Abstract
A systematics of grain boundary (GB) segregation transitions and critical phenomena has been derived to expand the classical GB segregation theory. Using twist GBs as an example, this study uncovers when GB layering vs. prewetting transitions should occur and how they are related to one another. Moreover, a novel descriptor, normalized segregation strength (ϕseg), is introduced. It can represent several factors that control GB segregation, including strain and bond energies, as well as misorientation for small-angle GBs (in a mean-field approximation), which had to be treated separately in prior models. In a strong segregation system with a large ϕseg, first-order layering transitions occur at low temperatures and become continuous above GB roughing temperatures. With reducing ϕseg, the layering transitions gradually merge and finally lump into prewetting transitions without quantized layer numbers, akin to Cahn's critical-point wetting model. Furthermore, GB complexion diagrams with universal characters are constructed as the GB counterpart to the classical exemplar of Pelton-Thompson regular-solution binary bulk phase diagrams.
Highlights
Grain boundary (GB) segregation (a.k.a. adsorption) is an important phenomenon for materials science because it can critically influence microstructural evolution and a broad range of materials properties [1, 2]
We have derived a systematics of GB segregation transitions and critical phenomena in binary regular-solution alloys
A normalized segregation strength φseg is introduced to represent the overall effects of strain and bond energies for both general and small-angle GBs, as well as the misorientation for small-angle GBs
Summary
Grain boundary (GB) segregation (a.k.a. adsorption) is an important phenomenon for materials science because it can critically influence microstructural evolution and a broad range of materials properties [1, 2]. Hondros and Seah [5] further suggested the existence of first-order segregation transition with strong adsorbateadsorbate attraction at GBs, in an analogy to the Fowler-Guggenheim surface adsorption model [6]; this segregation transition occurs when the effective GB regular-solution parameter is >2R (R is gas constant), thereby suggesting a GB “phase separation” [7]. Rickman et al suggested first-order GB layering transitions (based on a system resembling Cu-Ag) mostly based on elastic interactions in a micromechanical framework [13]. It is not yet known when GB prewetting vs layering transitions should occur and how they relate to each another, which represents the first motivation of this study
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.