Preparation of nanocrystalline Fe_(83)Nb_7B_9Cu_1 powders by mechanical alloying and their thermal stability

Nanocrystalline powder in Fe-Nb-B-Cu system was obtained by high-energy ball milling. The average grain size, thermal stability of α-Fe phase in the powder were studied by XRD, DSC and SEM. The results show that replacing pure boron powder with Fe-20B master alloy does not affect the dynamic process of mechanical alloying. During the course of ball milling, α-Fe supersaturation solid solution, with an average grain size of 18 nm, can be obtained after 5 h of ball milling. Then with prolonging time of ball milling, grain size decreases slowly. The average grain size gets to 9 nm after 45 h of ball milling. The α-Fe solid solution undergoes structure relaxation from 100 ℃, and undergoes phase transformation from 738.8 ℃. The transition from α-Fe supersaturation solid solution to α-Fe solid solution, Fe 3B, and FeB gets the exothermic peak at 803.6 ℃. Annealing at temperature below 550 ℃, the nanocrystalline has no significant grain growth. Annealing at the temperature between 770 ℃ and 950 ℃, the grain of nanocrystalline grows obviously, but its grain size is still at nanometer range.