测温,外接703型电位差计校温,温度波动范围在±10℃内。渗铬罐用低碳钢管焊成,管     

颗粒计数仪在氧化铝生产种分过程中的应用

通过对现代粒度分析方法的分类和比较,根据氧化铝生产种分过程中粒度分析的特点,认为电阻颗粒计数法是比较适合应用于氧化铝生产种分过程的粒度分析方法.对Elzone5382颗粒计数仪的原理及其在氧化铝生产中的应用进行了介绍,并对应用该粒度仪进行粒度测试过程中的影响因素进行了初步探讨.     

碳化钨颗粒增强钢基表层复合材料的热物理特性

采用真空实型铸渗(V-EPC)工艺制备碳化钨颗粒增强钢基表层复合材料,并测试其热膨胀系数和热导率,研究了工艺参数对热物理特性的影响。结果表明,随着测试位置与表层复合材料过渡区间距的增大热膨胀系数逐渐减小,而在相同位置同一温度下表层复合材料的热膨胀系数随着碳化钨颗粒的增大而增大。不同粒度碳化钨颗粒增强表层复合材料的热导率,均随着温度的升高呈增大趋势。当温度较低(40℃与105℃)时,不同碳化钨颗粒粒度的复合材料的热导率相差不大。但是当温度升高到一定值(大于170℃)时,复合材料的热导率随着碳化钨颗粒粒度的增大呈降低趋势。在预制层中加入Ni粉,可降低表层复合材料的热膨胀系数和热导率。     

α-Al2O3 P/Al复合材料无压渗透制备反应加工机制的探讨

本工作利用无压渗透法制备刚玉颗粒(α-Al₂O_3p)增强AlMg10合金复合材料,采用扫描电镜和EDS分析显微组织,并对无压渗透过程热力学研究,提出其反应加工机制:刚玉颗粒间隙内有限容积气氛(21%O₂,79%N₂),同熔融合金中铝(Al)镁(Mg)元素反应,形成固相,造成某种真空度,为无压渗透的驱动力。高温长时间条件下熔融基体AlMg10合金同刚玉颗粒和附加物的残留物发生化学反应。     

影响内氧化生成Al2O3/Cu表面复合层厚度及组织的因素

采用真空条件,用CuO作氧化剂,在一定的温度下使Cu-Al合金内氧化,获得Al₂O₃/Cu表面复合材料。金相分析发现,在较低温度下内氧化,表面复合层中Al₂O₃颗粒晶界处多于晶内;在较高温度下内氧化,复合层中Al₂O₃颗粒呈弥散状分布;表面复合层厚度随Al含量的增加而减薄,显微硬度随Al含量的增加而升高。      

Flux-assisted infiltration of liquid Al-6063 into TiC beds in air

This study details trials to produce aluminium metal matrix composites reinforced with TiC particles by means of a flux-assisted infiltration technique. Whilst no infiltration of TiC beds occurred, by using a K-Al-F flux infiltration was successful at temperatures as low as 680°C. Some reaction of TiC with the Al matrix, forming TiAl_2.3Si_0.1 and Al₄C₃, was observed in the microstructure along with flux trapped within the Al-6063 matrix. DSC showed exothermic oxidation of TiC to occur, until the flux melts at 545°C arresting and preventing further oxidation by spreading over, coating and cleaning the particle surfaces. As soon as the flux melts, it also starts dissolving the oxide layer on the Al alloy and prevents any re-oxidation by isolating the surface from the surrounding atmosphere. Sessile drop experiments suggest that when the alloy melts and the oxide layer has been dissolved by the flux, intimate contact occurs between the liquid and the particles. The low tensions for the solid/flux and liquid metal/flux interfaces facilitates spreading and wetting of liquid Al on the TiC particles, followed by infiltration of the bed and the displacement of the flux to the outer surfaces of the sample.     

Synthesis of Al2O3 matrix composites by reactive infiltration

Reactive infiltration of a NiO-base blended powder with molten aluminium was attempted at 1673 K in order to obtain Al2O3 matrix composites containing a dispersion of Al3Ni, AlNi and/or AlNi3. The NiO powder was barely infiltrated by the molten aluminium after a 3600 s holding time at 1673 K. A continuous layer of Al2O3 was observed to exist at the infiltration front, which prevented any further infiltration. TiB2 particles were added to the NiO powder in order to absorb the heat of reaction between NiO and aluminium. When the TiB2 particle content in the [NiO+TiB2] powder blend was greater than 20 vol%, spontaneous infiltration occurred completely. Thus, it was shown that the addition of the TiB2 particles assisted in the spontaneous infiltration. The specimens produced by the in situ reaction consisted of Al2O3, TiB2 and Al3Ni. Al3Ni was mainly located between the TiB2 and Al2O3. The effect of the TiB2 addition on the infiltration kinetics was to decrease the maximum attainable temperature caused by the exothermic reaction. This in turn prevented the formation of a continuous Al2O3 film at the infiltration front. This resulted in the production of pathways for the infiltration of the molten aluminium and made possible the complete infiltration. This revised version was published online in November 2006 with corrections to the Cover Date.     

