P. Jaśkiewicz

Kinetics of crystallization processes in AlYNiCo studied by electrical resistivity

Abstract Al90Y5Ni1Co4 amorphous and partially crystalline alloys were investigated by means of differential scanning calorimetry, direct current four probe method and X-ray diffraction. The process of crystallization of particles of the order of 10 nm (nanocrystallization) was induced by decreasing the rate of the quenching process from 54 to 39 rev/s or by annealing amorphous samples. The resistivity versus temperature isochronal relation for both groups of alloys was interpreted assuming diffusion controlled growth and zero nucleation rate. The effect of yttrium on the decrease of the growth rate was assumed to be a transformation mechanism leading to nano-size crystalline phase formation.

Electron Structure, Stability and Nanocrystallization of Al - Based Amorphous Alloys

Electron transport studies of Al-based alloys show that the strong bonds between Al-TM and Al-Y atoms arise by mixing of 3d and 4d electron states of TM and Y atoms with the 3s and 3p states from Al. Thermal stability of the Al-RE alloys is controlled by the low diffusity of heavy RE atoms. The results allow to optimize preparation conditions for nanocrystallizing Al-based alloys with enhanced mechanical properties.

Crystallization of Nanocrystalline Alloys Studied by Electron Transport, Magnetic and Dilatometric Methods

Amorphous alloys Fe77.5−xMxSi13.5B9 (M = Cu, Nb and Ta) transforming to the nanocrystalline phase exhibit during crystallization a specific behaviour of electrical resistivity due to the electron scattering on the grain boundaries. A relatively small structural contribution to electrical resistivity is found for the nanocrystallizing alloys. Structural resistivity is suppressed by the relaxation. The Debye temperature varies due to relaxation.

Electrical and magnetic study of bulk amorphous alloys Fe-Al-Ga-P-B-Si

Bulk amorphous alloys Fe-Al-Ga-P-B-Si were prepared by a single-roller melt spinning method. Electrical resistivity of alloys is of the order of 200 μΩcm. The structural and magnetic components of resistivity are separated. The anomalous rise of resistivity during crystallization observed in Fe-Al-Ga-P-B-Si alloys with higher Si content is related to the precipitation of high resistivity crystalline phases. The strong exchange interaction is revealed by the Curie temperatures reaching 640 K. The room temperature values of the effective magnetic moment vary between 1.79 and 1.83 μB depending weakly on alloy composition. The AC hysteresis loops were recorded in magnetic fields up to 50 A/cm and frequencies between 10 Hz to 400 kHz. The frequency variation of power losses shows that high resistivity reduces eddy current losses.

Method to study crystallization kinetics by electrical resistivity

A procedure of transformed material fraction evaluation from electrical resistivity isochronal measurements was characterized. The amorphous-to-crystalline transformation in Fe-B alloys was taken as the model eutectic and primary reaction. The results were applied to the experimental resistivity data obtained by Dehghan [9]. The interpretation was done with help of the latest ideas of activation energy spectrum developed for primary reaction.

Crystallization Kinetics of Metallic Glasses Co78−xFexSi9B13 Probed by Electrical Resistivity and Magnetization

Metallic glasses are metallic alloys distinguished by lack of a long range order of atoms. Their unique physical properties are caused by both the topological and chemical disorder in amorphous structure 1. Namely, the interplay of exchange interactions and casted in anisotropy along the ribbon length involves the asperomagnetic structure 2. On the other hand, the disorder modified structure factor changes electron scattering leading to increase in electrical resistivity 3.