Investigating the Impact of Indentation and Scratch on α-Al2O3 Thin Film Coated Al Substrate: A Molecular Dynamics Study

Alumina coated aluminium materials have several real-world applications due to aluminium being metal and has properties such as strength, ductility and alumina being a ceramic material providing chemical protection, resistance to corrosion, moisture and high temperature. Present study focuses on understanding the effect of α-Al 2 O 3 thin film on Al substrate using a nano-indenter. In particular it was able to model α-Al 2 O 3 by stacking layers of Al and O 2 at low temperatures ~0 K and performing equilibration after that. It was tried to observe the effect of grain size (cubic with each side being 100 Å, 150 Å, 200 Å), following surface orientation (100), (110) and temperature (~0 K, 10 K, 100 K, 300 K) on the observed properties. When indented on α-Al 2 O 3 of 10 Å thickness, it was observed that hardness and elastic moduli increase with increase in grain sizes. Notably, these mechanical properties are higher in the bulk region than at the grain boundaries. Upon indenting at 300 K, it was noticed a phase change in the amorphous region and created a raised region surrounding the indented area (piling up), similar phenomenon was observed while performing a scratch with Al (110) substrate, resulting in large increase in hardness.