Effect of External Impacts on the Structure and Martensitic Transformation of Rapidly Quenched TiNiCu Alloys

TiNi-TiCu quasibinary system alloys with a high Cu content produced by rapid quenching from liquid state in the form of thin amorphous ribbons exhibit pronounced shape memory effect after crystallization and are promising materials for miniaturized and fast operating devices. There is currently no complete clarity of the mechanisms of structure formation during crystallization from the amorphous state that determine the structure-sensitive properties of these alloys. This work deals with the effect of the initial amorphous state structure and crystallization method of the alloys on their structure and phase transformations. To this end the alloy containing 30 at.% Cu was subjected to thermal and mechanical impact in the amorphous state and crystallized using isothermal or electropulse treatment. We show that after all types of treatment in the amorphous state the structure of the alloy remains almost completely amorphous but the characteristic temperatures and enthalpy of crystallization become slightly lower. Isothermal crystallization of alloy specimens produces a submicrocrystalline structure with an average grain size in the 0.4–1.0 μm range whereas electropulse crystallization generates a bimorphic structure consisting of large 4–6 μm grains and 2–3 μm high columnar crystals in the vicinity of the surface. The grains have nanosized plate-like and subgrain structures. The largest grains are observed in thermally activated samples, meanwhile, mechanical impact in the amorphous state leads to the formation of equiaxed finer grains with a less defective subgrain structure and to the shift of the temperature range of the martensitic transformation toward lower temperatures.

Raman spectra of quasi-binary glasses As2S3−GeS2 doped with Er

This work is concerned with a study of chalcogenide glasses doped with the rare-earth element erbium. The study was carried out on samples of the quasibinary system As2S3−GeS2 doped with erbium at the concentrations of 0, 0.01, 0.1, 0.5 and 1 at %. Raman spectroscopy was used to identify the presence of particular structural units in the glass matrix. The spectra of all the samples are characterized by an intense peak appearing as a consequence of the stretching of the As-S and Ge-S bonds. Further, several low-intensity peaks of different origin were also registered. These peaks arise due to the stretching of the bonds in the ring S8 and the bonds resulting from the existence of the ethane-type molecules (GeSn) in some of the samples. The peaks in the spectrum of the sample with the highest erbium content are characterized by the peaks that can be attributed to the stretching of the bond Er-S.

Phase and Crystal Structure Evolution of MoSi2-AlCr2 Quasibinary System Alloys

On the principle of alloying modification of the same crystal structure compound, MoSi2-AlCr2quasibinary system alloys were prepared by mechanical activation and hot pressed sintering.The phase composition and crystal structure evolution were investigated by X-ray diffractometer(XRD).The results showed that the main phase composition of alloys were MoSi2and Mo(Si,Al)2,the crystal structure was gradually transformed from tetragonal C11bMoSi2to hexagonal C40 Mo(Si,Al)2. (Mo,Cr)(Si,Al)2phase has not found in alloys.

High Conducting Heterovalent Substituted NASICON-like Phases in ScPO4-Na3PO4Quasibinary System

Phase equilibria in quasibinary system ScPO4-Na3PO4 and formation of heterovalent Zr-substituted solid solutions (up to 10 mol%) for Sc3+ in Na3Sc2(PO4)3 complex phosphate were studied by ceramic technique at 1050°C. Obtained samples were investigated with X-ray powder diffraction and impedance spectroscopy. Zr-substituted (10 mol%) Na3Sc2(PO4)3has ionic conductivity of 3.18.10-1 S/cm at 300°C.

Peculiarities of structure state and mechanical characteristics in ion-plasma condensates of quasibinary system borides W2B5-TiB2

In order to create high-durable, wear-resistant materials for a wide range of functional applications, comparative investigations of the structure and mechanical characteristics of ion-plasma Ti-W-B nano-crystalline condensates were carried out. The range of condensation rates 0.11?0.25nm/s was found to be critical for the coatings obtained from the target with 80 vol% W2B5-20 vol% TiB2. Below this, a phase with a cubic lattice (W,Ti)B0.7?1.2(O,N,C)0.3?0.2 formed, while over this range, a solid solution (W,Ti)B2 with a hexagonal lattice and element composition close to the sputtered target was observed. The structure state of the material changed from cluster-crystalline (under low sputter potentials U=0.6?1.0 kV) to textured- crystalline (under U>2.2 kV). Structure perfection improvement with U increase results in higher hardness and elastic modulus of condensates. The conditions of cluster component formation and its effect on hardness and elastic modulus of condensates are discussed. .