Development of an electron work function-based novel methodology for designing advanced tribo-materials

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Materials science and engineering have a long history of developing theories and approaches to improve materials for enhanced resistance to failure. Microstructure engineering plays a crucial role in material design. However, microstructural features do not always provide clear clues for tailoring materials. With increased demands for applications under not only usual conditions but also extreme ones, material design has been required to rely on more fundamental principles. This project is proposed to develop new methodologies for structural material design with emphasis on tribo-materials on a feasible electronic base. Intrinsic properties of materials are fundamentally determined by their electron behavior, which governs the atomic bond strength and ductility. Great effort has long been made to correlate mechanical properties of materials to their electron state based on quantum mechanics, which is, however, complicated to be used in structural material design. It is highly desired to have simple but fundamental parameters, which reflect the electron behavior of materials, for material analysis and design in a feasible manner. The applicant's group has conducted extensive studies on electron work function (EWF) and demonstrated that EWF is correlated to many material properties, and is a promising indicator for guiding tailoring materials. However, material properties are dependent not only on properties of individual phases and grains in a material but also its microstructure. When second phases in polycrystalline materials with different EWFs are in contact, there exists electron transfer in order to establish thermodynamic equilibrium. These affect EWF distribution and thus overall performance. Thus, it is of significance to understand how microstructural constituents influence the overall EWF and its relationships with the overall or global material properties towards the development of new methodologies for realistic material design. This is the main goal or long-term objective of research proposed in this new Discovery project, which is distinct from that of applicant's previous Discovery project, which was focused on the correlation between EWF and properties of pure metals and homogeneous solid solutions. The followings will be included in the project: 1) studies on how microstructural constituents, including grain size, orientation, grain boundaries, and second phases (size, morphology, properties and interface), influence local and global EWFs of polycrystalline multiphase materials; and 2) studies on the correlation between EWF and properties of the multi-phase materials towards development of EWF-based approaches or methodologies for material design and tailoring with focus on tribo-materials.