단조용 초내열합금, Nimonic 80A 의 시효처리에 따른 석출거동 연구 = Transformations/Precipitation Behavior of Wrought Superalloy, Nimonic 80A with Aging Treatment

다국어 초록 (Multilingual Abstract)

Precipitation reaction during aging treatment has been investigated for Ni base superalloy, Nimonic 80A. The Rietveld analysis of X-ray diffraction profiles obtained from the powder samples, which had been electrochemically extracted and collected on the filter paper, has been employed for the quantification of the constituent phases such as γ' and carbides. The average particle size of γ' phase could be calculated from the Rietveld analysis. As the aging time increases, the fraction of γ' phase increases and its average particle size varies proportionally to (aging time)^½, which implies that the diffusion of solute atom is the controlling step for the γ' particle growth. The fractional increase of γ' phase is mostly caused by the particle growth controlled by the diffusion of solute elements like Ti and Al. The fractional change of γ' phase has been expressed against aging time in the form of the well known Avrami equation. Both MC-type carbide and M_(23)C_6-type carbide has been observed in as-solution treated alloy as well as the aged one. While MC carbide has been dissolved into γ matrix with aging treatment progressing. M_(23)C_6 carbide has been precipitated during aging treatment. This type of carbide reaction has been explained by calculating the thermodynamic equilibrium of Nimonic 80A.