Orientation and faulted structure of γ′-phases in lanthanum-alloyed Ni-Al-Cr superalloy

Nikonenko, Elena; Shergaeva, Lyubov’; Popova, Natalya; Koneva, Nina; Qin, Rongshan; Gromov, Victor and Fedorischeva, Marina (2017). Orientation and faulted structure of γ′-phases in lanthanum-alloyed Ni-Al-Cr superalloy. In: AIP Conference Proceedings, AIP Publishing, 1909, article no. 020149.

DOI: https://doi.org/10.1063/1.5013830

Abstract

The paper presents the transmission and the scanning electron microscope investigations of thin foils of Ni-Al-Сr-based superalloy, which is obtained by the directional crystallization technique. This superalloy contains γ′- and γ-phases. Additionally, lanthanum is introduced in the superalloy in 0.015, 0.10 and 0.30 wt % concentrations. The superalloy specimens are then subjected to 1273 K annealing during 10 and 25 h. It is shown that γ′-phase is major. In the superalloy, lanthanides La₂Ni₃ and Al₂La are detected along with carbide La₂C₃ particles located on dislocations of the major phase. The amount of phases in the superalloy depends on its thermal treatment and lanthanum concentration. The investigations include the effect of annealing on scalar density of dislocations in γ′-phase. It is demonstrated that lanthanum alloying modifies the preferred orientation of γ′-phase. Annealing of lanthanum-alloyed superalloy causes the orientation dispersion. In γ′-phase, the correlation is observed between the degree of heterogeneity of solid solution and scalar dislocation density. It is shown that this heterogeneity results in the formation of high-density dislocations in γ′-phase.

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