Evolutions of microstructure and lattice misfit in a γ′-rich Ni-based superalloy during ultra-high temperature thermal cycle. (August 2018)

• Record Type: Journal Article
• Authors: Luo, Liang; Ma, Yue; Li, Shusuo; Pei, Yanling; Qin, Lu; Gong, Shengkai
• Is Part Of: Intermetallics. Volume 99(2018:Aug.)
• Page Start: 18
• Page End: 26
• Publication Date: 2018-08
• Subjects: Lattice misfit -- Microstructure -- Secondary γ' phase -- Thermal cycle -- Ultra-high temperature; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2018.05.011
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: The microstructure and lattice misfit of a γ′-rich superalloy during an ultra-high temperature thermal cycle (25–1200 °C) were studied. The cubic γ' precipitate gradually dissolved as the temperature increased from 900 °C to 1200 °C. Upon subsequent cooling, numerous tiny secondary γ' phases precipitated from the supersaturated γ channel. The microstructure was composed of a bimodal distribution of coarsened primary γ' and secondary γ' after the first ultra-high temperature thermal cycle. In subsequent thermal cycles, the secondary γ' dissolved gradually (or re-precipitated), and the primary γ' remained relatively stable. The dissolution of the γ′ phase led to a smaller absolute value of the lattice misfit. Interestingly, the lattice misfit was strongly dependent on the variation of the γ′ volume fraction during the thermal cycles, which exhibited good inheritance. Highlights: Lattice misfit of a Ni-based superalloy during thermal cycle was determined by high-temperature XRD technique. Evolution mechanism of microstructure during multiple ultra-high temperature thermal cycles was analysed. The lattice misfit was strongly dependent on the variation of γ′ fraction during cycles, which exhibited good inheritance.