SiC陶瓷增韧的研究进展

碳化硅陶瓷以其优异的性能被广泛利用于各种领域，但其脆性限制了其性能的发挥，因此其增韧技术得到广泛研究并取得良好效果。综合评述了碳化硅陶瓷增韧机理和增韧方法的研究进展，包括晶须或纤维增韧、颗粒弥散增韧、表面改性技术增韧、自增韧、层状结构复合增韧的增韧机理和方法进。     

陶瓷基金属颗粒复合材料的本构关系及增韧效应分析

本文通过对延性金属颗粒增韧陶瓷复合材料(ductile metal particletoughened ccramic matrix composite)的材料微元的细观力学分析,导出了这一两相复合材料在外加应力作用下的宏观本构关系并在此基础上对静止裂纹尖端附近过程区中延性颗粒的塑性变形对宏观裂纹的屏蔽效应(即增韧效应)进行了理论计算,给出了材料宏观弹塑性行为及增韧值与材料组分相性能之间的关系,为进一步的材料设计提供了思路。      

脆性陶瓷材料的增韧方法及其应用现状

从陶瓷断裂的基本理论入手,对比了相变增韧、微裂纹增韧、纤维增韧和纳米颗粒增韧等技术应用到陶瓷领域的增韧机理及其实施方法,举例阐述了这些增韧方法的应用,并对其发展前景进行了展望。     

形状记忆合金的力学及界面参数和体积分数对大块金属玻璃基复合材料增韧的影响

采用考虑塑性的超弹性材料模型和基于损伤塑性的准脆性材料模型,建立了三维单胞有限元模型,模拟了形状记忆合金颗粒增韧大块金属玻璃基复合材料的单调拉伸行为。讨论了形状记忆合金的力学参数、体积分数、界面厚度和界面材料参数对金属玻璃增韧效果的影响。结果表明:提高形状记忆合金的相变应变和马氏体塑性屈服应力将显著提高形状记忆合金颗粒增韧大块金属玻璃基复合材料的拉伸失效应变;形状记忆合金弹性模量超过50.0GPa、马氏体塑性屈服应力超过1.8GPa后,复合材料的拉伸失效应变变化不大。能同时兼顾失效应变和失效应力的形状记忆合金体积分数为15%左右。复合材料界面弹性模量和界面屈服应力的增加将提高复合材料的失效应力,但对失效应变影响不大;复合材料界面厚度的增加在提高失效应变的同时,也降低了复合材料的失效应力。     

颗粒补强锆英石复相陶瓷的力学性能、残余应力和增韧行为研究

本文采用X射线衍射方法测定了颗粒补强锆英石基复相陶瓷基体中的残余应力,通过力学性能测试,结合显微结构观察;讨论了残余应力与补强颗粒增韧行为之间的关系．结果表明：在基体热膨胀系数小于补强颗粒的情况下,适当增大补强颗粒与基体间热膨胀失配,能够提高复相陶瓷的增韧效果．其增韧机制主要为;补强颗粒所引起的裂纹偏转和分支．利用残余应力场增韧模型计算得到的复相陶瓷断裂韧性增量与实际值能够较好的吻合．     

A12O3陶瓷复合材料的研究进展

介绍了Al2O3陶瓷增韧技术和A12O3陶瓷增强金属基复合材料的研究进展,指出复合增韧是未来A12O3认陶瓷增韧技术的发展方向;金属表面自生Al2O3防护层技术是提高金属耐蚀性,降低成本的有效方法;三维网络Al2O3陶瓷/金属复合材料具有更优良的力学性能;仿生设计和计算机模拟技术是开发新型网络Al2O3陶瓷骨架的重要手...     

A12O3陶瓷复合材料的研究进展

介绍了Al2O3陶瓷增韧技术和A12O3陶瓷增强金属基复合材料的研究进展,指出复合增韧是未来A12O3认陶瓷增韧技术的发展方向;金属表面自生Al2O3防护层技术是提高金属耐蚀性,降低成本的有效方法;三维网络Al2O3陶瓷/金属复合材料具有更优良的力学性能;仿生设计和计算机模拟技术是开发新型网络Al2O3陶瓷骨架的重要手段.     

