Correlation governs the impurity (Ti, Zr, Hf) diffusion in face−centered cubic iridium through first−principles calculation. (June 2022)

• Record Type: Journal Article
• Authors: Luo, Haiyu; Tang, Sai; Liang, Chaoping; Gong, Haoran
• Is Part Of: Calphad. Volume 77(2022)
• Publication Date: 2022-06
• Subjects: High-temperature alloys -- Transition metal alloys and compounds -- Diffusion -- Computer simulations -- First-principles calculation; Phase diagrams -- Data processing -- Periodicals; Thermochemistry -- Data processing -- Periodicals; Diagrammes de phases -- Informatique -- Périodiques; Thermochimie -- Informatique -- Périodiques; Thermodynamica; Electronic journals; 541.363
• DOI: 10.1016/j.calphad.2022.102433
• Languages: English
• ISSNs: 0364-5916

Abstract

Abstract: Solid state diffusion depends on many factors, including crystal structure, vacancy concentration, energy barrier, jump frequency, correlation, etc. . In this work, those factors were systematically investigated for dilute IVB transition metals X (X = Ti, Zr, Hf) diffusion in face−centered cubic (FCC) Ir using first−principles calculations together with quasi−harmonic thermodynamics, climb−image nudged elastic band (CINEB), and five−frequency diffusion model. The results show that correlation which is often neglected in low melting point metals and alloys plays a key role in the impurity diffusion in Ir. The correlation factor which ranges from 10 −13 at 500 K to 10 −1 at 2000 K overturns the contributions from other factors, like vacancy concentration, energy barrier, and jump frequency. The diffusion coefficient of Ir−X (X = Ti, Zr, Hf) systems follows DHf > DZr > DTi, different from our traditional knowledge. Our findings not only give a good recount to the counterintuitive experimental phenomena in Ir oxidation resistance coating or ultrahigh−temperature Ir-based superalloys, but also provide valuable diffusion data for rational design of Ir-based materials for applications with harsh environment. Graphical abstract: Image 1 Highlights: Impurity (Ti, Zr, Hf) diffusion coefficient in Ir is exactly determined. Correlation factor successfully explains counterintuitive phenomena in Ir. Valuable diffusion data are given for the design of Ir-based materials.