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<p>Models of single-crystal and polycrystal M50NiL steel were established by the classical molecular dynamics simulation (MD) method. The uniaxial tensile deformation behavior and microstructure evolution of single-crystal and polycrystalline M50NiL steel models at 300&#xa0;K and 0.02-Å/ps strain rate were studied in detail. The simulation results show that grain boundaries can reduce the compressive degree of the Fe matrix after relaxation and reduce the stress in the sample during the tensile process. The fracture time of polycrystalline M50NiL steel is earlier and the tensile strength of it is significantly lower than the single-crystal M50NiL steel, showing an inverse Hall–Petch law phenomenon. The main deformation mechanisms of both single-crystal and polycrystalline M50NiL steel samples are attributed to the glide of Shockley partial dislocations and the generation and expansion of stacking faults. Initially, the transformation of the FCC and HCP lattices occurs, during which defect atoms, stacking faults, and dislocation nucleation will be generated. As the number of FCC lattice atoms increases, dislocations begin to slip and leave stacking faults. Ultimately, due to dislocation reactions, micro-holes are formed and then evolve into cracks. As the number of dislocations decreases and the number of disordered atoms increases, cracks expand and fracture.</p>

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Molecular Dynamics Simulation of Effect of Grain Boundaries on Mechanical Properties and Deformation Mechanism of M50NiL Steel

  • 期刊论文

  • 发表日期：

    2025年5月9日

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  • Changchang Li,
  • Bo Li,
  • Maosheng Yang,
  • Xi Yong,
  • Xiaolong Zhou

摘要

Models of single-crystal and polycrystal M50NiL steel were established by the classical molecular dynamics simulation (MD) method. The uniaxial tensile deformation behavior and microstructure evolution of single-crystal and polycrystalline M50NiL steel models at 300 K and 0.02-Å/ps strain rate were studied in detail. The simulation results show that grain boundaries can reduce the compressive degree of the Fe matrix after relaxation and reduce the stress in the sample during the tensile process. The fracture time of polycrystalline M50NiL steel is earlier and the tensile strength of it is significantly lower than the single-crystal M50NiL steel, showing an inverse Hall–Petch law phenomenon. The main deformation mechanisms of both single-crystal and polycrystalline M50NiL steel samples are attributed to the glide of Shockley partial dislocations and the generation and expansion of stacking faults. Initially, the transformation of the FCC and HCP lattices occurs, during which defect atoms, stacking faults, and dislocation nucleation will be generated. As the number of FCC lattice atoms increases, dislocations begin to slip and leave stacking faults. Ultimately, due to dislocation reactions, micro-holes are formed and then evolve into cracks. As the number of dislocations decreases and the number of disordered atoms increases, cracks expand and fracture.