Growth and coarsening of eutectic M7C3 carbide in Fe–Cr–C alloy during isothermal aging: phase field simulation and experimental research

Autor: Leiji Li, Bin Wang, Ximin Zang, Wanming Li, Jiaxuan Jiang, Ming Chen
Rok vydání: 2021
Předmět:
Zdroj: Applied Physics A. 127
ISSN: 1432-0630
0947-8396
Popis: Combined with phase field simulation and experimental research, the growth and coarsening of M7C3 carbide precipitated from supersaturated austenite matrix were studied. Adopting the CALculation of PHAse Diagram (CALPHAD) method and thermodynamic database, the real Gibbs free energy of the austenite and M7C3 carbide phases in the Fe–Cr–C ternary alloy was established. The growth and coarsening of M7C3 carbide were simulated by phase field method. The microstructure and elements distribution of M7C3 carbide in Fe–Cr–C alloy were observed by field emission scanning electron microscope (FESEM) and energy-dispersive spectrometer (EDS) after various isothermal aging times (0 h, 0.5 h, 2 h) at 1273 K, respectively. Results show that the growth and coarsening of the precipitated M7C3 carbide phase undergo the following process during isothermal aging: first, a single precipitated phase nucleus is precipitated from the matrix; afterward, the single precipitated phase continues to coarsen and grow to form a plate-like structure, or two precipitated phases contact to form a single bar-like structure; then, several precipitated phase nucleuses contact to form an elongated bar shape, and finally, the elongated bar-shaped structure contacts and grows to form a typical lamellar eutectic carbide. In addition, through the analysis of the concentration field, the precipitated M7C3 carbide is a shell structure. The outer layer is a carbon-rich zone, and the inner part is a chromium-rich zone. By comparing the simulated morphology evolution with the experimental microstructure characterization and elements distribution via EDS, the correctness of the proposed phase field model has been verified.
Databáze: OpenAIRE
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