Characteristics of Thermal Parameters and Some Physical Properties of Mineral Eutectic Type: Petalite–Alkali Feldspars

The aim of the research was to check whether the system of three fluxes based on lithium aluminium silicate and alkali feldspars has a eutectic point, i.e., with the lowest melting temperature. Lithium was introduced into the mixtures in the form of petalite, which occurs naturally in nature (Bikita Zimbabwe deposit). Using naturally occurring raw materials such as petalite, sodium feldspar, and potassium feldspar, an attempt was made to obtain eutectics with the lowest melting point to facilitate thermal processing of the mineral materials. In addition, the high-temperature viscosity of the mineral alloys and physical parameters such as density, linear shrinkage, and open porosity were studied. The study showed that in these systems, there is one three-component eutectic at 1345 °C, with the lowest viscosity of 1·105 Pas and the highest density of 2.34g/cm3, with a weight content of petalite 20%, sodium feldspar 20%, and potassium feldspar 20%.

PHASE DIAGRAM OF THE PB-MNSE SYSTEM

Methods of physical and chemical analysis (DTA, MSA, RFA, as well as the definition of microhardness and density) studied the phase equilibrium in the system Pb-MnSe and built its state diagram. It is established that the Pb-MnSe system is a quasi-binary cross-section of the triple system Mn-Pb-Se and is of the eutectic type. The components Pb and MnSe form between the degenerate eutectic composition, which corresponds to 3 mol. % MnSe and melts at 310 ° C. It was found that solid solutions on the basis of MnSe in the system at room temperature reach 3.5 mol. % Pb, and solid solutions on the basis of Pb is practically not installed.

SYNTHESIS OF ALLOYS OF THE Sb2Se3-CuCr2Te4 SYSTEM AND PHYSICO-CHEMICAL PROPERTIES

The interaction in the quasi-ternary system Sb2Se3-CuTe-Cr2Te3 along the Sb2Se3-CuCr2Te4 section was studied by methods of physicochemical analysis: differential thermal (DTA), X-ray phase (XRD), microstructure (MSA), as well as by measuring the density and its microhardness and plotted. The phase diagram of the system is quasi-binary, eutectic type. The composition of the double eutectic formed in the system is 20 mol % CuCr2Te4 and a temperature of 490°C. As a result of the analysis of the microstructure, it was determined that there are single-phase fields based on the original components. It was found that at room temperature, solid solutions based on Sb2Se3 extend to 5 mol % CuCr2Te4, and on the basis of CuCr2Te4 solid solutions reach 13 mol % Sb2Se3.

RESEARCH CHEMICAL INTERACTIONS IN THE CuTe–As2Te3 SYSTEM

By the methods of DTA, XRD, MSA, as well as by measuring the microhardness and determining the density of the alloys, the CuTe–As2Te3 system was studied and a phase diagram was constructed. The system state diagram is of the eutectic type and it is characterized by one chemical compound of Cu3As4Te9 composition. Compounds Cu3As4Te9 melts incongruently at 3200C. Solid solutions based on As2Te3 reaches 8 mol %, and based on CuTe solid solutions are practically not installed. Cu3As4Te9 and As2Te3 form an eutectic composition of 45 mol % As2Te3 and temperature 2650C. The results of X-ray phase analysis have shown that the Сu3As4Te9 compounds is crystallized in the tetragonal syngony with lattice parameters: a = 13.86, c = 18.05 Å, Z = 9, ρpyk. = 6.96 g/cm3, ρrent. = 7.06 g/cm3

In situ Composites: A Review

The review of the works on the fabrication-technology studies, patterns of structure formation, and properties of in situ composites is presented. The main advantage of in situ (natural) composites is the thermodynamic stability of their composition and the coherence (conjugation) of the lattices of the contacting phases. All these ones provide the composite with a high level of the physical and mechanical properties. As shown, composite materials of this type are formed in the process of directed phase transformations, such as eutectic crystallization, eutectoid decomposition, etc., caused by a temperature gradient, as well as a result of diffusional changes in composition. The conditions for the growth of in situ composites are formulated. The mechanisms of growth of composite structures of the eutectic type are considered. The factors influencing on the morphology of structures of the eutectic type are indicated. The considered technological methods make it possible to obtain materials with predetermined properties, in which the size, volumetric composition, and spatial arrangement of phases are characteristic of in situ composites. The paper provides a large number of examples of in situ composites: from low-melting Bi-based alloys to refractory eutectics based on Mo and W (Bi–MnBi, Cd–Zn, Al–Al3Ni, Al–Al4La, Al–Al10CaFe2, Al–Al9FeNi, Al–Al3Zr, Al–Al3Sc, Au–Co, Si–TaSi2, Cr–HfC, Cr–ZrC, Cr–NbC, Cr–NbC, Cr–TaC, Nb–Nb5Si3, Mo–ZrC, Mo–HfC, W–TiC, W–ZrC, W–HfC, etc.). Processes and aspects of structure formation are considered. The influence of additional doping on the structure and properties of composite materials of the eutectic type of binary systems, as well as the features of the structure formation of ternary colonies in the composite are considered.

