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

复合材料的力学性能强烈依赖于成分相的结构，如弥散硬化合金中的弥散参数。高温复合材料通常是在高温下长时间保温和/或热循环的条件下使用。本课题旨在通过制备各种复合材料，并对其相界、结构稳定性和高温力学性能进行研究，为开发出性能优良的耐火材料奠定基础。具有热稳定和非共格颗粒的弥散硬化合金对高温强度非常苛刻，因为这些颗粒与位错有强烈的相互作用并阻碍运动。在Al-CuAl2片层-共晶复合材料中，高温保温过程中，由于Ostwald生长，成分相结构退化。由于Ostwald生长最好发生在端面，因此可以通过产生无任何强化终止的定向结构来改善这种退化。在Mo-TiC片层-共晶复合材料中，虽然没有发生Ostwald长大引起的退化，但发生了相界滑移，降低了高温强度。在组元热膨胀差异较大的Cu-W层状复合材料中，在热循环过程中，相界上会形成大量空洞，复合材料的强度下降。如上所述，界面对复合材料的高温结构稳定性和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.