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Fracture toughness of ceramics at elevated temperature and metallurgical factors for controlling the toughness

陶瓷高温断裂韧性及控制韧性的冶金因素

基本信息

批准号：
60550048
负责人：
MUTOH Yoshiharu
金额：
$ 1.22万
依托单位：
Technological University of Nagaoka
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60550048/
关键词：
Ceramics Fracture toughness Elevated temperature strength Sintering method Testing method for fracture toughness Fatigue precrack 窒化けい素

项目摘要

Three-point bend tests of four kinds of silicon nitrides with the same chemical composition, which were produced by different sintering methods and under different sintering conditions, were carried out at elevated temperature. Effects of sintering method and density on fracture strength were investigated. Effects of sintering method and density on fracture toughness evaluated by using the indentation method and fractographic method were also investigated. A new method for evaluating fracture toughness of ceramics, where fatigue precrack was introduced at elevated temperature, was developed. Main results are summarized as follows.(1) Fracture strengths were decreased with reducing density. The Weibull modulus m seemed to depend upon the sintering mehtod. (2) Fracture toughness values and also the Weibull modulus m were decreased with reducing density. (3) Fatigue precrack was successfully introduced into a notched bend specimen of silicon nitride at 1200゜C. The fatigue precrack specimen satisfied the conditions for fracture toughness specimen required by the standard of ASTM E399. (4) Fracture toughness values obtained by fatigue precracked specimens were almost equal to those obtained by using the indentation method. Fracture toughness malues up to the temperature of 1000゜C were almost the same as those at room temperature.

对四种化学成分相同、采用不同烧结方法和烧结条件制备的氮化硅陶瓷进行了高温三点弯曲试验。研究了烧结方法和密度对断裂强度的影响。研究了烧结方法和烧结密度对压痕法和断口形貌法测定断裂韧性的影响。提出了一种在高温下引入疲劳预裂纹的陶瓷材料断裂韧性的新方法。主要结果总结如下。(1)断裂强度随密度的降低而降低。Weibull模量m似乎取决于烧结方法。(2)断裂韧性值和威布尔模量m随密度的降低而降低。(3)在1200 ℃的氮化硅缺口弯曲试样中成功地引入了疲劳预裂纹。疲劳预裂纹试样满足ASTM E399标准对断裂韧性试样的要求。(4)疲劳预裂纹试样的断裂韧性值几乎等于那些通过使用压痕法得到的。在1000 ℃以下的断裂韧性值与室温下的断裂韧性值基本相同。