Brass/Invar bimetal by explosive welding Malakhov, Andrey; Saikov, Ivan; Denisov, Igor
International journal of advanced manufacturing technology,
05/2021, Volume:
114, Issue:
1-2
Journal Article
Peer reviewed
Thermostatic bimetals (thermobimetals) are materials consisting of layers with different coefficients of thermal expansion. The layer with a higher coefficient of thermal expansion is called active, ...with a lower—passive. Invar (Ni-Fe alloy) is mainly used as the passive layer and brass (Cu-Zn alloy) as the active layer. Strong adhesion of the layers along the entire length is one of the main requirements for all grades of thermobimetals. In this study, an Invar/brass thermobimetal plate was obtained by explosive welding (EW). The plate was subjected to metallographic, ultrasonic, and mechanical examination. Scanning electron microscope (SEM) showed that the weld interface had the form of uniform waves over its entire surface. Also, melted zones in the crests and troughs of the waves were observed. Energy-dispersive spectroscopy (EDS) line scanning showed that the melted zones consisted of a disordered Cu–Zn–Fe–Ni solid solution (predominately, of Zn and Cu) and undissolved Invar particles. The average microhardness of the melted zones was 350 H
V
. A 3-mm-wide strengthened zone along the weld interface was observed. The average tear strength of the Invar/brass weld joint was 550 MPa, which is higher than that of the individual initial metals. The bending testing has shown that the thermobimetal plate is resistant to delamination, which indicates the satisfactory quality of the weld joint. Based on the results obtained from this study, it can be concluded that EW can be used to produce high-quality Invar/brass thermobimetal plates.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper presents the results of a study of the morphology and structure at the weld interface in a brass-Invar bimetal, which belongs to the class of so-called thermostatic bimetals, or ...thermobimetals. The structure of the brass-Invar weld interface was analyzed using optical microscopy and scanning electron microscopy (SEM), with the use of energy-dispersive X-ray (EDX) spectrometry and back-scattered electron diffraction (BSE) to identify the phases. The distribution of the crystallographic orientation of the grains at the weld interface was obtained using an e-Flash HR electron back-scatter diffraction (EBSD) detector and a forward-scatter detector (FSD). The results of the study indicated that the weld interface had the wavy structure typical of explosive welding. The wave crests and troughs showed the presence of melted zones consisting of a disordered Cu-Zn-Fe-Ni solid solution and undissolved Invar particles. The pattern quality map showed that the structure of brass and Invar after explosive welding consisted of grains that were strongly elongated towards the area of the highest intensive plastic flow. In addition, numerous deformation twins, dislocation accumulations and shear bands were observed. Thus, based on the results of this study, the mechanism of Cu-Zn-Fe-Ni structure formation can be proposed.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This paper presents the implementation of the first stage of a study on the synthesis of the intermetallic compound in the Ni-Al system under shock-wave extrusion (SWE). A method was developed and ...experiments involving SWE of the reactive Ni–Al powder mixture were carried out. As a result, it was possible to obtain up to 56 vol.% of the final product and achieve 100% synthesis of NiAl. The results of metallographic analysis indicate that the process of high-velocity collapse of the tube created conditions for the formation of a cumulative flow, which directly affects the phase formation in NiAl. It was shown that the presence of the central hole in the powder sample reduced the effect of the Mach stem on the homogeneity of the NiAl structure. It was also determined that with a central hole with a 5 mm diameter, the effect of the Mach stem could not be observed at all. The goals of further studies are achieving 90–100 vol.% of the final product and reducing the porosity in the final product. Preliminary experimental studies have shown great potential for SWE to produce composite metal–intermetallic materials.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A functionally graded composite NiAl-AlMg6 was prepared using the pressure of gaseous reaction products (impurity gases) produced during the synthesis of reactive powders in a sealed reactor. It has ...been shown that this method can be used to prepare a NiAl/AlMg6 composite with both chaotically oriented pores in the NiAl layer and unidirectionally oriented pores (lotus-type pores). The pore shape in NiAl was found to be dependent on the pressure of the impurity gases and hydrogen present in the starting titanium powder. A mechanism for pore formation in NiAl and AlMg6 composite during SHS is proposed. Thus, functionally graded high-temperature composites can be produced by SHS in a sealed reactor using the chemical reaction energy and the pressure of impurity gases and hydrogen. Additionally, minimizing the influence of impurity gases on the contact zone increases the interface area between NiAl and AlMg6.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this study, SHS was used to produce metal-intermetallic-ceramic laminate AlMg6-NiAl-TiC composite. The experiment conducted without a cylindrical powder pellet holder produced no joint between the ...NiAl and AlMg6 sheet. On the other hand, the experiment conducted inside a cylindrical powder pellet holder (CPPH) with a blind hole produced a joint. It was found that the AlMg6 sheet had a temperature of 400–550 °C across its entire thickness during SHS. The study of the microstructure and energy-dispersive analysis (EDS) of AlMg6-NiAl-TiC composite showed that it had five layers: (1) ceramic layer of 7-mm-thick TiC; (2) the upper diffusion layer that formed at the interface between NiAl and TiC consisted of TiC + NiAl; (3) an intermetallic layer, which consisted of 13-mm-thick NiAl; (4) the lower diffusion layer, which formed at the interface between NiAl and AlMg6; and (5) a layer of 4-mm-thick aluminum alloy AlMg6. The EDS showed that during the synthesis of NiAl and its interaction with the surface of the AlMg6 sheet, mixing of the components of the initial materials (NiAl, AlMg6) in the joint interface occurs. At the interface of NiAl and AlMg6, the microhardness was 790–870 HV, which indicates the presence of quenching structures in the melted zones.
