Phase transitions in mechanically comminuted Fe78B13Si9 amorphous ribbon

✍ Scribed by Han-Ryong Pak; Jinn Chu; R.J. Deangelis; Kenji Okazaki

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 723 KB
• Volume: 118
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/0921-5093(89)90067-1

✦ Synopsis

Characterization of mechanically comminuted

Fe78B13Si ~ amorphous ribbon was performed by means of differential scanning calorimetry and X-ray diffraction. The amorphous structure remained unaltered on comminution in cases where powders were produced in brittle fracture modes. When powders were heavily deformed plastically during comminution, the amorphous structure was partially crystallized into Fe3B and tt-Fe. The large amount of Fe3B phase observed suggests that the formation of Fe~B is strain induced. On heating these powders, an endothermic reaction took place at temperatures immediately above the temperature range in which the two exothermic reactions associated with the crystallization of a-Fe and Fe3B occurred. On subsequent cooling, an exothermic reaction occurred as a reverse reaction of that endothermic. This pair of reactions indicates the occurrence of a reversible first-order phase transition, which is attributed to a stressinduced thermoelastic martensitic transition of Fe~B. The magnitude of the reversible thermal effect decreased when the cycle was repeated owing to thermal relaxation of the elastic stress fields formed during comminution.