SiCw增韧Al2O3／TiB2陶瓷复合材料的研究

根据对晶须与基体材料的热胀失配的分析，计算得出了Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ三元复合材料中ＳｉＣｗ的临界体积分数。采用ＴｉＢ２颗粒增韧和ＳｉＣｗ增韧两种途径来改善Ａｌ２Ｏ３的脆性，得到此复合材料的抗弯强度为７４０ＭＰａ，断裂韧性为７．７ＭＰａ·ｍ＾１／２。分析表明：当ＳｉＣｗ含量大于临界体积分数时，强度大幅降低的主要原因是由于致密度的降低和热残余拉应力的增大。     

新型复相陶瓷刀具材料Jx-2-I协同增韧补强机理的研究

本文研制成功的新型陶瓷刀具材料—ＳｉＣ晶须（ＳｉＣｗ）增韧和ＳｉＣ颗粒弥散增韧Ａｌ２Ｏ３陶瓷刀具Ｊｘ－２－Ｉ,该刀具材料具有高的抗弯强度和断裂韧性等优点;对比Ａ（Ａｌ２Ｏ３）、ＡＰ（Ａｌ２Ｏ３／ＳｉＣｐ）、ＡＷ（Ａｌ２Ｏ３／ＳｉＣｗ）、Ｊｘ－１（Ａｌ２Ｏ３／ＳｉＣｗ）和Ｊｘ－２－１（Ａｌ２Ｏ３／ＳｉＣｐ／ＳｉＣｗ）等陶瓷材料的力学性能可以看出,在Ｊｘ－２－Ｉ材料中具有明显的增韧补强叠加效应;本文在热失配分析和微观结构观察的基础上详细研究了Ｊｘ－２－Ｉ刀具材料的增韧补强机理,系统研究了Ｊｘ－２－Ｉ中各种增韧补强机理之间的协同效应。     

新型复相陶瓷刀具材料JX—2—Ⅰ协同增韧补强机理的研究

本文研制成功了一种新型陶瓷刀具材料－ＳｉＣ晶须增韧和ＳｉＣ颗粒弥散增韧Ａｌ２Ｏ３陶瓷刀具ＪＸ－２－Ⅰ，     

添加Cr2O3对Al2O3-TiC陶瓷烧结及纳米结构形成的影响

研究了Ａｌ２Ｏ３－ＴｉＣ陶瓷材料中Ｃｉ２Ｏ３添加剂对该陶瓷材料烧结致密度和力学性能的影响。Ｃｒ２Ｏ３与ＴｉＣ在高度有化学反应发生,反应产物在高温产生的液相有助于陶瓷材料的烧结。Ｃｒ２Ｏ３与Ａｌ２Ｏ３形成的连续固溶体,使Ａ２ｌＯ３晶格的活化从而也促进了Ａｌ２Ｏ３－ＴｉＣ陶瓷材料的烧结。ＴＥＭ研究表明：Ｃｒ离子高温时在ＴｉＣ中具有较高的溶解度,降温后淀析出许多纳米级含Ｃｒ的颗粒,使Ａｌ２Ｏ３－ＴｉＣ陶     

4Al＋3TiO_2＋3C化学反应的差热分析研究

通过差热分析曲线和物相分析等研究了４Ａｌ＋３ＴＯ_２＋３Ｃ普通化学反应和自燃烧化学反应的特点。研究结果表明，在一定的升温速率下Ａｌ、ＴｉＯ_２、Ｃ相互之间均能发生相互化学反应；随着升温速率的提高，Ａｌ、ＴｉＯ_２、Ｃ任意两组元之间的相互化学反应受到抑制。运用４Ａｌ＋３ＴｉＯ_２＋３Ｃ自蔓延高温合成反应制备了Ａｌ_２Ｏ_３－ＴｉＣ陶瓷复合材料。     

等离子喷涂Al2O3+TiO2复合陶瓷涂层的组织结构

利用ＳＥＭ,ＴＥＭ,ＥＤＡＸ及Ｘ射线等手段研究了Ａｌ２Ｏ３＋ＴｉＯ２／ＮｉＣｒＡｌＹ复合陶瓷等离子喷涂层的组织结构,涂层呈片层状,Ａｌ２Ｏ３＋ＴｉＯ２陶瓷涂层由γ－Ａｌ２Ｏ３,ＴｉＯ２及少量的α－Ａｌ２Ｏ３组成,由于喷涂层温度比较高,部分熔化的Ａｌ２Ｏ３和大部分熔化的ＴｉＯ２发生了一定程度的互熔,形成了Ａｌ２Ｏ３＋ＴｉＯ２共晶组织。片层内由Ｎｉ基固溶体及弥散分布其上的γ相（Ｎｉ３Ａｌ）组成,片间为     

