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

Abstract

The present work was undertaken to characterize mechanically mixed layers (MML) and wear debris formed during sliding wear of an Al-Si alloy and an Al-Si/SiCp metal matrix composite against M2 tool steel under dry sliding conditions. In particular, chemical, microstructural and crystallographic characteristics of the MMLs and wear debris have been investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), as well as Mössbauer spectroscopy. It was observed that MMLs were formed in the worn surfaces at a variety of sliding loads used in the present work. The results show that the mixed layers and wear debris generated from the sliding systems had similar microstructural features and were comprised of a mixture of ultrafine grained structures, in which the constituents varied depending on the sliding loads. At a low load, the ultrafine structures mainly consisted of the original base materials, i.e. α-Al solid solution and α-Fe from the steel. With an increase in sliding load, the ultrafine structures were incorporated with an Fe-Al(Si) intermetallic compound and an aluminum oxide. The formation mechanisms of the mechanically mixed layers and their influences on wear mechanisms of these multiphase materials were also studied on the basis of the microstructural observations.