Sn – Zn – Ga alloys for leadfree soldering obtained by rapid quenching

The paper presents the results of a study of the structural-phase state of the foil of eutectic near eutectic Sn – Zn alloys doped by Ga obtained by rapid melt quenching at a melt cooling rate of 105 K/s. Using the methods of X-ray diffraction analysis, scanning electron microscopy, and X-ray spectrometry, it was established that the foil solidifies with the formation of tin-based supersaturated solid solution and its microstructure is formed as a result of the decomposition of the solid solution by discontinuous mechanism at room temperature. The homogeneity of the composition and distribution of gallium and zinc inclusions over the volume of the foil was established. Using the electron backscatter diffraction technique, it was shown that the foils have a microcrystalline structure due to the deep supercooling of the melt, which leads to a high crystal nucleation rate. The grain size decreases depending on the distance to the mold. The increase in grain size is associated with a change in the solidification conditions over the thickness of the foil: deterioration of heat removal and a decrease in supercooling. There is no pronounced grain texture in the foils.

Crystallization Features of Amorphous Rapidly Quenched High Cu Content TiNiCu Alloys upon Severe Plastic Deformation

In recent years, the methods of severe plastic deformation and rapid melt quenching have proven to be an effective tool for the formation of the unique properties of materials. The effect of high-pressure torsion (HPT) on the structure of the amorphous alloys of the quasi-binary TiNi–TiCu system with a copper content of more than 30 at.% produced by melt spinning technique has been analyzed using the methods of scanning electron microscopy, X-ray diffraction analysis, and differential scanning calorimetry (DSC). The structure examinations have shown that the HPT of the alloys with a Cu content ranging from 30 to 40 at.% leads to nanocrystallization from the amorphous state. An increase in the degree of deformation leads to a substantial change in the character of the crystallization reflected by the DSC curves of the alloys under study. The alloys containing less than 34 at.% Cu exhibit crystallization peak splitting, whereas the alloys containing more than 34 at.% Cu exhibit a third peak at lower temperatures. The latter effect suggests the formation of regions of possible low-temperature crystallization. It has been established that the HPT causes a significant decrease in the thermal effect of crystallization upon heating of the alloys with a high copper content relative to that of the initial amorphous melt quenched state.

Crystallochemistry of Amorphous State in Ni(Co, Fe)-Nb(V, Ta, Mo+Zr) Alloy Systems

Effects of the crystallochemical factors on amorphous state formation in the Ni−Nb-based systems are studied. Alloys with compositions (Ni, Co, Fe)−(Nb, Ta, V, Mo+Zr) are prepared by rapid melt quenching method with various cooling rates. It was found that at given preparation conditions and at certain atomic size factor, glass forming ability depends on factor of electron concentration was defined as number of s+d electrons per atom. Atomic size factor is necessary take into account, too. High glass forming ability of Ni−Nb alloys are attributed to formation possibility of two distinct E93 type phases.

Effect of Concurrent ZnO Addition and AlF3Reduction on the Elastic Properties of Tellurite Based Glass System

New ternary zinc oxyfluorotellurite (ZOFT) with the composition(ZnO)x-(AlF3)y-(TeO2)z, where5≤x<35;5≤y≤25;60≤z≤70, has been successfully prepared by the conventional rapid melt quenching technique. Density, molar volume, and glass transition temperature have been assessed for each ZOFT glass sample. The longitudinal and transverse ultrasonic waves propagated in each glass sample were measured using a MBS8020 ultrasonic data acquisition system at 5 MHz frequency and room temperature. The longitudinal modulus (L), shear modulus (G), Young’s modulus (E), bulk modulus (K), and Poisson’s ratio (σ) are assessed from both velocity data and their respective density. The compositional dependence of the ultrasonic velocities and related parameters are discussed to understand the rigidity and compactness of the glass system studied.

Electrical Conductivity and Structural Studies on the Binary System BiI3-Ag2SO4

A new solid-state pseudo binary system BiI3_-Ag2SO4 involving bismuth triiodide (BiI3) and a silver oxysalt namely silver sulphate (Ag2SO4) has been prepared using rapid melt-quenching technique. AC conductivity studies have been carried out on the nine different samples of the (BiI3)x –- (Ag2SO4)(1-x) system with compositions corresponding to x=0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8 and 0.9 mole fraction at temperatures ranging from room temperature (298 K) to 433K. The bulk resistance values estimated using complex impedance plots indicated that electrical conductivity of the synthesized solid specimens would vary from 2.9 x10-2 to 3.4 x10-6Scm-1 thus suggesting the present system to be ionic in nature. The extent of ionic conduction due to Ag + cation has also been analyzed using Wagner’s dc polarization technique whereas detailed structural characteristics of the various compositions derived from Fourier transform infrared (FTIR) spectroscopy and features of surface morphology of these samples obtained using scanning electron microscopy (SEM) have further supported the ionic nature of the chosen system and suggested possible application as a solid electrolyte in electrochemical devices.

Effect of Site Disorder on Martensitic Transformation in Ferromagnetic Ni55Fe20Al25 Alloy as Inferred from Magnetic and Magneto-Transport Measurements

Neutron diffraction technique is used to identify the crystal structures and study the phase transformation in a ternary Ni55Fe20Al25 alloy, prepared in the ordered and site-disordered states by annealing and rapid-melt-quenching techniques. We report the observation of ‘step-like’ wavy structures in the thermomagnetic curves taken on ordered samples. No such features are observed in the site-disordered counterparts. Negative magnetoresistance at 10 K and in a magnetic field of 80 kOe in the disordered sample is nearly two times larger than that in the annealed sample. A tentative explanation for these phenomena is given.