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| INFLUENCE OF Nb ON STEADY-STATE CREEP BEHAVIOUR OF Ni-Cr-Ti TYPE WROUGHT SUPERALLOY |
| GUO Encai (Central Iron and Steel Research Institute; Ministry of Metallurgical Industry; Belling); HAN Zhiyuan; YU Shuyou(Research Institute of Qiqihar Steel Works)(Manuscript received 17 August; 1982; revised manuscript 26 August; 1983) |
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Cite this article:
GUO Encai (Central Iron and Steel Research Institute; Ministry of Metallurgical Industry; Belling); HAN Zhiyuan; YU Shuyou(Research Institute of Qiqihar Steel Works)(Manuscript received 17 August; 1982; revised manuscript 26 August; 1983). INFLUENCE OF Nb ON STEADY-STATE CREEP BEHAVIOUR OF Ni-Cr-Ti TYPE WROUGHT SUPERALLOY. Acta Metall Sin, 1984, 20(5): 305-312.
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Abstract The distribution of Nb among γ, γ' and carbide phases is found to be about 5: 3: 1 in the Ni-Cr-Ti type wrought superalloy of various Nb contents. With the increasing content of Nb, the stress-exponent, n, decreases and the apparent creep activation energy, Q_(app), increases and fulfils the expression: Q_(app)=B e~(kx/lge) The grain size of the alloy and the stacking fault energy of γ matrix may be decreased by the Nb added. The steady-state creep rate, ε, obeys the following relationship: s∝L~bγ_(SFE)~α The volume fraction, the particle radius and the long range order of the γ'-phase may be also increased by the Nb added. If the effective stress(σ-σ_b) was introduced to describe the stress relationship of the steady-state creep rate, the typicalcreep equation may be: S=A_1L~bγ_(SFE)~α(σ-σ_b)~n 0exp(-(Q_(app)/RT)where σ_b is the average tensile stress opposing dislocation motion in creep. An observation on the thin foil specimens under TEM shows that the perfect dislocation α/2[10] cutting γ'-phase in glide plane (111) is resolved into two partial dislocations α/6-[11] and α/6[2]. The spacings of superlattice dislocation pairs examined are about 100—165 which fit in nearly with the measured particle size of γ'-phase.
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Received: 18 May 1984
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4 Purushothaman, S.; Tien, J. K., Acta Metall., 26(1978) , 519．
5 Marcinkowrki, M. J. et al., Acta Metall., 9(1961) , 129．E |
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