Creep deformation of Co-Re-Ta-C alloys with varying C content-investigated in-situ by simultaneous synchrotron radiation diffraction

0489159 - ÚJF 2019 RIV CH eng J - Journal Article
Karge, L. - Gilles, R. - Mukherji, D. - Stark, A. - Beran, Přemysl - Schell, N. - Hofmann, M. - Strunz, Pavel - Hausler, J. - Rösler, J.
Creep deformation of Co-Re-Ta-C alloys with varying C content-investigated in-situ by simultaneous synchrotron radiation diffraction.
Materials Science and Engineering A Structural Materials Properties Microstructure and Processing. Roč. 719, č. 3 (2018), s. 124-131. ISSN 0921-5093. E-ISSN 1873-4936
Institutional support: RVO:61389005
Keywords : high temperature creep * Co alloys * synchrotron diffraction * neutron diffraction * dilatometer
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 4.081, year: 2018

The creep deformation of precipitation hardened Co-Re-Ta-C alloys is investigated during in-situ synchrotron diffraction experiment at 1373 K. At room temperature, the alloys have a structure consisting of epsilon-Co (hcp) and metastably retained gamma-Co (fcc) and are strengthened by precipitates of the mono-carbide of Ta, which are finely dispersed in the alloy matrix. The alloy exhibits an allotropic epsilon -> gamma-Co phase transformation when heating to >1173 K. A lower C content in the alloy generally promotes this transformation. It is shown that this transformation is strongly influenced by application of compressive load. The transformation epsilon -> gamma-Co at high temperature under load leads to microstructure refinement and subsequently to dissolution of hardening precipitates. This results in a considerable acceleration of the creep rate. Further, the equilibrium ratio of gamma/epsilon-Co phase is significantly altered under compressive load. This behavior is attributed to a volume relaxation as the epsilon- and gamma-Co phase have different unit cell volumes.
Permanent Link: http://hdl.handle.net/11104/0283629