燃烧合成/准热等静压TiC-Fe基复合材料耐磨损性能的研究

利用燃烧合成结合准热等静压技术(SHS/PHIP)原位合成了TiC颗粒增强铁基复合材料。利用SEM,XRD研究了复合材料的相组成和显微组织。结果表明:该复合材料由TiC增强颗粒和金属Fe粘结相组成,组织较为致密,球形的TiC颗粒相被包围在近于立体网状结构的Fe粘结相中。TiC颗粒相和金属Fe粘结相的界面结合良好。在橡胶轮式磨损试验条件下,TiC颗粒增强铁基复合材料表现出良好的耐磨性能。其磨损机制主要是磨粒磨损和少量硬质相脱落。     

The composition,structure, and properties of calcium-hydride powder of titanium carbide

The technology of obtaining titanium carbide powders by reduction-carbidization of titanium dioxide with calcium hydride and carbide at temperatures up to 1200°C is developed. The dispersity of the TiC particles is determined by thermal desorption and scanning electron microscopy: the average size of crystals is no larger than 1 μm. It is revealed by the methods of coulometry and energy dispersive spectrometry that calcium-hydride titanium carbide is characterized by a high content of bound carbon and a low content (0.01–0.03 wt %) of free carbon. It is established by X-ray structural analysis and transmission electron microscopy that TiC particles are uniform (their composition is close to stoichiometric TiC_1.0) and are single crystals. The investigation of the structure and properties of hard alloys of the compositions 60% TiC + 29.6% Ni + 10.4% Mo and 72% TiC + 18.3% Ni and 9.7% Mo, which were obtained on the basis of calcium-hydride titanium carbide powders, showed that they completely satisfy the requirements to tungsten-free hard alloys.     

The Influence of a TiN Film on the Electronic Contribution to the Thermal Conductivity of a TiC Film in a TiN-TiC Layer System

TiC and TiN films were deposited by reactive magnetron sputtering on Si substrates. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization of the microstructure and interface structure have been carried out and the stoichiometric composition of TiC is determined. Thermal conductivity and interface thermal conductance between different layers in the films are evaluated by the transient thermo reflectance (TTR) and three-omega (3-ω) methods. The results showed that the thermal conductivity of the TiC films increased with temperature. The thermal conductivity of TiC in the absence of TiN is dominated by phonon contribution. The electronic contribution to the thermal conductivity of TiC in the presence of TiN is found to be more significant. The interface thermal conductance of the TiC/TiN interface is much larger than that of interfaces at Au/TiC, TiC/Si, or TiN/Si. The interface thermal conductance between TiC and TiN is reduced by the layer formed as a result of interdiffusion.

     

A study on the kinetic process of reaction synthesis of TiC: Part I. Experimental research and theoretical model

The micromechanism and the macrokinetic process of synthesis TiC in preparing Al/TiC by direct reaction synthesis (DRS) have been investigated in detail by observing the microstructure of the water-quenched preform by scanning electron microscopy (SEM) and energy* dispersive X-ray (EDX) analysis. The results have shown that the micromechanism of reaction is a solution-precipitation mechanism, in which carbon powders in the preform were surrounded by a Ti-rich Al-Ti-C melt layer and reacted with titanium in the layer to synthesize TiC particles, and TiC precipitated from the layer and scattered over the alloy melt. The macrokinetic model of reaction synthesis of TiC can be divided into four stages: heating and melting stage, initial reaction stage, complete reaction stage, and cooling stage. In the end, a macrokinetic model has been set up based on the experimental results.     

