On the formation of disordered solid solutions in multi-component alloys

By Anil Kumar Singh, A. Subramaniam. Journal of Alloys and Compounds, 2014

180 citations recorded by the source corpus.

In high entropy alloys (HEA) a disordered solid solution (DSS) is entropically stabilized in competition with possible intermetallic compounds or phase separation. Ranges for many parameters (ΔRmax, ‘δ’, ΔHmix, ΔSmix, Ω) have been prescribed in literature for the formation of HEA. In the current investigation, we show that not withstanding the centrality of entropy in the stabilization of a DSS, other factors (parameters) like valence electron concentration, atomic size differences between the elements and enthalpy of mixing, play a significant role in the formation of phases. To illustrate the issues involved in the formation of DSS and to understand the phase formation, selected ternary (CoFeNi, CrFeNi), quaternary (CoCrFeNi, CuCoFeNi, AlCrFeNi) and penternary alloys (AlCuCoFeNi) are chosen for the experimental investigations and for the calculation of different parameters. It is shown that the ranges for the relevant parameters prescribed in literature are not satisfactory. It is possible that a (single) DSS can form, even if the entropy of mixing is small, provided all the relevant parameters are within favorable ranges. Contrastingly enough, violation of any of the parameters results in the formation of multiple phases or compounds. Strict and reduced definitions of HEA are invoked to understand the results.

Subfields: Aerospace Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/d08c637608ad82dcb6131b3039b1366f5d1a7332

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In Aerospace Engineering

1. E. Pickering
2. N. Jones
3. Huahai Mao
4. Hai-lin Chen
5. Qing Chen

In Mechanical Engineering

1. E. Pickering
2. N. Jones
3. Huahai Mao
4. Hai-lin Chen
5. Qing Chen
6. O. A. Zambrano

Citations in the corpus

• TCHEA1: A Thermodynamic Database Not Limited for “High Entropy” Alloys (2017, background): “Single Fcc structure was observed in the as-cast Co1Cr1Fe1Ni1 alloy,([32]) and the alloy annealed at 850 C for 24 h([33]) and 750 C for 800 h.”
• High-entropy alloys: a critical assessment of their founding principles and future prospects (2016, background): “Others have used alternative means of comparison – for instance, Singh et al.173 have suggested the use the parameter L = DSmix/d2, while Wang et al.266,271 replaced δ with a new parameter for the measure of atomic size mismatch, arguing that δ does not distinguish effectively enough between systems”
• Single-phase high-entropy alloys – an overview (2014, unknown): “CrFeCoNi AC a – [25] CrFeCoNi 850°C, 24 h a – [26] CrFeCoNi 1200°C, 24 h cF4-Cu,- M [27] CrCoNiMn 1100°C, 24 h cF4-Cu,- M [27] FeCoNiMn 1100°C, 24 h cF4-Cu,- M [27] CrFeNiMn 1100°C, 24 h a M [27] CrFeCoMn 1100°C, 24 h a M [27] CrFeCoNiMn 1200°C, 24 h cF4-Cu,- M [27] CrFeCoNiCu AC a – [25] Cr”