Unified interpritation of high temperature crecp in an inclusion bearing material

考虑基体与增强体之间失配应变的调节过程，建立了金属基复合材料的稳态蠕变模型，以综合解释弥散强化、复合强化和复合弱化过程。用5、15和20vol的原位Ti/TiB复合材料模型对模型进行了验证。具有良好的界面键合，合适的TiB尺寸和长径比，具有中等的扩散调节速率，无细氧化物。在1123 K时，Ti/15TiB蠕变的应力和应变速率呈双对数s型曲线，分为复合材料减弱对应的完全扩散调节区、扩散调节控制区和复合材料随应力增加而增强对应的塑性调节控制区。这三个区域的活化能分别接近Ti的体积活化能、界面活化能和体积扩散活化能。在塑性调节区，应变速率随体积分数的增加而减小，而在完全扩散调节区附近，应变速率几乎没有变化。在塑性调节控制区，横向蠕变的应变速率是纵向蠕变的10倍，而在完全扩散调节控制区，这种差异几乎没有观察到。

A steady-state creep model of a metal matrix composite was proposed considering the accommodation processes of the misfit strain between the matrix and reinforcements in order to comprehensively explain dispersion strengthening, composite strengthening and composite weakening. The proposed model was verified experimentally using the model composites, Ti/TiB in situ composites of 5, 15 and 20vol.%TiB, which have a good interfacial bonding, suitable size and aspect ratio of TiB for a moderate diffusional accommodation rate, and no fine oxides. A sigmoidal curve in a double-logarithmic scale of stress and strain rate was observed in the creep of Ti/15TiB at 1123 K and was classified into a complete-diffusional-accommodation region corresponding to composite weakening, a diffusional-accommodation controlled region and a plastic-accommodation-controlled region corresponding to composite strengthening with increasing stress. The activation energies in the three regions were close to those of the volume, interface and volume diffusion of Ti, respectively. In the plastic-accommodation-controlled region, the strain rate decreased with increasing volume fraction, while near the complete-diffusional-accommodation region, the strain rate scarcely changed. The strain rate of the transverse creep was ten times that of the longitude creep in the plastic-accommodation-controlled region, while the difference was scarcely observed near the complete-diffusional-accommodation region.