Crystal Plasticity Modeling of Strain Hardening Induced by Coherent Precipitates in Inconel 718 Superalloy

Area of Science:

• Materials Science
• Mechanical Engineering
• Computational Modeling

Background:

• Inconel 718 (IN718) is a critical superalloy for high-temperature applications.
• Understanding precipitate-dislocation interactions is key to predicting IN718's mechanical behavior.
• Coherent γ″ precipitates significantly influence deformation mechanisms in IN718.

Purpose of the Study:

• To investigate the interaction between dislocations and coherent γ″ precipitates in IN718 using crystal plasticity.
• To develop a finite element model for realistic IN718 microstructures.
• To analyze the influence of precipitate size on strain hardening and dislocation evolution.

Main Methods:

• Employed a crystal plasticity (CP)-based continuum modeling approach.
• Developed a finite element (FE) model with disk-shaped γ″ precipitates in a γ matrix.
• Conducted length-scale-dependent CP simulations informed by molecular dynamics (MD) findings.

Main Results:

• Three γ″ variants exhibit distinct behaviors under uniaxial loading, causing strain and stress heterogeneities.
• Dislocation shearing in γ″ variants reduces strain localization and dislocation densities in the γ phase.
• Geometrically necessary dislocation (GND) density, governed by strain gradients, significantly impacts strain hardening.

Conclusions:

• Precipitate size is a critical factor in IN718's strain hardening behavior.
• Smaller γ″ precipitates lead to stronger strain hardening.
• The size of γ″ precipitates substantially influences the evolution of GND density.