Effects of Initial Grain Size and Strengthening Phase on Thermal Deformation and Recrystallization Behavior of GH4096 Superalloy
LI Fulin1,2, FU Rui1,2(), BAI Yunrui3, MENG Lingchao1,2, TAN Haibing3, ZHONG Yan3, TIAN Wei3, DU Jinhui1,2, TIAN Zhiling2
1GaoNa Aero Material Co., Ltd., Beijing 100081, China 2Central Iron and Steel Research Institute Co., Ltd., Beijing 100081, China 3AECC Sichuan Gas Turbine Research Institute, Chengdu 610400, China
Cite this article:
LI Fulin, FU Rui, BAI Yunrui, MENG Lingchao, TAN Haibing, ZHONG Yan, TIAN Wei, DU Jinhui, TIAN Zhiling. Effects of Initial Grain Size and Strengthening Phase on Thermal Deformation and Recrystallization Behavior of GH4096 Superalloy. Acta Metall Sin, 2023, 59(7): 855-870.
GH4096 alloy were used for disks and shafts of advanced gas turbine engines owing to its excellent properties such as resistance to creep, fatigue, and corrosion as well as microstructure stability up to about 700oC. In this study, GH4096, a hard-to-deform disk superalloy, was processed through an advanced cast and wrought route to avoid the expensive power metallurgy (P/M) route. Many types of full-scale disk forgings possessing homogeneous fine-grained microstructures were successfully carried out, and the ultrasonic inspectability was comparative to that of the alloy produced by the P/M route. The effects of the initial grain size and strengthening phase on hot deformation behavior and dynamic recrystallization (DRX) were studied by OM, SEM, EBSD, and TEM under different deformation parameters. The results showed that as the initial grain size decreased within the temperature range of 1050-1120oC, the flow peak stresses decreased and the fractions of DRX increased. With an increase in the initial grain size, the thermal deformation temperature required for complete dynamic recrystallization decreased, and also the critical strain of dynamic recrystallization decreased. The initial grain size and the strain did not affect the recrystallized grain size when deformed at a sub-solvus temperature. The thermal deformation constitutive equations related to the initial grain sizes were established and the activation energies of thermal deformation related to the original grain sizes were calculated. The effect of γ' phase size on the thermal deformation behavior in as-cast microstructure was studied. In the sub-solvus temperature range, the thermal deformation resistance could be effectively reduced with the increase in the size of γ' phase, the critical strain of DRX was decreased, and the DRX fraction was also increased. The dynamic recrystallization mechanisms related to the γ' phase and initial grain size were also discussed. DRX nucleation takes place at the sub-grains near original grain boundaries for samples with larger initial grain size deformed at sub-solvus temperature. For samples with fine initial grain size, the interface slip of incoherent γ' phase is the significant dynamic softening mechanism during the sub-solvus temperature deformation. For as-cast samples, the main dynamic softening mechanism is original grain boundary bowing out DRX nucleation and coarse second-phase-induced DRX nucleation.
Fig.1 OM images of d1-d4 samples with different initial grain sizes before hot deformation (a) d1 (180 μm) (b) d2 (90 μm) (c) d3 (45 μm) (d) d4 (15 μm)
Fig.2 OM images (a, b) and SEM images of γ' phase (c, d) of as-cast samples treated by different processes before hot compression (a, c) c1 (1 μm) (b, d) c2 (2 μm)
Fig.3 True stress-strain curves (a-d) and peak stress curves (e) of samples d1-d4 under thermal compression at the strain rate of 0.1 s-1 and different temperatures (a) 1060oC (b) 1080oC (c) 1100oC (d) 1120oC (e) comparison of peak stress
Fig.4 True stress-strain curves of the two samples c1 and c2 in the as-cast state under hot compression at the sub-solvus solution temperatures of 1060oC (a) and 1080oC (b)
Fig.5 Critical strain of dynamic recrystallization (DRX) of samples c1 and c2 in as-cast state at the strain rate of 0.1 s-1
Sample
0.1
0.2
0.4
0.6
0.8
1.0
d1
0.0068
0.0066
0.0067
0.0070
0.0073
0.0076
d2
0.0073
0.0069
0.0069
0.0072
0.0078
0.0079
d3
0.0080
0.0079
0.0086
0.0092
0.0099
0.0098
d4
0.0098
0.0098
0.0104
0.0104
0.0103
0.0102
