Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108, USA.
Microsc Microanal. 2011 Dec;17(6):950-62. doi: 10.1017/S1431927611011895. Epub 2011 Oct 27.
The differences in artifacts associated with voltage-pulsed and laser-pulsed (wavelength = 532 or 355 nm) atom-probe tomographic (APT) analyses of nanoscale precipitation in a high-strength low-carbon steel are assessed using a local-electrode atom-probe tomograph. It is found that the interfacial width of nanoscale Cu precipitates increases with increasing specimen apex temperatures induced by higher laser pulse energies (0.6-2 nJ pulse(-1) at a wavelength of 532 nm). This effect is probably due to surface diffusion of Cu atoms. Increasing the specimen apex temperature by using pulse energies up to 2 nJ pulse(-1) at a wavelength of 532 nm is also found to increase the severity of the local magnification effect for nanoscale M2C metal carbide precipitates, which is indicated by a decrease of the local atomic density inside the carbides from 68 ± 6 nm(-3) (voltage pulsing) to as small as 3.5 ± 0.8 nm(-3). Methods are proposed to solve these problems based on comparisons with the results obtained from voltage-pulsed APT experiments. Essentially, application of the Cu precipitate compositions and local atomic density of M2C metal carbide precipitates measured by voltage-pulsed APT to 532 or 355 nm wavelength laser-pulsed data permits correct quantification of precipitation.
使用局部电极原子探针断层扫描评估了与高强度低碳钢中纳米级析出物的电压脉冲和激光脉冲（波长=532 或 355nm）原子探针断层分析相关的伪影差异。结果发现，随着激光脉冲能量的增加（波长为 532nm 时为 0.6-2nJ 脉冲(-1)），导致纳米级 Cu 析出物的界面宽度增加。这种效应可能是由于 Cu 原子的表面扩散所致。还发现，通过使用高达 2nJ 脉冲(-1)的激光脉冲能量（波长为 532nm）升高样品顶点温度，也会增加纳米级 M2C 金属碳化物析出物的局部放大效应的严重程度，这表现为碳化物内部的局部原子密度从 68±6nm(-3)（电压脉冲）降低到 3.5±0.8nm(-3)。基于与电压脉冲 APT 实验结果的比较，提出了一些解决这些问题的方法。本质上，将通过电压脉冲 APT 测量的 Cu 析出物组成和 M2C 金属碳化物析出物的局部原子密度应用于 532nm 或 355nm 波长激光脉冲数据，可以正确量化析出物。
