Abstract
The kinetics of the discontinuous ordering reaction in the Fe-50 at.% Co alloy has been studied in the temperature range 280–400°C. The misorientation parameters for 61 grain boundaries have been determined with the help of the electron backscattering diffraction technique. It is shown that for lowangle grain boundaries with a misorientation angle below 15° and for grain boundaries which were identified as close to the special Σ3〈111〉, Σ9〈011〉, Σ11〈011〉 and Σ17〈001〉 misorientations (here Σ is the reciprocal density of the coincidence sites in the two misoriented lattices) the reaction rate is very low. Contrarily, the GBs close to the special Σ19a〈011〉 and Σ19b〈111〉 exhibit high reaction rate. The reaction rates for the other large-angle grain boundaries vary considerably from boundary to boundary. This is discussed in terms of the effect of the grain boundary inclination on the observed reaction rate. The migration rate of large-angle random grain boundaries obeys the Arrhenius relationship: v = 2 × 1014exp(−132 kJ · mol−1/RT) m/s, where R and T are the gas constant and the absolute temperature, respectively. A model connecting the grain boundary velocity with the relaxation time of the order parameter in the grain boundary and its mobility is suggested.
Published Version
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