Preferential Au precipitation at deformation-induced defects in Fe–Au and Fe–Au–B–N alloys

• Fe–Au–B–N forms a good model alloy system for self healing of deformation damage.
• Solute Au atoms exclusively precipitate at grain boundaries, cracks and cavities.
• XPS indicates a strong tendency for Au segregation on free surfaces at 550 °C.
• Interstitial B and N form hexagonal BN on free surfaces at 550 °C.
• Selective Au precipitation at open volume defects can cause autonomous repair.

The influence of deformation-induced defects on the isothermal precipitation of Au was studied in high-purity Fe–Au and Fe–Au–B–N alloys. Preferential Au precipitation upon annealing at 550 °C is observed at local plastic indentations. In fractured Fe–Au–B–N, solute Au atoms were found to heterogeneously precipitate at grain boundaries and local micro-cracks. This is supported by in-situ creep tests that showed a strong tendency for Au precipitation at cracks and cavities also formed during creep loading at 550 °C. Complementary X-ray photoelectron spectroscopy experiments indicate a strong tendency of Au, B and N segregation onto free surface during aging. The observed site-specific precipitation of Au holds interesting opportunities for defect healing in steels subjected to creep deformation.