Microstructure‐Property Linkage in Thermally Aged 6061‐T651 Alloy for Extended Spent Nuclear Fuel Dry Storage Systems
Year: 2026
Type: article
Abstract: This study evaluates long‐term thermal aging degradation of 6061‐T651 aluminum alloy used as an internal structural material for basket rails/shims in spent nuclear fuel (SNF) dry storage systems. Specimens were exposed in air at 150, 200, and 240°C for 100–10,000 h to simulate storage‐relevant temperature conditions. Vickers hardness and tensile tests quantified mechanical property evolution, potentiodynamic polarization in 0.6 M NaCl was used to assess aging‐dependent electrochemical behavior, and scanning transmission electron microscopy (STEM)–energy‐dispersive X‐ray spectroscopy (EDS) with high‐resolution transmission electron microscopy (HRTEM)–fast Fourier transform (FFT) was used to identify precipitation changes. The as‐received (as‐rec.) alloy contained a dense dispersion of β ″ needles that provided peak strengthening, together with stable α‐Al(FeCr)Si dispersoids. Thermal aging caused progressive overaging: at 150°C, β ″ coarsened gradually and β ′/ B ′ emerged after long exposure; at 200°C, β ″ disappeared within 100 h and β ′/ B ′ became dominant; and at 240°C, severe coarsening occurred with the formation of Cu‐bearing Q ′/ C ‐type precipitates. Mechanical degradation accelerated with temperature, while ductility increased. The electrochemical response changed only modestly after aging at 150 and 200°C, whereas aging at 240°C markedly increased the corrosion current density, consistent with microgalvanic effects associated with noble Cu‐enriched precipitates. Two distinct time–temperature equivalency pairs were identified and used to derive Arrhenius‐type effective activation energies for accelerated aging assessments. The most severe degradation occurred at 240°C with increasing exposure time, where extensive precipitate coarsening and Q ′/ C ‐type precipitate formation produced substantial hardness/strength loss and increased electrochemical susceptibility. These results indicate that high‐temperature basket locations should be prioritized in time–temperature‐limited aging analyses. The present data provide a thermal‐aging baseline for aging management of 6061‐T651 dry storage internal structures.
DOI: 10.1155/er/2756701
Language: English
Subfield: Metals and Alloys
Field: Materials Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,700
OpenAlex ID: W7204271104