Laser additive manufacturing of steels
主讲嘉宾：张明星教授，昆士兰大学，澳大利亚
Guest Speaker: Prof. Mingxing Zhang, the University of Queensland, Australia
讲座时间：2025年4月24日 10:00-11:30
Date & Time: 10:00-11:30, April. 24, 2025
讲座地点：徐祖耀楼姚征报告厅（500）
Location: Yiucheng Lecture Hall（500），Xu Zuyao Building
邀请人：李扬欣副研究员
Inviter: Assoc.Prof. Yangxin Li
主讲嘉宾介绍/ Biography
Professor Zhang obtained his Bachelor of Engineering in 1984 from the Inner Mongolian University of Science and Technology and Master and Doctor of Engineering in 1987 and 1990, respectively, from Northwestern Polytechnical University in China. In 1997, he was awarded his PhD degree by the University of Queensland, Australia.
Professor Mingxing Zhang is an internationally renowned materials scientist. His major contributions to the field include: (1) invention of the edge-to-edge matching (E2EM) crystallographic model that can predict crystallographic features of diffusional solid-solid phase transformation from the first principle data; (2) successful application of the E2EM mode to grain refinement of cast metals and discovery a few new grain refiners for cast magnesium alloys, aluminum alloys, steels and zinc alloys, and promoting the research on crystallography of grain refinement; (3) through crystallographic calculations based on the E2EM model, discovered a few inoculants that can be used to improve the laser additive manufacturing processability and properties of a few alloys such as high strength aluminum alloys, titanium alloys, copper alloys and steels. He has published over 330 scientific journal papers with the majority in top international journals. These include: 32 in Acta Materialia (IF = 9.209); 3 in Nature Communications (IF = 17.694), 1 in Materials Today (IF = 21.1), 1 in International Materials Reviews (IMR) (IF = 15.750); 2 in Materials Science and Engineering R (IF = 31.0) and 1 Progress in Materials Science (PSM) (IF = 48.165). His publications received over citations of 17800 times (Google Scholar as on28/3/2025), which is associated with an h-index of 76. He has also authored 10 patents.
摘要/Abstract：
Heating and cooling dramatically change the microstructure and then properties of steels. This makes difficulty for the quality control of steel additive manufacturing (AM) due to the complicated thermal history of AM. Even in the simplest case, AM of 316 stainless steel only involves precipitation of d-ferrite from liquid and d to g transition, the coarse columnar structure causes anisotropic properties. AM of H13 tool steel leads to the formation of elongated, high-carbon retained g-films between the laths of martensite resulted from the rapid solidification and solute segregation. Such g-film is responsible for the high brittleness of the as AM-built H13 steel. To overcome this problem, we have identified TiN as an effective inoculant for steel AM based on crystallographic calculation. 0.5wt.% addition of TiN nanoparticles can not only lead to elimination of the property anisotropy, but also simultaneously increase strength (tensile strength of 2051 ± 48 MPa) and ductility (elongation of 7.4 ± 0.7%) of the SLM-fabricated H13 steel. However, AM of 4340 steel produces equiaxed grains with isotropic properties, which is even compatible with forged steel.
In addition, our recent results demonstrate that high mechanical performance can be achieved through metal AM of simple plain carbon steels, achieving tensile and impact properties comparable to, or even superior to those of low and medium alloy ultra-high strength steels and some Maraging steels. Our work indicates that alloying is not necessary for outstanding mechanical performance and geometric complexity. The key is the sequential nature of the micro-scale melting and solidification within the melt pools during metal AM, which provides sufficient cooling to directly form martensite or bainite in plain carbon steels. This process not only strengthens the steel but also ensures microstructural and property homogeneity throughout the parts without dimensional limitations, avoiding heat treatment distortions and cracking typical in conventional production. This is equivalent to the increased hardenability of plain carbon steels during AM.