Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 800, Issue -, Pages 163-173Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2019.05.348
Keywords
Directed energy deposition; GH4099; Heat treatment; Recrystallization; Mechanical properties; Deformation behavior
Categories
Funding
- National Key Research and Development Plan of China [2016YFB1100104]
- National Natural Science Foundation of China [51604227, 51501154, 51565041]
- Fundamental Research Funds for the Central Universities of China [3102015BJ(II) ZS013, 3102017jg02013]
- Natural Science Foundation of Shaanxi Province of China [2017JM5052]
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For additive-manufactured nickel-based superalloy, heat treatment is an effective method to modify the microstructure and mechanical properties. The strength and ductility of as-deposited GH4099 have been improved via heat treatment. The results indicate that the microstructure of as-deposited sample was mainly composed of epitaxial growth columnar grains. And the (gamma + gamma') eutectic phase formed at the terminal solidification stage because of the segregation of Al and Ti elements. After solution treatment at 1120 degrees C for 2 h, the columnar dendrites were replaced by smaller equiaxed grains with twin boundaries due to the occurrence of recrystallization. The gamma' phase precipitated in the matrix after the aging treatment at 800 degrees C for 8 h. By comparing the tensile properties at room temperature of three states samples, it could be found that the solution treated samples had the lowest strength with the highest plasticity, while the solution-aging treated samples had the best performance with high strength and ductility. After aging treatment, though the dislocation density decreased after solution treatment, the precipitated gamma' phase could block dislocation movement to improve the strength of GH4099. Additionally, the formation of refine equiaxed grains and twin boundaries promoted ductility to some degree during the tensile process. (C) 2019 Elsevier B.V. All rights reserved.
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