Dr. Yinyin Zhang
In the field of materials tribology, tribological loading of metallic materials leads to many surface and subsurface modifications to the microstructure and chemical composition, including but not limited to, microstructural refinement due to severe plastic deformation, and phase transformation owing to interaction with the environment. Such modifications contribute to formation of a continuous or patchy layer, often called tribomaterial or tribologically transformed structure (TTS), from which wear particles are produced. To obtain enhanced wear resistance for metals, one often turns to metal matrix composites (MMCs) that promote rapid formation of wear-resistant tribomaterial near the worn surface and indicate MMCs may be a route for obtaining self-organized microstructures that are exceptionally wear resistant. However, some fundamental questions such as formation, deformation mechanisms and strengthening mechanisms of those tribomaterials under tribological loading have not been well understood so far. In the present seminar, the above research questions will be answered by a case study of WC-reinforced Cu composite sliding against stainless steel. Moreover, it has been long challenging in tribology to make local observations of the stress-strain conditions for tribomaterials found inside a tribological contact. To overcome that, high-pressure torsion (HPT) was used to study microstructural evolution and deformation mechanisms occurring at early stage of tribological process. In addition, third body rheology in the contact was also examined numerically by a multibody meshfree model. Those results revealed a whole picture of a tribological contact at different scales and provided guidance to material design for high wear resistance and low friction.