Microstructural characterization of self-propagating high-temperature synthesis/ dynamically compacted and hot-pressed titanium carbides

Titanium-Carbide produced by combustion synthesis followed by rapid densification in a high-speed forging machine was characterized by optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM). The density of the combustion synthesized/dynamically compacted TiC reached values greater than 96 pct of theoretical density, based on TiC_0.9, while commercially produced hot-pressed TiC typically exceeded 99 pct of theoretical density. The higher density of the hot-pressed TiC was found to be attributable to a large volume fraction of heavy element containing inclusions. The microstructure of both TiCs consists of equiaxed TiC grains with some porosity located both at grain boundaries and within the grain interiors. In both cases, self-propagating high-temperature synthesis (SHS)/dynamically compacted (DC) and hot-pressed, the TiC is ordered cubic (NaCl-structure,B ₁; Space Group Fm3m) with a lattice parameter of ≈0.4310 nm, indicative of a slightly carbon deficient structure; stoichiometric TiC has a lattice parameter of 0.4320 nm. For the most part, the grains were free of dislocations, although some dislocation dipoles were found associated with the voids within the grain interiors. In one SHS/DC specimen, a new, complex Ti-Al-O(C) phase was observed. The structure could not be matched with any previously published phases but is believed to be hexagonal, with a c-axis/a-axis ratio of ≈6.6, similar to the AlCTi₂ phase which has a point group 6 mmm. In all other SHS/DC TiC samples, the grains and grain boundaries were devoid of any second-phase particles. The hot-pressed TiC exhibited a greater degree of porosity than the SHS/densified specimens and a large concentration of second-phase particles at grain boundaries and within grains. The structure and composition of these second-phase particles were determined by con-vergent beam electron diffraction (CBED) and X-ray microanalysis. This paper is based on a presentation made in the symposium “Reaction Synthesis of Materials” presented during the TMS Annual Meeting, New Orleans, LA, February 17–21, 1991, under the auspices of the TMS Powder Metallurgy Committee.     

表层富立方相超细晶梯度硬质合金微观结构

通过富氮气氛烧结WC?10TiC?0.5VC?0.5Cr2C3?12Co和WC?12Co硬质合金,研究梯度结构和均匀结构硬质合金的微观结构及力学性能.利用扫描电子显微镜观察合金断面的微观形貌,使用X射线衍射仪和能谱仪分析合金物相组成,并对合金表面和芯部的硬度与断裂韧性进行测试.结果表明:与均匀结构的WC?12Co硬质合...     

The effect of particle reinforcement on the creep behavior of single-phase aluminum

The effect of TiC particle reinforcement on the creep behavior of Al (99.8) and Al-1.5Mg is investigated in the temperature range of 150 °C to 250 °C. The dislocation structure developed during creep is characterized in these materials. The addition of TiC increases creep resistance in both alloys. In pure aluminum, the presence of 15 vol pct TiC leads to a factor of 400 to 40,000 increase in creep resistance. The creep strengthening observed in Al/TiC/15_p is substantially greater than the direct strengthening predicted by continuum models. Traditional methods for explaining creep strengthening in particle-reinforced materials(e.g., threshold stress, constant structure, and dislocation density) are unable to account for the increase in creep resistance. The creep hardening rate(h) is found to be 100 times higher in Al/TiC/15_p, than in unreinforced Al. When incorporated into a recovery creep model, this increase inh can explain the reduction in creep rate in Al/TiC/15_p. Particle reinforcement affects creep hardening, and thus creep rate, by altering the equilibrium dislocation substructure that forms during steady-state creep. The nonequilibrium structure generates internal stresses which lower the rate of dislocation glide. The strengthening observed by adding TiC to Al-1.5Mg is much smaller than that found in the pure aluminum materials and is consistent with the amount of strengthening predicted by continuum models. These results show that while both direct (continuum) and indirect strengthening occur in particle-reinforced aluminum alloys, the ratio of indirect to direct strengthening is strongly influenced by the operative matrix strengthening mechanisms. This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the 1994 TMS/ASM Spring meeting, held February 28–March 3, 1994, in San Francisco, California, under the auspices of the Joint TMS-SMD/ASM-MSD Composite Materials Committee.     

