Research ► Microstructure Design
Materials Design Based on Reliable Thermodynamics and Kinetics
Phase field simulations shown in this page was run by Dr. Wei Xiong using in-house code: WEIPHAM.
Atom Probe Images were performed using LEAP 3000X HR produced by IMAGO
Microstructure control is the key to the success of materials design. In my research studies, I use advanced experimental technique as well as modeling tools (ab initio, CALPHAD and phase field simulation) to study microstructure evolution in materials during processing.
2.1. Spinodal decomposition in stainless steels
In the animation showing as below, the LHS figure is the morphology evolution of the Fe-45Cr alloy, which the RHS is the contour evolution corresponding to the left one. (In order to see more fluently, you may need to wait until running two cycles to save some caches of the frames. Afterwards, please press 'F5' to refresh or reload this page, you will see synchronous animations for both.)
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Simulated 3D spinodal decomposition structure by using the phase field method
Althought it is helpful to understand the mechanism of spinodal decomposition using theoretical modeling, it is vital to validate and calibrate the model using key experiments. In the study of Fe-Cr binary alloys, we designed several alloys to study the modulated structure of phase separation near to the spinodal curve. As shown in the left figure. (a) is the alloy with 26.65 at.% which indicates the small isolated particles forming in the material. (b) is for the alloy with composition almost touching the predicted chemical spinodal curve, therefore, we could see spinodal-like nucleation. (c) is the modulated structure from the alloy well located in the spinodal region. The measure spinodal wave length is about 6 nm. Therefore, only 3D atom probe tomography is capable to capture this unique feature of microstructure evolution. |
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In one of our research work, we did experiments and CALPHAD together showing the importance of thermodynamic description on predicting the spinodal region. In that work, calorimetry, atom probe and CALPHAD were carefully discussed in the case of Fe-Cr. The left animation shows the sampling process during the atom probe tomography. Simulations from the phase field simulation can demonstrate the process of the atom probe tomography and assist the data analysis. The work is still in progress, but will soon be submitted for publication. We will discuss the simulation of the steel systems using the phase field simulation, and its comparable results with atom probe tomography. |
2.2. Grain growth and precipitation in stainless steels
2.3. Development of phase field model coupling with CALPHAD, experiments and ab initio calculations