How Nanoscale Dislocation Reactions Govern Low- Temperature and High-Stress Creep of Ni-Base Single Crystal Superalloys

0534080 - ÚFM 2021 RIV CH eng J - Journal Article
Bürger, D. - Dlouhý, Antonín - Yoshimi, K. - Eggeler, G.
How Nanoscale Dislocation Reactions Govern Low- Temperature and High-Stress Creep of Ni-Base Single Crystal Superalloys.
Crystals. Roč. 10, č. 2 (2020), č. článku 134. ISSN 2073-4352. E-ISSN 2073-4352
Institutional support: RVO:68081723
Keywords : electron-microscopy * planar defects * precipitation * mechanisms * anisotropy * phase * shear * microstructure * deformation * faults * dislocation reactions * single crystal Ni-base superalloys * shear creep testing * transmission electron microscopy * nucleation of planar fault ribbons
OECD category: Materials engineering
Impact factor: 2.589, year: 2020
Method of publishing: Open access
https://www.mdpi.com/2073-4352/10/2/134

The present work investigates gamma-channel dislocation reactions, which govern low-temperature (T = 750 degrees C) and high-stress (resolved shear stress: 300 MPa) creep of Ni-base single crystal superalloys (SX). It is well known that two dislocation families with different b-vectors are required to form planar faults, which can shear the ordered gamma'-phase. However, so far, no direct mechanical and microstructural evidence has been presented which clearly proves the importance of these reactions. In the mechanical part of the present work, we perform shear creep tests and we compare the deformation behavior of two macroscopic crystallographic shear systems [011 over bar ](111) and [112 over bar ](111). These two shear systems share the same glide plane but differ in loading direction. The [112 over bar ](111) shear system, where the two dislocation families required to form a planar fault ribbon experience the same resolved shear stresses, deforms significantly faster than the [011 over bar ](111) shear system, where only one of the two required dislocation families is strongly promoted. Diffraction contrast transmission electron microscopy (TEM) analysis identifies the dislocation reactions, which rationalize this macroscopic behavior.
Permanent Link: http://hdl.handle.net/11104/0312299