Voltage-pulsed and laser-pulsed atom probe tomography of a multiphase high-strength low-carbon steel.
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.
Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108, USA.
Michael D
MD
Mulholland
David N
DN
Seidman
D002244:Carbon / Q000032:analysis* / Q000737:chemistry; D003300:Copper / Q000032:analysis* / Q000737:chemistry; D004058:Diffusion; D004566:Electrodes; D007834:Lasers; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D053768:Metal Nanoparticles; D013232:Steel / Q000032:analysis* / Q000737:chemistry; D013696:Temperature; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*
D013232:Steel; D002244:Carbon; D003300:Copper