FORMATION OF B2 INTERMETALLIC NIAL AND FEAL BY MECHANICAL ALLOYING

Nanostructured B2 intermetallic compounds NiAl and FeAl have been prep ared by mechanical alloying (MA) the elemental powder mixtures and sub sequent heating. The structural evolution during MA was monitored by i n situ thermal analysis and X-ray diffraction (XRD). The final product s were characterized by transmission electron microscopy (TEM) and dif ferential scanning calorimetry (DSC). The results show that the nanocr ystalline intermetallic compound NiAl, which is difficult to disorder by milling, was synthesized directly after an exothermic explosive rea ction; whereas FeAl compound was formed after a thermal process of asm illed Fe(Al) solid solution obtained through interdiffusion during MA. The large heat of formation of NiAl compound is the main driving forc e for the exothermic explosive reaction, and the difference in diffusi vity between Ni-Al system and Fe-Al system is suggested to be the main cause of the different behaviors of formation between NiAl and FeAl c ompounds by MA.