EFFECTS OF SURFACE-ROUGHNESS ON FRICTION AND METAL TRANSFER IN LUBRICATED SLIDING OF ALUMINUM-ALLOYS AGAINST STEEL SURFACES

Twist-compression experiments were conducted with four aluminium alloys (1050, 5182, 6061-T6 and 2024-T351) sliding against hardened O1 tool steel anvils of smooth, medium and rough (R(a) = 0.05, 0.15 and 0.30-mu-m) surface finish at interface pressures of one-ninth of the Meyer hardness. Friction and metal transfer were governed by alloy composition alone in unlubricated sliding whereas anvil surface roughness became a significant variable in experiments with a non-compounded, 30 mm2 s-1 viscosity, mineral oil lubricant. Differences in friction, metal transfer and retransfer and surface damage to the specimen could be largely rationalized by considering the effects of strain hardening and ductility on asperity interactions, but there were also contributions best explained by differences in adhesion.