In situ structural investigation of amorphous and nanocrystalline Fe40Co38Mo4B18 microwires

Thermal evolution of the structure of glass-coated nanocrystalline FeCoMoB microwire during its devitrification has been studied. It is shown that annealing at the temperature above 411 degrees C leads to the formation of crystalline alpha-FeCo grains with diameter similar to 12 nm. Annealing at higher temperature increases the crystalline weight fraction up to 40% at 565 degrees C. However, crystalline grains size increases very weakly to similar to 13 nm. The thermal expansion coefficient of nanocrystalline microwire decreases by one half comparing to that of the amorphous precursor. (C) 2010 Elsevier B.V. All rights reserved.