Structure and chemical analysis of aluminum wear debris: Experiments and ab initio simulations

Sliding can produce severe plastic deformation and drive material far from equilibrium. Commonly, it also involves material transfer, mechanical mixing and formation of tribomaterial that influences both friction and wear. This paper describes aluminum wear debris generated by sliding in different environments. One portion of the debris is highly strained and another portion contains a large amount of oxygen, but not in the form of a simple oxide such as α-alumina. Annealing the debris allows strain relaxation, weight loss and changed electrical conduction characteristics. Characterization of debris before and after annealing suggests that the tribomaterial and the debris consist partly of an aluminum–oxygen solid solution and partly of hydroxylated material. These constituents are not normally formed in the absence of external forces. Quantum mechanical ab initio simulations were performed to complement the experiments. The simulations indicate that tetrahedral sites in aluminum are favored for oxygen in solid solution.