Criterion for Sigma Phase Formation in Cr- and V-Containing High-Entropy Alloys

By Ming-Hung Tsai, K.-Y. Tsai, Che-Wei Tsai, Chi Lee, Chien-Chang Juan, Jien‐Wei Yeh. 2013

362 citations recorded by the source corpus.

Formation of the σ phase has been observed in quite a few high-entropy alloys (HEAs) recently. The σ phase significantly enhances the hardness of the alloys but reduces their ductility. Thus, controlling the formation of σ phase through proper design is critical for HEAs. However, theories to predict the σ phase formation based on HEA composition are still not available. Here, we demonstrate that the σ phase formation is directly related to the valence electron concentration (VEC) of the alloy. The σ-phase-forming VEC range was systematically studied and revealed. Such finding is of crucial importance to the future design of HEAs.

Subfields: Aerospace Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/a088b893205f1a4f07a7d5ab3b43cbdb3ab40b64

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Citations in the corpus

Laves-phase formation criterion for high-entropy alloys (2017, methodology): “84 σ phase formation in Cr- and V-containing HEAs is expected.(15) The ΔSmix, ΔHmix, Ω, δr, γ, VEC, e/a, ΔχPauling and ΔχAllen parameters for the studied AlCrxNbTiV and AlxCrNbTiVZr alloys were calculated in accordance with formulas (1)–(9) and were summarised in Table 1.”
Phase selection rules for cast high entropy alloys: An overview (2015, background): “Interestingly, Tsai et al.50 found that the VEC rule can even be used to predict the formation of s phase in cast Cr and V containing HEAs, and furthermore, the VEC range for the formation of s phase is 6.88vVECv7.”
Effects of electro-negativity on the stability of topologically close-packed phase in high entropy alloys (2014, methodology): “used VEC to predict the existence of the s phase (the s phase is one type of the TCP phases) in HEAs [24].”
Effect of V content on microstructure and mechanical properties of the CoCrFeMnNiVx high entropy alloys (2015, background): “88, where transformation is expected of the fcc phase to a bcc phase [21] or sigma phase [33].”
A critical review of high entropy alloys and related concepts (2016, background): “Compositions for BCC and FCC phases are separated in as-cast AlxCoCrCuFeNi and AlxCoCrFeNi2 alloys (0 x 2) [29], and s phase formation is predicted in annealed alloys containing Cr and Fe along with Al, Co, Mn, Ni, Ti and/or V [159].”
Exploration and Development of High Entropy Alloys for Structural Applications (2014, methodology): “The average valence electron concentration, VEC, has also been used to rationalize formation of intermetallic phases [51].”
A second criterion for sigma phase formation in high-entropy alloys (2016, background): “[20,26] In particular, a criterion for sigma phase formation in HEAs was proposed.[26] The criterion states that HEAs containing Cr and V as A elements are prone to sigma phase formation if their valence electron concentrations (VECs) fall between 6.”
High-entropy alloys: a critical assessment of their founding principles and future prospects (2016, methodology): “For instance, the melting-point D values for Pt diffusion in Cu and W diffusion in Ni recorded by Brown and Ashby215 are below the lowest values measured for D in CrMnFeCoNi by Tsai et al.209 Aside from direct measurements of diffusivities, there is a great deal of experimental evidence that implies”