about gamma-alpha

solid-solid phase transformations, influence of stresses and strains
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shaojielv
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about gamma-alpha

Post by shaojielv » Mon Mar 14, 2022 9:50 am

I want to simulate the gamma→alpha phase transformation process, and the specific case simulation picture is as follows. From the picture, I think the alpha phase is set to anisotropy, but the same situation as the case is not realized in the simulation process. Could you please help me answer the reason
Thank you very much.
shaojie lyu
//
# Phase 2 ( BCC_A2 )
# ------------------
# [identical phase number]
# Simulation of recrystallisation in phase 2 (BCC_A2) ?
# Options: recrystall no_recrystall [verbose|no_verbose]
no_recrystall
# Is phase 2 (BCC_A2) anisotropic ?
# Optionen: isotropic anisotropic faceted_a faceted_b faceted[_c] antifaceted
anisotropic
# Crystal symmetry of phase 2 ( BCC_A2 ) ?
# Options: none cubic hexagonal tetragonal orthorhombic
cubic
# Should grains of phase 2 (BCC_A2) be reduced to categories?
# Options: categorize no_categorize
no_categorize
# Type of molar volume input ?
# Options: constant database [temp_extrapol] [conc_extrapol]
constant
# Value of molar volume ? ([cm**3/mol])
7.2757
//
Attachments
ANISO.png
ANISO.png (64.3 KiB) Viewed 948 times

Bernd
Posts: 1504
Joined: Mon Jun 23, 2008 9:29 pm

Re: about gamma-alpha

Post by Bernd » Mon Mar 14, 2022 10:23 am

Dear shaojielv,

There is nothing wrong about your setting of anisotropy in the phase data, but anisotropy must also be set in the phase interaction data. There, you need to set the interaction to "anisotropic" and define a static and kinetic coefficient.

Bernd

shaojielv
Posts: 100
Joined: Thu Apr 01, 2021 2:16 pm
anti_bot: 333

Re: about gamma-alpha

Post by shaojielv » Mon Mar 14, 2022 2:12 pm

Dear Bernd,
In the interaction, I also set the anisotropy between phase 1 (γ) and phase 2 (α), but why is the result different from what I want? What I want is the result in the first question above, and the following is my simulated result. I hope to get your answer, thank you very much for your answer.


//
# 1 (FCC_A1) / 2 (BCC_A2)
# -------------------------
# Simulation of interaction between 1 (FCC_A1) and 2 (BCC_A2) ?
# Options: phase_interaction no_phase_interaction identical phases nb
# [ standard | particle_pinning[_temperature] | solute_drag ]
# | [ redistribution_control ] or [ no_junction_force | junction_force ]
phase_interaction redistribution_control
# 'DeltaG' options: default
# avg ...[] max ...[J/cm^3] smooth ...[Deg] noise ...[J/cm^3] offset ...[J/cm^3]
avg 0. smooth 45
# I.e.: avg +0.00
# Type of interfacial energy definition between 1 (FCC_A1) and 2 (BCC_A2) ?
# Options: constant temp_dependent
constant
# Interfacial energy between 1 (FCC_A1) and 2 (BCC_A2) ? [J/cm**2]
# [max. value for num. interface stabilisation [J/cm**2]]
2.0000E-05
# Type of mobility definition between FCC_A1 and BCC_A2?
# Options: constant temp_dependent dg_dependent [fixed_minimum]
constant
# Kinetic coefficient mu between FCC_A1 and BCC_A2 [cm**4/(Js)] ?
2.20000E-06
# Is interaction isotropic?
# Options: isotropic
# anisotropic [junction_force] [harmonic_expansion]
anisotropic
# Anisotropy of interfacial stiffness? (cubic)
# 1 - delta * cos(4*phi), (delta =delta_stiffness =15*delta_energy)
# Coefficient delta (<1.) ?
0.05
# Anisotropy of interfacial mobility? (cubic)
# 1 + delta * cos(4*phi)
# Coefficient delta (<1.) ?
0.05
# Which phase diagram is to be used?
# Options: database [local|global[F]|globalG[F]] [start_value_{1|2}]
# linear linearTQ
database global
# Relinearisation interval for interface FCC_A1 / BCC_A2
# Options: automatic manual from_file none
none
# Please specify the redistribution behaviour of each component:
# Format: forward [backward]
# Options: nple para paratq normal [mob_corr] atc [mob_corr] [verbose]
# Component C:
normal
# Component MN:
nple
#
# 2 (BCC_A2) / 2 (BCC_A2)
# -------------------------
# Simulation of interaction between 2 (BCC_A2) and 2 (BCC_A2) ?
# Options: phase_interaction no_phase_interaction identical phases nb
# [ standard | particle_pinning[_temperature] | solute_drag ]
# | [ redistribution_control ] or [ no_junction_force | junction_force ]
phase_interaction
# Type of interfacial energy definition between 2 (BCC_A2) and 2 (BCC_A2) ?
# Options: constant temp_dependent
constant
# Interfacial energy between 2 (BCC_A2) and 2 (BCC_A2) ? [J/cm**2]
# [max. value for num. interface stabilisation [J/cm**2]]
2.00000E-05
# Type of mobility definition between BCC_A2 and BCC_A2?
# Options: constant temp_dependent dg_dependent [fixed_minimum]
constant
# Kinetic coefficient mu between BCC_A2 and BCC_A2 [cm**4/(Js)] ?
1.00000E-05
# Shall misorientation be considered?
# Options: misorientation no_misorientation
# [low_angle_limit (degrees)] default:15 [special_orient (nb)]
no_misorientation

# Input of the misorientation coefficients:
# Modification of interfacial energy for low angle boundaries
# Options: factor read-shockley
# factor
# Prefactor of interfacial energy for low angle boundaries?
# 0.1
# Modification of the mobility for low angle boundaries
# Options: factor humphreys [min_reduction + parameters B and N
#
# factor
# Prefactor of interfacial mobility for low angle boundaries?
# 0.1

# Please specify a criterion for the choice
# of the direction of the redistribution model:
# Options: local_velocity average_velocity bottom_temperature
average_velocity
//
Attachments
INTERFANCE.png
INTERFANCE.png (32.07 KiB) Viewed 943 times

Bernd
Posts: 1504
Joined: Mon Jun 23, 2008 9:29 pm

Re: about gamma-alpha

Post by Bernd » Mon Mar 14, 2022 2:46 pm

Dear shaojielv,

It seems that you have assumed the phase phase transformation kinetics as mobility controlled as you do not use a high mobility with mob_corr for diffusion limited growth, but a relatively small constant mobility value instead. Under these conditions, the kinetic driving force is big compared to the curvature contribution, so that static anisotropy is not taking any action. And the kinetic anisotropy is chosen so small (0.05) that you will hardly see any effect...

In case of diffusion control, small anisotropy values already can have a strong effect, if a morphological instability occurs (like for dendrites). In case of kinetic control, however strong anisotropy is needed to have notable effects.

Bernd

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