Carbon is known to improve the ductility and grain boundary strength of molybdenum. Scientific consensus to explain this phenomenon is that carbon either replaces oxygen impurities at grain boundaries or suppresses the diffusion of oxygen towards the grain boundaries. The aim of this study is to clarify the mechanism on how the carbides interact with the oxygen impurities and the molybdenum matrix, thus to provide a better understanding for designing molybdenum alloy compositions. Molybdenum alloyed with 4500 μg/g carbon was manufactured in the additive manufacturing process of Laser Powder Bed Fusion (LPBF). The cellular grain structure of molybdenum cells with surrounding molybdenum carbide caused by constitutional undercooling during the solidification process was investigated by Transmission Electron Microscopy (TEM) for morphology, composition and crystal structure. The carbide was identified to be orthorhombic ζ-Mo₂C, which has a solubility for oxygen. ζ-Mo₂C shows a semi-coherent interface with α-Mo. No cracks could be found at the α-Mo / α-Mo or the α-Mo / ζ-Mo₂C interfaces. Oxygen could not be detected at grain boundaries, but only within ζ-Mo₂C, which traps the oxygen, thus avoiding oxygen segregation to the grain boundaries and improving the grain boundary strength.

已知碳可改善钼的延展性和晶界强度。解释这种现象的科学共识是，碳要么替代了晶界处的氧杂质，要么抑制了氧向晶界的扩散。本研究的目的是阐明碳化物如何与氧杂质和钼基体相互作用的机理，从而为设计钼合金成分提供更好的理解。在激光粉末床熔合（LPBF）的增材制造过程中制造了含4500μg/ g碳的合金钼。用透射电子显微镜（TEM）研究了凝固过程中组织过冷引起的周围有碳化钼的钼电池的细胞晶粒结构，组成和晶体结构。碳化物被确定为斜方晶ζ-Mo₂ C，对氧具有溶解性。ζ-沫₂ C显示用α-沫半相干接口。无裂纹可能在α沫/α-Mo或α-沫/ζ-Mo系中找到_2个I2C接口。氧不能在晶粒边界被检测到，但是仅在ζ-沫₂ C，其捕获氧，从而避免氧偏析到晶界和提高晶界强度。