On the stress and temperature dependence of low temperature and high stress shear creep in Ni-base single crystal superalloys

0534084 - ÚFM 2021 RIV CH eng J - Journal Article
Bürger, D. - Dlouhý, Antonín - Yoshimi, K. - Eggeler, G.
On the stress and temperature dependence of low temperature and high stress shear creep in Ni-base single crystal superalloys.
Materials Science and Engineering A Structural Materials Properties Microstructure and Processing. Roč. 795, SEP (2020), č. článku 139961. ISSN 0921-5093. E-ISSN 1873-4936
R&D Projects: GA MŠMT(CZ) EF16_025/0007304
Institutional support: RVO:68081723
Keywords : steady-state creep * electron-microscopy * power-law * microstructure * deformation * anisotropy * reduction * metals * faults * Ni-base superalloy single crystals * Shear creep deformation * Low-temperature high-stress creep * Stress exponent * Activation energy * Dislocation mechanisms
OECD category: Materials engineering
Impact factor: 5.234, year: 2020
Method of publishing: Open access
https://www.sciencedirect.com/science/article/pii/S0921509320310339?via%3Dihub

In the present work, we investigate the stress and temperature dependence of low-temperature (750 + 20 degrees C) and high-stress (300 + 20 MPa) shear creep of a Ni-base single crystal superalloy. From continuous isothermal experiments and stress and temperature change tests the stress exponent n and the apparent activation energy Q(app) of the phenomenological Sherby-Dorn equation were determined for the two macroscopic crystallographic shear systems (MCSS) [01 (1) over bar](111) and [11 (2) over bar] (111). The activation parameters of creep, the stress exponents and the apparent activation energies were identified as 16 and 620 kJ/mol (MCSS: [01 (1) over bar](111)) and 14 and 460 kJ/mol (MCSS: [11 (2) over bar] (111)). We show that during shear creep testing these phenomenological parameters do not change between the early (0.5-1% strain) and later stages of creep (4.5-5% strain), in contrast to what was observed for uniaxial tensile testing. The results are discussed in the light of what is known about stress and temperature dependencies of deformation rates in the creep literature and in view of the recent work by Burger et al., 2020, who combined shear creep testing with analytical transmission electron microscopy to identify the elementary deformation mechanism, which governs low temperature and high stress creep.
Permanent Link: http://hdl.handle.net/11104/0312303