The feasibility of Al-based oxide precipitation in Fe–10%Cr alloy by ion implantation

Abstract

This paper reports the feasibility of nano-oxide precipitate formation in Fe–Cr alloy by ion implantation synthesis. High contents of Al⁺ and O⁺ ions were implanted into thin films of high purity Fe–10%Cr alloy at room temperature and were studied by transmission electron microscopy (TEM) and atom probe tomography (APT). In contrast, to the common two-stage implantation/annealing scheme of precipitate ensemble synthesis by ion beams, cluster formation took place at the implantation stage in our study, requiring no subsequent high-temperature annealing. The post-implantation microstructural examination revealed in the as-implanted thin foil an array of precipitates with diameters in the range of 3–30 nm. The precipitate number density distribution was found to depend on the foil thickness. The precipitate enrichment with both Al and O was confirmed by the energy-filtered TEM analysis. Judging from the electron diffraction pattern and high-resolution TEM analysis, the crystal lattice of precipitates corresponds to some cubic modification of aluminium-rich oxide or pure aluminium oxide. The precipitate lattice alignment with the host matrix was revealed for at least a part of precipitates. The analysis of APT data using cluster detection algorithm indicates the presence of local zones enriched in Al and O, even in those areas of as-implanted samples where no clusters were visible by TEM.

Keywords:

• Fe–Cr alloys
• ion implantation
• aluminium oxide
• precipitation
• transmission electron microscopy
• atom probe tomography

Acknowledgements

We are thankful to Lucie Delauche for help in thin foil preparation and the Semiramis staff of the CSNSM-JANNuS-Orsay facility for ion implantations. We are also thankful to Yann Colignon for his kind help during atom probe tomography experiment. Ce Zheng acknowledges the Master Nuclear Energy, Orsay, France (Université Paris-Sud, INSTN, ParisTech, Supélec, Ecole Centrale Paris) and the Doctoral School 534 MIPEGE (Université Paris-Sud, Orsay, France) for, respectively, internship and PhD funding. This project was partially funded by PF-Matériaux/Défi NEEDS/Mission Interdisciplinarité du CNRS, 2013.