Microstructural evolutions and variations in mechanical properties of ceramics caused by superplastic deformations

超塑性变形引起的陶瓷微观结构演变和机械性能变化

基本信息

批准号：
06650793
负责人：
MOTOHASHI Yoshinobu
金额：
$ 1.28万
依托单位：
Ibaraki University, School of Engineering
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06650793/
关键词：
Superplasticity Ceramics Zirconia Tension Compression Cavitation Hardness Fracture toughness 機械的性質

项目摘要

Tension and compression tests of a yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and Y-TZP/Al_2O_3 composite were conducted in air at temperatures from 1623 to 1823K with initial strain rates from 10^<-4> to 10^<-2> sec^<-1>. The flow stress vs.strain rate relations, strain rate sensitivity exponents (m-value) and apparent activation energies were evaluated. Each specimen was pulled or compressed to pre-determined strains and microstructural evolution and density loss were measured. The deformed specimens were subjected to thermal etching and the microstructures were observed by SEM.The amounts of cavities, deformation enhanced concurrent grain growths and changes in grain aspect ratios with the tensile and compressive strains were studied as functions of the temperature, strain rate and initial grain size.The following results were obtained. The region III in the flow stress vs.strain rate relations seemed to be not appear. The m-values observed were approximately 0.3 for both tension and compression. The flow stress under compression was larger than that under tension, whereas the activation energy evaluated for the compression was smaller than the tension, suggesting that rate contralling processes are somewhat different between the tension and compression. The amount of cavities increased with the tensile strain, while it decreased in an early stage of the compression and then it starts to increase with the compressive strain after showing a minimum value. The cavities have strong correlations with the hardness, bending strength and fracture toughness of the deformed specimens.

钇稳定四方氧化锆多晶(Y-TZP)和Y-TZP/Al_2O_3复合材料在空气中进行拉伸和压缩试验，温度为1623至1823K，初始应变率为10^<-4>至10^<- 2> 秒^<-1>。评估了流动应力与应变率关系、应变率敏感性指数（m 值）和表观活化能。每个样本都被拉伸或压缩到预定的应变，并测量微观结构的演变和密度损失。对变形样品进行热蚀刻，并通过 SEM 观察微观结构。研究了空腔数量、变形增强的并发晶粒生长以及晶粒长宽比随拉伸和压缩应变的变化，作为温度、应变速率和初始值的函数。晶粒尺寸。获得以下结果。流动应力与应变率关系中的区域III似乎没有出现。观察到的拉伸和压缩的 m 值约为 0.3。压缩下的流动应力大于拉伸下的流动应力，而评估的压缩活化能小于拉伸，这表明拉伸和压缩之间的速率控制过程有些不同。空洞数量随着拉应变的增加而增加，而在压缩的早期阶段空穴的数量减少，在呈现最小值后开始随着压应变的增加而增加。空洞与变形样品的硬度、弯曲强度和断裂韧性有很强的相关性。