Modeling of microstructure evolution and properties for Ni-based superalloys

Content
Brief overview of Ni-based supealloys
Computational model development
Microstructure modeling during specified heat treatments
Calculation of mechanical properties based on predicted microstructure

Brief overview of Ni-based supealloys

Composition of superalloys
Ni – base
Up to 40 wt % of a combination of five to
ten other elements
Primary phases – γ (nickel-based solid solution) and γ’ (Ni3Al)
An exceptional combination of high-temperature strength, toughness, and resistance to degradation in corrosive or oxidizing environments

Strengthening mechanisms
γ-phase solid-solution strengthening by refractory elements
Precipitation strengthening by γ’-phase
Grain size (directional solidifying)

Detrimental phases – topologically
closed-packed phases
Orthorhombic P phase, the tetragonal σ phase, the rhombohedral R, and rhombohedral μ phases
TCP-phases deplete strengthening elements and/or serve as crack-initiation site

Computational model development

Theoretical models and numerical method
TC-PRISMA adopts Kampmann-Wagner numerical method, based on the theory from Langer-Schwartz
Nucleation Growth/dissolution Coarsening

Nucleation rate

Growth rate
Simplified model - calculates the velocity of a moving phase interface in multicomponent systems using simply the tie-line across the bulk composition
Advanced model - identifies the operating tie-line
For coarsening the growth equation is applied

Input
Nucleation
Growth

Output
Volume Fraction
Number Density
Mean Radius
Also:
Particle size distribution
Matrix composition
Nucleation rate
Critical radius
Driving force
TTP/CCP diagrams

Microstructure modeling during specified heat treatments

Rene 80

Results #1