陶瓷复合体中晶须的作用研究

研究了ＳｉＣ，ＴｉＮ晶须增韧Ａｌ２Ｏ３＋ＴｉＣ，Ｓｉ３Ｎ４＋ＴｉＣ基陶瓷复合体的力学行为，验证和讨论了Ｐ．Ｆ．Ｂｅｃｈｅｒ提出的晶须增韧方程，并通过实验对晶须增韧陶瓷复合体的机械性能和切削性能进行了研究。     

Al_2O_3弥散强化铜的制备与性能影响因素

本文总结了弥散强化ＣＵ－Ａｌ_２Ｏ_３复合材料的制备方法,阐明内氧化法为最好的方法。概括了表征Ｃｕ－Ａｌ_２Ｏ_３复合材料物理力学性能的主要参数,并分析了影响Ｃｕ－Ａｌ_２Ｏ_３复合材料性能的主要因素。     

α—Al2O3／Cu复合镀层材料性能的研究

研究了用复合电沉积法制备的α—Ａｌ２Ｏ３／Ｃｕ复合材料的电性能和机械性能。结果表明，α—Ａｌ２Ｏ３颗粒的加入使材料硬度显著提高．当μ—Ａｌ２Ｏ３含量为２０ｖｏｌ％时，电导率可达７０％ＩＡＣＳ以上。     

TiC—Al2O3复合材料的自蔓延高温合成和致密化

以ＴｉＯ２，Ａｌ和Ｃ三种粉末为原料，采用自蔓延高温合成和加压的方法制备了ＴｉＣ－Ａｌ２Ｏ３复合材料。在１ＧＰａ压力下，可使样品达到理论密度的９５％。对未反应样品燃烧前在真空状态下预热脱气，则密度可达９８％。为避免样品开裂，必须控制冷却速度。对合成产品进行Ｘ射线分析，表明从ＴｉＯ２，Ａｌ，和Ｃ三种粉末原料制备密实的ＴｉＣ－Ａｌ２Ｏ３复合材料是可能的。     

Fine TiC dispersed Al2O3 composites fabricated via in situ reaction synthesis and conventional process

To further improve the mechanical performance and reduce the percolation threshold by controlling microstructures, Al₂O₃-TiC composites containing 0-20 vol% TiC were fabricated via in situ reaction synthesis. Graphite (ATC) and carbon nanotubes (ATCT) were used as carbon sources. The composites were also fabricated via a conventional process using a TiC starting powder (AT). X-ray diffraction analysis and scanning electron microscopy observation results indicated successful fabrication of the composites with various microstructures. TiC particles in ATCT were completely dispersed at grain boundaries, whereas in ATC and AT, these particles were either intragranular or intergranular dispersed. The composites could be listed as follows, ATCT > ATC > AT, that is, in descending order of the reinforcing flexural strength and fracture toughness. The nanoindentation measurement indicated the optimum hardening effect of ATCT. The ATCT composite also exhibited the highest fracture toughness, which was 49% higher than that of the monolithic Al₂O₃. Crack deflection was considered as the main toughening mechanism while crack bridging behavior also occurred in ATCT. For a given TiC content, ATCT exhibited the lowest electrical resistivity, owing mainly to the complete grain-boundary dispersion of the relatively large TiC particles. The similarity of the Al₂O₃ grain size and TiC particle size of ATCT contributed to the lowest percolation threshold achieved (11.2%), which (to date) is the lowest value that has been reported for the Al₂O₃-TiC system.     

Improvements in Mechanical Properties in SiC by the Addition of TiC Particles

Silicon carbide ceramics containing up to 24.6 vol% dispersed TiC particles yielded fully dense composites by hot-pressing at 2000°C with 1 wt% Al and 1 wt% C added. The micro-structure consists of fine TiC particles in a fine-grained SiC matrix. Addition of TiC particles increases the critical fracture toughness of SiC (to ∼6 MPa·m^1/2 at 24.6 vol% TiC) and yields high flexure strength (≥680 MPa), with both properties increasing with increasing volume fraction of TiC. The strengths at high temperatures are also improved by the TiC additions. Observations of the fracture path indicate that the improved toughness and strength are a result of crack deflection by the TiC particles.     

