Investigation on Mechanism of Microstructure Evolution during Multi-Process Hot Forming of GH4169 Superalloy Forging

Area of Science:

• Materials Science
• Metallurgy
• Superalloys

Background:

• GH4169 superalloy forgings require multi-process hot forming.
• Understanding microstructural evolution during hot working is crucial for optimizing properties.

Purpose of the Study:

• To investigate the microstructural evolution during hot working of GH4169 superalloy.
• To elucidate the role of δ phase precipitation and strain distribution on grain refinement and dynamic recrystallization.

Main Methods:

• A designed process route involving pre-deformation, aging treatment (AT), high-temperature holding (HTH), and final deformation.
• Analysis of microstructural evolution, δ phase precipitation, and recrystallization behavior.
• Evaluation of kernel average misorientation (KAM) values to understand dynamic recrystallization (DRX) nucleation.

Main Results:

• Uneven pre-deformation strain significantly impacts grain microstructure refinement due to coupled δ phase evolution and recrystallization.
• Fine-grain microstructures with rod-like δ phases form in high-strain regions, while necklace-like microstructures form in low-strain regions.
• Dynamic recrystallization nucleation is promoted by high KAM values and smaller average grain sizes in mixed-grain microstructures.

Conclusions:

• The study reveals the interaction mechanisms between δ phase and dynamic recrystallization nucleation.
• Optimizing pre-deformation strain is key to controlling the final microstructure and properties of GH4169 forgings.
• The findings provide insights into tailoring superalloy microstructures for enhanced performance.