Interphase-boundary Structure and Thermal Fatigue in Composite Materials with High Melting points

复合材料的力学性能很大程度上取决于组成相的结构，如弥散硬化合金中的弥散参数。高温复合材料通常在高温和/或热循环下长时间保温的条件下使用。然后，复合材料除了组分相之间的强结合外，还必须具有稳定的结构，才能实现良好的应力传递。本课题旨在通过制备各种复合材料，研究其相界面、结构稳定性和高温力学性能，为开发优良耐火材料奠定基础。得到的结果如下：1。具有热稳定和非共格颗粒的弥散硬化合金具有很高的高温强度，因为这些颗粒与位错有吸引的相互作用，从而延缓了运动。在Al-CuAl_2层状共晶复合材料中，由于高温保温过程中奥斯特瓦尔德生长导致了组分相结构的退化。这种降解可以通过产生没有任何增强终止的排列结构来改善，因为奥斯特瓦尔德生长更好地发生在终止处。在Mo-TiC层状共晶复合材料中，虽然没有发生Ostwald生长引起的降解，但却发生了相间边界滑动，降低了高温强度。当Cu-W片层复合材料的组分相热膨胀差异较大时，在热循环过程中会在相界面形成许多空洞，导致复合材料的强度下降。如上所述，相界面对复合材料的结构稳定性和高温力学性能起着重要的作用。

The mechanical properties of composite materials strongly depend on the structure of component phases,such as the dispersion parameters in dispersion hardened alloys. The composite materials for high temperature are usually used under the conditions of holding for long time at high temperature and /or thermal cyclling. Then, the composite materials have to have a stable structure under the conditions besides the strong bonding between the component phases for good stress transfar.The present project is to lay the foundation for developing excellent refractory materials by producing various kinds of composite materials and studing their interphase boundary, structure-stability and mechanical properties at high temperature.The results obtained are as follows.1. Disperesion hardened alloys with thermally stable and non-coherent particles are very excerent for high-temperature strength, because these particles have atractive interaction with dislocation and retard the motion.2. In the Al-CuAl_2 lamellar-eutectic composite, degradation of the structure of component phases yields due to Ostwald growth during holding at high temperature. This degradation can be improved by producing aligned structure without any reiforcement erminations, because the Ostwald growth occurs preferably at the terminations. In the Mo-TiC lamellar-eutectic composite, interphase-boundary sliding occur and lower the high-temperature strength though the degradation due to the Ostwald growth does not occur.3. In the Cu-W lamellar composite with a large different in thermal expansion of component phases, many voids form on the interphase boundary during thermal cycling and the strength of composite deteriorades.4. As mentioned above, the interphase boundary plays an important role in the structure stability and the mechanical properties of composite materials at high temperature.