Phase Separation and Solidification Sequence of Uranium-Based Amorphous Composites

The microstructure and composition distribution of U30.03Zr28.83Ti9.66Ni7.00Cu8.75Be15.73 uraniumbased amorphous composites were characterized using TEM and SEM in this study. The composite is a biphasic composite of alpha-U and amorphous phases dominated by zirconium and titanium. Both phases form a multilevel nested structure in the form of spherical precipitated phases. During cooling of the composite material, the phase separation of uranium and copper phases dominated by the nucleation-growth mechanism occurs first, and the other alloying elements are then preferably distributed according to the mixing enthalpy. The subsequent solidification is a two-step process: alpha-U solidification and amorphous transformation. A special structure with a transition layer is formed in the area where the amorphous phase is the spherical precipitated phase. These results provide new insights for the composition design and heat treatment adjustment of amorphous composite materials.