Plutonium alloys and delta phase stability: solute element diffusion plays an important part in the martensitic reversion process and the corrosion phenomenon

摘要

Plutonium metal is a very complex material. Far beyond itsradioactive character leading to swelling phenomenon itexhibits six crystal structures with a lot of different physicalproperties from room temperature to melting and it is verysensitive to corrosion.The stability range of the ductile fcc delta phase is quitenarrow but can be extended to room temperature by alloyingPu with ‘delta phase stabilizer’ elements such as aluminum,gallium. Nevertheless, thermal treatment below roomtemperature leads to a partial martensitic transformation ofdelta stabilized Pu alloys into the hard and brittlemonoclinic alpha prime-phase exhibiting a double C-curvekinetic in a Time-Temperature-Transformation diagram .Upon heating, reverse transformation exhibits a particularlycomplex behavior when direct alpha prime to delta phaseand indirect alpha prime to beta phase transformations are incompetition . Moreover, even if the plutonium isstabilized with ‘delta-phase stabilizer’ it suffers adegradation process by corrosion when handling,transporting and storaging.Thus, this work aims to show how the solute elementdiffusion process plays an important part both in martensiticreversion and corrosion process.