This study investigates the fully reversed force-controlled fatigue response of a newly developed laser powder bed fused (LPBF) Al-Mg-Zr-Mn alloy (EOS Al5X1) in the post-aged condition. The fatigue behavior revealed a defect-driven response with a fatigue strength of approximately 140 MPa at 5 million cycles. Comprehensive microstructural analyses, including grain size, texture, and precipitate characterization, were performed using advanced microscopy techniques. Additionally, X-ray computed micro-tomography (XCT) was employed to assess defect size and distribution, yielding a relative density of 99.93 %. Fracture surfaces of all fatigue-failed specimens were examined using optical and scanning electron microscopy to determine the primary failure mechanisms, with a focus on distinguishing between defect-driven and microstructural causes. The results indicated that nearly all specimens, tested across seven stress levels, exhibited crack initiation from process-induced volumetric defects, such as pores and lack of fusion. At lower stress levels (up to 195 MPa), single crack initiation sites driven by defects were identified at either surface or subsurface locations. In contrast, at higher stress levels (234 to 351 MPa), multiple crack initiation sites were observed, also at the surface or subsurface.

中文翻译：

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新开发的激光粉末床熔融无钪 Al-Mg-Zr-Mn 合金的疲劳特性


本研究研究了新开发的激光粉末床熔融 （LPBF） Al-Mg-Zr-Mn 合金 （EOS Al5X1） 在后老化条件下的完全反向力控制疲劳响应。疲劳行为揭示了缺陷驱动的响应，在 500 万次循环时疲劳强度约为 140 MPa。使用先进的显微镜技术进行了全面的微观结构分析，包括晶粒尺寸、织构和沉淀物表征。此外，采用 X 射线计算机显微断层扫描 （XCT） 评估缺损大小和分布，相对密度为 99.93 %。使用光学和扫描电子显微镜检查所有疲劳失效试样的断裂表面，以确定主要失效机制，重点是区分缺陷驱动的原因和微观结构原因。结果表明，在 7 个应力水平下进行测试的几乎所有试样都表现出由工艺引起的体积缺陷（如气孔和未熔合）引起的裂纹。在较低的应力水平（高达 195 MPa）下，在表面或地下位置识别出由缺陷驱动的单个裂纹萌生部位。相比之下，在较高的应力水平（234 至 351 MPa）下，在地表或地下也观察到多个裂纹萌生部位。