The effect of Ni on the microstructural evolution of high Cu reactor pressure vessel steel welds after thermal ageing for up to 100,000 h
To understand the contribution of the long term thermal ageing to Reactor Pressure Vessel embrittlement a series of weld materials containing systematic variations of Ni has been thermally aged for times up to 100,000 h at 330 °C and 365 °C. Microstructural characterisation using Atom Probe Tomograp...
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Veröffentlicht in: | Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2018-10, Vol.736, p.111-119 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | To understand the contribution of the long term thermal ageing to Reactor Pressure Vessel embrittlement a series of weld materials containing systematic variations of Ni has been thermally aged for times up to 100,000 h at 330 °C and 365 °C. Microstructural characterisation using Atom Probe Tomography was performed. Thermal ageing produced a high number density of nano-scale Cu-enriched clusters. Ni has a strong influence on Cu precipitation, enhancing the homogeneous nucleation of Cu clusters. The nanometre size Cu clusters have a Ni-Mn-Si rich interface which was found to be wider in steels with higher bulk Ni content. This interface reduces the interfacial energy of the Cu-enriched clusters through a combination of the minimising of unfavourable Fe–Cu bonds and reduction in lattice strain. Matrix Cu levels after ageing for 90,000–100,000 h were found to be around 0.06–0.08 at%, close to the expected solubility limits for Cu in Fe. |
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ISSN: | 0921-5093 1873-4936 |
DOI: | 10.1016/j.msea.2018.08.063 |