Dynamic recrystallization behavior of GH4169G alloy during hot compressive deformation

doi:10.1016/j.jmst.2019.04.018

Abstract

Abstract:

The microstructure evolutions and nucleation mechanisms of GH4169 G alloy were studied by optical microscope, electron backscatter diffraction (EBSD) and transmission electron microscope (TEM). The hot compression tests were performed different imposed reductions in the range of true strain from 0.12 to 1.2 at the temperatures of 930 ℃-1050 ℃ with strain rates of 0.01 s^-1-1 s^-1. It is found that cumulative and local misorientation increase firstly and then decrease when the strain is increased due to the progress of dynamic recrystallization (DRX). The low angle boundaries (LAGBs) rapidly develop to high angle boundaries (HAGBs) at relatively high deformation temperature or the low strain rate. There are three DRX mechanisms observed for GH4169 G alloy during hot deformation. Discontinuous dynamic recrystallization (DDRX) as the dominant mechanism for GH4169 G alloy is characterized by typical necklace structures and bulged-original boundaries. Besides, different deformation bands with dislocation cells formed in deformed matrix at low temperature and large strain, which indicates that continuous dynamic recrystallization (CDRX) contributed to the DRX process. The twin boundaries lost their coherent characteristics and provide sites for nucleation, which also accelerates the nucleation of DRX.

Key words: GH4169G alloy, Dynamic recrystallization, Nucleation mechanism

Dan Jia, Wenru Sun, Dongsheng Xu, Fang Liu. Dynamic recrystallization behavior of GH4169G alloy during hot compressive deformation[J]. J. Mater. Sci. Technol., 2019, 35(9): 1851-1859.

Figures/Tables 12

Fig. 1. Microstructure of the GH4169 G specimens soaked at 1020 ℃ for 1 h prior to hot compression: (a) orientation image microscopy map; and (b) misorientation angle distribution.

Fig. 2. Optical micrographs of GH4169 G alloy deformed to 1.2 true strain at different temperatures with various strain rates.

Fig. 3. OIM maps of specimens deformed to different of strains under conditions of 990 ℃ and 0.1 s-1: (a) 0.12; (b) 0.35; (c) 0.69; and (d) 1.2.

Fig. 4. Misorientation angle along the lines marked in Fig. 3: (a) A1; (b) A2; (c) B1; (d) B2; (e) C1; (f) C2; (g) D1; (h) D2.

Fig. 5. OIM maps of GH4169 G deformed to a true strain of 0.35 at 1000 ℃ and strain rates of (a) 0.01 s-1 and (b) 1 s-1.

Fig. 6. Misorientation angle along the lines marked in Fig. 5: (a) E1; (b) E2; (c) F1; (d) F2.

Fig. 7. OIM maps and misorientation distribution of specimens deformed at 0.1s-1 to a true strain of 1.2: (a) and (b) 950 ℃; (c) and (d) 1000 ℃.

Fig. 8. TEM micrographs of GH4169 G deformed at 990 ℃ and 0.1 s-1 at true strains of: (a) 0.12 and (b) 0.35.

Fig. 9. TEM micrographs show the deformed bands upon a true strain of 0.69 at 990 ℃/0.1 s-1.

Fig. 10. The fraction of different misorientation angle for GH4169 G alloy deformed to various strains at 990 ℃ and 0.1 s-1.

Fig. 11. TEM morphologies of the nucleation at twin boundaries at true strain of 0.12 under the condition of 1000 ℃/0.1 s-1.

Fig. 12. KAM map of nucleation at twin boundaries of the initial grain at 1000 ℃/0.1 s-1 and the strain of 0.35.

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