Speaker
Description
Body-centered-cubic (BCC) high entropy alloys show exceptional strengths up to 1900K [1]. Few such alloys have been tested. Fundamental understanding of the mechanisms that control strengthening is necessary to formulate theories that enable screening over the immense compositional HEA space.
Supported by the recent experimental findings in NbTaTiV and CrMoNbV alloys [2], we show with theory [3] that edge dislocations can control the yield strength in BCC high entropy alloys. We have also formulated a theory for screw dislocation strengthening [4], showing that the cross-kinking controls the high temperature strength of screw dislocations. Cross-kinking cannot persist up to high temperatures, where vacancy and self-interstitials migration can occur.
The theory of edge dislocation strengthening is based on the interaction of the edge dislocations with the random field of solutes in the HEAs. Theory rationalizes and captures experiments on BCC alloys. The theory is cast in an analytical form that is parameter-free and depends on physical quantities (alloy concentrations, lattice parameter, elastic constants, misfit volumes) that can be determined ab-initio or experimentally. By using the Vegard's law on the elemental quantities, we perform screening over 10 million compositions in the whole Al-Cr-Mo-Nb-Ta-W-V-Ti-Zr-Hf alloy family to find the strongest BCC HEAs.
References
[1] O. N. Senkov, G.B. Wilks, J.M. Scott, D.B. Miracle (2011) Intermetallics 19, 698-706.
[2] F. Maresca, C. Lee, R. Feng, Y. Chou, T. Ungar, M. Widom, K. An, J.D. Poplawsky, Y.-C. Chou, P.K. Liaw, W.A. Curtin (2020) Under Review (pre-pring available on Arxiv:2008.11671)
[3] F. Maresca, W.A. Curtin (2020) Acta Materialia 182, 235-249.
[4] F. Maresca, W.A. Curtin (2020) Acta Materialia 182, 144-162.
| Speaker Country | Netherlands |
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