Centrifugal metallothermic SHS of cast Co–Cr–Fe–Ni–Mn–(X) high-entropy alloys

A relatively new and promising approach to the development of new metal alloys with a view to replacing a number of existing commercially used alloys is the use of a new alloying concept based on the development of metal materials comprising several basic elements taken in approximately equal atomic concentrations. Such materials are called high-entropy alloys (HEA). Modern research has shown that the HEA microstructure can be formed by solid solutions with both BCC and FCC lattices, and also have ordered phases (intermetallics) in its composition. This approach to forming metal materials provides a wide range of opportunities for the development of new alloys with improved performance. Most of the current HEA research is focused on identifying a relationship between the microstructure and measured properties. Much less attention is paid to the study and development of new effective methods for HEA production. This paper investigates the possibility of obtaining HEA based on the CoCrFeNiMn-(X) system in the combustion mode using centrifugal SHS metallurgy methods. For the first time, the study made it possible to practice chemical technology methods of cast CoCrFeNiMn alloy modification directly (in situ) during synthesis by introducing alloying components into the original exothermic compounds. The microstructure and phase composition ofNiCrCoFeMn alloys obtained with the introduction ofthe Ti—Si—B(C) complex modifying additive and NiCrCoFeMn—Al_x excess aluminum were analyzed. The obtained data indicated that as the Ti—Si—B(C) additive content increases, the microstructure of synthesis products is formed based on a matrix of HEA with evolving new structural elements based on carbides and Ti borides. It was found that synthesis in the combustion of alloys with a high Al concentration (x > 0.6) leads to the formation of a composite structure consisting of the NiAl-based matrix with numerous nanoscale (~100 nm) dispersive precipitates formed from the Cr and Fe based solid solution. The obtained experimental data allows us to conclude that the HEA-based materials under study and the proposed method for obtaining them to form bulk nanostructural HEA-based materials have promising prospects.

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