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Avrami kinetics JMAK equation for non isothermal cases

Posted 31.03.2022, 05:18 GMT-4 Heat Transfer 4 Replies

Aswin P
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In the material processing module JMAK equations are provided to calculate resulting phases and its kinetics. JMAK equations are defined in Isothermal conditions. When using it to predict phase fractions in heat transfer problems where temperature is not constant certain assumptions are taken in general.

Just wanted to know , is it possible to use material processing module for non isothermal cases. Do we have to make any change in the existing set up.

4 Replies Last Post 15.04.2022, 15:02 GMT-4
Mats Danielsson COMSOL Employee

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Posted: 3 years ago 31.03.2022, 07:50 GMT-4

Hello. The implementation of the JMAK phase transformation model is done on a rate form (just like the other phase transformation models in the Metal Processing Module). The rate form has been derived by differentiating the "standard" JMAK equation with respect to time. So, within the assumptions leading to this rate form, you don't have to do anything special to use the model under a thermal transient.

Mats

Hello. The implementation of the JMAK phase transformation model is done on a rate form (just like the other phase transformation models in the Metal Processing Module). The rate form has been derived by differentiating the "standard" JMAK equation with respect to time. So, within the assumptions leading to this rate form, you don't have to do anything special to use the model under a thermal transient. Mats
Aswin P
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Posted: 3 years ago 11.04.2022, 00:36 GMT-4

Thanks Mats!

Just wanted to talk about a specific case with Ti6Al4V material. While using such material for analysising thermal based manufacturing processes (Laser etc..) for rapid cooling how should be the approach? Equilibirum phase fractions and other parameters (JMAK Exponent) will varry with temerature I believe. So can we define these arameters as Temperature depndent interpolation functions?

Thanks Mats! Just wanted to talk about a specific case with Ti6Al4V material. While using such material for analysising thermal based manufacturing processes (Laser etc..) for rapid cooling how should be the approach? Equilibirum phase fractions and other parameters (JMAK Exponent) will varry with temerature I believe. So can we define these arameters as Temperature depndent interpolation functions?
Mats Danielsson COMSOL Employee

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Posted: 3 years ago 13.04.2022, 01:00 GMT-4

Hello.

In modeling the decomposition of beta into different alpha phases (like grain boundary alpha, martensitic alpha, etc.) you'll have to identify a suitable modeling framework in the literature. With this at hand, you can simply start off by adding phase transformations and metallurgical phases to the physics interface. You are correct in that parameters are generally temperature dependent. For example, in the user input for the equilibrium phase fraction, you could define an interpolation function "int1", and type something like "int1(metp.T)". The program will automatically evaluate expressions that you enter.

Mats

Hello. In modeling the decomposition of beta into different alpha phases (like grain boundary alpha, martensitic alpha, etc.) you'll have to identify a suitable modeling framework in the literature. With this at hand, you can simply start off by adding phase transformations and metallurgical phases to the physics interface. You are correct in that parameters are generally temperature dependent. For example, in the user input for the equilibrium phase fraction, you could define an interpolation function "int1", and type something like "int1(metp.T)". The program will automatically evaluate expressions that you enter. Mats
Aswin P
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Posted: 3 years ago 15.04.2022, 15:02 GMT-4

Thank You, Will Try

Thank You, Will Try

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