Phase Diagram of Amorphous and Crystallized Fe-B Alloy System

A study of the structure change with temperature for Fe100-x B x alloys (x=2∼33 at.%B) fabricated by a rapid quenching technique has been carried out by measuring magnetization, electrical resistivity and thermal expansion and also by structural analysis by X-ray diffraction. The amorphous alloys with 11≦x≦13 at.%B transform into α-Fe(B) around 300°C which has a smaller lattice constant than that of α-Fe. Then α-Fe(B) decomposes into two stable α-Fe and Fe2B at about 450°C. For the amorphous alloys with 14≦x≦25 at.%B, the amorphous phase transforms into both α-Fe and tetragonal Fe3B compound at about 400°C. With further heating, an orthorhombic Fe3B compound can be observed clearly in addition to these 2 phases for 17≦x≦25 at.%B. For temperatures beyond 600∼700°C, they transform to the equilibrium phases of α-Fe and Fe2B compound.