2013/11/27 by Thomas Hammerschmidt, Arthur F. Bialon, Arthur Bialon +3 · 46 citations
Chemistry · Engineering · Materials Science · Physics and Astronomy · #Ab initio #Ab initio quantum chemistry methods #Advanced Materials Characterization Techniques #Binary number #Chemistry #Condensed matter physics #Crystallography #Electron #Lattice (music) #Materials science #Metal #Metallurgical and Alloy Processes #Microstructure and Mechanical Properties of Steels #Molecule #Physics #Quantum mechanics #Thermodynamics #Transition metal #Valence (chemistry) #Valence electron #cond-mat.mtrl-sci
paper · pdf · doi:10.1088/1367-2630/15/11/115016
published in New Journal of Physics 15(11), 115016 (IOP Publishing)
openalex publication_date 2013/11/27 · arxiv created 2016/05/17 · arxiv updated 2016/05/18 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
In steels and single-crystal superalloys the control of the formation of topologically close-packed (TCP) phases is critical for the performance of the material. The structural stability of TCP phases in multi-component transition-metal alloys may be rationalized in terms of the average valence-electron count and the composition-dependent relative volume-difference . We elucidate the interplay of these factors by comparing density-functional theory calculations to an empirical structure map based on experimental data. In particular, we calculate the heat of formation for the TCP phases A15, C14, C15, C36, χ , μ and σ for all possible binary occupations of the Wyckoff positions. We discuss the isovalent systems V/Nb–Ta to highlight the role of atomic-size difference and observe the expected stabilization of C14/C15/C36/ μ by at Δ N = 0 in V–Ta. In the systems V/Nb–Re, we focus on the well-known trend of A15 → σ → χ stability with increasing and show that the influence of is too weak to stabilize C14/C15/C36/ μ in Nb–Re. As an example for a significant influence of both and , we also consider the systems Cr/Mo–Co. Here the sequence A15 → σ → χ is observed in both systems but in Mo–Co the large size-mismatch stabilizes C14/C15/C36/ μ . We also include V/Nb–Co that cover the entire valence range of TCP stability and also show the stabilization of C14/C15/C36/ μ . Moreover, the combination of a large volume-difference with a large mismatch in valence-electron count reduces the stability of the A15/ σ / χ phases in Nb–Co as compared to V–Co. By comparison to non-magnetic calculations we also find that magnetism is of minor importance for the structural stability of TCP phases in Cr/Mo–Co and in V/Nb–Co.