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The results of complex studies on the brazing filler metal of the Cu–Mn–Co system alloyed with iron in the range of 1…5 wt. % are presented. The melting point was determined through calculation, and it was shown that increasing the concentration of iron from 1 to 5 wt. % leads to a slight (from 912 to 923 °C) increase in the temperature of the solidus and a significant increase in the temperature of the liquidus (from 931 to 1027 °C). At the same time, the melting temperature range expands to 104 °C. The results of experimental studies on the spread of brazing filler metal on Kovar and corrosion-resistant steel have established that an increase in the iron concentration up to 5 % contributes not only to an increase in the temperature of the liquidus but also to an increase in the spread area, which is due to the melting temperature of a copper-based solid solution. Local micro-X-ray spectral analysis established a discrete distribution of constituent elements and showed that the brazing filler metal, after spreading, contains two solid solutions: copper-based and manganese-based. The research results on the Kovar-corrosion-resistant steel brazed joints have demonstrated that the addition of iron to the Cu–Mn–Co–Fe alloy leads to an increase in microhardness and shear strength. [ABSTRACT FROM AUTHOR]

The paper gives the results of investigations on fluxless brazing of АD1М, AMts (Al-Mn), AD31 (Al-Mg-Si) aluminium alloys (Al-Mg-Si) with application of Al-25Ge-5Si-5Cu-1.5Mn-0.15Ti brazing filler metal at the temperature of 550 ± 5 °С in the atmosphere of high-purity nitrogen. The results of high-temperature differential thermal analysis were used to determine the solidus and liquidus temperatures of the brazing filler metal. Thermal effects on the derived thermal curve are indicative of the presence of three phases, which correlates with the results of X-ray microprobe analysis. It is shown that the brazing filler metal structure in the initial state is formed by two solid solutions, based on α-Al and β-GeSi and eutectics. Mechanical testing revealed that the short-term strength of the brazed joints is higher than that of the base metal, and fracture occurs in AD1M alloy. Application of steplike cooling of AD31 alloy brazed joint with soaking at the temperature of 500 C promotes increase of shear strength from 84 to 102 MPa. 42 Ref., 1 Tabl., 7 Fig. [ABSTRACT FROM AUTHOR]

When brazing of heat-resistant nickel alloys (HSN) with traditional industrial brazing filler metals of the Ni−Cr−(B, Si) systems, the formation of brittle intermetallic compounds, namely, silicides and borides, occurs in the brazed seams. In order to prevent the formation of such undesirable brittle phases in brazed joints of heat-resistant nickel alloys, investigation is conducted using high-entropy alloys as brazing filler metals. This work shows the possibility of creating multicomponent high-entropy brazing filler metals based on the NiCoCrPdGe system, using calculation methods, binary state diagrams of metal systems and taking into account the classic Hume-Rothery solid-solution formation criteria. A number of thermodynamic parameters (ΔSm, ΔHm, δ, Ωm, VECm) and the liquidus temperature are determined by calculation, and their corresponding dependences on the content of alloying components in the alloys of the NiCoCrPdGe system are constructed. The limiting range of alloying of experimental alloys is established, within which the values of these thermodynamic quantities correspond to the parameters applied to high-entropy alloys and contribute to the formation of a solidsolution structure with an f.c.c. lattice. Based on the obtained data, a section of the liquidus surface for the alloys of the NiCoCrPdGe system is plotted. According to the results of the conducted investigation, the limiting concentration limits of the depressant, namely, germanium, which ensure an acceptable melting temperature of the brazing filler metals when brazing heatresistant nickel alloys, are determined. According to the results of experimental studies, it is established that the alloy of the NiCoCrPdGe5 system is characterized by a two-phase dendritic structure. As determined by means of the calculation method, the volume fraction of the solid solution is of 72.54−75.47%. [ABSTRACT FROM AUTHOR]

Shape-memory alloys are becoming ever wider applied in different industries, in particular in aerospace, medical, automotive sectors and in consumer electronics manufacturing. Application of these materials as hybrid structure elements is a promising direction when creating products with a unique set of properties: high mechanical values, superplasticity, damping ability, higher wear resistance and thermomechanical memory. Production of nitinol permanent joints by welding leads to formation brittle phases of Ti2Ni type, which degrade the product quality. This review discusses the possibility of producing high-strength permanent joints of nitinol with nitinol and with other alloys by brazing. The main advantage, compared to other methods, is the fact that base metals do not melt, and some structural transformations can be avoided. At nitinol brazing in ambient air, brazing filler metals of Ag–Cu–Zn-Sn–Ni system haven proven themselves well, using 25AgCl–25KF–50LiCI flux. We should specially mention application of silver brazing filler metals and interlayers from pure metals, for instance, niobium, providing a strong metallurgical bond with the base metal. At brazing temperature of 1180 °С an alloy based on quasibinary NiTi–Nb eutectic system is formed, ensuring the reliability of brazed elements when creating prototypes of superplastic honeycomb shapes from titanium nickelide. 32 Ref., 4 Tabl., 8 Fig. [ABSTRACT FROM AUTHOR]

