Monitoring the precipitation of the hardening phase in the new VDM® Alloy 780 by in-situ high-temperature small-angle neutron scattering, neutron diffraction and complementary microscopy techniques

0564333 - ÚJF 2023 RIV CH eng J - Journal Article
Solís, C. - Kirchmayer, A. - de Silva, I. - Kummel, F. - Muhlbauer, S. - Beran, Přemysl - Gehrmann, B. - Haghighat, M. H. - Neumeier, S. - Gilles, R.
Monitoring the precipitation of the hardening phase in the new VDM® Alloy 780 by in-situ high-temperature small-angle neutron scattering, neutron diffraction and complementary microscopy techniques.
Journal of Alloys and Compounds. Roč. 928, DEC (2022), č. článku 167203. ISSN 0925-8388. E-ISSN 1873-4669
Institutional support: RVO:61389005
Keywords : Ni-base superalloys * precipitation * small-angle neutron scattering
OECD category: Materials engineering
Impact factor: 6.2, year: 2022
Method of publishing: Limited access
https://doi.org/10.1016/j.jallcom.2022.167203

The hardening phase precipitation process plays an important role in the development of new Ni-base superalloys. In the present work, we apply a powerful combination of complementary characterization techniques to characterize in-situ the gamma' precipitation in the new VDM (R) Alloy 780. During the whole heat treatment process, in-situ time-of-flight (TOF) neutron diffraction (ND) unambiguously identified the gamma' phase as well as its weight fraction and the misfit with the matrix while in-situ small-angle neutron scattering (SANS) provided precise precipitates' size analysis. Atom probe tomography (APT) and scanning electron microscopy (SEM) provided detailed microstructural characterization and chemical composition of the phases necessary for a proper neutron scattering data evaluation. This contribution reveals more de-tailed information on the nucleation, growth, and Ostwald ripening processes starting from the early precipitation stage in bulk samples using the complementary microstructure investigation methods. The nucleation and growth kinetics of precipitates at 720 degrees C depend on heating rates and the size distribution obtained in the pre-heating history of the sample. A subsequent heat treatment step at 620 degrees C, typically used in Ni-base superalloys, does not lead to similar progressive precipitation or growth. The expected matrix-diffusion-controlled Ostwald ripening process of the gamma' precipitates was in-situ monitored by SANS on a full precipitation hardened sample at expected operating temperatures (750 degrees C) showing slower coarsening kinetics than other reported Ni-based superalloys.
Permanent Link: https://hdl.handle.net/11104/0336007