Effect of Yttrium on Mechanical Properties, Phases, and Microstructure of Feconialcrb High Entropy Alloys Prepared by Sps

Abstract

In the present work, FeCoNiAlCrB and FeCoNiAlCrBY0.1 high entropy alloys were prepared by high energy ball milling and spark plasma sintering (SPS) technique. The effects of Yttrium (Y) addition on phases, microstructure, Vickers hardness, local nano hardness and effective modulus, and fracture toughness of FeCoNiAlCrB alloy were investigated. Both of the alloys with and without Yttrium were almost fully dense (> 99%). Results show that, the fracture toughness of the Y-contained alloy was improved by ~50% with only ~10% decrease in Vickers hardness. With the addition of Y, the main phases of the alloy did not change, but the relative volume fraction of FeCrB phase increased. The continuous borides are observed to be more refined and dispersed in alloy with Y addition. High-speed mapping of nano hardness and modulus values reveal local variations in the composition and phase separation of the sample lead to local variations in properties at the micro-nano scale. The significantly increased fracture toughness could be due to the microstructure refinement and uniform dispersion of brittle borides and the lattice distortion caused by addition of Y which results in a decrease in elastic modulus.

Keywords: High entropy alloy, Yttrium doping, Microstructure, Mechanical properties