TiC／Ti复合材料动态拉伸的裂纹形成及扩展机制

采用熔铸法制备的原位自生TiC／Ti复合材料，在SEM中静载动态拉伸，原位观察和研究了裂纹的萌生及扩展机制。结果表明，TiC颗粒表面及应力集中处最容易萌生微裂纹；在不同位置萌生的微裂纹中，处于有利位向的微裂纹不断扩展，并与周围的裂纹连接形成主裂纹；主裂纹扩展主要是通过自身扩展与周围的裂纹连接相结合的方式进行，当裂纹扩展受阻时，裂纹前方颗粒处形成新的裂纹或基体中形成塑性坑，并通过扩展相互连接；裂纹扩展到一定程度后，试样全面失稳而迅速断裂。根据试验观察与分析建立了裂纹萌生与扩展模型。

Crack Forming and Propagation Mechanisms Tension of TiC/Ti Composites during Dynamic

The in-situ TiC particles reinforced Ti-matrix composites were fabricated by melting-casting. The mechanisms of crack forming and propagation were investigated during dynamic tension under static load by SEM. The results showed that microcracks easily appeared on the surface of TiC particles with stress concentration. The microcracks in advantageous orientation propagated continuously mainly by self-propagation and combination with ambient cracks among the micocracks in different position, forming the dominant crack by connection with surrounding cracks. When the crack propagation was baffled, new cracks formed on the front TiC particle in front of cracks or plastic pits formed in the matrix, and the cracks were connected with each other by propagating, so that the samples losed the stability and fractured rapidly after the cracks propagated to some extent. A model of crack forming and propagation was established according to the results.