Solid state amorphization in the Ni-Nb-Y system by mechanical alloying

Abstract Amorphous and heterogeneous amorphous Ni-based alloys have shown promise as electrocatalytic materials for various reactions. The Ni-Nb-Y system is of particular interest due to the immiscibility of Nb and Y that facilitates a heterogeneous amorphous-amorphous or amorphous-nanocrystalline structure. Amorphous alloys in the Ni-Nb-Y system have been previously limited to those produced through rapid solidification processing. In this study, a high energy ball milling process was successfully used for the first time to mechanically alloy novel amorphous-based Ni-Nb-Y alloys. A thermodynamic model of the Ni-Nb-Y alloy system was developed to guide the ternary alloy design while X-ray diffraction and transmission electron microscopy characterized the microstructure of the Ni-Nb-Y alloys. The targeting of high melting Ni Y and Ni Nb intermetallic compounds facilitated the amorphization process. A novel amorphous Ni79.2Nb12.5Y8.3 alloy was produced after 6 h of cryogenic ball milling. Partial crystallization of the amorphous structure was observed upon prolonged milling with the formation of a secondary nanocrystalline Ni5Y phase in an amorphous matrix. The alloying design strategy shows promise in analogous alloy systems where immiscibility exists among the alloy constituents.