Fatigue crack growth rate and propagation mechanisms of SiC particle reinforced Al alloy matrix composites

 This study aims to investigate the fatigue crackpropagation behavior of SiC particle-reinforced 2124 Al alloy composites underconstant amplitude axial loading at a stress ratio of R = 0.1. For thispurpose, it is performed experiments and comparatively analyze the results byproducing 5, 10, 15 Vol.% SiCp-reinforced composites and unreinforced 2124 Alalloy billets with powder metallurgy (PM) production technique. With thePM production technique, SiCp-reinforced composite and unreinforced 2124 Al alloybillets were produced at 5%, 10%, 15% volume ratios. After the produced billetswere extruded and 5 mm thick plates were formed, tensile and fatigue crackpropagation compact tensile (CT) samples were prepared. Optical microscopeexaminations were carried out to determine the microstructural properties ofbillet and samples. To determine the SiC particle–matrix interactions due tothe composite microstructure, unlike the Al alloy, which affects the crackinitiation life and crack propagation rate, detailed scanning electronmicroscopy (SEM) studies have been carried out. Optical microscope examinationsfor the determination of the microstructural properties of billet and samplesshowed that although SiC particles were rarely clustered in the Al alloy matrix,they were generally homogeneously dispersed. Fatigue crack propagation rateswere determined experimentally. While the highest crack initiation resistancewas achieved at 5% SiC volume ratio, the slowest crack propagation rate in thestable crack propagation region was found in the unreinforced 2124 Al alloy. Atvolume ratios greater than 5%, the number of crack initiation cycles decreasesand the propagation rate increases. As a requirement of damage tolerancedesign, the fatigue crack propagation rate and fatigue behavior of materials tobe used in high-tech vehicles such as aircraft structural parts should be wellcharacterized. Therefore, safer use of these materials in critical structuralparts becomes widespread. In this study, besides measuring fatigue crackpropagation rates, the mechanisms causing crack acceleration or decelerationwere determined by applying detailed SEM examinations.