Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006, Australia.
Ultramicroscopy. 2012 Jan;112(1):32-8. doi: 10.1016/j.ultramic.2011.10.003. Epub 2011 Oct 25.
Nitrided steels are widely used in the engineering field due to their superior hardness and other attractive properties. Atom probe tomography (APT) was employed to study two Nb-microalloyed CASTRIP steels with different N contents. A major challenge of using APT to study this group of materials is the presence of tails after Fe peaks in the mass spectra, which overestimates the composition for alloying elements such as Nb and Cu in the steels. One important factor that contributes to the tails is believed to be delayed field evaporation from Fe²⁺. This artefact of the mass spectrum was observed to be the most severe when voltage pulsing was used. The application of laser pulses with energy ranging from 0.2 to 1.2 nJ successfully reduced the tails and lead to better compositional measurement accuracy. Spatial resolution in the z-direction (along the tip direction) was observed to be less affected by changing laser energy but deteriorates in x-y direction with increasing laser energy. This investigation suggests that pulsed-laser atom probe with ∼0.4 nJ laser energy can be used to study this group of materials with improved mass resolution while still maintaining high spatial resolution.
氮化钢由于其优异的硬度和其他有吸引力的特性，在工程领域得到了广泛的应用。原子探针层析技术（APT）被用于研究两种具有不同氮含量的铌微合金化 CASTRIP 钢。使用 APT 研究这组材料的主要挑战是在质谱中 Fe 峰之后存在尾部，这会高估钢中合金元素（如铌和铜）的成分。人们认为导致尾部的一个重要因素是 Fe²⁺的延迟场蒸发。当使用电压脉冲时，观察到质谱中的这种伪影最为严重。使用能量范围为 0.2 至 1.2 nJ 的激光脉冲的应用成功地减少了尾部，并导致更好的成分测量精度。在 z 方向（沿尖端方向）的空间分辨率观察到受激光能量变化的影响较小，但随着激光能量的增加，在 x-y 方向上会恶化。这项研究表明，使用约 0.4 nJ 激光能量的脉冲激光原子探针可以用于研究这组材料，从而提高质量分辨率，同时仍然保持高空间分辨率。
