3D printing technology is rapidly changing traditional production methods and lifestyles. As a strategic emerging industry, 3D printing technology integrates digital technology, manufacturing technology, laser technology and new material technology, and is known as a representative technology that is expected to become the "third industrial revolution." Metal laser 3D printing technology is the most advanced and promising technology in the entire 3D printing system, and is an important development direction of advanced manufacturing technology. Among them, the main feature of Selective Laser Melting (SLM) based on automatic powder coating is high processing precision, and almost no machining is required in the subsequent process. It can directly manufacture various complex and precise metal parts, realize structural function integration and light weight. In aerospace, biomedical manufacturing and other fields have a wide range of application needs.
At present, the materials used in SLM technology have covered titanium alloys, high-temperature alloys, iron-based alloys, cobalt-chromium alloys and a small number of low-strength aluminum alloy materials. High-strength aluminum alloys, as a lightweight material widely used in the industrial field, are increasingly demanding in the SLM field. However, compared with other materials that have been successfully applied to SLM, high-strength aluminum alloy has high thermal conductivity and high reflectivity to laser, and has a high degree of alloying and a wide crystallization range, which makes it strong in SLM forming. The tendency of hot cracking severely limits its engineering application.
In order to solve the thermal cracking problem of the existing SLM forming high-strength aluminum alloy materials, Zhang Hu and Nie Xiaojia, Ph.D. students of the Laser Advanced Manufacturing Research Team of Wuhan Optoelectronic National Laboratory, under the guidance of Professor Zhu Haihong, from the perspective of traditional aluminum alloy material design, A dense and crack-free sample was obtained by adding trace elements to the SLM forming high-strength aluminum alloy. While successfully suppressing hot cracks, the SLM forming efficiency is greatly improved; unlike the original coarse columnar crystal microstructure, the microstructure after the trace element modification is an equiaxed crystal of the order of 1 mm; in the fine grain strengthening and precipitation strengthening Together, the ultimate tensile strength is increased by 12%.
The research results break through the process bottleneck of the existing SLM technology to form high-strength aluminum alloy, and it is expected to accelerate the industrial application of aluminum alloy materials in the field of laser 3D printing. In June 2017, the research result "Effect of Zirconium addition on crack, microstructure and mechanical behavior of selective laser melted Al-Cu-Mg alloy" was published in the journal Metala Metallurgical Engineering Journala Materialia (IF: 3.305, DOI: 10.1016/j .scriptamat.2017.02.036).