Fabrication and mechanical properties of Al2O3-SiCw-TiCnp ceramic tool material

Whiskers and nanoparticles are usually used as reinforcing additives of ceramic composite materials due to the synergistically toughening and strengthening mechanisms. In this paper, the effects of TiC nanoparticle content, particle size and preparation process on the mechanical properties of hot pressed Al₂O₃-SiC_w ceramic tool materials were investigated. The results showed that the Vickers hardness and fracture toughness of the materials increased with the increasing of TiC content. The optimized flexural strength was obtained with TiC content of 4 vol% and particle size of 40 nm. The particle size has been found to have a great influence on flexural strength and small influence on hardness and fracture toughness. It was concluded that the flexural strength increased remarkably with the decreasing of the TiC particle size, which was resulted from the improved density and refined grain size of the composite material due to the dispersion of the smaller TiC particle size. SEM micrographs of fracture surface showed the whiskers to be mainly distributed along the direction perpendicular to the hot-pressing direction. The fracture toughness was improved by whisker crack bridging, crack deflection and whisker pullout; the TiC nanoparticles in Al₂O₃ grains caused transgranular fracture and crack deflection, which improved the flexural strength and fracture toughness with whiskers synergistically. Uniaxial hot-pressing of SiC whisker reinforced Al₂O₃ ceramic composites resulted in the anisotropy of whiskers’ distribution, which led to crack propagation differences between lateral crack and radical crack.     

纳米SiC增韧Al_2O_3陶瓷复合材料的制备、表征及力学性能研究

以SiC和Si微米粉为添加剂,采用无压烧结工艺制备了纳米SiC增韧的Al2O3陶瓷复合材料,探讨了SiC含量、烧结气氛和烧结温度对复合材料的烧成收缩率、微观形貌、抗弯强度、维氏硬度及断裂韧性的影响。结果显示：SiC的添加使复合材料的烧成收缩率下降,惰性气氛下复合材料的收缩率要大于氧化气氛和还原气氛时的收缩率。在氧化性气氛下烧结时,当SiC添加量为4%时,复合陶瓷的体积密度为3.80 g·cm^-3,抗弯强度、断裂韧性及维氏硬度均达到最大值,分别为480 MPa、5.12 MPa·m1/2、16.2 GPa。添加SiC后所得复合材料的基体颗粒为椭圆状,粒径为2μm左右,颗粒与颗粒之间结合紧密,颗粒形状的改变可能是因为烧结机理发生变化所致。纳米SiC颗粒位于晶界处,形成了由Al2O3-SiC-Al2O3搭桥联结的晶界,提高了晶界强度,导致裂纹只能在晶内传播。     

Fine Ti‐dispersed Al2O3 composites and their mechanical and electrical properties

Al₂O₃/Ti composites containing 0‐30 vol% dispersed fine Ti particles were fabricated using a hot‐press sintering method at 1500°C from mixtures of Al₂O₃ and TiH₂ powders. During sintering, TiH₂ decomposed to form metallic Ti. The effects of the Ti content on the mechanical and electrical properties of the composites were then investigated. No Ti‐Al intermetallic compounds were detected by X‐ray diffraction, and energy‐dispersive X‐ray spectroscopy indicated the presence of Al‐Ti‐O solid solution and Ti‐O phases. The composites showed enhanced densification; the measured densities were higher than the calculated theoretical values. Microstructural observation revealed homogeneously distributed fine Ti particles dispersed in the Al₂O₃ matrix. The Ti particle size ranged from submicrometer to a few micrometers depending on the Ti content. The fracture mode of the composites was primarily transgranular, in contrast to the intergranular fracture mode of monolithic Al₂O₃. Although the flexural strength was decreased with increase in Ti content, the composite containing 20 vol% Ti displayed the maximum fracture toughness of 4.3 MPa·cm^1/2, which was 37% greater than that of monolithic Al₂O₃. The composites containing more than 15 vol% Ti exhibited drastic decreases in resistivity (~10^?1 Ωcm), which were attributed to the formation of interconnected Ti networks at these Ti contents. The percolation threshold volume for electrical conduction in the present system was calculated to be 13.8 vol%. The results indicate that dispersing fine Ti particles into Al₂O₃ increased the fracture toughness and improved the conductivity of Al₂O₃.     

(Ti,V)_3AlC_2/Al_2O_3复合材料的制备及力学性能

为了提高Ti_3Al C_2陶瓷的力学性能,本研究以Ti C粉、Ti粉、Al粉和V2O5粉为起始反应原料,采用原位热压技术在1350°C下反应烧结合成出了(Ti,V)_3AlC_2/Al_2O_3复合材料。利用X-射线衍射和扫描电子显微技术对合成产物的物相和微观结构进行了表征,并分析了复合材料的合成机制。最后,对(Ti,V)_3AlC_2/Al_2O_3复合材料的力学性能进行了研究。测试结果表明:(Ti_(0.92),V_(0.08))_3Al C_2/10wt%Al_2O_3复合材料具有最佳的力学性能,其硬度、断裂韧性及抗弯强度分别为5.56 GPa、12.93 MPa·m~(1/2)和435 MPa,相比于单相Ti_3Al C_2材料分别提升了60%、108%和31%。     