Fabrication of Al/TiB2 composites through gas pressure infiltration

Titanium diboride is being evaluated as a replacement of SiC in metal/ceramic composites for thermal management. Albeit these composites are produced by gas pressure infiltration, no study of the process is available. This work presents an analysis of the threshold pressure for infiltration of Al into TiB₂ compacts and of the infiltration kinetics. Particles of diameters 14 and 20 μm, and spans of 1.62 and 1.77, were packed obtaining a volume fraction of 0.63. The compacts were infiltrated in air with pure Al at 700 °C. Despite of the fact that the average particle radii differ in a 50%, the threshold pressure for the coarser particles is only a 4% lower, while intrinsic compact permeabilities (derived from infiltration of a wetting organic liquid) are identical. The origin of this apparently odd behavior is the almost identical specific surface areas that those two particles have. Contact angles derived from infiltration experiments are shown to be compatible with sessile drop results.     

AlCl_3-EMIC室温离子液体制备Al-Al_2O_3复合涂层

首次在室温下用含10g/L Al2O3颗粒的AlCl3-EMIC室温离子液体电沉积制备出Al-Al2O3复合镀层。沉降试验表明,Al2O3颗粒在酸性AlCl3-EMIC室温离子液体中能形成稳定的悬浮液。通过SEM观察镀层表面和断面形貌,发现Al2O3颗粒均匀地分布在镀层中。显微努氏硬度检测结果表明,Al-Al2O3复合镀层的硬度高于纯Al镀层,其中Al镀层的硬度随着电流密度的增大而增高,而Al-Al2O3复合镀层的硬度却随着电流密度的增大而呈降低的趋势。本文还讨论了Al2O3颗粒在离子液体中的分散机制,以及和颗粒共沉积的过程。     

A fine cobalt-toughened Al2O3-TiC ceramic and its wear resistance

Mechanical ball milling is the most common method for mixing ceramic powders with a ductile phase such as metal particles. In this paper, a new powder processing way is presented. Al2O3 and TiC powders are coated with a layer of metal cobalt using the chemical deposition process. The thickness of the metal cobalt film can be controlled by adjusting the deposition conditions. The Co-coated Al2O3 (Al2O3–Co) and TiC (Tic–Co) powders are mixed at the rate of 7:3 and hot-press sintered into a fine Al2O3–TiC–Co (ATC) ceramic. The main properties, erosion behaviour, abrasion behaviour, wear mechanism and wear resistance of Al2O3-TiC-Co and Al2O3–30 wt% TiC (AT30) ceramics are determined by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, etc. It is shown that the ATC ceramic possesses improved mechanical properties. Because of the existence of metal cobalt in the grain boundaries, the bonding strength between grains is increased, and this prevents spalling of grains during wear. Experimentation indicates that ATC is more resistant to wear than Al2O3–TiC ceramic. The relationship between their mechanical properties and wear resistance is also discussed in this paper.     

粉末增塑挤压制备Al2O3/430L复合型蜂窝材料的组织与性能

为制备性能优良的Al_2O_3/430L复合型蜂窝载体材料,本文以430L不锈钢合金粉末、Al_2O_3粉末、粘结剂为原料,采用粉末增塑挤压技术挤压成形,并在1 100℃真空中烧结2 h获得Al_2O_3/430L复合型蜂窝材料.借助SEM、XRD及万能试验机,研究了添加Al_2O_3对Al_2O_3/430L复合型蜂窝材料的组织与性能的影响.研究表明:金属粉末颗粒在烧结过程中结合形成的基体组织为α-Fe(Cr),在基体晶粒间孔隙处和表面弥散分布着Al_2O_3颗粒.添加少量的Al_2O_3可提高烧结密度,制件表面光滑.随着Al_2O_3添加量增加,蜂窝材料表面负载催化涂层的能力增强;抗压强度随Al_2O_3添加量的增加先升高后降低,在Al_2O_3含量为2.5wt.%时,最大抗压强度达27 MPa.添加2.5wt.%Al_2O_3所制备的Al_2O_3/430L复合型蜂窝材料力学性能最佳、表面负载催化涂层的能力优良.