Design of new Co-Al-W-based alloys
Start date: Sep 1, 2013,
End date: Aug 31, 2017
"New Co-Al-W-base superalloys will become an essential technology for high efficiency energy generation and transportation. As more pressure is placed on currently available single-crystal Ni-based superalloys to perform at even higher temperatures, Co-Al-W-base superalloys are likely to become their replacement in the future. Recent studies have shown that this new class of alloys possesses interesting high-temperature properties, including pronounced anomalous yield strength, good high temperature creep properties, and low segregation upon solidification. The small gamma/gamma’ lattice misfit means that a high fraction of gamma’ precipitates can grow semi-coherently within the gamma matrix maintaining a cuboidal morphology, the optimal microstructure for components in the hottest parts of gas turbines and jet engines. Unfortunately, the stability of the gamma’ strengthening phase is still questionable, and adopting experimentation to study the full alloy design space is impractical. The overall aim of this proposal is to develop and apply state-of-the-art modelling methods to address the stability and performance of these alloys, reducing the alloy design space considerably. A few attempts to use ab initio simulations to investigate the stability of the gamma’ phase have been made, but these have failed to either prove or disprove the presence of the gamma’ phase in the Co-Al-W ternary system as no entropy contributions were evaluated. Understanding whether the gamma’ phase is stable, and determining how alloying can be used to stabilise it, will significantly impact the design of these alloys as well as provide insights on several aspects of physical metallurgy. The results of this work are expected to guide future experimentation and lead to new high-performance alloy candidates for use in the gas turbines and jet engines, building considerable positive industrial, financial and environmental impact."
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