层状复合陶瓷断裂特性

层状复合是一种新型陶瓷增韧构型。本文着重讨论了层状复合陶瓷断裂特性，包括几种主要的增韧机制的分析和影响因素和讨论。     

层状复合陶瓷断裂特性

层状复合是一种新型陶瓷增韧构型。本文着重讨论了层状复合陶瓷断裂特性，包括几种主要的增韧机制的分析和影响因素的讨论。     

铬粒弥散增韧氧化铝复合材料的研究

本文以金属铬粉弥散增韧氧化名陶瓷为研究对象，具体地探讨了增韧的结果与两相界面结合强度之间的关系，试验结果表明，约有２５％的铬颗粒与基体裂纹发生桥联作用，并且产生一定的颈缩塑性变形，从而吸怍能量达到增韧的目的，基体对颗粒的变形具有一定的约束作用。较高的界面结合强度使得铬颗粒在很小的塑性变形下发生脆断，而较低的界面结合强度将导致颗粒的拔出。     

Stress corrosion characteristics of toughened glasses and ceramics

A method for evaluating stress corrosion characteristics of thermally or chemically toughened glasses and ceramics is outlined. Values of the stress corrosion indexn (V = AKⁿ) have been obtained and these are in excellent agreement with values for untreated materials. The analysis also explains the slightly greater absolute strength degradation observed for toughened glasses and ceramics.     

Weibull modulus of fracture strength of toughened ceramics subjected to small-scale contacts

The Weibull modulus of toughened ceramics was evaluated. The fracture of the toughened ceramics was assumed to be initiated by surface cracks induced during small-scale contacts such as grinding and polishing and an exponential function was selected to describe the R-curve behavior. Based on a brief theoretical analysis, a numerical simulation procedure was designed to predict the fracture strength for toughened ceramics with different R-curve characteristics. The Weibull modulus of each toughened ceramic was estimated and compared with that of the un-toughened base material. It was concluded that an increase in Weibull modulus can always result from toughening. The increase in Weibull modulus was found to be related directly to the relative crack tolerance, i.e., the ratio of the initial crack size to the critical crack size. This suggests that the improvement in crack stability due to toughening is the main reason for the increased Weibull modulus.     

陶瓷材料相转变增韧的研究进展

介绍了几种相转变韧化机制，主要包括ZrO2相变增韧、铁电／压电性畴转变增韧、铁弹性畴转变增韧的增韧机理和研究进展。提出一种新的相转变增韧机制——铁磁性畴转变增韧机制，即利用铁磁相的磁畴转变或压磁效应来实现能量耗散，从而达到增韧效果，探讨了其可能性。     

INFLUENCE OF MICROSTRUCTURE ON WEAR RESISTANCE PARAMETER OF CERAMIC CUTTING TOOLS

This report examines the role of microstructure of a new type of cutting tool material on an existing relationship between its abrasion wear resistance, fracture toughness (K_IC), and hardness (H). Three alumina-silver composites with different amounts of metal particles have been prepared, and their hardness and fracture toughness properties have been determined together with the assessment of their microstructural features such as volume fraction of the second phase, porosity, etc. The mechanical wear on the flanks of cutting tool inserts, made from the developed composites, has also been estimated by machining experiments against 0.45% carbon steel. The results indicate that flank wear resistance of these silver toughened ceramic cutting tool inserts is not proportional to an existing wear resistance parameter K_IC^3/4H^1/2. A modified relation between flank wear resistance, hardness, and fracture toughness has been suggested here for these cutting tool materials. The modification incorporates consideration of the volume fraction of the second phase and the porosity in the developed metal toughened ceramics.     

Ceramics in engines – process requirements and research activity

Abstract

A brief introduction to the areas of ceramics research concerned in thedevelopment of ceramics for internal combustion engines is presented which includes outlines of the high-purity powder production and compaction process, the sintering process, and of toughened ceramics. Much of the academic research current in the UK is supported by the Science and Engineering Research Council and both present activity and future development are briefly discussed.

MST/456     

Hardmetals

Uncertainties of supply, diminishing resources and prospects of improved properties have stimulated research on finding substitutes for the constituents in tungsten-carbide/cobalt hardmetals and for finding replacements. The direction of the research varies in different countries and for different applications. The materials involved are hardmetals containing alloy binder phases or complex carbo-nitrides, or are cermets or toughened ceramics.     

爆炸压实ZrB_2-SiC超高温陶瓷的密度与组织

为了研究炸药对ZrB2-SiC超高温陶瓷密度与组织的影响,采用爆炸压实工艺制备了SiC纳米颗粒和SiC晶须分别增韧的两类ZrB2基超高温陶瓷复合材料.研究发现：选择低速的硝酸铵或高速的黑索今时,两类ZrB2-SiC爆炸压实坯密度都比较低,而选择混合炸药时致密效果较好;采用225 g黑索今与75 g硝酸铵的混合炸药时,Z...     

陶瓷基复合材料循环疲劳的研究

本文对陶瓷基复合材料的循环疲劳研究现状及发展趋势进行了最新述评。主要内容有:非相变增韧陶瓷、相变增韧陶瓷、晶须(或纤维)增强陶瓷基复合材料的循环疲劳行为和疲劳裂纹扩展机理。最后,还对进一步研究陶瓷基复合材料的循环疲劳特性提出了一些粗浅的看法。