Effect of the Rare Earth Element Yttrium on the Structure and Properties of Boron-Containing High-Entropy Alloy

The effects of rare earth yttrium with 0.1, 0.2 and 0.5 atomic ratios on the microstructure and properties of FeCoNi1.5CuB high-entropy alloy were investigated. The results show that the lattice distortion of the matrix alloy is increased after yttrium addition. There are three characteristic zones: the bulk trivalent boride phase zone, basement zone and yttrium-rich precipitate zone. When the yttrium atom ratio is > 0.2, the nanoscale YB6 particles disperse uniformly in the yttrium-rich zone, which can improve the strength of the alloy. As for the mechanical properties, the FeCoNi1.5CuBY0.2 alloy has the highest strength. The corresponding compressive strength, yield strength and maximum compression ratio have been increased by 19.9%, 75.4% and 37%, respectively, compared with those of FeCoNi1.5CuB alloy. This is attributed to the solid solution, grain refinement and dispersion strengthening in the presence of yttrium addition.