V S Ignahin’s research while affiliated with Petrozavodsk State University and other places

We report about formation mechanism, crystallization kinetics and magnetic properties observed in the series of rapidly solidified F e80−xCoxP14B6 metallic glasses with x = 25, 32, 35 and 40 at.%. Magnetic soft F e80−xCoxP14B6 metallic glasses have 15–25 µm thick and 2–8 mm wide. The ribbon samples were created to meltspun onto the massive copper wheel from the RF-melted superheated master ingots.

The paper presents the possibility to build a tension gauge capable to discriminate different kinds of deformations: compression and twisting (induced by torsion strain) based on the magnetoelastic effect in new metallic glasses Fe80−x Cox P14B6. Applied loads increase coercive field H c, saturation induction B s and rectangularity of magnetic hysteresis loop. For example, hysteresis loop traced for 1 mm narrow, 50 cm long and 30 μm thick Fe40Co40P14B6 straight ribbon subjected to longitudinal stress of 346 MPa shown increased B s from 1.24 to 1.7 T and squareness from 0.55 to 0.88 compared to unloaded specimen. For twisting, on the contrary, both squareness and coercive field vary whereas the value of B s remains unchanged.

Crystallization kinetics and magnetic properties were studied in series of rapidly solidified metallic glasses Fe80-ξCoξP14B6 with ξ = 25, 32, 35 and 40 at. %. Differential scanning calorimetry (DSC) was employed to determine crystallization temperature and to demonstrate the incubation phenomenon at isothermal annealing. Fitting DSC traces recorded in non-isothermal and isothermal regimes, we obtained the same activation energy Q. It describes atomic transfer across crystal/amorphous interface in Kolmogorov-Johnson-Mehl- Avrami (KJMA) model of the transition of metallic glasses into crystalline state. As-quenched metglas ribbons have amorphous structure and superior soft magnetic properties: coercive field 4 A/m, ac magnetic permeability as high as 110 000 at 60 Hz.