Table 1 ɑ values of samples d1-d4 under different true strains
Sample
α / MPa-1
n
Q / (kJ·mol-1)
d1
0.0070
4.64
1713
d2
0.0074
4.27
1489
d3
0.0087
4.09
1230
d4
0.0010
3.27
400
Table 2 Average ɑ values, stress index n and thermal deformation activation energies Q of samples d1-d4
Fig.6 Peak stress of sample d2 as a function of strain rate () (a) and temperature (T) (b)
Fig.7 Peak stress of samples d1 (a) and d2 (b) as a function of Z parameters
Fig.8 OM images of samples d1 (a, b), d2 (c, d), d3 (e, f), and d4 (g, h) under hot compression at different temperatures, the strain rate of 0.1 s-1, and the engineering strain of 50% (a, c, e, g) 1120oC (b, d, f, h) 1080oC
Fig.9 OM images of fine grained d4 sample deformed at 1100oC, 0.1 s-1 and different engineering strains (a) 30% (b) 50% (c) 70%
Fig.10 Dynamic recrystallization critical strain of the samples d1-d4 during thermal compression
Fig.11 Grain boundary-subgrain boundary recrystallization structure evolution diagrams (a-d) and orientation analyses (e-g) of d2 sample obtained by EBSD after hot compression at 1100oC (HAGB—high angle grain boundary, LAGB—low angle grain boundary, SB—subgrain boundary) (a, e) 50% engineering strain (b, f) 70% engineering strain (c, d, g) 80% engineering strain
Fig.12 EBSD images of the grain boundary-subgrain boundary recrystallization structure of d4 sample after hot compression at 1100oC (a) 30% engineering strain (b) 50% engineering strain
Fig.13 TEM images of coarsen grained d2 samples after hot compression at 1100oC, 0.1 s-1 (a) 30% engineering strain (b) 50% engineering strain
Fig.14 TEM images of fine grained d4 samples after hot compression at 1100oC, 0.1 s-1 and different engineering strains (SF—stacking fault) (a) 30% engineering strain (b) 50% engineering strain (c, d) 70% engineering strain
Fig.15 EBSD images of grain boundary-subgrain boundary of cast samples c1 (a, c) and c2 (b, d) after hot compression (50%, 0.1 s-1) (a, b) 1060oC (c, d) 1080oC
Fig.16 SEM images of c2 sample after thermal deformation at 1060oC, 50%, and 0.1 s-1, showing the interaction between γ' phase and recrystallized grains (a) coasening of the γ' phase in the DRX grain boundary (b) DRX grains interacting with γ' phase
Fig.17 TEM images of as-cast c1 and c2 samples after hot compression 50% at 1060oC, 0.1 s-1 (a, b) c1 sample, grain boundary absorbing lots of dislocation lines (c, d) c2 sample, showing γ' stimulated DRX nucleation
1
Tian W, Zhong Y, Liu Y F, et al. Development and testing of novel casted & wrought GH4096 alloy labyrinth disk [J]. Rare Met. Mater. Eng., 2021, 50: 1325
Tian S F, Zhang G Q, Li Z, et al. The disk superalloys and disk manufacturing technologies for advanced aero engine [J]. J. Aeronaut. Mater., 2003, 23(suppl.1) : 233
Du J H, Lv X D, Dong J X, et al. Research progress of wrought superalloys in China [J]. Acta Metall. Sin., 2019, 55: 1115
doi: 10.11900/0412.1961.2019.00142
Zhang R, Liu P, Cui C Y, et al. Present research situation and prospect of hot working of cast & wrought superalloys for aero-engine turbine disk in China [J]. Acta Metall. Sin., 2021, 57: 1215
doi: 10.11900/0412.1961.2021.00153
Sellars C M, McTegart W J. On the mechanism of hot deformation [J]. Acta Metall., 1966, 14: 1136
doi: 10.1016/0001-6160(66)90207-0
9
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
10
Wang Y, Shao W Z, Zhen L, et al. Tensile deformation behavior of superalloy 718 at elevated temperatures [J]. J. Alloys Compd., 2009, 471: 331
doi: 10.1016/j.jallcom.2008.03.082
11
Srinivasan N, Prasad Y V R K, Rao P R. Hot deformation behaviour of Mg-3Al alloy—A study using processing map [J]. Mater. Sci. Eng., 2008, A476: 146
12
Monajati H, Taheri A K, Jahazi M, et al. Deformation characteristics of isothermally forged UDIMET 720 nickel-base superalloy [J]. Metall. Mater. Trans., 2005, 36A: 895
13
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
14
Mostafaei M A, Kazeminezhad M. Hot deformation behavior of hot extruded Al-6Mg alloy [J]. Mater. Sci. Eng., 2012, A535: 216
15
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
16
Samantaray D, Mandal S, Bhaduri A K. Optimization of hot working parameters for thermo-mechanical processing of modified 9Cr-1Mo (P91) steel employing dynamic materials model [J]. Mater. Sci. Eng., 2011, A528: 5204
17
