Equiaxed grain growth in presence of Latent heat

[pakanatiakash]

Hi

I am new to micress and I am interested in studying the grain evolution for equiaxed grains. For this purpose, I have tweaked the example files of Al-Cu equiaxed grain growth. I have managed to conduct simulations for Al-4.7%Cu but without considering latent heat. I am trying to add latent heat module but I am not able to run the program. Could you guys kindly advise on the correct way to update the file.

I am attaching the input file for the case without latent heat.

Regards
Akash

[Bernd]

Dear Akash,

Welcome to the MICRESS forum!


For equiaxed solidification, regarding latent heat, we typically use two different approaches, a simple one which strictly speaking is only correct for small samples ("DTA approximation") and which is represented in the standard example AlCU_Equiaxed_dri, and a more complicated one like in AlCu_Temp1d_dri which uses the "Homoenthalpic approximation". Let's assume you want to start with the simple one.
In case of TQ coupling like in AlCU_Equiaxed_dri there is little input necessary because the enthalpy and heat capacity of the phases is automatically taken from database. Latent heat release is averaged over the domain and interacts with the heat extraction rate (per volume) which you define in the section "Boundary Conditions". As a result, temperature is calculated.
In case of linearized phase diagrams, you need to specify enthalpies and heat capacity. It is important to note that latent heat is the difference between the enthalpies of the phases, while the absolute values of enthalpies don't matter.

Does this answer your questions? Please explain specific problems with more details.

Best regards

Bernd

[pakanatiakash]

Hi

Thank you for the prompt response. This is my current configuration for latent heat and heat extraction.

# Parameters for latent heat and 1D temperature field
# ===================================================
# Simulate release of latent heat?
# Options: lat_heat lat_heat_3d[matrix phase] no_lat_heat no_lat_heat_dsc
lat_heat
# Enthalpy of phase 0? ([J/m^3])
9.67e8
# Specific heat capacity (Cp) of phase 0? ([J/(m^3*K)])
2468700.
# Enthalpy of phase 1? ([J/cm^3])
0.0
# Specific heat capacity (Cp) of phase 1? ([J/(m^3*K)])
2468700.
# Simulation with release of pseudo-3D latent heat of phase 1 (FCC_A1)?
# Options: pseudo_3d [crit. matrix fraction] no_pseudo_3
#no_pseudo_3D
# Interval for updating enthalpy data [s]
#0.10000
#
#
# Boundary conditions
# ===================
# Type of heat flow trend?
# Options: linear linear_from_file
linear
# Number of connecting points? (integer)
0
# Initial temperature at the bottom? (real) [K]
930.0000
# Temperature gradient in z-direction? [K/cm]
0.0000
# Heat flow? [J/s*cm^3]
-1.382e1

I would like to clarify regarding the following variables.

# Enthalpy of phase 0? ([J/m^3]) I calculate as - L(J/kg)*rho(kg/m^3) = 3.92e5*2468.7 = 9.67e8
# Specific heat capacity (Cp) of phase 0? ([J/(m^3*K)]) - I calculate as Cp(J/(K kg))*rho(kg/m^3) = 1000*2468.7 = 2468700.
# Heat flow? [J/s*cm^3] I calculate as rho(kg/m^3)*Cp(J/K*kg)*coolingrate (K/s) = 2468.7*1000*5.6 = -13.82

Coolingrate is 5.6 K/s


But with the calculated heat flow I am not able to solidify. I do not see any nucleation. This is where I am stuck at the moment. Could you advise what i am doing wrong here?

Akash

[Bernd]

Dear Akash,

The length unit for MICRESS input is cm, not m!

This makes a factor of 100 ^3 = 1.0E6 by which both enthalpies and heat capacities should be smaller.


Bernd

[pakanatiakash]

Hullo

Thank you for the reply and I think I have managed to do what i wanted to do. I am struggling a little in the next step. So far i have been able to simulate a group of grains and their growth. Now I want to focus only on a single grain and its morphology evolution. To be more precise, I want to simulate the growth of a quarter of a grain with periodic boundary conditions. I drew this simple image of a globular grain to show what i want and i have attached. I am also attaching the Micress file which I have used to simulate multiple grains.

[ralph]

You can set the center outside of the domain to get a section, only. Be aware that it will show up on the opposite side if you set periodic boundary conditions.
I would recommend setting a grain with the center a corner, radius 0 and "stabilisation" for the applied small grain growth model.

Cheers,
Ralph

[pakanatiakash]

Thank you for the response. But how do you set the center of the grain at the corner?

[ralph]

Just give the coordinates in micrometer of the corner cell.

Example:
Cells: 10 x 10
Spacing: 1 micrometer

Lower left corner : 0.5 x 0.5
Lower right corner : 9,5 x 9,5 , i.e.[ (CellsX x spacing) - spacing/2 ]

Cheers,
Ralph

[pakanatiakash]

Hullo

I did some testing but it did not work for me. I am able to place the grain at a corner but when I run the simulation the phase change does not occur. Even after reaching the eutectic temperature by cooling the domain with heatflux, I do not see any solid phase. The fraction of solid always remains zero inspite of cooling the domain. I am assuming something is wrong with BCs. I am attaching the setup file and it would be great if you can provide any inputs.

Regards
akash

[ralph]

Hi Akash,

your initial temperature is higher than the equilibrium temperature for your initial concentration of 20.1 percent of component 1 in liquid
According to your linear phase diagram, it should be around 860 K.

You set a pure component 0 grain:
# initial concentrations
input
20.10
0.

Is that meaningfull?
Better to use the equilibrium composition:
#initial concentration
equilibrium
20.10

Cheers,
Ralph