NiAl/TiC金属陶瓷的燃烧合成

对Ni-Al-Ti-C燃烧合成体系进行热力学计算,并运用热力学原理分析该燃烧合成体系的平衡产物相.计算结果表明,Ni-Al-Ti-C燃烧合成体系的绝热燃烧温度为1 911 K,燃烧合成平衡相为NiAl和TiC.燃烧合成产物经XRD分析与热力学分析结果相吻合,说明该燃烧合成反应进行的较为彻底,证实热力学分析结果可信.原位合成NiAl/TiC复合材料中,NiAl基体出现了明显熔化特征,TiC颗粒在基体中分布不均匀.     

Microstructures and Properties of Nanocrystalline NiFe Alloy With and Without Particulate TiC Reinforcement by Mechanical Alloying

In the current study, Ni₅₀Fe₅₀ alloy powders were prepared using a high-energy planetary ball mill. The effects of TiC addition (0, 5, 10, 20, and 30 wt pct) and milling time on the sequence of alloy formation, the microstructure, and microhardness of the product were studied. The structure of solid solution phase, the lattice parameter, lattice strain, and grain size were identified by X-ray diffraction analysis. The correlation between the apparent densities and the milling time is explained by the morphologic evolution of the powder particles occurring during the high-energy milling process. The powder morphology was examined using scanning electron microscopy. It was found that FCC γ (Fe–Ni) solid solution was formed after 10 hours of milling, and this time was reduced to 7 hours when TiC was added. Therefore, brittle particles (TiC) accelerate the milling process by increasing crystal defects leading to a shorter diffusion path. Observations of polished cross section showed uniform distribution of the reinforcement particles. The apparent density increases with the increasing TiC content. It was also found that the higher TiC amount leads to larger lattice parameter, higher internal strain, and lower grain size of the alloy.     

稀释剂对原位合成TiC_p/钢基硬质涂层组织和性能的影响

为提高钢基硬质涂层的表面质量和显微硬度,采用真空消失模铸造法引发自蔓延高温合成(SHS)反应,在铸件表面制备原位合成TiC颗粒增强钢基硬质涂层。通过X-ray、OM、SEM、EDS及显微硬度测试等方法,研究了稀释剂TiC的加入量对钢基硬质涂层微观组织和力学性能的影响。结果表明:硬质涂层与基材之间呈冶金结合,涂层组织由TiC颗粒和α-Fe基体相构成;随外加TiC含量的增加,可降低燃烧反应温度,提高涂层组织致密度,原位合成的TiC颗粒细小呈圆球或近圆球形状,均匀分布在基体组织中,显著提高了TiC颗粒总体积分数和硬质涂层显微硬度,其中TiC加入量为10%(质量分数)时,涂层的综合性能最佳。     

Effect of flux addition on the microstructure and hardness of TiC-reinforced ferrous surface composite layers fabricated by high-energy electron beam irradiation

Surface composites reinforced with TiC particulates were fabricated by high-energy electron-beam irradiation. In order to investigate the effects of flux addition on the TiC dispersion in surface composite layers, four kinds of powder mixtures were made by mixing TiC with 5, 10, 20, and 40 wt pct of the flux components (MgO-CaO). To fabricate TiC-reinforced surface composites, the TiC-flux mixtures were deposited evenly on a plain carbon steel substrate, which was subjected to electron-beam irradiation. Microstructural analysis was conducted using X-ray diffraction and Mossbauer spectroscopy as well as optical and scanning electron microscopy. The microstructure of the surface composites was composed of a melted region, an interfacial region, a coarse-grained heat-affected zone (HAZ), a fine-grained HAZ, and an unaltered original substrate region. TiC agglomerates and residual pores were found in the melted region of materials processed without flux, but the number of agglomerates and pores was significantly decreased in materials processed with a considerable amount of flux. As a result of irradiation, TiC particles were homogeneously distributed throughout the melted region of 2.5 mm in thickness, whose hardness was greatly increased. The optimum flux amount, which resulted in surface composites containing homogeneously dispersed TiC particles, was found to be in the range of 10 to 20 pct to obtain excellent surface composites.     

