Simulation of thermal decomposition of ?' -Fe₄N using molecular dynamics method

JX Zhu and JP Wang, AIP ADVANCES, 13, 025234 (2023).

DOI: 10.1063/9.0000606

alpha '' -Fe16N2 is a promising environmentally friendly rare-earth-free permanent magnet material with ultra-high saturation magnetization. Recent research has demonstrated experimentally through a thermally quenching treatment using gamma ' phase Fe4N as a precursor to synthesize alpha '' -Fe16N2 in bulk format. In this research using Molecular Dynamics (MD) simulation, we investigated the gamma ' -Fe4N phase thermal decomposition process and the potential phase transition from face center cubic (fcc)-phase to body center tetragonal (bct)-phase. As nitrogen concentration is higher in gamma ' -Fe4N (5.9 wt. %) than that in alpha ' -Fe8N or alpha '' -Fe16N2 (3 wt. %), Nitrogen bond formation through atom diffusion is studied with a "Nitrogen-rich " grain boundary (GB) model to find out whether lower- Nitrogen content bct Fe-N solid solution can be formed. Modified Embedded Atom Method (MEAM) interatomic potential of Fe-N system is applied. Post-processing including Nitrogen bond mapping/tracking is also performed for the thermostat-controlled heating and quenching simulation process. We also applied virtual XRD computation to characterize the material crystallographic texture before and after the thermal treatment.

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