Surface and Subsurface Behavior of Selected Al-Cu Alloys in Sliding Wear

Abstract

As materials are pushed to higher levels of performance, the nature of friction and wear phenomena occurring in sliding contact is of even greater importance in view of energy efficiency and maintained functional integrity. The present study investigated unlubricated sliding wear from the standpoint of transfer layer behavior. Microscopic studies of selected Al-4.5 Cu structures confirmed that asperity contact damage is very localized, as was the case for previously studied solid solutions. The subsurface region was found to consist of very fine crystallites lacking a stable, definable texture. Macroscopic wear testing was performed by three different methods using Cu-Al solid solutions. It was demonstrated that test multiplicity has the advantages of establishing machine-dependent results and also showing conditions for which a given parameter is rate controlling. Surface-sensitive tests using aluminum bronzes are dominated by surface oxide effects. The soft Cu2 O component of films on low percentage solute alloys behaves as a solid lubricant. When tests are employed that produce more severe wear, bulk properties of the substrate predominate except for alloys with highly abrasive surface oxides. Results of this study have been found to be in good correlation with related transfer layer investigations.