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.

Yttria稳定的四方氧化锆多晶体（Y-TZP）和Y-TZP/AL_2O_3复合材料的张力和压缩测试在1623至1823K的空气中进行，从10^<-4>至10^<-4>至10^<-2> sec^> sec^<-1>> 1623至1823K的空气中进行。评估了流动应力与峰值关系，应变速率敏感性指数（M值）和明显的激活能。将每个标本拉或压缩到预定的菌株中，并测量微结构的演化和密度损失。对变形的试样进行热蚀刻，并通过SEM观察到微观结构。腔，变形的量增强了并发的谷物生长和晶粒纵横比的变化，其拉伸和压缩菌株作为温度，应变速率和初始晶粒尺寸的功能研究。获得了以下结果。获得了以下结果。流动应力中的III与峰值关系的关系似乎没有出现。对于张力和压缩，观察到的M值约为0.3。压缩下的流动应力大于张力下的流动应力，而对压缩的激活能量小于张力，这表明速率相反的过程在张力和压缩之间有所不同。随着拉伸应力的增加，腔量增加，而在压缩的早期阶段下降，然后在显示最小值后随着压缩应变的增加而开始增加。腔与变形标本的硬度，弯曲强度和断裂韧性具有很强的相关性。