Corrosion fatigue behavior of continuous gradient porous Ti-15Mo alloy prepared by selective laser melting

In this work, porous Ti-15Mo scaffolds with different porosity gradient structures (uniform gradient structures [U-BCC], level gradient structures [LG-BCC], and vertical gradient structures [VG-BCC]) were fabricated by selective laser melting, and the corrosion fatigue testing in Hank's solution was conducted for the first time. The fatigue strength order, when considering the same fatigue life, follows the sequence of LG-BCC structure > U-BCC structure > VG-BCC structure. Cyclic ratcheting is a prominent factor leading to fatigue failure. The sequence of crack initiation and propagation in the latter stage of corrosion fatigue can be listed as follows: LG-BCC structure < U-BCC structure < VG-BCC structure. During the corrosion fatigue process, the grain refinement occurs, and the deformation twinning is generated, leading to a dissipation of energy and an increase of the fatigue resistance. The corrosive effect of Hank's solution induces the surface roughening of the sample, accelerating crack initiation and propagation.