Indium-containing metal-carbon composites from volcano-fumarole mineralization of Great fissure Tolbachik eruption

The results of studies of metal-carbon composites, unique in composition and origin, in which the metal component is a tin-aluminum alloy with an admixture of In, Cu, Fe, Cr, Se, are discussed. The morphology and internal structure of particles, variations in the chemical composition, and the isotopic of carbon impurities are analyzed. Based on the diagram of the eutectic type, a conclusion was made about the crystallization of alloys in the temperature range 650—150 °С. The question of the indium content of volcanic products in Kamchatka as a new and possibly industrially promising type of phase-diverse indium mineralization is discussed.

Characterizing the Soldering Alloy Type Zn–Al–Cu and Study of Ultrasonic Soldering of Al7075/Cu Combination

The aim of the research was to characterize the soldering alloy type Zn–Al–Cu and study the fluxless ultrasonic soldering of the combination of aluminum alloy type Al7075 with copper substrate. The Zn–Al–Cu solder is of the close-to-eutectic type with two phase transformations: the eutectic transformation at 378 °C and the eutectoid transformation at 285 °C. The solder microstructure is formed of a matrix composed of the solid solutions of aluminum (Al) and zinc (Zn) in which the copper phases CuZn4 and CuAl2 are precipitated. The shear strength of the soldering alloy type Zn5Al with copper addition reaches values from 167 to 187 MPa and it depends on the copper content in the solder. The bond with aluminum alloy type Al7075 is formed due to the solubility of Al in zinc solder at the formation of solid solution Al. Contrary to this observation, the bond with the copper substrate is in this case formed due to the interaction of zinc and aluminum with the copper substrate. Two new intermetallic phases, namely Al(Cu,Zn)2 and Cu3.2Zn0.7Al4.2, were formed. The average shear strength of Al7075/Zn5Al3Cu/Cu joints attained was 134.5 MPa. For comparison, the Cu/Zn5Al3Cu/Cu joint attained an average shear strength of 136.5 MPa.

ФИЗИКО-ХИМИЧЕСКОЕ ИССЛЕДОВАНИЕ СИСТЕМЫ Bi2Te3-Ho2Тe3

The chemical interactions in the Bi2Te3-Ho2Te3 system are investigated by methods of physicochemical analysis (DTA, XRD, MSA, microhardness measurements and density determination), a state diagram is constructed. As a result, it was revealed that the system state diagram is a quasi-binary eutectic type. In the Bi2Te3Ho2Te3 system, in a 1: 1 ratio of components, one ternary compound of the HoBiTe3 composition, incongruently melting at 610°C, is formed. According to the results of X-ray phase analysis, it was found that the HoBiTe3 compound crystallizes in the tetragonal system with lattice parameters: a = 19.99; c = 13.82 Å, Z = 3, density ρpikn. = 7.30 g/cm3 ρrent. = 7.35 g/cm3.On the basis of the initial components, regions of solid solutions were found, which on the basis of Bi2Te3 reach 5 mol % Ho2Te3, and on the basis of Ho2Te3 -3 mol % Bi2Te3. Compounds Bi2Te3 and Ho2Te3 form a eutectic with a composition of 20 mol % Ho2Te3 and a temperature of 465°C.

Hopeful high-strength casting alloys based on Al―Mg―Ge(Si) ternary systems

The relative analysis of phase equilibria in the Al-corner of the ternary phase diagrams of Al―Mg―Ge(Si) systems is carried out. Both systems are characterized by the presence of a quasi-binary cross-section of the eutectic type, which is shifted towards Mg-enriched alloys, and sufficiently width range existence of the univariant eutectic transformation L-Al + Mg2Ge(Si). The melting point of quasi-binary eutectic (-Al + Mg2Ge) in the Al―Mg–Ge system and (-Al + Mg2Si) in the Al―Mg―Si is 629 °С and 597 °С, respectively, and the content of the strengthening phase ((Mg2Ge or Mg2Si) in eutectics is 7% (vol.) и 13% (vol.). The properties of non-alloyed alloys with different volume content of eutectic are investigated and the basic compositions of alloys with the optimal strength/ductility ratio for subsequent doping are selected as well. Taking into account the coordinates of the corresponding eutectic transformations, the doping system with the participation of Zn, Cu and other elements is determined. The heat treatment regimes for multicomponent eutectic alloys were selected, to ensure precipitation of Zn(Cu)-nanoparticles that strengthen matrix solid solution. It was shown that according to the level of mechanical properties, these alloys belong to high-strength alloys with property ranges: -Al + Mg2Ge) ― В = 470―590 МPа, 0,2 = 350―520 МPа, = 8,0―15,5%; -Al + Mg2Si) ― В = 400―560 МPа, 0,2 = = 430―520 МPа, = 2,3–-4,5%. Using a complex U-like Nechenji―Kuptsov test, casting properties were determined and it was shown that the fluidity of (-Al + Mg2Si) alloy was 1,3 times higher than that of the AK7ch cast alloy. In terms of the combination of mechanical and casting properties, the new multicomponent eutectic alloys based on the Al―Mg―Ge(Si) ternary systems are superior to the best modern industrial casting aluminum alloys. Keywords: casting aluminum alloys, ternary Al―Mg―Ge(Si) systems, eutectic alloys, alloying, microstructure, mechanical properties, fluidity.