In this work two Co53.5Fe10X5.5B31 (X = Ta, W) alloys were synthesized from high purity (≥ 99.9%) powder elements by means of mechanical alloying. In case of Ta-addition, mechanical alloying resulted in formation of two component material with nanocrystalline phase embedded in amorphous matrix. On the other hand, substitution of Ta by W retards partial amorphization induced by mechanical alloying. High pressure-temperature stability of both alloys was monitored using in situ energy dispersive X-rays.