A Study on the Fatigue Crack Propagation Behavior of $Al_2O_3/AC4C$ Composites Made by Squeeze Casting Process

용탕단조법으로 제조된 $Al_2O_3/AC4C$ 복합재료의 피로균열 전파거동에 관한 연구

This study has been conducted with the purpose of examining the fatigue crack growth characteristics of $Al_2O_3$ short fiber reinforced aluminum matrix composites made by squeeze casting process with different applied pressure and binder amount. Fatigue crack growth experiments have been performed under constant load amplitude method with a fixed load ratio. The rate of crack propagation was decreased with binder amount as well as applied pressure. Also fatigue crack growth path in matrix was changed from flat to rough mode with an increase of applied pressure. In the composites, fatigue crack was propagated to interface between matrix and reinforcement at 10MPa, but it was propagated to reinforcement at 20MPa. The major reason of thee result was considered that interfacial bonding force and microstructure of matrix were improved due to an increase of applied pressure. Localized ductile striation in the composites was observed at low growth rate region and such a phenominon was remarkable with an increase of applied pressure. At high growth rate region, the propensity of fracture appearance was changed from interfacial debonding to reinforcement fracture with an increase of applied pressure.