| Abstract Scope |
Repeatability and reproducibility are major hurdles in developing standards for metal-based additive manufacturing (AM). The AM community has dedicated considerable time and effort to understand the complex influence of process variables, spatially non-uniform thermal cycles, and machine-to-machine variations on the properties and performance of printed parts; however, the contribution from feedstock chemistry is often overlooked. The 2025 Additive Manufacturing Benchmark Test series addressed this gap through the AMB2025-01 set of benchmarks, which studied the impact of powder feedstock variations on microstructure evolution. Three lots of Alloy 625 powders with distinct variations in chemical composition were acquired from different powder manufacturers, and each material was printed with identical laser powder bed fusion processing parameters and overall build geometry to isolate the effects of feedstock composition. Selected samples were subjected to stress-relief and homogenization heat treatments to probe susceptibility to precipitate formation. Precipitate types, phase fractions, and grain morphologies were characterized in the as-deposited, stress-relieved and homogenized materials using high resolution techniques including scanning and transmission electron microscopy, high energy synchrotron X-ray diffraction, energy dispersive spectroscopy, and electron backscatter diffraction. The results show that subtle differences in powder chemistry, especially interstitial and minor alloying elements, play a decisive role in microstructure evolution and can lead to radically different microstructures. Unlike wrought counterparts, AM alloy 625 materials can be particularly sensitive to these variations. In addition to the findings of the AMB2025-01 benchmarks, the resulting challenges that feedstock variability imposes on standardization efforts will be discussed. |