Equivalent Characterization Of The Friction And Wear Behavior During Hot Extrusion Of6061Aluminum Alloy

The friction contact conditions are of great influence on the accuracy of the finiteelement simulation results. However, the research of frictional contact in the bearingchannel during hot aluminum extrusion is not mature enough nowadays. The frictionfactor was usually selected as a constant from0.3to0.6for the FE simulations, whichobvious is inaccurate. Therefore, the issue of the friction contact during hot aluminumextrusion is required exhaustive research. In order to study the friction and wearbehavior and the characterization of friction boundary conditions in the bearingchannel, ball-on disc tests were carried out on6061aluminum alloy samples attemperatures of200℃,300℃,400℃and500℃and normal loads of1N,3N,5N and10N and sliding velocity of1mm/s,2mm/s, and4mm/s.The morphology and composition of the worn surface were studied by means ofoptical microscope, SEM and EDS. The research indicates that a mild to severe weartransition occurs obviously and the friction coefficient shows a trend of increasingfirstly and then decreasing with the increase of temperature. However, th e normalload and sliding velocity have an unconspicuous effect on both the wear mechanismand the friction coefficient of6061aluminum alloy.In the present study, the new models capable of separating the plowing frictionand shear friction during high temperature ball-on-disc tests were developed on thebasis of Tayebi’s model and Goddard’s model for scratch tests. The results show thatthe plowing friction accounts for only about1%, while the shear friction plays adominant role in determining the apparent friction measured. The friction shear stresscalculated from the built models shows a trend of much more stable than the shearfriction coefficient, and the former is not affected by changes in the contact area,which make it more suitable to reflect the real contact between hot aluminum andextrusion dies. The former model is more preferable to determinate the boundaryconditions because of its higher accuracy. In addition, the average contact stress ofdifferent normal loads calculated from these two models is close to each other, andthe normal force reversed by the average contact stress is in good agreement with thenormal load applied, which confirm the reliability and accuracy of the models.