Leaded bronzes have been widely used as bulk material or as coating of steel pieces for applications as bearings, shafts or hydraulic pumps. Lead acts as an efficient solid lubricant in systems functioning under boundary or dry conditions. For environmental and legal reasons, efforts are being made to remove lead from bearing alloys. Numbers of materials are already proposed as alternative to leaded alloys, in particular metallic composites containing selflubricant particles like graphite, MoS2 or PTFE [1–4]. Increasing the wear performances of alternative materials to leaded bronze requires a scientific understanding of the relevant mechanisms, and in particular of the relationship between materials microstructure and tribological behavior. However the present understanding of the mechanisms by which lead improves the tribological properties of alloys is limited.