Nanostructured B2-CoAl has been successfully synthesized directly by MA of nominal composition of
Co50Al50. The CoAl phase was found to be formed in an ordered structure via a gradual reaction which
completed in less than 10 h. However, further milling up to 45 h led to disordering of the CoAl with a relatively
constant long-range order parameter of 0.82. Lattice parameter measurements showed that disordering
of CoAl was caused by triple defect mechanism. The results of isothermal annealing showed that
the grains grew after isothermal annealing up to 0.7 Tm but still remained below 100 nm. The grain
growth behavior was well described by the parabolic kinetics equation. The grain growth exponent remained
constant above 873 K offering that grain growth mechanism does not change at high temperatures.
The grain growth exponents and activation energies offered the mechanism of diffusing Co and Al atoms in
the two separate sublattices at high temperatures. The equation 4 4 13
D D0 6 10 exp 175 RT t was
suggested to describe the grain-growth kinetics of nano-crystalline CoAl during isothermal annealing at
temperatures above 0.5Tm (873 K).
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