Microstructural characterization of mechanically mixed layer and wear debris in sliding wear of an Al alloy and an Al based composite

The present work was undertaken to characterize mechanically mixed layers ( MML) and wear debris formed during sliding wear of an AI-Si alloy and an AI -Si/SiCp metal matrix composite against M2 tool steel under dry sliding con ditions. In particular, chemical, microstructural and crystallographic char acteristics of the MMLs and wear debris have been investigated using scanni ng electron microscopy (SEM), transmission electron microscopy (TEM) with e nergy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), as well as Mossbauer spectroscopy. It was observed that MMLs were formed in the worn surfaces at a variety of sliding loads used in the present work. The result s show that the mixed layers and wear debris generated from the sliding sys tems had similar microstructural features and were comprised of a mixture o f ultrafine grained structures, in which the constituents varied depending on the sliding loads. At a low load, the ultrafine structures mainly consis ted of the original base materials, i.e. alpha -AI solid solution and alpha -Fe from the steel. With an increase in sliding load, the ultrafine struct ures were incorporated with an Fe-AI(Si) intermetallic compound and an alum inum oxide. The formation mechanisms of the mechanically mixed layers and t heir influences on wear mechanisms of these multiphase materials were also studied on the basis of the microstructural observations. (C) 2000 Publishe d by Elsevier Science S.A.