High strength TiC matrix Fe28Al toughened composites prepared by spontaneous melt infiltration

Fe28Al bound TiC matrix composites with TiC content of 75–90% in volume (vol.%) were successfully fabricated by spontaneous melt infiltration. Amounts of Fe28Al in excess and below the pore volume of the TiC preform were used for optimization of fabrication techniques. Young's modulus, hardness, flexural strength and fracture toughness of the composites were measured. Four-point bending strength of Fe28Al/90–75 vol.% TiC ranges to 990–1260 MPa. The high strength is attributed to the good infiltration ability of molten Fe28Al in the porous TiC preform and to processing refinements. TiC preform pre-sintering and indirect infiltration all lead to fully dense and defect-free composites. The relationship between Vickers hardness and indentation fracture toughness and the dependence of mechanical properties on microstructure of the composites were also studied. Results of SEM and XRD analysis show TiC and Fe28Al as the only crystalline phases of the composite. Fe28Al ligaments have ductile behaviour and greatly toughen the composites. Crack front deviation during fracture also increased the fracture resistance of the composites.     

Effect of rigid particle size on the toughness of filled polypropylene

The role of rigid particle size in the deformation and fracture behavior of filled semicrystalline polymer was investigated with systems based on polypropylene (PP) and model rigid fillers [glass beads, Al(OH)₃]. The regularities of the influence of particle content and size on the microdeformation mechanisms and fracture toughness of the composites at low and high loading rates were found. The existence of the optimal particle size for fixed filler content promoting both maximum ultimate elongation of the composite at the tensile and maximum toughness at impact test was shown. The decrease of the toughening effect with both decreasing and increasing particle size regarding the optimal one was explained by dual role of particle size, correspondingly as either “adhesive” or “geometric” factors of fracture. The adhesive factor is due by the increase of debonding stress with the particle size decrease and the voiding difficulty resulting in the restriction of plastic flow. The geometric factor consists in the dramatic decrease of the composite strength at break if the void size exceeds the critical size of defect (for a given matrix) at which the crack initiation occurs. The analysis of the filled polymer toughness dependencies upon the particle size revealed that a capacity of rigid particles for the energy dissipation at the high loading rate depends on two factors: (i) ability of the dispersed particles to detach from matrix and to initiate the matrix local shear yielding at the vicinity of the voids and (ii) the size of the voids forming. Based on the findings it was concluded that the optimal minimal rigid particle size for the polymer toughening should answer the two main requirements: (i) to be smaller than the size of defect dangerous for polymer fracture and (ii) to have low debonding stress (essentially lower compared to the polymer matrix yield stress). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1917–1926, 2004     

Microstructure and mechanical properties of functionally graded TiCp/Ti6Al4V composite fabricated by laser melting deposition

Crack-free functionally graded TiC particle (TiC_p) reinforced Ti6Al4V (TiC_p/Ti6Al4V) composite was manufactured by laser melting deposition (LMD) technology with TiC volume fraction changing gradually from 0% to 50%. This research focuses on the relationship between the microstructure and mechanical properties (microhardness and tensile properties) of TiC_p/Ti6Al4V composites under different TiC volume fractions. Besides the unmelted TiC particles, the granular and chain shaped eutectic TiC phases are observed in the composite with 5 vol% TiC due to the melting and dissolution of TiC particles into matrix. The granular and dendritic primary TiC phases are obtained in the composite with 10 vol% TiC, while the chain shaped eutectic TiC phases can scarcely be seen. The main reinforcement phases are primary TiC phases when the TiC volume fraction exceeds 15%. (i) The quantity of unmelted TiC particles, (ii) the quantity and size of primary TiC phases and (iii) the porosity of composite increase gradually when the TiC volume fraction increases. The interfaces exhibit good bonding between consecutive layers. The microhardness of the functionally graded TiC_p/Ti6Al4V composite increases gradually with TiC volume fraction increasing. It is attributed to the C element in solid solution and the appearance of eutectic and primary TiC phases. The microhardness at the top layer with 50 vol% TiC is improved by nearly 94% compared with that at the Ti6Al4V side. The tensile strength of TiC_p/Ti6Al4V composite with 5 vol% TiC is enhanced by nearly 12.3% compared with that of the Ti6Al4V matrix alloy. However, both the tensile strength and elongation of composite decrease gradually when the TiC volume fraction exceeds 5%. The reason is that the quantity of brittle unmelted TiC particles and the quantity and size of dendritic TiC phases increase with TiC volume fraction increasing. The fracture mechanism of the TiC_p/Ti6Al4V composite is quasi-cleavage fracture.     

无压烧结Al2O3／SiC纳米复相陶瓷的研究

将粒径为30～35nm的β-SiC粉,加入亚微米尺寸的α-Al