Heat treatment of rapidly solidified Fe?Cr?Zr?B alloys

The crystallization behaviour of amorphous melt spun Fe_82?x?yCr₁₈Zr_xB_y (x=0–8, y=10–20) ribbons have been investigated using differential scanning calorimetry. The crystallization temperature and crystallization behaviour change with varzing Zr and B content. The microstructural development during annealing of amorphous Fe₆₄Cr₁₈Zr₈B₁₀ has been investigated by a combination of transmission electron microscopy and energy dispersive X-ray microanalysis. Isothermal annealing for 2 h at temperatures in the range 600–1000°C produces a variety of different microstructures depending on the annealing temperature. At 600°C, the amorphous alloy partially crystallizes to a form a microstructure consisting of 9 nm sized bee ferrite grains embedded in an amorphous matrix. At temperatures in the range 700–900°C, the alloy microstructure transforms into a mixture of bee ferrite, faulted fcc MB₁₂ boride particles and tetragonal M₃B boride particles. At 1000°C, the faulted fcc MB₁₂ boride particles are replaced by orthorhombic M₄B boride particles.