Phase formation processes in equiatomic AlCoCuFeNiCr high-entropy alloys have been studied by means of x-ray diffraction method, microstructure analysis and microhardness measurements. Thermodynamic and structural criteria for predicting the phase composition of the alloys were considered. It is shown that in AlCoCuFe, AlCoCuFeNi and AlCoCuFeNiCr alloys the two-phase mixture of solid solutions on the base of the BCC and FCC lattices is formed. With a decrease in the fraction of Al atoms, the tendency to disordering of BCC solid solution occurs. It was also established that alloys under investigation reveal a dendritic structure in which Cu-enriched FCC phase is deposited in the regions between the dendrites of the main BCC phase. The correlation between microhardness of the alloys and volume fractions of phase constituents and their thermodynamic characteristics are revealed.