Effect of cooling rate on phosphorus segregation behavior and the corresponding precipitation of γ″ and γ′ phases in IN718 alloy

doi:10.1016/j.jmst.2019.02.006

Abstract

Abstract:

Effect of segregation behaviors of P at different cooling rates on the precipitation of γ″ and γ′ phases and the corresponding strength are investigated. The precipitation of γ″ and γ′ phases during cooling is sensitive to P concentration. With increasing the concentration of P, the amount of γ″ and γ′ particles increases after air cooling. With decreasing the cooling rate, the accelerating effect of P on the precipitation of γ″ and γ′ phases decreased first and then increased, which demonstrates the concentration of P dissolved in the grain interior decreases first and then increases. The different effects of P on γ″ and γ′ phases with different cooling rates were analyzed by the kinetic characteristic of nonequilibrium grain-boundary segregation. The characteristic of nonequilibrium grain-boundary segregation of P in superalloy is further confirmed, and the phenomenon caused by critical cooling rate is captured.

Key words: Phosphorus, IN718 alloy, Segregation behavior, γ″ and γ′ phases

Anwen Zhang, Sha Zhang, Fang Liu, Feng Qi, Xiaoyu Yao, Yuanguo Tan, Dan Jia, Wenru Sun. Effect of cooling rate on phosphorus segregation behavior and the corresponding precipitation of γ″ and γ′ phases in IN718 alloy[J]. J. Mater. Sci. Technol., 2019, 35(7): 1485-1490.

Figures/Tables 9

Fig. 1. Specifications of the alloys for micro-hardness test.

Fig. 2. Grain sizes of the alloys with different P contents annealed at 1120 ℃ for various time.

Fig. 3. Micro-hardness, γ″ and γ′ phases and corresponding [001] SAD patterns of the alloys treated by 1120 ℃ × 3 h AC.

Fig. 4. Tensile strengths of the IN718 alloys treated by 1120 ℃ × 3 h AC.

Fig. 5. Micro-hardness and corresponding γ″ and γ′ phases at the positions with various distances from the ends of bars along the axial.

Fig. 6. AES spectrum of the positions with various distances from the end of the W3 bar along the axial: (a) the P peak of AES spectrums of the positions with various distances from the end of the bar; (b) the average P contents of the positions with various distances from the end of the bar.

Fig. 7. Micro-hardness and γ″ and γ′ phases at the positions with various distances from the sides of the cubes along the axial, alloy 2: (a) 20 mm × 20 mm × 20 mm; (b) 30 mm × 30 mm × 30 mm; (c) 40 mm × 40 mm × 40 mm.

Fig. 8. Micro-hardness and γ″ and γ′ phases at the positions with various distances from the sides of the cubes along the axial, alloy 2: (a) 20 mm × 20 mm × 20 mm; (b) 30 mm × 30 mm × 30 mm; (c) 40 mm × 40 mm × 40 mm.

Fig. 9. Micro-hardness of the positions with various distances from the sides of the cube along the axial, alloy 1 pre-treated by 1120 ℃/1 h + 1190 ℃/3 h WQ： (a) 30 mm × 30 mm × 30 mm, 1120 ℃/3 h AC; (b) 40 mm × 40 mm × 40 mm, 1120 ℃/3 h AC; (c) 30 mm × 30 mm × 30 mm, 1050 ℃/3 h AC; (d) 40 mm × 40 mm × 40 mm, 1050 ℃/3 h AC.

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