Fatigue Crack Propagation Behavior and Fatigue Strength of Al_2O_3/A6061 MMCs at Room and High Temperatures

摘要

In order to investigate the effects of alumina short fiber volume fraction on the fatigue property at room and elevated temperature, the rotating bending fatigue test were carried out on alumina short fiber reinforced aluminum alloy composites (MMCs). The four kind of MMCs with 0 percent, 10 percent, 18 percent and 25 percent volume fraction were prepared and the five temperature conditions with room temperature, 200, 350, 400 and 450 deg C were projected. As the results, the fatigue strength at 10~7 cycles increased with increase in alumina short fiber volume fraction at all test temperature conditions. As results of investigating about fatigue crack property such as fracture surface observation by FE-SEM and surface crack observation using replication technique, it was found the next followings. However, because the large size alumina short fibers, some kind of cluster of short fibers and large size alumina particles act as the fatigue crack origin, the alumina short fiber volume fraction affect the crack initiation, the fatigue crack propagation property is affected by the strength of matrix part, for the fatigue crack propagates in the matrix part. And again, the strength of matrix part was related to the test temperature. Accordingly, the fatigue properties of these MMCs were driven by the alumina short fiber volume fraction and test temperature.