Development and mechanical behaviour of Co-Cr-Mn-Ni-Ta high entropy alloys

Abstract

In the realm of materials science and engineering, high-entropy alloys (HEAs) have garnered significant research attention. Unlike conventional alloys, which typically consist of only one or two base elements, HEAs are composed of multiple principal elements, resulting in a wide range of possible compositions. HEAs possess remarkable characteristics such as exceptional specific strength, superior mechanical performance at high temperatures, remarkable ductility and fracture toughness at cryogenic temperatures, and even exhibit superconductivity. This unique combination of properties distinguishes HEAs from conventional alloys. With a minimum requirement of four principal elements, HEAs represent a breakthrough in the domain of alloy design and open up new avenues for investigating novel materials and their properties. Previous investigations have shown that HEAs exhibit high resistance to softening at elevated temperatures and display sluggish diffusion kinetics. Therefore, they are considered highly promising materials for high-temperature applications. However, a major technical challenge lies in achieving desired mechanical properties for HEAs. Single-phased HEAs, although ductile, suffer from limited robustness when possessing a face-centered cubic (FCC) crystal structure. Conversely, single-phase HEAs with a body-centered cubic (bcc) crystal structure exhibits high strength but are prone to brittleness. Notably, there are no reports of HEAs that demonstrate exceptional strength and tensile ductility in a balanced manner. Our research focused on investigating a high-entropy alloy based on CoCrNiMn, which exhibits a single-phase face-centered cubic (FCC) structure. Subsequently, we introduced tantalum (Ta) into the alloy, resulting in the formation of a Laves phase based on Nickel and Cobalt. This addition enhanced the strength of the alloy and allowed us to examine the trade-off between Strength and Ductility. Furthermore, it is worth mentioning that Tantalum has limited solubility in the FCCstructure.despite the significant size difference that induces lattice deformation in the crystal of the material.