Progress has been made in the study of fatigue performance of titanium alloy by additive manufacturing

Additive manufacturing (also known as 3D printing), as a new manufacturing method, has many advantages, such as fast manufacturing, material saving and customizable, etc., attracting more and more attention in aviation, aerospace, automobile, medical equipment and other fields. Due to the demand of industrial applications, the fatigue properties (especially the ultra high cycle fatigue properties) and the fatigue mechanism of additive manufacturing materials have become one of the urgent scientific problems to be solved.

The research group of Microstructure and Mechanical Properties of Metal Materials in Institute of Mechanics, Chinese Academy of Sciences (CAS) has recently carried out a series of research work on fatigue properties of titanium alloy Ti-6Al-4V. The high cycle and ultra-high cycle fatigue properties of titanium alloy manufactured by additive were tested. Based on the observation of fatigue fracture, a new phenomenon was reported that both high cycle and ultra-high cycle fatigue cracks originated from internal holes and unfused defects of titanium alloy manufactured by additive material, and formed fisheye fracture morphology. This is quite different from the fatigue characteristics and crack initiation mechanism of traditional forging metal materials. According to the distribution characteristics of crack source size, the statistical correlation between fatigue performance and crack size was established. Based on the fatigue life data of the material and the size of the fatigue crack, the P-S-N analysis of probability statistics was carried out, and the relationship between the high cycle and ultra-high cycle fatigue failure probability of the material and the fatigue life and applied load was obtained. In addition, in order to further explore the fatigue crack propagation characteristics, the in situ fatigue loading device was used to obtain the crack propagation rates of Ti-6Al-4V at different temperatures and with different preparation orientations, revealing the mechanism of fatigue crack propagation of titanium alloy with different orientations.

This study not only provides effective fatigue performance data for the engineering application of additive manufacturing titanium alloys. At the same time, it has laid a theoretical foundation for exploring the mechanism of crack initiation and propagation in additive manufacturing titanium alloy.