Effect of Microstructure Instability on Hot Plasticity During Thermomechanical Processing in PM Nickel-Based Superalloy
Ming ZHANG1,2, Guoquan LIU1,2(), Benfu HU1
1 School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China 2 Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China
Cite this article:
Ming ZHANG, Guoquan LIU, Benfu HU. Effect of Microstructure Instability on Hot Plasticity During Thermomechanical Processing in PM Nickel-Based Superalloy. Acta Metall Sin, 2017, 53(11): 1469-1477.
High alloying Ni-based powder metallurgy (PM) superalloys show excellent fatigue performance and damage tolerance properties, and good creep resistance at 750 ℃, and are used for advanced gas turbine disks and other hot components. The hot-working window of high alloying PM superalloy is narrow because of its poor workability. The formation of the γ+γ′ microduplex structure during the thermomechanical processing always results in a decrease in flow stress and a promotion of hot plasticity. However, the stability of the γ+γ′ microduplex structure has not been evaluated. The high temperature flow behavior of a Ni-based superalloy FGH98 prepared by hot isostatic pressing has been examined by means of uniaxial compression testing isothermally at 1060, 1105, 1138 and 1165 ℃ and at constant true strain rates between 0.01 and 10 s-1. The microstructural evolution and instabilities during plastic flow have been studied. Under all testing conditions, the as-hipped material exhibits flow hardening, flow softening and steady-state flow sequentially with the true strain increased. The dynamic recrystallization occurs and the γ+γ′ microduplex structures are generated when steady state flow or highest strains achieved at temperatures below the γ′ solvus. The formation of the γ+γ′ microduplex structures results in a remarkable decrease in grain size and a promotion of hot plasticity. The relationships between steady-state grain sizes and steady-state stresses during deformation and the formation mechanism of the γ+γ′ microduplex structure were analyzed. The possibility of the microstructure controlling during hot working was discussed.
Fund: Supported by National High Technology Research and Development Program of China (No.2015AA034201) and National Natural Science Foundation of China No.51371030
Fig.1 Quantities for sizing irregular planar grain
Fig.2 Microstructure of hot isostatic pressed FGH98 alloy at 1180 ℃, 130 MPa, 3 h (a) and morphology of γ′ phase (b)
Fig.3 True stress-true strain (σ-ε) curves of hot isostatic pressed FGH98 alloy at 1060 ℃ (a), 1105 ℃ (b), 1138 ℃ (c) and 1165 ℃ (d)
Fig.4 Microstructures of as-deformed FGH98 alloy at T=1105 ℃, =1 s-1 and ε =0.2 (a), 0.4 (b), 0.6 (c) (T—temperature, —strain rate)
Fig.5 Microstructures of as-deformed FGH98 alloy at ε =0.6, =1 s-1 and T=1060 ℃ (a), 1105 ℃ (b), 1138 ℃ (c) and 1165 ℃ (d)
Fig.6 Microstructures of as-deformed FGH98 alloy at ε =0.6, T=1105 ℃ and =0.01 s-1 (a), 0.1 s-1 (b), 1 s-1 (c) and 10 s-1 (d)
Fig.7 TEM image of γ+γ′ microduplex structure
Fig.8 Strain induced γ-γ′ interface migration led to dissolution (a) and re-precipitation (b) of γ′phase (D, E and F are the new microduplex structures formed in discontinuous dynamic recrystallization. The arrows indicate the migration of γ-γ′ interface)
Fig.9 Processing maps at ε =0.2 (a), 0.4 (b) and 0.6 (c)
Fig.10 Effect of true strain on grain size (λ), σ and efficiency of power dissipation (η) at T=1105 ℃, =1 s-1
Fig.11 Effect of temperature on grain size, steady-state stress and efficiency of power dissipation at ε =0.6, =1 s-1 (σs—steady state stress)
Fig.12 Relationships between steady-state stress and steady-state grain size at ε =0.6
[1]
Gessinger G H, Bomford M J.Powder metallurgy of superalloys[J]. Int. Metall. Rev., 1974, 19: 51
[2]
Wilkinson N A.Technological considerations in the forging of superalloy rotor parts[J]. Met. Technol., 1977, 4: 346
[3]
Immarigeon J P A, Van Drunen G, Wallace W. The hot working behaviour of Mar M200 superalloy compacts [A]. Superalloys 1976: Proceedings of the Third International Symposium[C]. Seven Springs, PA: TMS, 1976: 463
[4]
Coyne J E.Microstructural control in titanium-and nickel-base forgings; An overview[J]. Met. Technol., 1977, 4: 337
[5]
