► Novel deformation mechanism in FeCo alloys via severe plastic deformation. ► Observation of the strip formation (“Noodles”) at an initial stage of milling. ► Self-nanoscaling that leads to grains of about 8nm. ► Correlation between the morphology and magnetic properties. Nanocrystalline Fe100−xCox (x=20, 35, 50, 60) alloys have been prepared by mechanical alloying of Fe and Co powders via high energy ball milling. The alloy formation process and microstructure evolution of the samples have been investigated. Energy filtered transmission microscopy (EFTEM) observations revealed the strip formation of the Fe and Co phases at an initial stage of milling. The final grain size of the equiaxed grains in the obtained alloys reached 8nm upon milling for 20h. The saturation magnetization of the mixtures of Fe and Co increases with milling time, indicating an increasing homogeneity in composition and the phase formation. It is found that the saturation magnetization is also dependent on the Co content, which reaches the highest value of 240emu/g at Fe65Co35. The phase transformation of the as-prepared FeCo alloys was also studied using differential scanning calorimetry.