Diffusivities matrix
Posted: Wed Nov 25, 2009 3:56 pm
Hallo
I have a question about the diffusivity matrix in DICTRA/MICRESS. One can directly obtain the diffusivity matrix in DICTRA which is needed for the Fick's first law. For carbon flux in steel, for example, the concentration gradient of other alloying elements will affect the carbon diffusion flux. That's why we need to put other components in the diffusivity matrix (D fe,c,x) in the Fick's equation. Am I right?
I understand that the elements like Mo for sure reduces the diffusivity of carbon. If we have Fe-C-Mo system and if the Mo concentration is homogeneous, no concentration profile appears. How will the D fe,c,mo can affect the Jc? The term D fe,c,mo must be multiplied by the concentration gradient of Mo, which is now zero. Then the term relating Mo should be zero.
In this case, does only D fe,c,c affect the diffusion of carbon? To my understanding, it should not be like that because Mo should have at least some effect on carbon diffusion even the Mo concentration is homogenous. So D fe,c,c is anyway not the effective carbon diffusivity in the steel.
Can you give me any clue how one can obtain an 'effective' diffusivity of carbon under the influence of other alloying elements, or any reference?
Thank you very much and best regards,
nokkikku
I have a question about the diffusivity matrix in DICTRA/MICRESS. One can directly obtain the diffusivity matrix in DICTRA which is needed for the Fick's first law. For carbon flux in steel, for example, the concentration gradient of other alloying elements will affect the carbon diffusion flux. That's why we need to put other components in the diffusivity matrix (D fe,c,x) in the Fick's equation. Am I right?
I understand that the elements like Mo for sure reduces the diffusivity of carbon. If we have Fe-C-Mo system and if the Mo concentration is homogeneous, no concentration profile appears. How will the D fe,c,mo can affect the Jc? The term D fe,c,mo must be multiplied by the concentration gradient of Mo, which is now zero. Then the term relating Mo should be zero.
In this case, does only D fe,c,c affect the diffusion of carbon? To my understanding, it should not be like that because Mo should have at least some effect on carbon diffusion even the Mo concentration is homogenous. So D fe,c,c is anyway not the effective carbon diffusivity in the steel.
Can you give me any clue how one can obtain an 'effective' diffusivity of carbon under the influence of other alloying elements, or any reference?
Thank you very much and best regards,
nokkikku