Effect of Heat Treatment Parameters on Microstructure and Hot Workability of As-Cast Fine Grain Ingot of GH4720Li Alloy

doi:10.11900/0412.1961.2019.00205

Acta Metall Sin

2020, Vol. 56

Issue (2): 182-192 DOI: 10.11900/0412.1961.2019.00205

Current Issue | Archive | Adv Search

Effect of Heat Treatment Parameters on Microstructure and Hot Workability of As-Cast Fine Grain Ingot of GH4720Li Alloy

WANG Tao,WAN Zhipeng(

),LI Zhao,LI Peihuan,LI Xinxu,WEI Kang,ZHANG Yong

Science and Technology on Advanced High Temperature Structural Materials Laboratory, AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China

Cite this article:

WANG Tao,WAN Zhipeng,LI Zhao,LI Peihuan,LI Xinxu,WEI Kang,ZHANG Yong. Effect of Heat Treatment Parameters on Microstructure and Hot Workability of As-Cast Fine Grain Ingot of GH4720Li Alloy. Acta Metall Sin, 2020, 56(2): 182-192.

Download:

HTML

PDF(23934KB)
Export: BibTeX | EndNote (RIS)

Abstract

GH4720Li was Ni-Cr-Co base precipitation strengthened superalloy and widely used for high performance applications such as disks and blades of either aircraft engines or land-based gas turbines attributing to its excellent properties including resistance to creep and fatigue, together with corrosion, fracture and microstructural stability for the intended applications. Compared with the double-melting process (vacuum induction melting (VIM)+electroslag remelting (ESR) or VIM+vacuum arc remelting (VAR), a triple-melting process (VIM+ESR+VAR) can eliminate the segregation coefficient of the alloying elements and reduce the content of impurity elements, while the ingot fabricated by the triple-melting process also exhibited lots of shortcomings, such as the coarse grains, dendritic structure, microstructure defects and high forging temperature. The as-cast fine grain ingot prepared by grain refining casting process can eliminate the microscopic shrinkage, reduce the differences among three crystalline regions and improve the hot workability as a result. However, it was hardly to avoid the microstructure defects by simply improving the casting process attributing to its large number of alloying elements. Therefore, the homogenization treatment was always performed on the superalloy ingot. In this work, the optimized homogenization parameter was identified according to the investigation on the microstructure evolution under various homogenization treatment conditions and hot workability of as-cast fine grain ingot after homogenization treatment. The relationships of one-stage as well as two-stage homogenization treatment parameters and segregation coefficient as well as volume fraction of eutectic phase were investigated indepth. The hot workability of the homogenized samples under various conditions was also analyzed with the help of hot compression tests. Experimental results revealed that the increased homogenization treatment temperature and extended holding time were able to decrease the volume fraction of eutectic phase and segregation coefficient of the alloying element significantly. Hot compression tests by the Gleeble 3800 dynamic thermal-mechanical testing machine indicated that the samples suffered two-stage homogenization treatment followed by the slowly cooling rate (1140 ℃, 12 h+1170 ℃, 10 h, 0.2 ℃/min furnace cooling to 1010 ℃, and then air cooling) exhibited better hot workability (the maximum reduction rate of 50% deformed at 1120 ℃, 1 s^-1). Discontinuous dynamic recrystallization was identified as the mainly nucleation mechanism of the alloy, and the recrystallized grains preferred to nucleate at the boundaries of the original grains according to the microstructure observation of hot compressed samples. In additions, the M(C, N) type precipitates were able to promote the occurrence of dynamic recrystallization behavior. Homogenization treatment experiments and microstructure observation suggested that the optimized treatment parameters of the as-cast fine grain ingot was 1140 ℃, 12 h+1170 ℃, 10 h, 0.2 ℃/min furnace cooling to 1010 ℃, and then by air cooling.

