Effect of structural order on oxidation kinetics and oxide phase evolution of Al-Zr alloys

To reveal the fundamental role of structural order of the parent alloy on the oxidation mechanism, thermal oxidation of amorphous and crystalline Al-Zr alloys with identical compositions were investigated in detail. An (Al0.68Zr0.32)O-1.66 amorphous oxide emerged on crystalline Al2Zr, whereas an (Al0.33Zr0.67)O-1.83 amorphous oxide formed on amorphous Al68at.%Zr32at.% under the same conditions. Oxidation kinetics was fast and linear for crystalline Al2Zr but slow and parabolic for amorphous Al68at.%Zr32at.%. The underlying mechanisms of such striking differences were disclosed by molecular dynamics simulations. The findings thus offer new prospects in the field of surface engineering.