Diffusion between Two Phases: Uniform Initial Compositions
Purpose: Learn to perform diffusion simulation at constant temperature for a diffusion couple with the two sides having different phase structure and uniform composition through each side before diffusion.
Module: PanDiffusion
Thermodynamic and Mobility Database: FeCrNi.tdb
Batch file: Example_#4.3.pbfx
Calculation Procedures:
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Create a workspace and select the PanDiffusion module following Pandat User's Guide: Workspace;
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Load FeCrNi.tdb following the procedure in Pandat User's Guide: Load Database , and select all three components;
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Click on the menu "PanDiffusion → Diffusion Simulation" and set up the calculation condition as shown in Figure 1. First select "Region Composition Distribution" as Uniform, which means that composition in each region is uniform before diffusion. Click on Region_1 and set the composition of the left side of the diffusion couple as 30Cr-10Fe-60Ni (at%), then click on Region_2 and set the composition of the right side of the diffusion couple as 55Cr-40Fe-5Ni (at%) (which is not shown in Figure 1).
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The length of both Region_1 and Region_2 is set to be 100 mm, and the total number of grids (# of Grids) is 100.
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The Thermal History is holding the diffusion couple at 1000 °C for 200 hours.
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In the settings shown in Figure 1, composition profiles only at the initial and final stages will be outputted. Click OK to perform calculations.
Post Calculation Operation:
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Change graph appearance and add text following the procedure in Pandat User's Guide: Property. The calculated plot is show in Figure 2
Information obtained from this calculation:
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The two sides of the diffusion couple locate at different phase fields, one in Fcc and the other in Bcc as shown in the isotherm of Fr-Cr-Ni at 1000°C in Figure 3, therefore diffusion between them pass through the Fcc+Bcc two-phase field;
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After holding the diffusion couple at 1000 °C for 200 hours, boundary between the Fcc and Bcc moved.