Key words: as-cast fine grain ingot of GH4720Li alloy homogenization heat treatment microstructure evolution hot workability

Received: 21 June 2019

ZTFLH:

TG146.1

	Service

	E-mail this article
	Add to citation manager
	E-mail Alert
	RSS
	（）
	Articles by authors
	Tao WANG
	Zhipeng WAN
	Zhao LI
	Peihuan LI
	Xinxu LI
	Kang WEI
	Yong ZHANG

URL:

https://www.ams.org.cn/EN/10.11900/0412.1961.2019.00205 OR https://www.ams.org.cn/EN/Y2020/V56/I2/182

Table 1 One-stage homogenization heat treatment (OSHT) schedules for the GH4720Li alloy

Table 2 Two-stage homogenization heat treatment (TSHT) schedules for the GH4720Li alloy

Fig.1 Macrostructures of as-cast fine grain ingot of GH4720Li alloy(a) overall profile of ingot (b) horizontal direction (c) vertical direction

Fig.2 OM (a) and SEM (b) images of as-cast fine grain ingot of GH4720Li alloy at R/2 region (Insets show the morphology of γ' precipitates in the interdendritic and dendrite regions, R—radius of the as-cast fine grain ingot)

Table 3 Element segregation analyses of initial as-cast fine grain ingot of GH4720Li alloy at R/2 between dendrite core and interdendritic regions

Fig.3 Microstructures of as-cast fine grain ingot of GH4720Li alloy under heat treatment temperatures of 1130 ℃ (a), 1140 ℃ (b), 1150 ℃ (c), 1160 ℃ (d), 1170 ℃ (e), 1180 ℃ (f), 1200 ℃ (g) and 1220 ℃ (h) for 1 h (Insets show the morphologies of incipient melting phase)

Fig.4 Volume fraction of eutectic phase of GH4720Li alloy under different heat treatment temperatures for 1 h

Fig.5 Microstructures of as-cast fine grain ingot of GH4720Li alloy under one-stage homogenization heat treatment parameters (Insets show the morphologies of eutectic γ+γ' phase and γ' precipitate)(a) OSHT 1 (b) OSHT 2 (c) OSHT 3 (d) OSHT 4 (e) OSHT 5 (f) OSHT 6 (g) OSHT 7

Fig.6 Volume fraction of eutectic phase during various one stage homogenization treatment parameters of as-cast fine grain ingot of GH4720Li alloy

Fig.7 Elemental segregation coefficient of as-cast fine grain ingot of GH4720Li alloy under different homogenization heat treatment parameters

Fig.8 Microstructures of as-cast fine grain ingot of GH4720Li alloy under different two-stage homogenization heat treatment parameters (Insets show the morphologies of eutectic γ+γ' phase and γ' precipitate)(a) TSHT 1 (b) TSHT 2 (c) TSHT 3 (d) TSHT 4 (e) TSHT 5

Fig.9 The volume fraction of eutectic phase of as-cast fine grain ingot of GH4720Li alloy under different two-stage homogenization treatment parameters

Table 4 Critical reduction for crack initiation of homogenized as-cast fine grain ingot of GH4720Li alloy samples during hot compression tests (%)

Fig.10 True stress-strain curves of as-cast fine grain ingot of GH4720Li alloy under homogenization treatment parameter of TSHT 5 at 1140 ℃ (a) and 0.01 s^-1 (b)

Fig.11 Microstructures of as-cast fine grain ingot of GH4720Li alloy under homogenization treatment parameter of TSHT 5 (Inset shows the morphology of locally magnified microstructure, T—temperature,

ε ˙

—deformation rate, ε—strain, DRX—dynamic recrystallization, CDRX—continuous dynamic recrystallization, DDRX—discontinuous dynamic recrystallization)(a) T=1160 ℃,

