NOVEL APPARATUS USING SCANNING LASER EXTENSOMETRY FOR HIGH-TEMPERATURE MATERIALS TESTING AND ITS APPLICATION TO MECHANICAL SPECTROSCOPY STUDIES ON METAL MATRIX COMPOSITES

在这项为期两年的研究项目中，我们获得了教育部科学、科学、体育和文化部科研资助项目（项目编号08555161）(a)(2)的资助，在标准伺服液压机上构建了一套新型的高温材料测试实验装置；它具有基于便携式“扫描激光卡尺”的高精度延伸测量系统，使我们能够在循环单轴加载的低频（1cHz-1dHz）次谐振条件下测量材料在300至1373 K温度范围内的动态非弹性响应。利用该装置对Al-SiC、Al-9Al_2O_32B_2O_3和Ni-ZrO_2体系的金属-陶瓷复合材料进行了动态杨氏模量和内摩擦的测量；这些材料的实验数据均显示出明显的两个分离温度下的非弹性弛豫。在更多的温度范围内，即观察到两个内摩擦峰，同时动态杨氏模量明显下降。详细分析了这些弛豫现象的动力学方面；这包括从内摩擦峰顶温度的频率依赖性中确定活化能和松弛时间的指数前因子，并将实验确定的动力学参数与理论模型的预测进行比较。分析表明，由于黏性晶界滑动，观测到的其中一个峰为众所周知的柯氏峰。作为剩余峰值的可能来源，我们提高了沿金属-陶瓷相边界的应力导向扩散质量流，并进行了基于微力学的计算，得出了复合材料动态杨氏模量和内摩擦的理论表达式。理论与实验的对比也证明了该松弛机制的现实性。少

In this two-year research project, supported by a Grant-in-Aid for Scientific Research (A) (2) from the Ministry of Education, Science, Sports and Culture under Contract 08555161, we have constructed a novel experimental setup for high-temperature materials testing on a standard servo-hydraulic machine ; it features a high-precision extensometric system based on a portable "scanning laser caliper" and enabls us to measure the dynamic anelastic response of a material over a temperature range from 300 to 1373 K under low-frequency (1cHz-1dHz) subrresonant conditions of cyclic uniaxial loading. Using the apparatus, the measurements of dynamic Young's modulus and internal friction have been carried out on metal-ceramic composite materials including Al-SiC,Al-9Al_2O_32B_2O_3 and Ni-ZrO_2 systems ; the experimental data on these materials all show clear evidence of anelastic relaxation in two well-separated temperature all show clear evidence of anelastic relaxation in two well-separated tem … More perature ranges, i.e.two internal friction peaks are observed together with marked decreases in dynamic Young's modulus. Kinetic aspects of these relaxation phenomena have been analyzed in detail ; this involves the determination of the activation energy and pre-exponential factor of the relaxation time from the frequency dependence of the peak-top temperature of internal friction, and the comparison of the experimentally determined kinetic parameters with predictions of theoretical models. The analysis identifies one of the observed peaks as the well-known Ke's peak due to viscous grain-boundary sliding. As a possible origin of the remaining peak, we raise the stress-directed diffusive mass flow along metal-ceramic phase boundaries, and make a micromechanics-based calculation to derive theoretical expressions for the resulting dynamic Young's modulus and internal friction of composite materials. The comparison between theory and experiment also proves the actuality of this relaxation mechanism. Less