Microstructure and Properties of Eu-Ni Alloys Prepared by Levitation Melting

With the rapid development of the nuclear power industry, the requirement for nuclear structural materials is continuously growing. Eu-Ni intermetallic alloys are promising structural candidates for nuclear applications, while relevant fundamental investigations and underlying mechanisms remain insufficient worldwide. In this work, four Eu-Ni alloys with Eu mass fractions from 30 wt.% to 75 wt.% were fabricated via vacuum electromagnetic levitation melting. Thermodynamic calculations were performed to analyze high-temperature evaporation behaviors of Eu and Ni, and desired compositions were accurately achieved by evaporation loss compensation. XRD, SEM-EDS, TEM-SAED and hardness measurements were used to characterize phase constituents, microstructure and mechanical properties. The maximum evaporation rates of Eu and Ni increase with rising respective elemental contents. As Eu content increases, the dominant phase evolves from hexagonal EuNi5 to EuNi2 and finally FCC Eu-rich Eu0.56Ni0.44. The average grain size decreases from 127.82 μm to 67.59 μm, and intergranular spacing increases from 9.09 μm to 17.72 μm. Grain-boundary segregation of Eu softens the matrix, leading to a gradual hardness reduction from 529.2 kg/mm2 to 247.4 kg/mm2. This study clarifies composition-dependent evolution rules and provides fundamental data for industrial preparation and nuclear application of Eu-Ni alloys.