The Evolution of Intermetallic Compounds in High-Entropy Alloys: From the Secondary Phase to the Main Phase

Abstract

High-performance structural materials are critical to the development of transportation, energy, and aerospace. In recent years, newly developed high-entropy alloys with a single-phase solid-solution structure have attracted wide attention from researchers due to their excellent properties. However, this new material also has inevitable shortcomings, such as brittleness at ambient temperature and thermodynamic instability at high temperature. Efforts have been made to introduce a small number of intermetallic compounds into single-phase solid-solution high-entropy alloys as a secondary phase to their enhance properties. Various studies have suggested that the performance of high-entropy alloys can be improved by introducing more intermetallic compounds. At that point, researchers designed an intermetallic compound-strengthened high-entropy alloy, which introduced a massive intermetallic compound as a coherent strengthening phase to further strengthen the matrix of the high-entropy alloy. Inspired from this, Fantao obtained a new alloy—high-entropy intermetallics—by introducing different alloying elements to multi-principalize the material in a previous study. This new alloy treats the intermetallic compound as the main phase and has advantages of both structural and functional materials. It is expected to become a new generation of high-performance amphibious high-entropy materials across the field of structure and function. In this review, we first demonstrate the inevitability of intermetallic compounds in high-entropy alloys and explain the importance of intermetallic compounds in improving the properties of high-entropy alloys. Secondly, we introduce two new high-entropy alloys mainly from the aspects of composition design, structure, underlying mechanism, and performance. Lastly, the high-entropy materials containing intermetallic compound phases are summarized, which lays a theoretical foundation for the development of new advanced materials.

Atomic Radius Mismatch: A Key Parameter for Design and Synthesis of High‐Entropy Physical Vapor Deposition Coatings—Review

“…In the past, material scientists expected this issue to lead to the emergence of numerous unwanted phases, particularly intermetallic compounds that could cause brittleness in the material, [2][3][4][5] which is true for many combinations. [6] However, the synthesis of alloys with more principal elements can lead to the formation of a new category of materials known as high-entropy materials (HEMs).…”

Detonation Spraying of Ni-Based Composite Coatings Reinforced by High-Entropy Intermetallic Particles

“…HEICs potentially provide an interesting avenue to combining the properties of ordered intermetallic compounds (ICs) and HEAs into a singular material and, hence, to fabricating novel alloys with superior properties compared to those of either conventional ICs or HEAs. Recently, several HEICs with interesting mechanical and functional properties have been developed, which have been reviewed elsewhere [2,[7][8][9]. To name a few, the compressive yield strength of 2.25 GPa and the fracture strength of 2.52 GPa have been reported for a non-equiatomic Fe 0.75 Co 0.75 Ni 0.75 Cu 0.75 TiZrHf HEIC that exhibits a B2-type ordering [10].…”