|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Characterization of Minerals, Metals, and Materials
||Creation of Thermally Stable Precipitate Structures in a Ni-Base Superalloy through Compositional Modification
||Donald McAllister, Andrew Detor, Richard DiDomizio, Rongpei Shi, Yunzhi Wang, Michael Mills
|On-Site Speaker (Planned)
Ni-base superalloy 718 with compositional modifications has been shown to have complex precipitates which enhance thermal stability. Altering the (Al+Ti)/Nb ratio increases the likelihood of producing complex particles. Adding γ′ formers inverts the apparent precipitation sequence. Low quantities of γ′ formers allow the γ′′ phase to precipitate first, but γ′ nucleates first when the (Al+Ti)/Nb ratio is increased. High resolution high angle dark field imaging coupled with energy dispersive x-ray spectroscopy has been used to confirm the presence of the γ′ and γ′′ phase, as well as their proximity to one another. Following slow continuous cooling from solution, alloys high in γ′ formers showed heterogeneous precipitation of large γ′′ on a preexisting large γ′. Alloys low in γ′ formers allow small γ′ to heterogeneously nucleate on prexisting γ′′. This understanding is being used to develop alloys that precipitate thermally stable, fine-scale precipitate populations in large scale forging upon slow cooling.
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