Título

COMPUTATIONAL THERMODYNAMICS AS A TOOL TO UNDERSTANDING AND DESIGNING INTERCRITICAL HEAT TREATMENT OF STEELS

COMPUTATIONAL THERMODYNAMICS AS A TOOL TO UNDERSTANDING AND DESIGNING INTERCRITICAL HEAT TREATMENT OF STEELS

Autoria

Cotrim, Francisco de Assis Diniz; Tolomelli, Flávia Tereza dos Santos Fernandes; Silva, André Luiz V. da Costa e

DOI

10.5151/2594-5297-32496

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Resumo

Intercritical heat treatments are used during the processing of many steels. The possibilities associated with the partitioning of carbon between ferrite and austenite and the formation of different austenite decomposition products on cooling has been the reason for the wide acceptance of these treatments. However, the result of the intercritical treatments may deviate from equilibrium predictions. Treatment temperature, heating (or cooling rate) to the treatment temperature, and holding time at temperature are known to have significant effects on the resulting microstructure at the end of the intercritical treatment. Different approaches have been used to model these transformations and better understand the related phenomena. Equilibrium and para-equilibrium calculations have been used, diffusion model with different degrees of complexity have been applied and phase field modeling has also been used. In this work we compare the results of intercritical treatments performed in different steels to the predictions that can be obtained using common computational thermodynamic tools: equilibrium, para-equilibrium and diffusion controlled transformation. As a result of this comparisons we highlight how computational thermodynamics can help in understanding and design intercritical heat treatment of steels and, to some extent, alloy design of these steels. Furthermore, the current limitations of the technique are discussed and further work to improve it, where justified, is suggested.

 

Intercritical heat treatments are used during the processing of many steels. The possibilities associated with the partitioning of carbon between ferrite and austenite and the formation of different austenite decomposition products on cooling has been the reason for the wide acceptance of these treatments. However, the result of the intercritical treatments may deviate from equilibrium predictions. Treatment temperature, heating (or cooling rate) to the treatment temperature, and holding time at temperature are known to have significant effects on the resulting microstructure at the end of the intercritical treatment. Different approaches have been used to model these transformations and better understand the related phenomena. Equilibrium and para-equilibrium calculations have been used, diffusion model with different degrees of complexity have been applied and phase field modeling has also been used. In this work we compare the results of intercritical treatments performed in different steels to the predictions that can be obtained using common computational thermodynamic tools: equilibrium, para-equilibrium and diffusion controlled transformation. As a result of this comparisons we highlight how computational thermodynamics can help in understanding and design intercritical heat treatment of steels and, to some extent, alloy design of these steels. Furthermore, the current limitations of the technique are discussed and further work to improve it, where justified, is suggested.

Palavras-chave

Computational thermodynamics; TRIP; DuAL PHASE; DIFFUSION

Computational thermodynamics; TRIP; DuAL PHASE; DIFFUSION