Camille Flament (CEA Saclay DEN - SRMA)
Mercredi 7 mai, 14h, CSNSM Salle de réunion du Bât 108
The age hardening 6061-T6 aluminum alloy has been chosen for the confection of the core vessel of the Material Testing Jules Horowitz Reactor.
The alloy contains incoherent Al(Cr,Fe,Mn)Si dispersoids whose characterization by EFTEM analysis shows a (Fe,Mn)core/Crshell organization tendency for some of them. Since dispersoid will undergo neutron irradiation in JHR service, the assessment of the stability of such particular organization under irradiation is of interest.
TEM Characterization on the same particles, before and after 1 MeV electron irradiation, reveals that the core/shell organization is more complete after irradiation. It is proposed that the high level of point defects, created by irradiation, ensures a radiation-enhanced diffusion process favorable to the unmixing forces between (Fe,Mn) and Cr.
Shell formation may result in the low energy surface segregation of Cr atoms within the (Fe,Mn) system. Hence, the intermetallic Al(Cr,Fe,Mn)Si dispersoid is driven to its equilibrium configuration, thought unreachable by means of thermal annealing due to the low fusion temperature of the aluminum host matrix.
The matrix is also strengthened by (Mg, Si) nano-scale needle-shaped precipitates called β’’ phases which represent the other major subject of this study. Because of the impact of these metastable phases on the mechanical properties of the alloy, it is necessary to study their stability under irradiation.