I am currently trying to model the incipient melting of niobium carbide particles in a nickel-matrix. I am using simply a cubical particle for test purposes. In principle, liquid phase is formed at the interface between both phases – as expected. But I am getting numerical instabilities, which seem to be related to the thermodynamics.
Such as:
trying hard phases 2 0 level: 4 zp= 2349 error= 1
trying harder! Error = 1
trying hard phases 2 0 level: 4 zp= 2342 error= 1
Additionally it can be observed that at the interface slightly negative concentrations are occurring. I have already tried around with changing the interface energies and mobilities as well as averaging the driving force at the interface, however this had nearly no influence on the simulation results.
I am wondering on how to tackle this issue – especially how the general strategy in such cases is.
Images:
- Initial configuration of the simulation domain
- NbC_Ni_1_vtk.png (30.42 KiB) Viewed 5557 times
- Situation after some melt has formed at the interface
- NbC_Ni_2_vtk.png (47.57 KiB) Viewed 5557 times
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# Flags and settings
# ==================
#
# Geometry
# --------
# Grid size?
# (for 2D calculations: CellsY=1, for 1D calculations: CellsX=1, CellsY=1)
# Cells in X-direction (CellsX):
70
# Cells in Y-direction (CellsY):
1
# Cells in Z-direction (CellsZ):
70
# Cell dimension (grid spacing in micrometers):
# (optionally followed by rescaling factor for the output in the form of '3/4')
5
(…)
# Time input data
# ===============
# Finish input of output times (in seconds) with 'end_of_simulation'
# 'regularly-spaced' outputs can be set with 'linear_step'
# or 'logarithmic_step' and then specifying the increment
# and end value
# ('automatic_outputs' optionally followed by the number
# of outputs can be used in conjuction with 'linear_from_file')
# 'first' : additional output for first time-step
# 'end_at_temperature' : additional output and end of simulation
# at given temperature
linear_step 0.1 100
end_of_simulation
# Time-step?
# Options: fix ...[s] automatic automatic_limited
automatic_limited
# Options: constant from_file
constant
# Limits: (real) min./s, [max./s], [phase-field factor], [segregation factor]
1e-5 0.1 0.5 0.5
# Number of steps to adjust profiles of initially sharp interfaces [exclude_inactive]?
10
# Phase data
# ==========
# Number of distinct solid phases?
2
#
# Data for phase 1:
# -----------------
# Simulation of recrystallisation in phase 1?
# Options: recrystall no_recrystall [verbose|no_verbose]
no_recrystall
# Is phase 1 anisotrop?
# Options: isotropic anisotropic faceted antifaceted
anisotropic
# Crystal symmetry of the phase?
# Options: none cubic hexagonal tetragonal orthorhombic
cubic
# Should grains of phase 1 be reduced to categories?
# Options: categorize no_categorize
categorize
#
# Data for phase 2:
# -----------------
# [identical phase number]
# Simulation of recrystallisation in phase 2?
# Options: recrystall no_recrystall [verbose|no_verbose]
no_recrystall
# Is phase 2 anisotrop?
# Options: isotropic anisotropic faceted antifaceted
isotropic
# Should grains of phase 2 be reduced to categories?
# Options: categorize no_categorize
Categorize
(…)
# Data for phase interaction 1 / 2:
# ---------------------------------
# Simulation of interaction between phase 1 and 2?
# Options: phase_interaction no_phase_interaction identical phases nb
# [standard|particle_pinning[_temperature]|solute_drag]
# | [redistribution_control] or [no_junction_force|junction_force]
1 2 phase_interaction
# 'DeltaG' options: default
# avg ... [] max ... [J/cm**3] smooth ... [degrees] noise ... [J/cm**3]
avg 0.50 max 1000 smooth 45.0
# I.e.: avg +0.50 smooth +45.0 max +1.00000E+03
# Type of surface energy definition between phases 1 and 2?
# Options: constant temp_dependent
constant
# Surface energy between phases 1 and 2? [J/cm**2]
# [max. value for num. interface stabilisation [J/cm**2]]
6.7e-07
# Type of mobility definition between phases 1 and 2?
# Options: constant temp_dependent dg_dependent thin_interface_correction [fixed_minimum]
constant
# File for kinetic coefficient between phases 1 and 2? [ min. value ] [cm**4/(Js)]
1.000000e-05
# Is interaction isotropic?
# Optionen: isotropic anisotropic [harmonic_expansion]
isotropic
end_phase_interactions
(…)
# Phase diagram - input data
# ==========================
#
# List of phases and components which are stoichiometric:
# phase and component(s) numbers
# List of concentration limits (at%):
# <Limits>, phase number and component number
# List for ternary extrapolation (2 elements + main comp.):
# <interaction>, component 1, component 2
# Switches: <stoich_enhanced_{on|off}> <solubility_{on|off}>
# End with 'no_more_stoichio' or 'no_stoichio'
interaction
no_stoichio
#
#
#
#
# Is a thermodynamic database to be used?
# Options: database database_verbose no_database
database
#
# Name of Thermo-Calc *.GES5 file without extension?
NbC_Ni
# TQ's 'workspace' size? (in kilo-bytes), default:800
workspace_size 40000
# Which global relinearisation mode shall be used?
# Options: manual from_file none
manual
# Relinearisation interval [s]
1.000000000000
# Input of the phase diagram of phase 0 and phase 1:
# --------------------------------------------------
# Which phase diagram is to be used?
# Options: database [local|global|globalF][start_value_{1|2}] linear linearT
database local
# Relinearisation mode for interface 0 / 1
# Options: automatic manual from_file none
none