Phase transformations in M2 steel powders subjected to ball milling

The mechanical alloying process of M2 high speed steel resulted in the formation of the powders with average particle size about 4 mum and round-in-shape morphology. The X-ray diffraction studies revealed the formation of nanoferrite characterized by the values of crystallite size and lattice strain of 12 nm and 1%, respectively. The Mossbauer measurements allowed to distinguish between ferrite and alloyed ferrite and to estimate the content of both phases after 100 h of mechanical alloying as 20 and 71%, respectively. Moreover, the content of iron containing carbides was found to be 9%, most probably of the M7C3 and/or M23C6 types. Differential scanning calorimetry measurements revealed two exothermic effects during the heating of the mechanically alloyed powders, corresponding to ferrite lattice strain decrease and carbide and ferrite crystallite growth, respectively.