Abstract: 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 18nm, can be obtained after 5h of ball milling. Then with prolonging time of ball milling, grain size decreases slowly. The average grain size gets to 9nm after 45h 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, Fe3B, 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.
Preparation of nanocrystalline Fe83Nb7B9Cu1 powders by mechanical alloying and their thermal stability
Abstract:
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.