Multi-component NiFeCrWMo high entropy alloy, resulted from mechanical alloying

In this work, the evolution of the structure and phase composition of the multicomponent Ni-Fe-Cr-W-Mo system during mechanical alloying (MA) of an equiatomic mixture of elemental metal powders in a planetary mill is investigated. The formation of the phase composition and structure of the powdered equiatomic high-entropy NiFeCrWMo alloy at different stages of mechanical alloying was determined by scanning electron microscopy, X-ray diffraction and X-ray spectral analysis. It was found that during 10 hours of МА, a single-phase high-entropy alloy with the structure of a BCC solid solution in the nanostructural state with a crystallite size of 22 nm and a lattice strain (microstress) of 0.61 % was formed. It was shown that the metal components were completely dissolved in the solid state during mechanical alloying, in contrast to their limited solubility under equilibrium conditions. Moreover, despite the different features of the formation of solid solutions in high-entropy alloys and traditional materials, the order of dissolution of element atoms in the lattice of a solid solution follows general principles and occurs depending on the melting point in the following sequence: Ni→Fe→Cr→Mo→W. The average particle size of the produced powdered NiFeCrWMo high-entropy alloy is 3.8 μm, and their shape is predominantly spherical or close to spherical. The microstructure of the particles of the powdered NiFeCrWMo high-entropy alloy at the early stage (1.5 hours) of mechanical alloying is a layered structure formed in the process of grinding, deformation, and cold welding of particles of elemental metal powders. After 10 hours of МА, the microstructure of the alloy particles becomes homogeneous and contains a small amount of WC inclusions as a result of milling due to wear of grinding bodies in the MА process. The obtained NiFeCrWMo high-entropy alloy can be used in the future as a component/binder for other composite materials, for example, hard alloys based on WC to replace Co. Keywords: high-entropy alloy, mechanical alloying, structure, phase composition, solid solution, nanostructure