Kinetics of Fatigue Crack Growth in Cast Al-SiC Particulate Composites

摘要

The Al-SiC particulate composites are important due to their light weight and good mechanical properties. In this study a 2124 alloy has been used to prepare cast composites with 10 and 20 wt% SiC and 20μm particulate size.The experimental study included microstructural characterization, evaluation of tensile properties and fatigue crack growth rate. The measurement of crack closure was also done using compliance technique. The particulate phase was found to increase the proof stress by 25 to 50 % but decreased the tensile strength and ductility significantly.The fatigue crack growth rate was found to have a tendency to decrease in presence of particulate phase particularly in low AK regime. In higher AK regime however, fatigue crack growth rate (da/dN) increased marginally with particulate phase. The |¤K effective values were calculated and correlated with da/dN of materials. The composites were found to exhibit better crack growth resistance and the same is considered mainly due to crack diversion along the particulates leading to crack branching and mode change. In the base alloy, however, the crack closure is found to play a significant role for its improved performance. The fracture micromechanism studies were also conducted and the results discussed.