【摘要】 激光选区熔化的高温度梯度与高冷却速度导致成形零件具有显著的各向异性，进而导致零件在不同构建方向的承载能力不同。采用0°、30°、60°、90°4个角度成形金相试样、狗骨棒疲劳试样与疲劳紧凑拉伸试样，表征不同构建角度下316L不锈钢的显微组织差异，以及在660 MPa,R=0.1交变应力条件下的疲劳性能变化。结果表明，随着构建角度增大，平均晶粒尺寸从12.45μm降低至8.36μm,并且大角度晶界比例也随构建角度增大而升高。大角度晶界比例的增加引起位错塞积，降低了疲劳萌生寿命，因此0°试样疲劳寿命最长，90°试样寿命最短。4种构建角度分为两种疲劳裂纹扩展(FCG)模式：裂纹沿柱状晶晶粒“底部”扩展(FCG00与FCG30),阻力大、扩展慢；裂纹沿柱状晶晶粒“侧面”扩展(FCG60与FCG90),阻力小、扩展快。综上，在设计零件摆放角度时，建议调整沉积方向与主要载荷方向垂直。更多还原

【Abstract】 The high temperature gradient and high cooling rate of selective laser melting(SLM) result in significant anisotropy of the formed parts, which in turn leads to different load-bearing capacities of the parts in different build directions This article uses four angles of 0°, 30°, 60°, and 90° to form metallographic specimens, dog bone fatigue specimens, and fatigue compact tensile specimens to characterize the differences in microstructure of 316 L stainless steel under different building angles, as well as the changes in fatigue performance under 660 MPa and R=0.1 alternating stress conditions. It was found that the average grain diameter decreased from 12.45 μm to 8.36 μm with the increase of the angle. The proportion of large-angle grain boundaries also increases with the increase of build angle.The increase in the proportion of large angle grain boundaries causes dislocation accumulation, which reduces the fatigue initiation life. Therefore, the 0° specimen has the longest fatigue life and the 90° specimen has the shortest life.The four building angles are divided into two fatigue crack growth(FCG) modes: cracks grow along the "bottom" of columnar grains(FCG00 and FCG30), with high resistance and slow propagation; Cracks grow along the “side” of columnar grains(FCG60 and FCG90), with low resistance and fast propagation.In summary, when designing the placement angle of parts, it is recommended to adjust the deposition direction to be perpendicular to the main load direction.更多还原