Analysis of Deformation in a High Entropy Alloy Using an Internal State Variable Model
- 1 Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA
- 2 Boyer School of Natural Sciences, Mathematics, and Computing, Saint Vincent College, Latrobe, PA, USA
Abstract
Deformation in the model high entropy alloy CoCrFeMnNi is assessed using an internal state variable constitutive model. A remarkable property of these alloys is the extraordinarily high strain hardening rates they experience in the plastic region of the stress strain curve. Published stress-strain measurements over a range of temperatures are analyzed. Dislocation obstacle interactions and the observed high rate of strain hardening are characterized in terms of state variables and their evolution. A model that combines a short-range obstacle and a long-range obstacle is shown to match experimental measurements over a wide range of temperatures and grain sizes. The long-range obstacle is thought to represent interactions of dislocations with regions of incomplete mixing or partial segregation. Dynamic strain aging also is observed at higher temperatures. Comparisons with measurements in austenitic stainless steel show some common trends.
- Zhang, Y., Zuo, T.T., Tang, Z., Gao, M.C., Dahmen, K.A., Liaw, P.K. and Lu, Z.P. (2014) Microstructures and Properties of High-Entropy Alloys. Progress in Materials Science, 61, 1-93. https://doi.org/10.1016/j.pmatsci.2013.10.001
- Otto, F., Dlouhy, A., Somsen, Ch., Bei, H., Eggeler, G. and George, E.P. (2013) The Influences of Temperature and Microstructure on the Tensile Properties of a CoCrFeMnNi High-Entropy Alloy. Acta Materialia, 61, 5743-5755. https://doi.org/10.1016/j.actamat.2013.06.018
- Licavoli, J.J., Gao, M.C., Sears, J.S., Jablonski, P.D. and Hawk, J.A. (2015) Microstructure and Mechanical Behavior of High-Entropy Alloys. Journal of Materials Engineering and Performance, 24, 3685-3698. https://doi.org/10.1007/s11665-015-1679-7
- Laplanche, G., Gadaud, P., Horst, O., Otto, F., Eggeler, G. and George, E.P. (2015) Temperature Dependencies of the Elastic Moduli and Thermal Expansion Coefficient of an Equiatomic, Single-Phase CoCrFeMnNi High-Entropy Alloy. Journal of Alloys and Compounds, 623, 348-353. https://doi.org/10.1016/j.jallcom.2014.11.061
- Follansbee, P.S. (2014) Fundamentals of Strength—Principles, Experiment, and Applications of an Internal State Variable Constitutive Formulation. The Minerals, Metals, and Materials Society, John Wiley & Sons, Hoboken, NJ. https://doi.org/10.1002/9781118808412
- Follansbee, P.S. (2015) Structure Evolution in Austenitic Stainless Steels. Materials Sciences and Applications, 6, 457-463. https://doi.org/10.4236/msa.2015.66049