Metallic glass has a combination of amorphous structure and metallic bond. Metallicglasses have been regarded as potential structural and functional materials with unique disordered atomic configuration [ 1 , 2
In this study, the temperature-heating rate diagram of the main crystallization process of two metallic glasses, Fe74Ni3.5Mo3B16Si3.5 and Fe41Ni38Mo3B18, was obtained from one experimental differential scanning calorimetry (DSC) scan and the knowledge of their activation energy
as determined by an isoconversional method. A good concordance was observed between the diagram curves obtained by calculation
(isoconversional approach) and the experimental data, which verifies the reliability of the method and the validity of the
kinetic approach in these alloys.
The advent of bulk metallicglasses (BMGs) has achieved a great interest due to their superior physical and chemical properties. The formation of BMGs in multi-component metallic alloys has also widened the
Radionuclide X-ray fluorescence (XRF) and particle induced X-ray emission (PIXE) methods have been used for a rapid and nondestructive analysis of metallic glasses. The methods are compared in accuracy and precision with the atomic absorption method. Some results of analyses of FexNi80-xB20 materials are briefly reviewed. The distribution of elements along the width as well as length and a qualitative analysis of the composition of material surfaces are considered.
Authors:G. Luciani, A. Costantini, F. Branda, P. Scardi, and L. Lanotte
A traditional TG apparatus was modified by placing two permanent magnets producing a controlled magnetic field (TG(M): Magneto
Thermogravimetry). This technique proved to be useful to study both structural relaxation and crystallisation of ferromagnetic
metallic glasses. Results obtained for the amorphous alloys Fe40Ni40P14B6 and Fe62.5Co6Ni7.5Zr6Nb2Cu1B15, are reported in this paper. Structural relaxation can be evaluated by measuring changes in Curie temperature induced by
thermal treatments. Crystallisation in TG(M) is detected through a change in the measured apparent mass (difference between
the sample mass and magnetic force driving it upward). These results were confirmed by DSC analysis. Whether the obtained
crystalline phase is ferromagnetic, it can be identified through its Curie temperature, measured by TG(M). In fact the value
of 770C measured as Curie temperature of crystallised Fe62.5Co6Ni7.5Zr6Nb2Cu1B15led to conclude that the only ferromagnetic crystalline phase is a-Fe. These hypothesis was confirmed by XRD analysis, showing
that the first crystallisation yields to a-Fe nanocrystals.
The development of bulk metallic glasses as a prominent class of functional and structural materials has attracted considerable
interest in the last years. One of the fundamental physical quantities necessary to describe the mechanical properties of
the materials is the bulk modulus. In the present article, a simple method to estimate the bulk modulus and its pressure derivative
is proposed. It is shown that these quantities can be estimated from the values of the constituent elements and their compositions.
Comparison with measured data shows good agreement. The physical background of the method is discussed based on the jellium
model of metals.
The crystallization behaviour and Curie temperatures of Fe−(Nb,Cu)−Si−B metallic glasses were studied by means of differential
scanning calorimetry (DSC), thermomagnetic gravimetry (TMG) and X-ray diffraction. The agreement between the DSC and TMG results
was complete. For all Fe−Si−B amorphous alloys, two-peak crystallization was observed with the primary crystallization of
α-Fe(Si) followed by eutectic crystallisation. The effects of Cu and Nb additions on the crystallization behaviour and on
the activation energies for each stage of the crystallization process of Fe−Si−B glass were investigated.
method for describing the lengths of induction periods at linear-heating measurements,
is employed for the study of induction periods in the crystallisation of metallic
glasses. For Fe75Si15B10
glass, close values of the related kinetic parameters were obtained from isothermal
and nonisothermal measurements. On the basis of the results obtained, the
absence of induction period in the first crystallisation step of Al90Fe7Nb3
glass in the isothermal DSC measurement has been elucidated.
The destructive technique for the determination of the depth concentration profile in metallic glasses of composition B20FexNi80–x (for x from 40 to 70) is presented. The etching technique with HNO3 has been proposed for removing surface layers of the thickness from 1 to 12 m. In the residual surfaces the concentration of Fe and Ni has been determined by the PIXE method with 1.4 MeV4He+ ions of the JINR Van de Graaff accelerator. With an emphasis on the solution of matrix effects in Fe–Ni systems, empirical correction methods have been applied.