Theory of strengthening in BCC high entropy alloys

William Curtin, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

The refractory BCC High Entropy Alloys (HEAs) in the class of Mo-Nb-Ta-V-W are very strong (1-1.5 GPa) at room temperature and have exceptional retained strengths of 400-500 MPa at 1600 °C. The mechanistic origin of these outstanding properties is not yet understood, in spite of extensive experimental studies of these and related alloys. Here, we present a parameter-free theory for the strength versus temperature in this class of BCC HEAs. Excellent agreement with results from direct large-scale atomistic simulations at T=0K is achieved for a range of alloys. Moreover, very good agreement with experiments is achieved for the same alloys at T=300 °C, and for the two alloys MoNbTaW and MoNbTaVW that have been studied up T=1600 °C. The fundamental origins of the high retained strength are explained. The theory then enables computationally-guided design of new alloy compositions aiming for the highest retained strengths and strength-to-weight ratios in this family of alloys, and several compositions are proposed.

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Session M2: Moday, 25 June 2018

Start: 02:15 p.m.
End: 03:00 p.m.