ε ˙

=1 s^-1, ε=0.3 (b) T=1160 ℃,

ε ˙

=1 s^-1, ε=0.8(c) T=1160 ℃,

ε ˙

=0.01 s^-1, ε=0.8 (d) T=1140 ℃,

ε ˙

=0.01 s^-1, ε=0.8

[1]	Gopinath K, Gogia A K, Kamat S V, et al. Dynamic strain ageing in Ni-base superalloy 720Li [J]. Acta Mater., 2009, 57: 1243
[2]	Pang H T, Reed P A S. Microstructure effects on high temperature fatigue crack initiation and short crack growth in turbine disc nickel-base superalloy Udimet 720Li [J]. Mater. Sci. Eng., 2007, A448: 67
[3]	Wang T, Wan Z P, Sun Y, et al. Dynamic softening behavior and microstructure evolution of nickel base superalloy [J]. Acta Metall. Sin., 2018, 54: 83
[3]	(王涛, 万志鹏, 孙宇等. 镍基变形高温合金动态软化行为与组织演变规律研究 [J]. 金属学报, 2018, 54: 83)
[4]	Gopinath K, Gogia A K, Kamat S V, et al. Low cycle fatigue behaviour of a low interstitial Ni-base superalloy [J]. Acta Mater., 2009, 57: 3450
[5]	Na Y S, Park N K, Reed R C. Sigma morphology and precipitation mechanism in Udimet 720Li [J]. Scr. Mater., 2000, 43: 585
[6]	Jackson M P, Reed R C. Heat treatment of UDIMET 720Li: The effect of microstructure on properties [J]. Mater. Sci. Eng., 1999, A259: 85
[7]	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
[8]	Wan Z P, Wang T, Sun Y, et al. Dynamic softening mechanisms of GH4720Li alloy during hot deformation [J]. Acta Metall. Sin., 2019, 55: 213
[8]	(万志鹏, 王涛, 孙宇等. GH4720Li合金热变形过程动态软化机制 [J]. 金属学报, 2019, 55: 213)
[9]	Semiatin S L, Kramb R C, Turner R E, et al. Analysis of the homogenization of a nickel-base superalloy [J]. Scr. Mater., 2004, 51: 491
[10]	Miao Z J, Shan A D, Wu Y B, et al. Quantitative analysis of homogenization treatment of INCONEL718 superalloy [J]. Trans. Nonferrous Met. Soc. China, 2011, 21: 1009
[11]	Sohrabi M J, Mirzadeh H, Rafiei M. Solidification behavior and Laves phase dissolution during homogenization heat treatment of Inconel 718 superalloy [J]. Vacuum, 2018, 154: 235
[12]	Hosseini S A, Madar K Z, Abbasi S M. Effect of homogenization heat treatments on the cast structure and tensile properties of nickel-base superalloy ATI 718Plus in the presence of boron and zirconium additions [J]. Mater. Sci. Eng., 2017, A689: 103
[13]	Yang J X, Sun Y, Jin T, et al. Microstructure and mechanical properties of a Ni-based superalloy with refined grains [J]. Acta Metall. Sin., 2014, 50: 839
[13]	(杨金侠, 孙元, 金涛等. 一种细晶铸造镍基高温合金的组织与力学性能 [J]. 金属学报, 2014, 50: 839)
[14]	Zhang Y, Li P H, Jia C L, et al. Research progress of melting purification techniques and equipment for cast & wrought superalloy [J]. Mater. Rev., 2018, 32: 1496
[14]	(张勇, 李佩桓, 贾崇林等. 变形高温合金纯净熔炼设备及工艺研究进展 [J]. 材料导报, 2018, 32: 1496)
[15]	Gao Z T, Guo W, Zhang C W, et al. Development of fine-grained structure in Ni-Cr-W based superalloy and its effect on the mechanical properties [J]. Mater. Sci. Eng., 2017, A682: 156
[16]	Ma Y, Sun J H, Xie X S, et al. An investigation on fine-grain formation and structural character in cast IN718 superalloy [J]. J. Mater. Process. Technol., 2003, 137: 35
[17]	Men H, Jiang B, Fan Z. Mechanisms of grain refinement by intensive shearing of AZ91 alloy melt [J]. Acta Mater., 2010, 58: 6526
[18]	Chang L T, Jin H, Sun W R. Solidification behavior of Ni-base superalloy Udimet 720Li [J]. J. Alloys Compd., 2015, 653: 266
[19]	Gong L, Chen B, Yang Y Q, et al. Effect of N content on microsegregation, microstructure and mechanical property of cast Ni-base superalloy K417G [J]. Mater. Sci. Eng., 2017, A701: 111
[20]	Qin L, Pei Y L, Li S S, et al. Effect of thermal stability of γ' phase on the recrystallization behaviors of Ni-based single crystal superalloys [J]. Mater. Des., 2017, 130: 69
[21]	Zhang H, Liu Y, Chen X, et al. Microstructural homogenization and high-temperature cyclic oxidation behavior of a Ni-based superalloy with high-Cr content [J]. J. Alloys Compd., 2017, 727: 410
