Additive manufacturing (also known as 3D printing), as a new manufacturing method, has the advantages of rapid manufacturing, material saving, and user customization. It is increasingly valued in the fields of aviation, aerospace, automotive, medical equipment, and so on. Due to the needs of industrial applications, the fatigue performance of additive manufacturing materials (especially ultra-high cycle fatigue performance) and the corresponding fatigue mechanism have become one of the urgent scientific problems to be solved in the field of additive manufacturing research.
The Research Group of Microstructure and Mechanical Properties of Metal Materials, Institute of Mechanics, Chinese Academy of Sciences has recently carried out a series of research work on the fatigue properties of additive manufacturing titanium alloys (Ti-6Al-4V). The research team conducted fatigue performance tests on additive-manufactured titanium alloys and obtained high-cycle and ultra-high-cycle fatigue properties of the material. Through observation of fatigue fractures, it was reported that high-cycle and ultra-high-cycle fatigue cracks of titanium alloys produced by additive manufacturing originated from the internal holes and unfused defects of the material, and formed a new phenomenon of "fish-eye" fracture morphology. This is very different from the fatigue characteristics and crack initiation mechanism of traditional forged metal materials. According to the distribution characteristics of the size of the crack source, a statistical correlation between fatigue performance and crack size is constructed. Based on the material fatigue life data and fatigue crack defect size, a probabilistic statistical P-S-N analysis was performed to obtain the relationship between the high-cycle and ultra-high-cycle fatigue failure probability of the material and the fatigue life and applied load. In addition, in order to further explore the fatigue crack growth characteristics, the team used the in-situ fatigue loading device to obtain the Ti-6Al-4V crack growth rate at different temperatures and different preparation orientations, revealing the fatigue crack growth of titanium alloys produced by different orientation additives Mechanisms.
This research not only provides effective fatigue performance data for engineering applications of additive manufacturing of titanium alloys. At the same time, it laid a theoretical foundation for exploring the crack initiation and propagation mechanism of additive-manufactured titanium alloys.
Related work was recently published in the International Journal of Fatigue, which was highly evaluated by international peers.