Fatigue crack growth in SiC particle reinforced Al alloy matrix composites at high and low R-ratios by in situ X-ray synchrotron tomography

• Report on in situ X-ray tomography on fatigue crack growth of MMCs at two R-ratios for the first time.
• Three-dimensional (3D) renderings of the particles and fatigue crack.
• Four-dimensional (4D) visualizations were made to understand damage evolution.
• At R = 0.1 particles rarely fracture ahead of crack tip and crack bypasses particles.
• At R = 0.6 crack often travels through particles that fracture ahead of crack tip.

Metal matrix composites (MMCs) offer high strength, high stiffness, low density, and good fatigue resistance, while maintaining cost an acceptable level. Fatigue resistance of MMCs depends on many aspects of composite microstructure. Fatigue crack growth behavior is particularly dependent on the reinforcement characteristics and matrix microstructure. The goal of this work is to obtain a fundamental understanding of fatigue crack growth behavior in SiC particle-reinforced 2080 Al alloy composites. In situ X-ray synchrotron tomography was performed on two samples at low (R = 0.1) and at high (R = 0.6) R-ratios. The resulting reconstructed images were used to obtain three-dimensional (3D) rendering of the particles and fatigue crack. Behaviors of the particles and crack, as well as their interaction, were analyzed and quantified. Four-dimensional (4D) visual representations were constructed to aid in the overall understanding of damage evolution.