On the nucleation of planar faults during low temperature and high stress creep of single crystal Ni-base superalloys

• Published in: Acta materialia Vol. 144; pp. 642 - 655
• Main Authors: Wu, X., Dlouhy, A., Eggeler, Y.M., Spiecker, E., Kostka, A., Somsen, C., Eggeler, G.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2018
• Subjects: Gamma channel dislocations; Low temperature and high stress primary creep; Ni-base superalloy single crystals; Nucleation of planar faults; Ni-base superalloy single crystals; Low temperature and high stress primary creep; Nucleation of planar faults; Gamma channel dislocations
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2017.09.063

The present work studies the nucleation of planar faults in the early stages of low temperature (750 °C) and high stress (800 MPa) creep of a Ni-base single crystal superalloy (SX). Two families of 60° dislocations with different Burgers vectors were detected in the transmission electron microscope (TEM). These can react and form a planar fault in the γ′ phase. A 2D discrete dislocation model helps to rationalize a sequence of events which lead to the nucleation of a planar fault. First, one 60° channel dislocation approaches another 60° interface dislocation with a different Burgers vector. At a distance of 5 nm, it splits up into two Shockley partials. The interface dislocation is pushed into the γ′-phase where it creates a small antiphase boundary. It can only move on when the leading Shockley partial joins it and creates an overall 1/3 superdislocation. This process is fast and therefore is difficult to observe. The results obtained in the present work contribute to a better understanding of the processes which govern the early stages of low temperature and high stress primary creep of SX. Nucleation of stacking fault in single crystal Ni-base superalloy. [Display omitted]