In the past 30 years, metal additive manufacturing technology (commonly known as metal 3D printing ) has developed rapidly, and has made profound changes in the fields of aerospace, automobiles, national defense, chemicals, medicine, energy, etc. Laser powder bed melt additive manufacturing (also known as laser selection melting) is one of the most widely used technologies. However, to date, the academic community has not yet had a deep understanding of laser-matter interactions, and the definition of laser melting mode is still vague and there is no consensus yet. This makes it still difficult to manufacture defect-free and microstructure-controllable components, limiting further breakthroughs in the laser powder bed melt additive manufacturing industry.
Figure 1. Melting mode in metal laser additive manufacturing
(a) The physical basis of melting mode definition; (b)-(c) Definition based on static analysis; (d) Definition based on dynamic process
Recently, Assistant Professor Zhao Cang of the Department of Mechanical Engineering of Tsinghua University published a review paper "Laser melting modes in metal powder bed fusion additive manufacturing" in the authoritative journal of the international physics community "Reviews of Modern Physics" (Reviews of Modern Physics). The author first elaborates on the general physical process in the melt additive manufacturing of metal laser powder beds, highlighting two key coupled phenomena: melting and vaporization, liquid protrusions in the front wall of the keyhole and keyhole instability. These physical phenomena drive the morphological evolution of the melt pool and keyhole and are the cornerstone of the definition of laser melting mode. Afterwards, the authors divided the laser melting mode into two categories according to the characterization measurement methods of the melt pool and keyhole (Fig. 1). The first type is based on static post-metal analysis, while the second type is based on in-situ and dynamic process visualization. In comparison, the definition based on process visualization is more rigorous and physical, providing new production guidelines and new research directions for melt additive manufacturing of metal laser powder beds. The author emphasizes the importance of keyholes and points out that additive manufacturing based on the steady-state keyhole melting mode is more efficient, sustainable and robust. The implementation of this concept will depend on the development of multi-physical models, multi-information transcription (Figure 2), and cross-platform cross-scale process metrology.
Figure 2. Multiple information transcription and knowledge transfer
Zhao Cang is the independent first author of the paper and the independent corresponding author . The authors also include Du Dong, a professor of mechanical engineering at Tsinghua University, PhD in PhD in 2021, and PhD in 2019, Chen Shuailei, an associate professor at the University of Virginia in the United States, Brian Simonds, a researcher at the National Institute of Standards and Technology, Kamel Fezzaa, a researcher at the Argonne National Laboratory, and Anthony Rollett, a professor at Carnegie Mellon University. The research was funded by the National Natural Science Foundation of China, Tsinghua University - Imperial College of Technology Research Innovation Seed Fund and other funds.
"Modern Physics Review" was founded in 1929. It is the most authoritative review journal in the international physics community. It publishes thirty to forty academic papers every year, including the Nobel Prize in Physics speech. The journal aims to make historical summary, expound principles, current status analysis and trend predictions on major hot issues in today's physics research. This paper is the first paper published by Tsinghua University in this journal as the first completed unit and the only communication unit. It is the first paper published by the Chinese manufacturing and metallurgy field in this journal, and it is also the first paper published by the international additive manufacturing field in this journal.
Contributed by: Tsinghua University
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