Soft anti-friction alloys are metal-metal composites used in journal bearings as a functionally graded system, The physical processes occurring during severe wear of these products are analysed and placed within the framework of theories on tribolayer formation. A simplified analysis of the thermodynamics of the phenomena permits analysing the anti-friction properties of the alloys in terms of the activity coefficients of their constituents and indicates that during wear, a wear-resistant contact layer is formed which retards further damage.