Characteristics of the Friction Between Aluminium and Steel at Elevated Temperatures During Ball-on-Disc Tests

Appropriate specification of the frictional boundary condition for the finite-element (FE) simulation of metal-forming processes is of great importance to the trustworthiness of the results. The research reported in this communication aimed at understanding the interfacial contact between aluminium and steel at elevated temperatures and determining friction coefficients at this material mating. A series of high-temperature ball-on-disc tests were carried out with the AA7475 aluminium alloy as the material of disc and the hardened H11 steel as the material of ball. A mathematical model developed in the preceding research was employed to account for the evolution of the contact interface during ball-on-disc tests. Friction coefficients at different temperatures and over a number of laps were determined. The shear friction stresses and mean contact pressures along with the progress of the tests at 350-500 A degrees C were calculated. It was found that the friction coefficients obtained from ball-on-disc tests alone were insufficient to represent the frictional interaction between deforming aluminium and steel at elevated temperatures. The evolution of the contact interface with increasing sliding distance must be taken into consideration and the friction behaviour can be reasonably characterized by using friction stress.