The rotating bending fatigue (RBF) behavior (fully reversed, R = −1) of additively manufactured (AM) Ti–6Al–4V alloy produced via laser powder bed fusion (PBF-L) was investigated with respect to different microstructures achieved through novel heat treatments. The investigation herein seeks to elucidate the effect of microstructure by controlling variables that can affect fatigue behavior in Ti–6Al–4V, such as chemistry, porosity, and surface roughness. In order to control these variables, different hot isostatic pressing (HIP) treatments at 800 °C, 920 °C, and 1050 °C with a 920 °C temper were applied to three sets of Ti–6Al–4V cylinders that originated from the same PBF-L build, such that there were 30 tests per condition. After HIP treatment, the specimens were machined and tested. The highest runout stress was achieved after sub- transus HIP at 800 °C for 2 h at 200 MPa of pressure. A significant drop in fatigue strength was attributed to large prior- grains and grain boundary resulting from super- transus HIP treated specimens. For the sub- transus HIP specimens, differences in fatigue strength were attributed to lath thickness, relative dislocation density, and dislocation boundary strengthening.

中文翻译：

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微观结构对采用新型热处理激光粉末床熔合生产的 Ti-6Al-4V 旋转弯曲疲劳行为的影响

通过激光粉末床熔合 (PBF-L) 生产的增材制造 (AM) Ti-6Al-4V 合金的旋转弯曲疲劳 (RBF) 行为（完全反转，R = -1）通过新颖的方法获得的不同微观结构进行了研究热处理。本文的研究旨在通过控制可影响 Ti-6Al-4V 疲劳行为的变量（例如化学成分、孔隙率和表面粗糙度）来阐明微观结构的影响。为了控制这些变量，对三组 Ti-6Al-4V 气缸进行了 800 °C、920 °C 和 1050 °C 的不同热等静压 (HIP) 处理，并进行 920 °C 回火。相同的 PBF-L 构建，因此每个条件有 30 次测试。 HIP 处理后，对样品进行机加工和测试。最高跳动应力是在 800 °C、200 MPa 压力下进行亚转变 HIP 2 小时后获得的。疲劳强度的显着下降归因于超转变 HIP 处理的样品产生的大的原始晶粒和晶界。对于跨层下 HIP 样品，疲劳强度的差异归因于板条厚度、相对位错密度和位错边界强化。