Abstract
An experimental plate steel with the composition Fe-1.39Cu-2.7Ni-0.58Al-0. 48Mn-0.48Si-0.065Nb-0.05C (wt pct) or alternatively Fe-1.43Cu-2.61Ni-1.21Al-0. 48Mn-0.98Si-0.039Nb-0.23C at. pct has been recently produced at Northwestern University for use in Naval hull and deck applications - it is designated NUCu-140. To understand the microstructural changes occurring in NUCu-140 steel after gas-metal arc welding (GMAW), a detailed study of the heat-affected and fusion zones was performed throughout the weld cross section using microhardness, metallographic, chemical, and atom-probe tomographic analyses. Local-electrode atom-probe (LEAP) tomography was employed to measure the morphology and compositions of Cu-rich precipitates from each region. The mean radius, number density, volume fraction, and compositions of the precipitates, as well as the interfacial concentration profiles, are measured. The Cu precipitates dissolve partially from the heat-affected zone (HAZ) thermal cycle, and freshly formed sub-nanometer radius Cu-rich precipitates nucleate in both the HAZ and fusion zone (FZ) during cooling; however, the precipitation of Cu during cooling in the HAZ and FZ is not sufficient to restore the lost strength. The precipitation in the FZ is reduced compared to the HAZ due to a mismatched Cu composition of the weld. Multi-pass welding is suggested to restore strength in the GMAW sample by promoting Cu precipitate nucleation and growth in the HAZ and FZ.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1741-1759 |
| Number of pages | 19 |
| Journal | Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science |
| Volume | 44 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 2013 |
Funding
This research was funded by the Office of Naval Research under grants N00014-09-1-0361 and N00014-07-1-0331, Dr. W. W. Mullins, grant monitor. LEAP tomographic measurements were performed at the Northwestern University Center for Atom-Probe Tomography (NUCAPT). The LEAP tomography system was purchased with funding from NSF-MRI grant DMR-0420532, with initial funding from ONR-DURIP grant N00014-0400798, and with funding for upgrades from N00014-0610539 and N00014-0910781. The authors thank Dr. Dieter Isheim for managing NUCAPT, helpful discussions, and assistance with this project. DNS thanks Prof. Emeritus M. E. Fine for generously introducing him to the subject of NU-Cu steels, which he developed over many years at Northwestern University.
ASJC Scopus subject areas
- Condensed Matter Physics
- Mechanics of Materials
- Metals and Alloys