In Situ Synthesis of Heat Resistant Gradient Composite on Steel Surface

 A heat resistant gradient composite was synthesized in situ on steel with the self propagating high temperature synthesis (SHS) reaction of 3Ni Al Ti C system during casting. The phases, microstructure, and composition of the composite were analyzed by using an X ray diffractometer (XRD), and a scanning electron microscope (SEM) coupled with an energy dispersive X ray spectroscope (EDS). The formation mechanism of the composite is also discussed. TiC/Ni3Al/steel gradient composite is achieved by forming the gradient distributions of Fe, Ni, and Al, accompanied with the gradient variation of the microstructure from TiC/Ni3Al, to TiC/Ni3Al/steel, and to steel. The composite is in situ synthesized through whole reaction of 3Ni Al Ti C system in liquid steel and densification procedure, and the liquid steel infiltrates into pores in the SHS product and forces liquid Ni3Al to form self compaction further.     

TiC/耐热钢钢结硬质合金原位反应合成研究

以钛铁粉、铬铁粉、铁粉、胶体石墨等为原料，原位反应合成了TiC/耐热钢钢结硬质合金，并用扫描电镜(SEM)、X射线衍射等测试方法对所制备的试样进行了组织结构分析。研究结果表明：反应合成的钢结硬质合金主要相组成为TiC Fe—Cr固熔体，所合成的硬质相TiC颗粒细小，随烧结温度升高TiC颗粒略有长大。当加入一定的钼与硼后，钢结硬质合金硬度和致密度提高，TiC颗粒尺寸减小，分布更均匀。     

原料粉末粒度对TiCN基金属陶瓷微观组织的影响

采用纳米TiNmm添加到微米TiCpm复合陶瓷粉未和纳米TiCNcm固溶体陶瓷粉未中，用无压烧结方法分别制备出TCermet A和Cermet B两种新型金属陶瓷材料。SEM研究表明，在两种材料的显微组织中，陶瓷相均呈现芯-壳结构特征，即Cermet A陶瓷相由黑色的芯和灰色的壳构成，而Cermet B陶瓷相兼有黑白两种芯和灰色的壳结构。EDS能谱分析指出，黑色的芯由纯的TiC组成，白色的芯和灰色的壳均由（Ti，W，Mo）C固溶体构成。力学性能测试得出Cermet A具有比Cermet B更高的强韧性。TEM观察表明，适量添加的纳米TiN颗粒可分布于陶瓷相品界处，起到增韧增强陶瓷基体的作用。     

Al-TiC composites In Situ-processed by ingot metallurgy and rapid solidification technology: Part I. Microstructural evolution

The present work was undertaken to highlight a novel in situ process in which traditional ingot metallurgy plus rapid solidification techniques were used to produce Al-TiC composites with refined microstructures and enhanced dispersion hardening of the reinforcing phases. Microstructures of the experimental materials were comprehensively characterized by optical microscopy, electron microscopy, and X-ray diffraction. The results show that the in situ-synthesized TiC particles possess a face-centered cubic crystal structure with an atomic composition of TiC_0.8 and a lattice parameter of 0.431 nm. The typical ingot metallurgy microstructures exhibit aggregates of TiC particles segregated generally at the α-Al subgrain or grain boundaries and consisting of fine particles of 0.2 to 1.0 μm in size. The rapidly solidified microstructures formed under certain thermal history conditions contained a uniform, fine-scale dispersion of TiC phase particles with a size range of 40 to 80 nm in an α-Al supersaturated matrix of 0.30 to 0.85 μm in grain size. These dispersed TiC particles generally have a semicoherent relationship with the α-Al matrix. Based on the experimental results, a comprehensive kinetic mechanism of in situ TiC synthesis, which includes a solid-liquid interface reaction between the carbon particles and the Al melt and multiple nucleation and growth of TiC from the Al melt, was proposed. Then, the evolution of the aggregate TiC particles in a superheated melt before rapid solidification, i.e., dissolution, nucleation, and growth of the regenerated TiC dispersed particles, was analyzed. Furthermore, the behavior of rapid solidification kinetics, the nucleation of α-Al on TiC-dispersed particles, and the interaction between TiC particles and the solidification front were documented experimentally and theoretically. These studies provided the theoretical criteria and an experimental basis for the optimum design of this kind of composite.     

