Thermodynamics of steels: the carbon-carbon interaction energy. @bhadeshia123

Uploaded November 2025 | Updated September 2026, 2 weeks ago

Investigates the behaviour of carbon atoms within austenite and ferrite lattices in steel. The research focuses on the carbon-carbon interaction energy and its role in calculating the thermodynamics of interstitial solid solutions. The author presents both new and existing theoretical and experimental data to model the interaction energy, particularly noting that the model parameter, ω, should be positive, indicating a repulsive interaction between carbon atoms. The text includes several mathematical equations and tables to support the theoretical framework and compare results derived from different models and temperatures. Ultimately, the paper concludes that the present work's model accurately represents the interaction energy and improves upon earlier models.

phase-trans.msm.cam.ac.uk/abstracts/carbon-carbon.html

Thermodynamics of steels: the carbon-carbon interaction energy.

$Kinetics of niobium carbide precipitation in steels Kinetics and thermodynamics of niobium carbide precipitation in steels Welcome back to the channel! In this lecture, we take a deep dive into the physical metallurgy, thermodynamics, and kinetics of niobium carbide (NbC) precipitation in steels. Very often we think about niobium carbide purely in terms of equilibrium solubility products, but in real-world applications, we need to understand how fast it can precipitate and how it behaves over time. Whether you are a student, a researcher, or a professional metallurgist, this video breaks down the mathematical models and physical phenomena that control phase transformations in steel. Thermodynamics & the effect of Mmnganese: We begin by exploring thermodynamic calculations using databases and how empirical experimental data proves that adding manganese actually increases the solubility of niobium carbide in austenite. Ostwald ripening & coarsening: Discover the history of coarsening, tracing back to Ostwalds 1900 paper on interfacial energy (surface tension) and Geoffrey Greenwoods pioneering theory. Learn exactly why incredibly small particles dissolve while larger particles grow to maintain a constant volume fraction. Diffusion & particle growth: Understand the complexities of local equilibrium at the particle interface. We tackle a major problem in precipitation kinetics: how a particle can grow when carbon diffuses orders of magnitude faster than niobium, and how the ternary phase diagram provides a flat carbon concentration gradient to compensate. Nucleation & impingement: A look at the classic equations for nucleation rates, the crucial role of the number density of nucleation sites, and the beautifully simple Johnson-Mehl-Avrami-Kolmogorov theory for calculating how growing particles collide and impinge on one another. Software modelling & bold predictions: Learn the limitations of using commercial software like Dictra or MatCalc, the danger of simply fitting data without generalised parameters, and how to use these models creatively to make bold predictions—like predicting the formation of room-temperature bainite. Real-world engineering applications: We conclude with an exciting real-world application of phase transformation theory: the design of a brand new, highly resilient steel alloy for the shafts of Rolls-Royce civil aircraft engines. Free resource: Everything discussed in this video regarding phase transformations and kinetics is covered in depth in my book. You can download it entirely free of charge from my website! Also, check out the free biography of Geoffrey Greenwood available to download to learn more about the crazy, pioneering history of materials science. If you found this lecture helpful, please leave a like, subscribe for more materials science deep-dives, and let me know your thoughts in the comments below!$

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