Title

A BRIEF THERMODYNAMIC EVALUATION OF PRECIPITATION MODELS IN MICROALLOYED STEELS

A BRIEF THERMODYNAMIC EVALUATION OF PRECIPITATION MODELS IN MICROALLOYED STEELS

Authorship

Silva, André Luiz Vasconcellos da Costa e

DOI

10.5151/1983-4764-32160

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Abstract

The knowledge of the amount of microalloying elements in solution and precipitated during processing of steels is very important to properly design the steel and the thermomechanical processing (TMP). Models have been formulated to describe the precipitation phenomena during TMP in great detail. Some of these models use simple solubility products, however, together with complex phenomenological equations to describe the changes in the steel during TMP. In this work two of these simple solubility products frequently used are compared with results calculated with computational thermodynamics. The results suggest that they are not able to predict the same values as those calculated by computational thermodynamics. If the later are correct, the simple solubility products are probably introducing “correcting” factors in the phenomenological equations in order to reproduce experimental results. Furthermore, if this is the case, the ability of the models to extrapolate, a basic condition in alloy design, can be questioned.

 

The knowledge of the amount of microalloying elements in solution and precipitated during processing of steels is very important to properly design the steel and the thermomechanical processing (TMP). Models have been formulated to describe the precipitation phenomena during TMP in great detail. Some of these models use simple solubility products, however, together with complex phenomenological equations to describe the changes in the steel during TMP. In this work two of these simple solubility products frequently used are compared with results calculated with computational thermodynamics. The results suggest that they are not able to predict the same values as those calculated by computational thermodynamics. If the later are correct, the simple solubility products are probably introducing “correcting” factors in the phenomenological equations in order to reproduce experimental results. Furthermore, if this is the case, the ability of the models to extrapolate, a basic condition in alloy design, can be questioned.

Keywords

Computational thermodynamics, microalloying, Steel, Precipitation, Nb

Computational thermodynamics, microalloying, Steel, Precipitation, Nb