> For the complete documentation index, see [llms.txt](https://dante-solutions-inc.gitbook.io/dante-6.3-help-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dante-solutions-inc.gitbook.io/dante-6.3-help-documentation/readme/material-models-for-steels/austenite-decomposing-model.md). # Austenite Decomposing Model Phase transformations during cooling or quenching is one of the most important phase transformations for heat treatment process modeling, which includes the decomposing of austenite to ferrite, pearlite, bainite, and martensite. This section briefly describes the austenite decomposing material models and material data definition, including Austenite to Ferrite, Austenite to Pearlite, Austenite to Bainite, and Austenite to Martensite phase transformations. **Below is the austenite decomposing equation from austenite to ferrite or pearlite.** $$\frac{dF}{dt} = v\_1 \cdot \frac{1}{\exp(v\_2 + v\_3 \cdot \ln\left(\frac{v\_4 - T}{v\_5}\right))} \cdot F^{v\_6} \cdot (1 - F)^{v\_7} \cdot A$$ Where *F* is volume fraction of the diffusive phase (ferrite or pearlite), *t* is time, *v1*, *v2*, *v3*, *v4*, *v5*, *v6*, *and v7* are constants, *A* is volume fraction of austenite phase, and *T* is temperature. The austenite decomposing model parameters to diffusive phases are defined by keywords: **\*STEEL\_KIN\_AFERR** for the transformation from austenite to ferrite; **\*STEEL\_KIN\_APEAR** for the transformation from austenite to pearlite. For each keyword, the first two data lines are for defining the alloy composition effect on transformation rate, and the third data line is the phase transformation data of the model parameters for the nominal composition. The following shows examples of the material data definition for Austenite to Ferrite and Austenite to Pearlite transformations. ``` ** Austenite-->Ferrite *STEEL_KIN_AFERR ** Line 1: Alloy Effect on Mobility: B1+B2X+B3X^2+B4N+B5N^2 ** Line 2: Effect by Moly Content (0.0, Nominal, 5.0) ** Line 3: Kinetics (9 values) 1.0, 6.0, 0.0, 0.0, 0.0 0.1, 1.0, 10.0 520.0, 760.0, 0.10073, 7.9851, 0.6903, 815.42, 153.46, 0.8117, -0.7588 ** Austenite-->Pearlite *STEEL_KIN_APEAR ** Line 1: Alloy Effect on Mobility: B1+B2X+B3X^2+B4N+B5N^2 ** Line 2: Effect by Moly Content (0.0, Nominal, 5.0) ** Line 3: Kinetics (9 values) 1.0, 6.0, 0.0, 0.0, 0.0 0.1, 1.0, 10.0 520.0, 750.0, 2.712E-02, 10.499, 0.723, 793.14, 130.72, 0.796, -0.2968 ``` In the example above, ***X*** is alloy factor, and ***N*** is nitrogen percentage * Line 1: Alloy factor and nitrogen effects on austenite decomposing to ferrite or pearlite\ \- Variables *a, b and c are coefficients for alloy factor; d and e are coefficients for nitrogen effect*. * Line 2: Moly element effect on transformation rate: *a, b, and c* - Variable *b* is the factor of current Moly content effect on transformation rate - Variable a is the Moly effect factor when Moly =0.0, with mobility term *v1*/a - Variable c is the Moly effect factor when Moly is 5.0%, with mobility term *v1*/c * Line 3: Variables for Austenite to Ferrite or Pearlite transformation parameters - Parameter 1: Low temperature bound for austenite decomposing - Parameter 2: High temperature bound for austenite decomposing - Parameters 3-9: Variable values for *v1*, *v2*, *v3*, *v4*, *v5*, *v6*, *and v7* in the austenite decomposing equation to ferrite and pearlite The austenite decomposing model parameters to bainite is similar to those parameters to ferrite and pearlite. The keyword is **\*STEEL\_KIN\_ABAIN** for the transformation from austenite to bainite. For each keyword, the first two data lines are for defining the alloy $$\frac{dB}{dt} = v\_1 \cdot \frac{1}{\exp(v\_2 + v\_3 \cdot \ln\left(\frac{v\_4 - T}{v\_5}\right))} \cdot (F + v\_8 \cdot (1 - A - B))^{v\_6} \cdot (1 - F)^{v\_7} \cdot A \cdot (v\_9 - B)$$ Where *B* is volume fraction of the Bainite phase, *t* is time, *v1*, *v2*, *v3*, *v4*, *v5*, *v6*, *v7*, *v8*, and *v9* are constants, *A* is volume fraction of austenite phase, and *T* is temperature. One example of austenite decomposing to bainite is shown below. ``` ** Austenite-->Bainite *STEEL_KIN_ABAIN ** Line 1: Alloy Effect on Mobility: B1+B2X+B3X^2+B4N+B5N^2 ** Line 2: Effect by Moly Content (0.0, Nominal, 5.0) ** Line 3: Kinetics (13 values) 1.0, 6.0, 0.0, 0.0, 0.0 0.5, 1.0, 2.0 300.0, 450.0, 560.0, 0.259, 2.428, 2.0527, 567.12, 116.57, 0.50496, -0.992, 0.2, 1.0, 1.0 ``` In the example above, ***X*** is alloy factor, and ***N*** is nitrogen percentage * Line 1: Alloy factor and nitrogen effects on austenite decomposing to bainite\ \- Variables *a, b and c are coefficients for alloy factor; d and e are coefficients for nitrogen effect*. * Line 2: Moly element effect on transformation rate: *a, b, and c* - Variable *b* is the factor of current Moly content effect on transformation rate - Variable a is the Moly effect factor when Moly =0.0, with mobility term *v1*/a - Variable c is the Moly effect factor when Moly is 5.0%, with mobility term *v1*/c * Line 3: Variables for Austenite to Ferrite or Pearlite transformation parameters - Parameter 1: Low temperature bound for austenite decomposing - Parameter 2: Temperature to separate lower bainite and upper bainite - Parameter 3: High temperature bound for austenite decomposing - Parameters 4-: Variable values for *v1*, *v2*, *v3*, *v4*, *v5*, *v6*, *v7*, *v8*, *v9* in the austenite decomposing equation to bainite **Austenite transformation to martensite is diffusionless, and the equation is below.** $$\frac{dM}{dT} = v\_1 \cdot (M + v\_4 \cdot D)^{v\_2} \cdot (1 - v\_5 \cdot M)^{v\_3} \cdot A$$ Where *M* is volume fraction of martensite phase, *v1*, *v2*, *v3*, *v4*, and *v5* are constants, *A* is volume fraction of austenite phase, D is volume fraction of diffusive phase, and *T* is temperature. The austenite phase decomposing material data are defined in the material data \*.CQT file. The keyword ***\*STEEL\_KIN\_AMART*** is used to define the transformation from austenite to martensite. There are three data lines following the ***\*STEEL\_KIN\_AMART*** keyword, and they are explained below. ``` ** Austenite-->Martensite *STEEL_KIN_AMART ** Line 1: Alloy Effect on Ms: A+BX+BX^2+CN+CN^2 (Unit:C) ** Line 2: Alloy Effect on Mobility : A+BX+BX^2+CN+CN^2 ** Line 3: Kinetics data; 1st(Ms); 2nd(Mobility); 3rd(Alpha); 4th(Beta); ** 5th(Diffusive phase effect beginning); 6th(Diffusive phase effect end) 0.0, 0.0, 0.0, 0.0, 0.0 1.0, 0.0, 0.0, 0.0, 0.0 414.85, 7.76336E-02, 0.752566, 0.66888, 0.20, 0.00 ``` In the example above, ***X*** is alloy factor, and ***N*** is nitrogen percentage * Line 1: Alloy factor and nitrogen effects on martensite start temperature (Ms) - Variables *a, b and c are coefficients for alloy factor; d and e are coefficients for nitrogen effect*. * Line 2: Alloy factor and nitrogen effects on martenstitic transformation rate - Variables *a, b and c are coefficients for alloy factor; d and e are coefficients for nitrogen effect*. * Line 3: Variables for martensitic transformation - Parameter 1: martensite start temperature, Ms - Parameters 2-5: are the variables *v1*, *v2*, *v3*, *v4*, and *v5* in martensite transformation equation Note: *v4* affects the effect of diffusive phases on martensite transformation rate at the beginning, and *v6* affects the diffusive phases on martensite transformation rate at the end. Carbon value, grain size, and alloy composition can be specified in the model to affect the material's hardenability. Austenite decomposing to diffusive phases can often be viewed by TTT diagram, which can be generated using DANTE utility tool, [**TTT Generator**](https://github.com/DANTE-Solutions/DANTE-6.3-Docs/blob/main/docs/utility-tools/ttt-generator/README.md).
Austenite decomposing to martensite can be viewed by continuous cooling dilatometry curve, which can be generated using DANTE utility tool, [**Mat Simulator**](https://github.com/DANTE-Solutions/DANTE-6.3-Docs/blob/main/docs/utility-tools/mat-simulator/README.md).
DANTE austenite decomposing model has the feature of simulating the rejection of carbon from forming ferrite. It is well known that the solubility of carbon in ferrite is low, resulting in the rejection of carbon from the matrix as ferrite is formed. The additional carbon enters the austenite matrix, locally increasing the carbon concentration. This increase in carbon affects subsequent phase transformations from austenite and should be, and is, simulated for accurate phase transformation timings. An example below shows the effect of forming ferrite on further martensitic transformation for AISI 4120 steel. The dilatometry strain curve is calculated from DANTE material database using [**Mat Simulator**](https://github.com/DANTE-Solutions/DANTE-6.3-Docs/blob/main/docs/utility-tools/mat-simulator/README.md). ![](https://github.com/DANTE-Solutions/DANTE-6.3-Docs/blob/main/docs/.gitbook/assets/pic0007%20\(2\).jpg) --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://dante-solutions-inc.gitbook.io/dante-6.3-help-documentation/readme/material-models-for-steels/austenite-decomposing-model.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.