The effect of microstructure on the fatigue behavior of titanium alloy graded porous structures fabricated by selective laser melting

The bionic-inspired Ti-15Mo gradient porous structures were fabricated by selective laser melting (SLM) for the first time in this work. The compression-compression fatigue behavior of functional gradient Ti-15Mo porous structures is investigated, with emphasis on understanding the relationship between fatigue performance and microstructure. The microstructure of the samples was analyzed both before and after fatigue, and correlated with the fatigue performance. During cyclic deformation, the pillars exhibited a non-uniform local stress distribution, primarily attributed to the disparity of gradient density distribution. Fatigue cracks typically initiate at the place with the defects and subsequently propagate until structural damage occurs. Fatigue ratcheting effect occurs throughout the entire fatigue process while the fatigue damage typically initiates at a later stage in the fatigue process. The results indicated that the fatigue performance of the lateral gradient (LG) structure was superior to that of the homogeneous structure, while the vertical gradient (VG) structure exhibited the poorest fatigue performance.