High cycle fatigue behavior of selective laser melting TC4 alloy

Abstract

An experimental study on high cycle fatigue behavior of selective laser melting (SLM) TC4 alloy was carried out. The fatigue properties of the alloy under two sampling directions (horizontal and vertical) and two temperatures (room temperature and 400 ℃) were compared and analyzed. Also the feasibility of improving the fatigue properties of the alloy by hot isostatic pressing (HIP) was explored. The results show that the fatigue properties of the alloy after annealing are significantly anisotropic, and the fatigue properties of the vertical samples are higher than that of the horizontal ones. Compared with room temperature, the fatigue life of the alloy at 400 ℃ is reduced, but the anisotropy still exists. After hot isostatic pressing, the fatigue life of the alloy presents a certain degree of improvement, and the anisotropy of fatigue properties decreases. The fracture analysis shows that the cracks of SLM TC4 alloy mainly originate from surface and subsurface defects which are mainly pores. The statistical analysis shows that the source defect size of vertical samples is lower than that of horizontal samples, which is the main reason for the decrease of fatigue properties of horizontal samples. After hot isostatic pressing, cracks in both horizontal and vertical samples of the alloy are generated at the surface slip, and the porosity of the alloy is significantly reduced without obvious defects, and the decrease in the number of defects is the main reason for the improvement of fatigue properties of the alloy.

Keywords

• selective laser melting
• tc4 alloy
• high cycle fatigue
• anisotropy
• defect
• hot isostatic pressing