In situ structural investigation of amorphous and nanocrystalline Fe40Co38Mo4B18 microwires

▶ The thermal expansion coefficient of nanocrystalline microwire decreases by one half comparing to that of the amorphous precursor. ▶ Annealing at 411 °C leads to the formation of α-FeCo grains with diameter ∼12 nm. ▶ grain size increases very weakly to ∼13 nm with annealing at higher temperature. ▶ Annealing increases the crystalline weight fraction up to 40% at 565 °C.