**7. Future Research Directions**

As the main technology in metal AM, L-PBF is evolving toward a greater efficiency, precision, speed, and fabrication of large-sized parts. However, spattering has caused negative influence on the product quality during L-PBF. The following trends characterize the directions of research on L-PBF spatter behavior:


tective gas flow field. The addition of an in situ spatter detection system enables the dynamical feedback of the control of the gas flow field.

**Author Contributions:** Conceptualization, J.Y. and Z.L.; methodology, J.Y. and L.H.; investigation, Y.L. (Yang Liu), Z.N. and W.D.; resources, J.Y. and Z.L.; writing—original draft preparation, Z.L. and H.L.; writing—review and editing, J.Y., L.C., L.K., D.W., P.Z. and Y.L. (Yan Li); supervision, J.Y., L.W., K.Z., Z.Z., L.G. and L.H.; Project administration, L.H., J.Y., X.L., D.Y. and K.G.; Funding acquisition, L.H., J.Y., Z.L. and Y.L. (Yan Li). All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was financially supported by the National Natural Science Foundation of China (61805095, 51675496, 51902295, 52175359, 51905279, 52175237), the Science and Technology Project of the Hubei Province (2021BEC010), the Wuhan Applied Foundational Frontier Project (2020010601012172), the Hubei Province Natural Science Foundation grant (2020 CFB170), and the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan).

**Acknowledgments:** The authors gratefully appreciate Cang Zhao from Tsinghua University and Zhenyu Yan from China Academy of Launch Vehicle Technology for fruitful discussions.

**Conflicts of Interest:** The authors declare no conflict of interest.
