Seminars and Events

Strength and stability of Co 3 (Al,W) L12γ'

Date/Time: 16.09.2014. 2:45 p.m.
Place: Ruhr-Universität Bochum, Bochum, Germany

Chris Wolverton, Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois, USA

Although Co-based superalloys are considered as a promising next-generation turbine blade material, there are critical issues concerning poor high-temperature mechanical properties and phase stability that must be addressed before practical application is possible. We explore the fundamental properties for the base Co3 (Al,W) L12γ' using density functional theory. We have predicted the thermodynamic stability of Co3 (Al,W) γ' and found that at low temperatures, γ' is a thermodynamically metastable phase. At higher temperatures, entropy-driven effects may potentially stabilize the structure. We have also predicted the antiphase boundary (APB) energies, a fundamental thermodynamic quantity that influences the high-temperature yield strength anomaly. The Al/W composition dependence of 100 and 111 APB energies are explored for Co3 (Al,W) L12γ'. From these results, we suggest possible methods for improving mechanical properties and phase stability in γ', particularly from alloying.

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