Dependence of the Mechanical Behavior of Alloys on Electron Work Function—A Promising Alternative Parameter for Materials Characterization and Design

• Author / Creator

  Lu, Hao

• With rapid advance in materials technology, structural material design has been required to rely on more fundamental principles. Conventional metallurgical rules have been successfully used in materials design for centuries but limitations are still there. Many expensive and time-consuming trial-and-error experiments are needed before a new material is successfully developed. It is known that the intrinsic mechanical behavior of metallic materials is largely governed by their electron behavior, which determines the atomic bond strength. Great effort has long been made to correlate mechanical properties of materials to their electron configurations based on quantum mechanics. However, the quantum theory of materials is complicated and not easily applied by materials engineers for materials design. Thus, it is highly desired to have a simple and fundamental parameter, which can largely reflect or characterize the electron behavior and can be easily used by materials developers to guide material design on a feasible electronic base. Recent studies have shown that electron work function (EWF) is such a promising parameter. There has been growing interest in both experimental and theoretical investigation of the relationship between EWF and mechanical deformation of materials. Since EWF is related to many mechanical properties of metals, it is desired to use EWF as an alternative parameter to guide designing and tailoring metallic materials on a feasible electronic base. In this study, attempts are made to establish relationships between EWF and mechanical properties of metallic materials. EWF may reflect the depth of the potential well of electrons approximately. EWF reflects the stability of an electron state or the difficulty to break an atomic bond. A greater energy is required to change its electron state if the material has a higher EWF. This consequently generates higher barriers to any attempt to change its mechanical state, which are related to the electron state-governed atomic bond strength. Clear correlations between EWF and mechanical properties of materials, including pure metals, solid solution alloys and multi-phase alloys, have been shown experimentally and theoretically. Studies have demonstrated that the overall mechanical behavior is correlated with the overall EWF to a certain degree, although the former is microstructure dependent. A method to extract the EWFs of binary solid solutions from their phase diagrams is proposed. And a single-parameter model using EWF as an indicator to evaluate the capability of solute atoms in solid solution hardening is suggested. An approach of using EWF as an indicator in evaluating fracture toughness and interfacial bonding strength of materials is also investigated. It demonstrates that EWF could be used as a guiding parameter for material characterization and design. This parameter is promising to build a bridge towards the development of alternative or complementary approaches or methodologies for materials design on a feasible electronic base.

• Subjects / Keywords

  • Materials characterization
  • Metallic materials
  • Materials design
  • Electron work function
  • Mechanical behavior

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3K931M0V

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.