# Simulation and Experimental Study of Laser Processing NdFeB Microarray Structure

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## Abstract

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## 1. Introduction

## 2. Numerical Simulation Modeling

- The laser has a Gaussian profile. The ablation process is stable, and the reflection of the laser beam on the surface of the crater is neglected.
- Solid metals are considered very viscous fluids, and molten metals are incompressible non-Newtonian fluids under laminar flow.
- Effects such as the shielding effect of the plasma are ignored.

#### 2.1. Heat Transfer Modeling

#### 2.2. Heat Transfer Boundary Condition

#### 2.3. Solid–Liquid Interface Treatment

#### 2.4. Flow Modelling

#### 2.5. Ablation Deformation Modelling and Meshing

## 3. Simulation and Experiment Procedures

## 4. Results and Discussion

#### 4.1. Temperature Field and Flow Fields Analysis

#### 4.2. Effect of Laser Scanning Speed on the Processing Morphology

#### 4.3. Effect of Average Power on the Processing Morphology

## 5. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 3.**Microstructure morphology and temperature field distribution at different pulse cycles (Average power = 8 W, pulse width = 40 ns, frequency = 150 kHz, scanning speed = 100 mm/s).

**Figure 4.**Experimental results of laser processing (Average power = 8 W, pulse width = 40 ns, frequency = 150 kHz, scanning speed = 100 mm/s).

**Figure 5.**Maximum temperature and ablation depth variation. (

**a**) Maximum temperature and ablation depth variation in single pulse cycle. (

**b**) Maximum temperature variation in five pulse cycles.

**Figure 6.**Flow field velocity of the melt pool. (Average power = 8 W, pulse width = 40 ns, frequency = 150 kHz, scanning speed = 100 mm/s).

**Figure 7.**SEM morphology of microstructure after laser processing. (Average power = 8 W, pulse width = 40 ns, frequency = 150 kHz, scanning speed = 100 mm/s).

**Figure 8.**Temperature field distribution and flow field velocity at different scanning speeds (Average power = 8 W, pulse width = 40 ns, frequency = 150 kHz).

**Figure 9.**Experimental results of laser processing at different scanning speeds (Average power = 8 W, pulse width = 40 ns, frequency = 150 kHz).

**Figure 10.**The comparison results of laser ablation depth and the variation of the flow velocity at different scanning speeds.

**Figure 11.**Temperature field distribution and flow field velocity at different average powers (Pulse width = 40 ns, frequency = 150 kHz, scanning speed = 100 mm/s).

**Figure 13.**Experimental results of laser processing at different average powers (Pulse width = 40 ns, frequency = 150 kHz, scanning speed = 100 mm/s).

**Figure 14.**The comparison results of laser ablation depth and the variation of the flow velocity at different average power.

Property | Symbol | Value | Unit |
---|---|---|---|

Melting temperature | T_{m} | 1811.2 | K |

Vaporizing temperature | T_{v} | 3135.2 | K |

Ambient temperature | T_{a} | 293.15 | K |

Solid phase density | ρ_{s} | 7500 | kg/m^{3} |

Liquid phase density | ρ_{l} | 6500 | kg/m^{3} |

Specific heat of solid phase | C_{ps} | 440 | J/(kg∙K) |

Specific heat of liquid phase | C_{pl} | 551 | J/(kg∙K) |

Solid phase thermal conductivity | k_{s} | 9 | W/(m·K) |

Liquid phase thermal conductivity | k_{l} | 7 | W/(m·K) |

Latent heat of fusion | L_{m} | 2.466 × 10^{5} | J/kg |

Latent heat of vaporization | L_{v} | 6.071 × 10^{6} | J/kg |

Coefficient of heat transfer | h_{1} | 15 | W/(m^{2}·K) |

Temperature transition interval of melting | ∆T | 50 | K |

Dynamic viscosity of liquid phase | μ_{l} | 8 × 10^{−3} | Pa·s |

The surface tension of the pure metal | γ | 1.84 | N/m |

Surface tension temperature coefficient | A_{γ} | −5 × 10^{4} | N/(m∙K) |

Mushy zone constant | A_{m} | 10^{6} | kg/m^{3}∙s |

Groups | Average Power | Scanning Speed |
---|---|---|

1 | 8 | 100, 500, 1000 |

2 | 5, 8, 13 | 100 |

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**MDPI and ACS Style**

Zhao, Y.; Wang, S.; Yu, W.; Long, P.; Zhang, J.; Tian, W.; Gao, F.; Jin, Z.; Zheng, H.; Wang, C.;
et al. Simulation and Experimental Study of Laser Processing NdFeB Microarray Structure. *Micromachines* **2023**, *14*, 808.
https://doi.org/10.3390/mi14040808

**AMA Style**

Zhao Y, Wang S, Yu W, Long P, Zhang J, Tian W, Gao F, Jin Z, Zheng H, Wang C,
et al. Simulation and Experimental Study of Laser Processing NdFeB Microarray Structure. *Micromachines*. 2023; 14(4):808.
https://doi.org/10.3390/mi14040808

**Chicago/Turabian Style**

Zhao, Yong, Shuo Wang, Wenhui Yu, Pengyu Long, Jinlong Zhang, Wentao Tian, Fei Gao, Zhuji Jin, Hongyu Zheng, Chunjin Wang,
and et al. 2023. "Simulation and Experimental Study of Laser Processing NdFeB Microarray Structure" *Micromachines* 14, no. 4: 808.
https://doi.org/10.3390/mi14040808