Thermal analysis, measurements of saturation magnetization and microstructure observations were used to determine the effects of silicon content (0<x<4.33 wt.%) on the liquidus-solidus temperatures, phase transformations and critical cooling rate during solutioning of Fe48−xCr28Co2xSix magnets. It was found that the addition of silicon on the investigated alloy (i) decreased the liquidus-solidus temperatures, the temperature changes for the solidus being greater than for the liquidus, and (ii) distinctly influenced the phase transition temperatures: The lower temperature of the range pfγ-phase existence and the Curie temperature decreased, theγ-phase region became narrower and theσ-phase region became slightly broader.