Characterization of Crack Evolution and Subsurface Damage in AA7075-T6, Anodized AA6061-T6, and Al-15 vol.% SiC T4 Composite Under Wear and Indentation Loading

This study investigated the deformation behavior and damage evolution of AA7075-T6, Anodized AA6061-T6-T6 (oxide layer with an average thickness of 8.71 µm), and Al-15 vol.% SiC-T4 (particle size range of 3.1–8.3 µm) under scratch, Hertzian-type indentation, and nanoindentation loading conditions. Through controlled mechanical testing, the materials’ responses to varying test conditions were characterized in terms of penetration depth and width, resistance to deformation, and cracking mechanisms on surface and sub-surface. Results revealed that Al-15 vol.% SiC T4 exhibited the highest stability and scratch resistance due to the reinforcing effect of SiC particles, while AA7075-T6 demonstrated moderate strength with noticeable plastic deformation. Anodized AA6061-T6 showed enhanced surface hardness post processing but increased susceptibility to brittle cracking and coating delamination under higher loads and reciprocating passes. Findings indicated a transition from load-controlled to structure-controlled behavior at elevated forces, influenced by strain hardening and microstructural constraints. Hertzian-type indentation further highlighted differences in subsurface damage and crack propagation patterns among the materials. Holistically, the study established a clear correlation between microstructural features and mechanical performance, guiding material selection and surface engineering for improved wear and contact damage resistance.