The article is devoted to the study of the characteristics of shock-wave processing of powder mixtures capable of an exothermic reaction of the synthesis of metal-ceramic materials. Experiments on ...shock-wave initiation of synthesis in systems based on Ti-B and Ti-C with 10% and 20% Ni content were carried out. Explosive loading was carried out by oblique throwing of a steel drummer with speeds of 1000 m / s and 1500 m / s. X-ray phase analysis of synthesis products showed the presence of TiB2 diboride and TiC carbide in the nickel bond. The significant role of the mechanical activation of powder mixtures in increasing the sensitivity of SHS-mixtures to shock-wave loading is shown.
The parameters of combustion synthesis and shock-wave initiation of reactive W/PTFE/Al compacts are investigated. Preliminary thermodynamic calculations showed the possibility of combustion of the ...W/PTFE/Al system at high adiabatic temperatures (up to 2776 °C) and a large proportion of condensed combustion products. The effect of the Al content (5, 10, 20, and 30 wt%) in the W/PTFE/Al system on the ignition and development of exothermic reactions was determined. Ignition temperatures and combustion rates were measured in argon, air, and rarefied air. A correlation between the gas medium, rate, and temperature of combustion was found. The shock initiation in W/PTFE/Al compacts with different Al content was examined. The extent of reaction in all compacts was studied by X-ray diffraction. The compositions with 10 and 20 wt% Al showed the highest completeness of synthesis after combustion and shock-wave initiation.
Current treatments for salivary gland (SG) hypofunction are palliative and do not address the underlying cause or progression of the disease. SG-derived stem cells have the potential to treat SG ...hypofunction, but their isolation is challenging, especially when the tissue has been damaged by disease or irradiation for head and neck cancer. In the current study, we test the hypothesis that multipotent bone marrow-derived mesenchymal stem cells (BM-MSCs) in a rat model are capable of trans-differentiating to the SG epithelial cell lineage when induced by a native SG-specific extracellular matrix (SG-ECM) and thus may be a viable substitute for repairing damaged SGs.
Rat BM-MSCs were treated with homogenates of decellularized rat SG-ECM for one hour in cell suspension and then cultured in tissue culture plates for 7 days in growth media. By day 7, the cultures contained cell aggregates and a cell monolayer. The cell aggregates were hand-selected under a dissecting microscope, transferred to a new tissue culture dish, and cultured for an additional 7 days in epithelial cell differentiation media. Cell aggregates and cells isolated from the monolayer were evaluated for expression of SG progenitor and epithelial cell specific markers, cell morphology and ultrastructure, and ability to form SG-like organoids in vivo.
The results showed that this approach was very effective and guided the trans-differentiation of a subpopulation of CD133-positive BM-MSCs to the SG epithelial cell lineage. These cells expressed amylase, tight junction proteins (Cldn 3 and 10), and markers for SG acinar (Aqp5 and Mist 1) and ductal (Krt 14) cells at both the transcript and protein levels, produced intracellular secretory granules which were morphologically identical to those found in submandibular gland, and formed SG-like organoids when implanted in the renal capsule in vivo.
The results of this study suggest the feasibility of using autologous BM-MSCs as an abundant source of stem cells for treating SG hypofunction and restoring the production of saliva in these patients.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A library of peptidomimetics was assembled combinatorially into dimers on a triazine-based core. The pharmacophore corresponds to β-turns of the neurotrophin polypeptides neurotrophin-3 (NT-3), nerve ...growth factor (NGF), or brain-derived neurotrophic factor (BDNF). These are the natural ligands for TrkC, TrkA, and TrkB receptors, respectively. The linker length and the side-chain orientation of each monomer within the bivalent mimics were systematically altered, and the impact of these changes on the function of each ligand was evaluated. While the monovalent peptidomimetics had no detectable binding or bioactivity, four bivalent peptidomimetics (2c, 2d, 2e, 3f) are selective TrkC ligands with antagonistic activity, and two bivalent peptidomimetics (1a, 1b) are TrkC and TrkA ligands with antagonistic activity. All these bivalent compounds block ligand-dependent receptor activation and cell survival, without affecting neuritogenic differentiation. This work adds to our understanding of how the neurotrophins function through Trk receptors, and demonstrates that peptidomimetics can be designed to selectively disturb specific biological signals, and may be used as pharmacological probes or as therapeutic leads. The concept of altering side-chain, linker length, and sequence orientation of a subunit within a pharmacophore provides an easy modular approach to generate larger libraries with diversified bioactivity.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This paper studies the weld interface microstructure and mechanical properties of AlMg6-stainless steel and AlMg6-titanium bimetals produced using explosive welding. The microhardness (HV), tear ...strength, and microstructure of the weld seams were evaluated. The interface of the weld zones had a flat profile. No structural disturbances or heterogeneity in the AlMg6-titanium weld interface were observed. On the other hand, the bimetal AlMg6-stainless steel had extensive zones of cast inclusions in the 10–30 µm range. SEM/energy-dispersive X-ray spectroscopy (EDS) analysis showed the presence of a hard and brittle intermetallic compound of Al and FeAl3 (with 770–800 HV). The microhardness of the AlMg6-titanium bimetal grew higher closer to the weld interface and reached 207 HV (for AlMg6) and 340 HV (for titanium). Both bimetals had average tear strength below 100 MPa. However, the tear strength of some specimens reached 186 and 154 MPa for AlMg6-titanium and AlMg6-stainless steel, respectively. It is also worth mentioning that heat treatment at 200 °C for one hour led to a uniform distribution of tear strength along the entire length of the bimetals. The study shows that one of the possible solutions to the problem of the formation of the brittle intermetallic compounds would be the use of intermediate layers of refractory metals.
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