THERMAL-STABILITY OF NANOCRYSTALLINE IRON-IRON CARBIDE COMPOSITES - AMOSSBAUER STUDY

Mechanically synthesized nanocrystalline iron-iron carbide nanocomposi tes were subjected to isothermal cycles of one hour duration. As-treat ed and annealed powders were characterized by means of Mossbauer spect roscopy and X-ray diffraction. The grain growth was studied in a tempe rature range in which epsilon and chi iron carbides, detected in the t reated amples, have a low thermal stability. Cementite results are sub stantially stable up to 1100 K and, according to a simplified model of crystal growth, show a low activation energy for crystal growth.