In this diploma thesis, an iron-based alloy with the nominal composition Fe-25%Co-15%Mo (mass%) was investigated. Its aging behavior is similar to that of age-hardenable Al-alloys. Such alloys exhibit a relatively low hardness after solution treatment and quenching, but a strong increase in hardness upon aging. The microstructure after aging consists of a cobalt-martensite with micron-sized intermetallic precipitates. The hardness increase during aging is caused by the formation of nm-sized precipitates. The aim of this diploma thesis was to determine whether a complete dissolution of the primary intermetallic phase leads to a significant increase in hardness and subsequently how the mechanical properties are influenced. The phase transformations were studied by dilatometer and differential-scanning-calorimetry (DSC) experiments. The mechanical properties were obtained by tensile, compressive and fracture toughness tests. It was revealed that the maximum attainable hardness could not be increased even by annealing at temperatures, which allowed the almost complete dissolution of the primary intermetallic phase. Only minor improvements in mechanical properties in contrast to lower austenitizing temperatures were found. This behaviour was explained by the higher amount of molybdenum in solution, which leads to an unchanged precipitation behavior.