真空原位碳热还原法制备纳米碳化钛粉体

分别以钛酸四丁酯和蔗糖为钛源、碳源,采用溶胶—凝胶法制备前驱体并在真空条件下原位碳热还原制备纳米碳化钛。采用X射线衍射仪和扫描电镜对产物物相、形貌进行分析,并根据谢乐公式计算所得TiC晶粒尺寸。结果表明:在1 300℃的真空碳热还原条件下能够得到纳米碳化钛,随着碳含量的增加碳化钛的纯度提高,晶粒尺寸减小;随碳热还原温度从1 300℃升高到1 500℃,碳化钛的形貌由长径为100 nm左右的长条状变为粒径为20~30 nm的球形颗粒,但TiO相含量相对增加。     

原位生成TiC颗粒对铁基合金组织及性能的影响

通过向Fe—Al-B合金中添加C和Ti元素的方法，在合金中原位生成了TiC颗粒，利用X射线衍射(XRD)、扫描电子显微镜(SEM)和能谱仪分析了添加TiC前后材料中相的变化、显微组织的变化及材料中各相的化学成分。结果表明，在合金中原位生成TiC颗粒后，合金组织明显得到细化，其耐熔锌腐蚀性能及强度也有大幅度提高。     

颗粒增强低成本钛基复合材料

采用TiC颗粒和熔铸法制备TiCp／TIMETAL62S复合材料，研究了钛基复合材料的显微组织和室温力学性能。结果表明：TiCp／TIMETAL62S复合材料的组织由针状αa相、少量β相和TiC颗粒组成；TiC颗粒改变了基体合金原有组织，促进了复合材料组织的细化；钛基复合材料具有良好的室温强度和塑性，复合效果良好。     

TiB_2和TiC复合熔敷棒的制备及电火花涂层特性

利用粉末冶金法制备TiB2和TiC复合材料熔敷棒,并通过电火花沉积在点焊镀锌钢板用电极的表面制备TiB2和TiC复合涂层。利用SEM和XRD分析涂层的微观结构和物相,运用点焊实验测试涂层电极的使用寿命。结果表明:复合材料熔敷棒中TiB2和TiC颗粒细小均匀,电火花涂层致密无分层,涂层物相为Cu、TiB2和TiC;Cu从基体扩散到涂层表面,涂层表面Cu含量(原子分数)达到28%,过渡层出现Cu和Ti的梯度分布,涂层与基体间为牢固的冶金结合;复合涂层存在少量裂纹,其显微硬度达到850HV,高于TiB2涂层和TiC涂层硬度;点焊时电极头部的平均磨损率大大降低,电极的点焊寿命比无涂层电极提高4倍。     

Al+TiC_(0.47)+B系掺杂制备多晶立方氮化硼烧结过程分析

应用X射线衍射分析技术，对以Al＋TiCO0.47＋B系掺杂制备多晶立方氮化硼时各物相在高温高压烧结过程中发生的化学反应、物相变化和新生物相在烧结过程中的作用，以及CBN颗粒在烧结过程中的变化等进行了研究与探讨。结果表明，Al＋TiC0.47＋B和CBN经高压高温烧结后，在CBN颗粒间形成由AlN、AlB2、TiN、TiB2和TiC等难熔化合物组成的粘结相。其中的AlN相有效抑制了CBN的六方化。