Crystallization of metallic glasses

After some introductory comments on materials classification and a brief historical outline, this review seeks to identify those fundamental physical phenomena that underlie the major technical properties of ferromagnetic amorphous alloys. Those phenomena are reviewed and an attempt is made to compare existing data and, where possible, to synthesize new perspectives. A fundamental approach is taken in the sense that we move from consideration of the local atomic structure to its consequences for the electronic structure and from the electronic structure finally to the physical properties it determines. We focus on the aspects of the structure‐property sequence that set amorphous metallic alloys apart from their crystalline counterparts. Such a review would be incomplete without addressing the new issues and insights raised by the discovery of the quasicrystalline state. The very existence and better understood atomic arrangements of quasicrystals help to define and illuminate their amorphous cousins.

Physics of ferromagnetic amorphous alloys

Changes in the structure of the amorphous alloy Fe73.5Cu1Nb3Si13.5B9 were investigated after annealing for 1 h in a temperature range from 450-800 degrees C using X-ray diffraction scattering and Mossbauer effect spectroscopy. Between 520 and 550 degrees C nanocrystalline Fe80Si20 grains with the DO3 structure (diameter of about 10 nm) are embedded in an amorphous grain boundary phase. Above 650 degrees C the grain size increases and the amorphous grain boundary phase disappears. The Fe-B phases form and a new paramagnetic phase is observed. Furthermore the kinetics of the amorphous-to-nanocrystalline phase transition of this alloy was examined by X-ray diffraction observing the development of crystallization with time at a fixed annealing temperature of 520 degrees C. The beginning of crystallization appears at times less than 2 min, most grains developing in the first 10 to 20 min while after about 5 min the grain size remains constant with a diameter of about 10 nm.

https://iopscience.iop.org/article/10.1088/0953-8984/4/12/013/pdf

Crystallization of Fe73.5Cu1Nb3Si13.5B9 structure and kinetics examined by X-ray diffraction and Mossbauer effect spectroscopy

Thermodynamic optimization of the B–Fe system

Undercooling of Ni-B and Fe-B alloys and their metastable phase diagrams.

A study of the structure change with temperature for Fe100-xBx 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 11x13 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 14x25 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 17x25 at.%B. For temperatures beyond 600~700°C, they transform to the equilibrium phases of α-Fe and Fe2B compound.

https://iopscience.iop.org/article/10.1143/JJAP.20.1821/pdf

Phase Diagram of Amorphous and Crystallized Fe-B Alloy System

https://iopscience.iop.org/article/10.1143/JJAP.16.1711/pdf

Temperature Dependence of the Saturation Magnetization in Amorphous Fe–B Alloys

Temperature Dependence of Saturation Magnetization in Amorphous Co–B Alloys

Temperature Dependence of the Magnetic Moment in Rapidly Quenched Ni–B Alloys

The structure of rapidly quenched Ni-B alloys with compositions in the range from 15 to 50 at. % B including some eutectic compositions has been studied by X-ray diffraction, metallurgical microscopy and electron microscopy. It is found by X-ray diffraction that amorphous alloys can be obtained for narrow concentration ranges near the eutectic compositions; (18.5-19 at. % B) and (38-40 at. % B). However, even for these compositions, a small amount of crystallites is present in the amorphous matrix. No indication of which crystalline phase (Ni, Ni3B or Ni2B) appears preferentially near the boundary between the amorphous and the crystalline phases is obtained by electron microscopic observation.

https://iopscience.iop.org/article/10.1143/JJAP.19.2335/pdf

Minoru Takahashi

Papers

Phase Diagram of Amorphous and Crystallized Fe-B Alloy System

Temperature Dependence of the Saturation Magnetization in Amorphous Fe–B Alloys

Temperature Dependence of Saturation Magnetization in Amorphous Co–B Alloys

Temperature Dependence of the Magnetic Moment in Rapidly Quenched Ni–B Alloys

Observation of Structures in Rapidly Quenched Ni-B Alloys. I