Semiatin S L, McClary K E, Rollett A D, et al. Plastic flow and microstructure evolution during thermomechanical processing of a PM nickel-base superalloy[J]. Metall. Mater. Trans., 2013, 44A: 2778
[6]
Wu K, Liu G Q, Hu B F, et al.Effect of processing parameters on hot compressive deformation behavior of a new Ni-Cr-Co based P/M superalloy[J]. Mater. Sci. Eng., 2011, A528: 4620
[7]
Ning Y Q, Yao Z K, Li H, et al.High temperature deformation behavior of hot isostatically pressed P/M FGH4096 superalloy[J]. Mater. Sci. Eng., 2010, A527: 961
[8]
Alniak M O, Bedir F.Modelling of deformation and microstructural changes in P/M René 95 under isothermal forging conditions[J]. Mater. Sci. Eng., 2006, A429: 295
[9]
Liu Y H, Ning Y Q, Yao Z K, et al.Plastic deformation and dynamic recrystallization of a powder metallurgical nickel-based superalloy[J]. J. Alloys Compd., 2016, 675: 73
[10]
He G A, Liu F, Si J Y, et al.Characterization of hot compression behavior of a new HIPed nickel-based P/M superalloy using processing maps[J]. Mater. Des., 2015, 87: 256
[11]
Zhang C, Zhang L W, Li M F, et al.Effects of microstructure and γ′ distribution on the hot deformation behavior for a powder metallurgy superalloy FGH96[J]. J. Mater. Res., 2014, 29: 2799
[12]
Zhang H B, Zhang K F, Lu Z, et al.Hot deformation behavior and processing map of a γ′-hardened nickel-based superalloy[J]. Mater. Sci. Eng., 2014, A604: 1
[13]
Wu K, Liu G Q, Hu B F, et al.Characterization of hot deformation behavior of a new Ni-Cr-Co based P/M superalloy[J]. Mater. Charact., 2010, 61: 330
[14]
Zhang M J, Li F G, Wang S Y, et al.Characterization of hot deformation behavior of a P/M nickel-base superalloy using processing map and activation energy[J]. Mater. Sci. Eng., 2010, A527: 6771
[15]
Kandeil A Y, Immarigeon J P A, Wallace W, et al. Flow behaviour of Mar M200 powder compacts during isothermal forging[J]. Met. Sci., 1980, 14: 493
[16]
Alniak M O, Bedir F.Change in grain size and flow strength in P/M René 95 under isothermal forging conditions[J]. Mater. Sci. Eng., 2006, B130: 254
[17]
Kikuchi S, Ando S, Shu F, et al.Superplastic deformation and microstructure evolution in PM IN-100 superalloy[J]. J. Mater. Sci., 1990, 25: 4712
[18]
Yu Q Y, Yao Z H, Dong J X.Deformation and recrystallization behavior of a coarse-grain, nickel-base superalloy Udimet720Li ingot material[J]. Mater. Charact., 2015, 107: 398
[19]
Chen J Y, Dong J X, Zhang M C, et al.Deformation mechanisms in a fine-grained Udimet 720LI nickel-base superalloy with high volume fractions of γ′ phases[J]. Mater. Sci. Eng., 2016, A673: 122
[20]
Zhang B J, Zhao G P, Zhang W Y, et al.Deformation mechanisms and microstructural evolution of γ+γ′ duplex aggregates generated during thermomechanical processing of nickel-base superalloys [A]. Proceedings of the 13th International Symposium on Superalloys[C]. Seven Springs, PA: TMS, 2016: 487
[21]
Exner H E.Analysis of grain-and particle-size distributions in metallic materials[J]. Int. Metall. Rev., 1972, 17: 25
[22]
Hu B F, Jin K S, Li H Y, et al.The interaction of recrystallizing interfaces with precipitates in a P/M nickel-base superalloy[J]. J. Univ. Sci. Eng. Beijing, 1993, 15: 14(胡本芙, 金开生, 李慧英等. FGH95合金再结晶界面与晶内析出γ′相的作用[J]. 北京科技大学学报, 1993, 15: 14)
[23]
Menzies R G, Davies G J, Edington J W.Microstructural changes during recrystallization of powder-consolidated nickel-base superalloy IN-100[J]. Met. Sci., 1981, 15: 217
[24]
Prasad Y V R K, Gegel H L, Doraivelu S M, et al. Modeling of dynamic material behavior in hot deformation: Forging of Ti-6242[J]. Metall. Trans., 1984, 15A: 1883
[25]
Prasad Y V R K, Seshacharyulu T. Modelling of hot deformation for microstructural control[J]. Int. Mater. Rev., 1998, 43: 243
[26]
Immarigeon J A, Floyd P H.Microstructural instabilities during superplastic forging of a nickel-base superalloy compact[J]. Metall. Trans., 1981, 12A: 1177
[27]
Lin Y C, Wu X Y, Chen X M, et al.EBSD study of a hot deformed nickel-based superalloy[J]. J. Alloys Compd., 2015, 640: 101
[28]
Chen X M, Lin Y C, Wen D X, et al.Dynamic recrystallization behavior of a typical nickel-based superalloy during hot deformation[J]. Mater. Des., 2014, 57: 568
[29]
Menzies R G, Edington J W, Davies G J.Superplastic behaviour of powder-consolidated nickel-base superalloy IN-100[J]. Met. Sci., 1981, 15: 210
