Influence of the chemical composition of rapidly quenched amorphous alloys (Ni, Fe, Cr)-B-Si on its crystallization process

This paper presents results of research of the structure and phase transformations during the multistage crystallization of the metallic glasses with the compositions Ni_71,5Cr₆,₈Fe₂,₇B₁₁,₉Si_7,1 and Ni_63,4Cr₇,₄Fe₄,₃Mn₀,₈B₁₅,₆Si_8,5 labeled as AWS BNi-2 according to American Welding Society. Differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX) were used as experimental research methods. The influence of the alloys chemical composition (boron, manganese and iron) on the temperatures and the exothermic heat effects of phase transformations, as well as on the phase composition of alloys at three stages of crystallization was analyzed. We present a thermodynamic explanation of the observed heat effects. It has been shown that manganese has the main influence on the phase transformations temperatures and heat effects in these two alloys. It is also assumed that at the final crystallization stage simultaneously with the formation of phases Ni₃B and β₁-Ni₃Si should occur the nucleation of borides of CrB type with high Cr and low Si content. (paper)