Magnetostriction of the polycrystalline Fe80Al20 alloy doped with boron

The doping of Fe80Al20 polycrystalline alloy with 2% of boron increased the total magnetostriction twofold compared to a sample without boron. A value close to 80 ppm was achieved at 300 K. The microstructures of the boron-doped alloys show a dendritically solidified matrix with interdendritic α-FeAl and/or Fe3Al and Fe2B eutectic between the grains. The XRD analysis reveals an increase in the volume fraction of α-FeAl and a correspondent decrease of the Fe3Al phase volume fraction as the boron content increases. The increase of the volume fraction of this tetragonal Fe2B phase in the samples doped with boron causes the decrease of the strong volume magnetostriction that was observed in the alloy without boron. There is some evidence that the improvement of the magnetostriction magnitude due to the addition of boron to the Fe80Al20 alloy could reach the maximal magnetostriction if the 1:1 optimal ratio of the volume fractions of the α-FeAl and Fe3Al phases could be reached.

► Fe80Al20 polycrystalline alloy magnetostriction 40 ppm increased to 80 ppm due to 2% of B doping.
► B stabilizes α-FeAl phase and a coexistence of α-FeAl + Fe3Al improves magnetostriction.
► Presence of Fe2B phase causes domain rearrangement revealed by the decrease of the volume magnetostriction.