• Neumeier, S.
• Bezold, A.
• Förner, Andreas
• Göken, Mathias
• Huber, L.-K.
• Völkl, J.
• Freund, L. P.

Abstract

<jats:title>Abstract</jats:title><jats:p>Recent studies revealed the excellent high temperature properties of polycrystalline CoNi-base superalloys. However, their underlying deformation behavior has been reported only scarcely so far. In this work, the deformation mechanisms of four polycrystalline compositionally complex CoNi-base superalloys with slightly varying chemical compositions were investigated by compression and creep experiments at temperatures between 750 °C and 850 °C and strain-rates between 10<jats:sup>–3</jats:sup> and 10<jats:sup>–8</jats:sup> s<jats:sup>−1</jats:sup>. In the two (Ta + Ti)-rich alloys, a transition of the deformation mechanism from shearing by APB-coupled dislocation pairs to stacking fault shearing and finally also to microtwinning is observed with decreasing strain-rate and increasing temperature. In contrast, APB-based shearing mechanisms represent the dominant mechanism in both (Al + W)-rich alloys in all conditions. At high temperatures and low strain-rates, dislocation glide-climb processes also contribute to plastic deformation in all alloys. By correlating the underlying defect structures with the mechanical properties of these alloys, it becomes evident that a transition to stacking fault shearing and microtwinning leads to a lower strain-rate dependency and superior high-temperature strength in comparison with APB-based mechanisms. Reasons for the different deformation mechanisms, the influence of segregation processes, the consequences for mechanical properties and implications for a mechanism-based alloy design are discussed.</jats:p>

Topics

• impedance spectroscopy
• polymer
• experiment
• strength
• chemical composition
• dislocation
• deformation mechanism
• creep
• superalloy
• defect structure
• stacking fault