At brazing dissimilar joints of AD1 aluminium to VT1-0 titanium at the temperature of 605…610 °С by Al–12Si brazing filler metal in argon application of reactive flux of KAlF4 –10K2 SiF6 system with additives of CoF2, K2 ZrF6 compounds, promotes production of a sound joint due to formation of a low-melting alloy of Al-Si system on the contact surface. The low-melting alloy of Al-Si system newly-formed at reactive-flux brazing can independently fulfill the function of brazing filler metal at formation of a dissimilar metal joint. Cobalt reduced from the flux has little influence on weld structure and joint strength. At application of Al–12Si brazing filler metal and reactive flux of KAlF4 –10K2 SiF6–5K2 ZrF6 system, which contains potassium-zirconium fluoride (K2 ZrF6 ), a certain refinement of the structure (dendrites of aluminium-based solid solution) is observed from the aluminium side that promotes an improvement of shear strength of aluminium-titanium brazed joints. 33 Ref., 3 Tabl., 8 Fig. [ABSTRACT FROM AUTHOR]

The main goal of this work is to determine the melting temperature range and phase composition of multicomponent Ni-based alloys by applying the methods of design of alloys (CALPNAD method) in combination with statistical processing of the results. In particular, the liquidus and solidus temperatures for a number of experimental alloys of the Ni–Cr–Co–Al–(Ме) system are calculated. The degree of influence of adhesive-active elements (Ti, Nb, Zr) on the liquidus temperature and phase composition of alloys of this system is established. The approximate content of alloying elements to ensure the required melting point of experimental filler metals is determined. As shown, alloying zirconium significantly reduces the solidus temperature thus significantly expanding the melting range of experimental alloys. This effect is associated with the formation of low-temperature zirconium eutectic. The influence of titanium and niobium on the amount and thermal stability of the γ′-phase in experimental alloys is studied. The influence of refractory components (Mo, W, Re) on the presence of topologically close-packed (TCP) phases is studied. As noted, partial replacement of tungsten by rhenium in experimental Ni–Cr–Co–Al–(Ме)-based alloys significantly reduces the amount of harmful µ- and p-phases. [ABSTRACT FROM AUTHOR]

The work presents the results of metallographic and X-ray microspectral studies of molybdenum-Kovar overlap joints, which were produced by vacuum brazing with application of brazing filler metal based on Cu-Mn-Co system. The influence of soaking at brazing temperature on brazed seam structure formation was studied. Local X-ray microspectral analysis was used to determine the number of structural components of the brazed seam: copper-based solid solution, individual iron-based grains, reaction layer in the form of a continuous band on molybdenum - brazing filler metal interface. It was found that longer soaking at the brazing temperature promotes an increase of the reaction layer width from 1 to 3 ~m and leads to formation of a faceted morphology from the brazed seam side and to microcracks initiation in it, but it does not affect molybdenum concentration, which at different soaking (1…15 min.) is in the range of 55.81…59.05 wt. %. In the solid solution (matrix) manganese concentration decreases with longer soaking, copper concentration rises, but the quantity of iron practically does not change, and it is in the range of 4.52… 4.95 wt. %. In single grains of the dark phase, observed near the interface with Kovar, longer soaking promotes an increase of iron and nickel concentration and lowering of manganese and copper content. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies of the influence of cobalt on the structure and mechanical properties of kovar (29НК)-stainless steel (12X18H10) brazed dissimilar joints obtained by vacuum brazing using brazing filler metal of the Cu-Mn-Co system. Micro X-ray spectral studies of brazed dissimilar joints prove that a structure of a solid solution based on copper is formed in brazed joints, which contains a small amount of discrete grains of the γ-phase (solid solution based on Fe-Mn-Co). An increase in the concentration of cobalt in the initial brazing filler metal from 0.5 to 4.5% wt. leads to a slight increase in its concentration in a solid solution based on copper and a significant increase in its concentration in discrete grains of the γ-phase--from 8.44 to 19.7% mass. Such structural features of brazed joints positively affect their mechanical properties and contribute to an increase in the shear strength of kovar-stainless steel brazed overlap dissimilar joints from 374 to 434 MPa. [ABSTRACT FROM AUTHOR]

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)