Phase composition of AlxFeNiCrCo high entropy alloys prepared by sintering and arc-melting methods

Highlights: • Sintering of pure metallic powders below 1000^oC successfully leads to HEA formation. • The sintering process results in large and chemically homogeneous HEA grains. • Transition from fcc to bcc via their coexistence is observed in Al_xFeNiCrCo with x. • Chemical segregation of elements occurs in arc-melted HEA samples. • Annealing of HEA leads to dendritic phases with close chemical compositions. Al_xFeNiCrCo ($0\le x\le 1.5$) high entropy alloys (HEA) have been investigated experimentally in systematic way in order to complete the existing results as well as to testify the alternative method of HEA sample preparation based on sintering of pure metallic powders. Structural properties have been studied by X-ray and neutron diffraction measurements, which allowed to identify the crystal structures and their contributions in HEA samples. The phase compositions were determined from electron microscopic measurements (EDX, EBSD). The amounts of observed BCC/B2 and FCC phases obtained using these complementary techniques remains in good agreement. Within two detected crystallographic structures, three phases with different stoichiometries were identified and their appearance, composition and contribution in the investigated HEA were found to be dependent on Al content. Comparing overall results obtained for sintered and melted samples, it was shown that the phase composition of Al_xFeNiCrCo alloys are very similiar, but the corresponding microstructures are quite different, i.e. dendritic structure is observed for melted samples while large regular grains for sintered ones.