Electron irradiation-enhanced core/shell organization of Al(Cr, Fe, Mn)Si dispersoids in Al–Mg–Si alloys

Abstract

The age hardening 6061-T6 aluminium alloy has been chosen as structural material for the core vessel of the material testing Jules Horowitz nuclear reactor. The alloy contains incoherent Al(Cr, Fe, Mn)Si dispersoids whose characterization by energy-filtered transmission electron microscopy (EFTEM) analysis shows a core/shell organization tendency where the core is (Mn, Fe) rich, and the shell is Cr rich. The present work studies the stability of this organization under irradiation. TEM characterization on the same particles, before and after 1 MeV electron irradiation, reveals that the core/shell organization is enhanced after irradiation. It is proposed that the high level of point defects, created by irradiation, ensures a radiation-enhanced diffusion process favourable to the unmixing forces between (Fe, Mn) and Cr. Shell formation may result in the low-energy interface segregation of Cr atoms within the (Fe, Mn) system combined with the unmixing of Cr, Fe and Mn components.

Keywords:

• aluminium alloys
• intermetallic phases
• electron irradiation
• TEM
• irradiation effects
• core/shell

Acknowledgements

This study was made in the frame of the MTRJH project. The CEA Saclay, SRMA high-voltage TEM facility part of the EMIR network is gratefully acknowledged.