[22]	Pan X L, Wang B, Sun W R, et al. Effect of homogenization treatment on the hot deformation of GH742 alloy [J]. Acta Metall. Sin., 2012, 48: 1403
[22]	(潘晓林, 汪波, 孙文儒等. 均匀化处理对GH742合金热变形行为的影响 [J]. 金属学报, 2012, 48: 1403)
[23]	Dong J X, Li L H, Li H Y, et al. Effect of extent of homogenization on the hot deformation recrystallization of superalloy ingot in cogging process [J]. Acta Metall. Sin., 2015, 51: 1207
[23]	(董建新, 李林翰, 李浩宇等. 高温合金铸锭均匀化程度对开坯热变形的再结晶影响 [J]. 金属学报, 2015, 51: 1207)
[24]	Hegde S R, Kearsey R M, Beddoes J C. Designing homogenization-solution heat treatments for single crystal superalloys [J]. Mater. Sci. Eng., 2010, A527: 5528
[25]	Du J H, Qu J L, Deng Q, et al. As-cast microstructure and homogenization process of alloy GH720Li [J]. J. Iron Steel Res., 2005, 17(3): 60
[25]	(杜金辉, 曲敬龙, 邓群等. GH720Li合金的铸态组织和均匀化工艺 [J]. 钢铁研究学报, 2005, 17(3): 60)
[26]	Liu F F, Chen J Y, Dong J X, et al. The hot deformation behaviors of coarse, fine and mixed grain for Udimet 720Li superalloy [J]. Mater. Sci. Eng., 2016, A651: 102
[27]	Cao L, Zhou Y Z, Jin T, et al. Effects of Re on surface eutectic formation for Ni-base single crystal superalloys during directional solidification [J]. J. Mater. Sci. Technol., 2017, 33: 1308
[28]	Mishin Y, Herzig C. Diffusion in the Ti-Al system [J]. Acta Mater., 2000, 48: 589
[29]	Liu M C, Sheng G M, He H J, et al. Microstructural evolution and mechanical properties of TLP bonded joints of Mar-M247 superalloys with Ni-Cr-Co-W-Ta-B interlayer [J]. J. Mater. Process. Technol., 2017, 246: 245
[30]	Neumeier S, Rehman H U, Neuner J, et al. Diffusion of solutes in fcc cobalt investigated by diffusion couples and first principles kinetic Monte Carlo [J]. Acta Mater., 2016, 106: 304
[31]	Ruan J J, Ueshima N, Oikawa K. Phase transformations and grain growth behaviors in superalloy 718 [J]. J. Alloys Compd., 2018, 737: 83
[32]	Yang C, Mo D G, Lu H Z, et al. Reaction diffusion rate coefficient derivation by isothermal heat treatment in spark plasma sintering system [J]. Scr. Mater., 2017, 134: 91
[33]	Egbewande A T, Chukwukaeme C, Ojo O A. Joining of superalloy Inconel 600 by diffusion induced isothermal solidification of a liquated insert metal [J]. Mater. Charact., 2008, 59: 1051
[34]	Viswanathan G B, Sarosi P M, Henry M F, et al. Investigation of creep deformation mechanisms at intermediate temperatures in René 88 DT [J]. Acta Mater., 2005, 53: 3041
[35]	Sinharoy S, Virro-Nic P, Milligan W W. Deformation and strength behavior of two nickel-base turbine disk alloys at 650 ℃ [J]. Metall. Mater. Trans., 2001, 32A: 2021
[36]	Henry M F, Yoo Y S, Yoon D Y, et al. The dendritic growth of γ' precipitates and grain [J]. Metall. Trans., 1993, 24A: 1733
[37]	Fahrmann M, Suzuki A. Effect of cooling rate on gleeble hot ductility of Udimet alloy 720 billet [A]. Superalloys 2008 [C]. Warrendale: TMS, 2008: 311
[38]	Liu G W, Han Y, Shi Z Q, et al. Hot deformation and optimization of process parameters of an as-cast 6Mo superaustenitic stainless steel: A study with processing map [J]. Mater. Des., 2014, 53: 662
[39]	Kumar S S S, Raghu T, Bhattacharjee P P, et al. Work hardening characteristics and microstructural evolution during hot deformation of a nickel superalloy at moderate strain rates [J]. J. Alloys Compd., 2017, 709: 394
[40]	Kumar S S S, Raghu T, Bhattacharjee P P, et al. Strain rate dependent microstructural evolution during hot deformation of a hot isostatically processed nickel base superalloy [J]. J. Alloys Compd., 2016, 681: 28
[41]	Han Y, Liu G W, Zou D N, et al. Deformation behavior and microstructural evolution of as-cast 904L austenitic stainless steel during hot compression [J]. Mater. Sci. Eng., 2013, A565: 342

