The mechanical properties of ASTM F1684 (Invar 36) alloy manufactured via laser beam powder-bed-fusion (PBF-LB) technique are strongly influenced by the non-equilibrium solidification microstructure. Due to the complexity of printed microstructure, , the presence of melted pools, nano-precipitates, and high-density dislocations, it is very challenging to disentangle the specific mechanisms responsible for the fatigue properties. Here, a comparative investigation of the fatigue properties between PBF-LB and conventionally manufactured (CM) samples was conducted. Dedicated characterizations, including electron channeling contrast imaging (ECCI), and high-angular resolution EBSD (HR-EBSD), were performed. The mid-cycle (10–10 cycles) fatigue behaviors of both samples are comparable, while the fatigue resistance of PBF-LB sample becomes inferior at high-cycle range (10 cycles). This disparity can be ascribed to the competing effect between crack nucleation and propagation. PBF-LB samples are more susceptible to fatigue crack initiation due to the printed macro-defects. Whereas, the homogeneous plastic deformation and the grain fragmentation, both triggered by the ultrafine cellular structure, efficiently mitigate crack propagation rates. Based on these findings, the current understanding of the underlying mechanisms governing the fatigue performance of PBF-LB Invar 36 alloy is deepened, emphasizing the significant advantages of non-equilibrium solidification microstructure in retarding fatigue crack propagation.

中文翻译：

---

增材制造与传统制造 Invar 36 合金疲劳性能的比较研究


通过激光束粉末床熔合 (PBF-LB) 技术制造的 ASTM F1684 (Invar 36) 合金的机械性能受到非平衡凝固微观结构的强烈影响。由于打印微观结构的复杂性、熔池、纳米沉淀物和高密度位错的存在，解开导致疲劳性能的具体机制非常具有挑战性。在这里，对 PBF-LB 和传统制造（CM）样品的疲劳性能进行了比较研究。进行了专门的表征，包括电子通道对比成像 (ECCI) 和高角分辨率 EBSD (HR-EBSD)。两个样品的中循环（10-10 个循环）疲劳性能相当，而 PBF-LB 样品的抗疲劳性能在高循环范围（10 个循环）变得较差。这种差异可以归因于裂纹成核和扩展之间的竞争效应。由于印刷的宏观缺陷，PBF-LB 样品更容易产生疲劳裂纹。而由超细蜂窝结构引发的均匀塑性变形和晶粒破碎，可以有效降低裂纹扩展速率。基于这些发现，加深了目前对PBF-LB Invar 36合金疲劳性能潜在机制的理解，强调了非平衡凝固组织在延缓疲劳裂纹扩展方面的显着优势。