Anomalous behavior of amorphous Fe-B alloys

The density of Fe-B amorphous alloys is constant at 7.5 g/cm
3
for 13 ≤ at.% B < 20 and decreases for B > 20 at.%. Hardness increases with B content up to 20% and less steeply for B > 20 at.%. A model based on the dense random packing of spheres of two sizes with densities
d_{1}p
and
d_{2}p
is presented to account for the anomalous behaviour in density of Fe-B alloys.