Gu Y, Zhong Z, Yuan Y, et al. An advanced cast-and-wrought superalloy (TMW-4M3) for turbine disk applications beyond 700oC [A]. Superalloys 2012 [C]. Hoboken: Wiley, 2012: 903
18
Ning Y Q, Yao Z K, Lei Y Y, et al. Hot deformation behavior of the post-cogging FGH4096 superalloy with fine equiaxed microstructure [J]. Mater. Charact., 2011, 62: 887
doi: 10.1016/j.matchar.2011.06.004
19
Mirzadeh H, Cabrera J M, Prado J M, et al. Hot deformation behavior of a medium carbon microalloyed steel [J]. Mater. Sci. Eng., 2011, A528: 3876
20
Ozturk U, Cabrera J M, Calvo J. High-temperature deformation of inconel 718PlusTM [J]. J. Eng. Gas Turbines Power, 2017, 139: 032101
21
Huron E, Srivatsa S, Raymond E. Control of grain size via forging strain rate limits for R'88DT [A]. Superalloys 2000 [C]. Warrendale: TMS, 2000: 49
22
Zhou H T, Liu R R, Liu Z C, et al. Hot deformation characteristics of GH625 and development of a processing map [J]. J. Mater. Eng. Perform., 2013, 22: 2515
doi: 10.1007/s11665-013-0558-3
23
Wang Y, Shao W Z, Zhen L, et al. Hot deformation behavior of delta-processed superalloy 718 [J]. Mater. Sci. Eng., 2011, A528: 3218
24
Li H Y, Gao Z H, Yin H, et al. Effects of Er and Zr additions on precipitation and recrystallization of pure aluminum [J]. Scr. Mater., 2013, 68: 59
doi: 10.1016/j.scriptamat.2012.09.026
25
Ning Y Q, Yao Z K, Fu M W, et al. Recrystallization of the hot isostatic pressed nickel-base superalloy FGH4096: I. Microstructure and mechanism [J]. Mater. Sci. Eng., 2011, A528: 8065
26
Fahrmann M, Suzuki A. Effect of cooling rate on gleeble hot ductility of UDIMET alloy 720 billet [A]. Superalloys2008 [M]. Warrendale, PA: TMS, 2008: 311
27
Wang C Y, Song X J, Zou J W, et al. Effect of original microstructure on thermal compression deformation behavior and microstructure of FGH96 alloy [J]. Hot Work. Technol., 2019, 48(11): 39
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]. Superalloys 2016: Proceedings of the 13th Intenational Symposium of Superalloys [C]. Warrendale, PA: TMS, 2016: 487
29
Fu R, Li F L, Yin F J, et al. Microstructure evolution and deformation mechanisms of the electroslag refined-continuous directionally solidified (ESR-CDS®) superalloy Rene88DT during isothermal compression [J]. Mater. Sci. Eng., 2015, A638: 152
30
Lu X D, Du J H, Deng Q, et al. Effect of slow cooling treatment on hot deformation behavior of GH4742 superalloy [J]. J. Alloys Compd., 2009, 486: 195
doi: 10.1016/j.jallcom.2009.07.020
31
Li F L, Fu R, Yin F J, et al. Impact of γ' (Ni3(Al, Ti)) phase on dynamic recrystallization of a Ni-based disk superalloy during isothermal compression [J]. J. Alloys Compd., 2017, 693: 1076
doi: 10.1016/j.jallcom.2016.09.258
32
Liu Y. Study of hot deformation behavior of Ni-Cr-W base superalloy [D]. Xi'an: Northwestern Polytechnical University, 2010
刘 毅. Ni-Cr-W基高温合金的热变形行为研究 [D]. 西安: 西北工业大学, 2010
33
Yuan H, Liu W C. Effect of the δ phase on the hot deformation behavior of Inconel l718 [J]. Mater. Sci. Eng., 2005, A408: 281
34
Dehghan-manshadi A, Hodgson P D. Dependency of recrystallization mechanism to the initial grain size [J]. Metall. Mater. Trans., 2008, 39A: 2830
35
Belyakov A, Miura H, Sakai T. Dynamic recrystallization in ultra fine-grained 304 stainless steel [J]. Scr. Mater., 2000, 43: 21
doi: 10.1016/S1359-6462(00)00373-0
36
Oudin A, Barnett M R, Hodgson P D. Grain size effect on the warm deformation behaviour of a Ti-IF steel [J]. Mater. Sci. Eng., 2004, A367: 282
37
Fu R, Li F L, Yin F J, et al. Application of multiple integral forging in preparation of wrought superalloy FGH96 turbine disk [J]. Chin. J. Rare Met., 2017, 41: 113
Poliak E I, Jonas J J. Initiation of dynamic recrystallization in constant strain rate hot deformation [J]. ISIJ Int., 2003, 43: 684
doi: 10.2355/isijinternational.43.684
39
Stewart G R, Jonas J J, Montheillet F. Kinetics and critical conditions for the initiation of dynamic recrystallization in 304 stainless Steel [J]. ISIJ Int., 2004, 44: 1581
doi: 10.2355/isijinternational.44.1581
40
Liu C, Yao Z H, Jiang H, et al. The feasibility and process control of uniform equiaxed grains by hot deformation in GH4720Li alloy with millimeter-level coarse grains [J]. Acta Metall. Sin., 2021, 57: 1309
doi: 10.11900/0412.1961.2020.00415