[1]	GONG Shengkai, LIU Yuan, GENG Lilun, RU Yi, ZHAO Wenyue, PEI Yanling, LI Shusuo. Advances in the Regulation and Interfacial Behavior of Coatings/Superalloys[J]. 金属学报, 2023, 59(9): 1097-1108.
[2]	LI Jingren, XIE Dongsheng, ZHANG Dongdong, XIE Hongbo, PAN Hucheng, REN Yuping, QIN Gaowu. Microstructure Evolution Mechanism of New Low-Alloyed High-Strength Mg-0.2Ce-0.2Ca Alloy During Extrusion[J]. 金属学报, 2023, 59(8): 1087-1096.
[3]	WANG Fa, JIANG He, DONG Jianxin. Evolution Behavior of Complex Precipitation Phases in Highly Alloyed GH4151 Superalloy[J]. 金属学报, 2023, 59(6): 787-796.
[4]	FANG Yuanzhi, DAI Guoqing, GUO Yanhua, SUN Zhonggang, LIU Hongbing, YUAN Qinfeng. Effect of Laser Oscillation on the Microstructure and Mechanical Properties of Laser Melting Deposition Titanium Alloys[J]. 金属学报, 2023, 59(1): 136-146.
[5]	LI Zhao, JIANG He, WANG Tao, FU Shuhong, ZHANG Yong. Microstructure Evolution of GH2909 Low Expansion Superalloy During Heat Treatment[J]. 金属学报, 2022, 58(9): 1179-1188.
[6]	LIANG Chen, WANG Xiaojuan, WANG Haipeng. Formation Mechanism of B2 Phase and Micro-Mechanical Property of Rapidly Solidified Ti-Al-Nb Alloy[J]. 金属学报, 2022, 58(9): 1169-1178.
[7]	MA Minjing, QU Yinhu, WANG Zhe, WANG Jun, DU Dan. Dynamics Evolution and Mechanical Properties of the Erosion Process of Ag-CuO Contact Materials[J]. 金属学报, 2022, 58(10): 1305-1315.
[8]	XU Jinghui, LI Longfei, LIU Xingang, LI Hui, FENG Qiang. Thermal-Stress Coupling Effect on Microstructure Evolution of a Fourth-Generation Nickel-Based Single-Crystal Superalloy at 1100^oC[J]. 金属学报, 2021, 57(2): 205-214.
[9]	LIU Chao, YAO Zhihao, GUO Jing, PENG Zichao, JIANG He, DONG Jianxin. Microstructure Evolution Behavior of Powder Superalloy FGH4720Li at Near Service Temperature[J]. 金属学报, 2021, 57(12): 1549-1558.
[10]	LIU Chenxi, MAO Chunliang, CUI Lei, ZHOU Xiaosheng, YU Liming, LIU Yongchang. Recent Progress in Microstructural Control and Solid-State Welding of Reduced Activation Ferritic/Martensitic Steels[J]. 金属学报, 2021, 57(11): 1521-1538.
[11]	WU Yun, LIU Yahui, KANG Maodong, GAO Haiyan, WANG Jun, SUN Baode. Microstructure Evolution of K4169 Alloy During Cyclic Loading[J]. 金属学报, 2020, 56(9): 1185-1194.
[12]	JIANG He,DONG Jianxin,ZHANG Maicang,YAO Zhihao,YANG Jing. Stress Relaxation Mechanism for Typical Nickel-Based Superalloys Under Service Condition[J]. 金属学报, 2019, 55(9): 1211-1220.
[13]	Yingjun GAO, Yujiang LU, Lingyi KONG, Qianqian DENG, Lilin HUANG, Zhirong LUO. Phase Field Crystal Model and Its Application for Microstructure Evolution of Materials[J]. 金属学报, 2018, 54(2): 278-292.
[14]	Zongyi MA, Qiao SHANG, Dingrui NI, Bolv XIAO. Friction Stir Welding of Magnesium Alloys: A Review[J]. 金属学报, 2018, 54(11): 1597-1617.
[15]	Yizhe MAO, Jianguo LI, Lei FENG. Effect of Coarse β(Al₃Mg₂) Phase on Microstructure Evolution in 573 K Annealed Al-10Mg Alloy by Uniaxial Compression[J]. 金属学报, 2018, 54(10): 1451-1460.

No Suggested Reading articles found!

Viewed

Full text

Abstract

Cited

Shared

Discussed