A new temperature versus heating rate transformation (T-HR-T) diagram; To study the crystallization behaviour of Fe sub 67. 5 Co sub 15 Nb sub 1. 5 B sub 16 metallic glass

Journal Article · Wed Jan 01 04:00:00 EST 1992 · Acta Metallurgica; (United States)

OSTI ID:7293878

Surinach, S; Baro, M D; Diego, J A; Clavaguera-Mora, M T ^[1]; Clavaguera, N ^[2]

---

1. Fisica de Materials, Dept. de Fisica, Facultat de Ciencies, Univ. Autonoma de Barcelona, 08193 Bellaterra (ES)
2. Dept. d'Estructura i Constituents de la Materia, Facultat de Fisica, Univ. de Barcelona, Diagonal 647, 08028 Barcelona (ES)

This paper discusses a new approach based on a temperature-heating rate-transformation (T-HR-T) curves, useful when heating an amorphous sample under continuous heating conditions, together with the traditional time-temperature-transformation (T-T-T) diagram is presented in the study of the crystallization behaviour of Fe{sub 67.5}CO{sub 15}Nb{sub 1.5}B{sub 16} metallic glass, prepared by planar flow casting. The study has been carried out by differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. The calorimetric results show that there are two separate stages of crystallization. The second stage of crystallization is described correctly by the Johnson Mehl Avrami Erofe'ev equation, with an Arrhenius form of the rate constant, under both isothermal and continuous heating conditions. A more complicated kinetic behaviour is obtained for the first stage of crystallization. Transmission electron microscopy of the specimens after controlled heat treatment shows that the primary crystallization of {alpha}-(Fe,Co) dendrites in the amorphous matrix occurs in the first stage of crystallization with, in addition, sporadically secondary precipitation of (Fe,Co){sub 3}B crystals. X-ray diffraction experiments confirm these results and show that a progressive enrichment in Fe in the {alpha}-(Fe,Co) phase occurs on the first stage of crystallization. From the crystallization kinetic results the low temperature part of the T-T-T and T-HR-T curves of the two exothermic crystallization processes are deduced.

• OSTI ID: 7293878
• Journal Information: Acta Metallurgica; (United States), Journal Name: Acta Metallurgica; (United States) Vol. 40:1; ISSN 0001-6160; ISSN AMETA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
664400 -- Experimentally Derived Information on Atomic & Molecular Properties-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
BORIDES
BORON COMPOUNDS
CALORIMETRY
CHEMICAL REACTION KINETICS
COBALT BORIDES
COBALT COMPOUNDS
COHERENT SCATTERING
CRYSTALLIZATION
DATA
DIFFRACTION
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
FABRICATION
HEAT TREATMENTS
INFORMATION
IRON BORIDES
IRON COMPOUNDS
KINETICS
MATERIALS WORKING
METALLIC GLASSES
MICROSCOPY
NIOBIUM BORIDES
NIOBIUM COMPOUNDS
NUMERICAL DATA
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
REACTION KINETICS
REFRACTORY METAL COMPOUNDS
SCATTERING
THERMODYNAMIC PROPERTIES
THERMOMECHANICAL TREATMENTS
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION