Mechanical Properties of High Entropy Alloys Based on Rare Earth Elements with Yttrium and Scandium

Abstract

The paper reports the research outcomes on the structural and chemical composition of the equiatomic GdTbDyHoSc and GdTbDyHoY high-entropy alloys, which are potential materials for magnetic cold generators. The solidus and liquidus temperatures of the alloys were determined using differential scanning calorimetry. Based on these findings, an experimental mode of thermal cyclic treatment was selected. No signs of alloy destruction were observed after five test cycles for thermal resistance under exposure at a temperature of 1073 K (~0.6 of the melting point) for 15 minutes followed by quenching in room-temperature water. The applied heat treatment resulted in an increase in the hardness of alloys by 2–3 times and a decrease in wear resistance by 4–40 times depending on the alloy composition and the number of heat treatment cycles. Significant changes in the properties of alloys are associated with the formation of oxides, including REM₂О₃, not only on the surface but also within their volume, which is due to the high chemical activity of rare-earth metals. The data presented in this study will be beneficial in the development of thermal and thermomechanical treatment methods for studied alloys.