Dislocation network with pair-coupling structure in {111} γ/γ' interface of Ni-based single crystal superalloy

Area of Science:

• Materials Science
• Metallurgy
• Crystallography

Background:

• Gamma/gamma prime interface dislocation networks are known to enhance creep resistance in single crystal superalloys.
• These networks are typically observed at the {001} interface.

Purpose of the Study:

• To investigate a newly discovered dislocation network at the {111} gamma/gamma prime interface.
• To understand the formation mechanism and characteristics of this network in a model superalloy.

Main Methods:

• High-temperature creep testing of a single crystal model superalloy at 1100°C/100 MPa.
• Microstructural analysis to identify and characterize the dislocation network.

Main Results:

• A novel dislocation network composed of screw dislocations with Burgers vectors of 1/2 a<110> was identified at the {111} gamma/gamma prime interface.
• These dislocations exhibit a unique pair-coupling structure.
• The network formation is linked to the degradation of the gamma prime raft structure and the cutting of dislocations through the interface.
• The pair-coupling structure facilitates the removal of anti-phase boundaries and acts as diffusion channels, leading to the dissolution of unstable gamma prime particles and the formation of a zigzag interface.

Conclusions:

• The formation of the {111} interface dislocation network is influenced by negative misfit, low-alloying gamma prime particles, and specific creep conditions.
• This network represents a new mechanism for improving high-temperature creep resistance in superalloys by altering the gamma/gamma prime interface morphology.