在对激光选区熔化成形Ti-6Al-4V试样静态力学性能测试和分析的基础上，研究激光选区熔化成形Ti-6Al-4V试样在循环载荷下，表面缺陷、内部缺陷和微观组织对疲劳性能的影响。采用刚度拟合疲劳周期方法，获取试样在疲劳周期各阶段的循环周次，发现在疲劳源形核阶段试样疲劳寿命产生差异。直接成形试样的表面黏粉现象严重，在表面形成多个疲劳源，导致疲劳寿命很低。抛光处理可以降低表面粗糙度，退火处理可以改善试样微观组织结构，提升试样疲劳性能，但是表面处理后，内部缺陷暴露在表面，不同类型和不同尺寸的缺陷形核疲劳源周期差异很大，导致疲劳性能呈现较大的离散性。

Based on the analysis of the static mechanical properties of Ti-6Al-4V specimens fabricated by selective laser melting, the effects of surface defects, internal defects and microstructures on the fatigue properties of specimens are investigated under cyclic loading. The stiffness-fitting fatigue cycle method is used to obtain the cycle times of the specimen in each stage of the fatigue cycle. It is found that the fatigue source nucleation stage is the main reason for the difference in fatigue life of the specimen. The surface of directly formed specimens is seriously viscous and forms several fatigue sources, resulting in very short fatigue life. Polishing treatment can reduce the surface roughness, and the annealing treatment can improve the microstructure and enhance the specimen fatigue performance. After polishing treatment, however, internal defects are exposed on the surface. The cycle of defect nucleation fatigue source of different types and different sizes has a large difference, leading to a greater discreteness of fatigue performance.