AFM, SEM and TEM study of damage mechanisms in cyclically strained mar-M247 at room temperature and high temperatures

0525280 - ÚFM 2021 RIV NL eng J - Journal Article
Šulák, Ivo - Obrtlík, Karel
AFM, SEM and TEM study of damage mechanisms in cyclically strained mar-M247 at room temperature and high temperatures.
Theoretical and Applied Fracture Mechanics. Roč. 108, AUG (2020), č. článku 102606. ISSN 0167-8442. E-ISSN 1872-7638
R&D Projects: GA MPO(CZ) EG15_019/0002421
Institutional support: RVO:68081723
Keywords : Nickel-based superalloy * Low-cycle fatigue * High temperature * SEM * FIB * TEM * AFM
OECD category: Materials engineering
Impact factor: 4.017, year: 2020
Method of publishing: Limited access
https://www.sciencedirect.com/science/article/pii/S0167844220301828?via%3Dihub

Cylindrical specimens of ´precipitate strengthened superalloy MAR-M247 were cyclically strained under total strain control conditions using a symmetrical push–pull cycle at 23 °C, 700 °C and 800 °C in air. The fatigue hardening/softening curves and low cycle fatigue life curves are presented. Special attention is paid to the effect of temperature on plastic strain localisation and fatigue crack initiation at 23 °C, 700 °C and 800 °C. Plastic strain localisation into dislocation-rich slabs parallel to the {111} slip planes was found at 23 °C and 700 °C. Plastic strain localisation manifested itself by the formation of pronounced surface relief, known as persistent slip markings (PSMs), at locations where dislocation-rich bands emerged on the surface. PSMs consisted of extrusions accompanied by parallel intrusions, where the intrusions were identified as primary crack nucleation sites at 23 °C. With an increase in the testing temperature to 700 °C, the impact of PSMs on fatigue crack initiation was reduced. At 800 °C, the appearance of both PSMs and dislocation arrangement changed significantly. The short PSMs with a wavy character appeared and bands of superlattice stacking faults (SSFs) on {111} planes with Burgers vector b of 〈112〉 type were identified. At 800 °C, fatigue cracks were initiated at the defects and carbides.
Permanent Link: http://hdl.handle.net/11104/0310344