Iuliia Nikolaevna Maliutina

In this study, a layered composite material consisting of alternating aluminum and niobium layers and cladded on both sides with titanium plates was obtained by explosive welding. Microstructure of the composite was thoroughly studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as well as by energy dispersive X-ray spectroscopy (EDX) and electron backscattered diffraction (EBSD). Microhardness measurements, tensile test, and impact strength test were carried out to evaluate the mechanical properties of the composite. Formation of mixing zones observed near all interfaces was explained by local melting and subsequent rapid solidification. Mixing zones at Nb/Al interfaces consisted of metastable amorphous and ultrafine crystalline phases, as well as NbAl₃ and Nb₂Al equilibrium phases. Niobium grains near the interface were significantly elongated, while aluminum grains were almost equiaxed. Crystalline grains inside the mixing zones did not have a distinct crystallographic texture. Microhardness of Al/Nb mixing zones was in the range 546–668 HV, which significantly exceeds the microhardness of initial materials. Tensile strength and impact strength of the composite were 535 MPa and 82 J/cm², respectively. These results confirm the high bonding strength between the layers.

In this study, the multilayered composite materials consisting of niobium and aluminum foils were produced by explosive welding. The conducted microstructural studies with the use of scanning electron microscopy (SEM) have shown that the boundaries of welded seams have predominantly a wave structure with a partial local melting of interacting materials. At the niobium/aluminum boundary, in the mixing zones, micro volumes with a non-uniform chemical composition were presented. Mechanical tests have shown that the strength properties, as well as the toughness of composite materials, are at an intermediate level relative to the initial materials.

Intermetallic clads were obtained on the basis of the titanium workpieces. The cladding was carried out using a non-vacuum electron beam treatment technique. A powder mixture which contained 16.97 Al - 28.27 Ti - 41.07 CaF₂ - 13.69 LiF (wt. %) was used for cladding. Two regimes with the beam current of 16 mA and 18 mA were used. The beam current influenced significantly the structure and phase composition of clads. In case of the electron beam treatment with a beam current of 16 mA a lamellar structure consisted of a mixture of AlTi₃ and A1Ti was fabricated. An increase of the beam current to 18 mA led to the formation of an AlTi₃ acicular structure. Microhardness and wear resistance of the intermetallic coating was significantly higher in comparison with cp-Ti. The maximum microhardness of clads was 480 HV. A wear rate of clads was 10 times lower than that of cp-Ti.

Analysis of structural variations taking place at the stainless steel (09Cr18Ni10Ti) - bronze (CuBe2Ni) interface obtained by explosive welding was conducted in the current work. The produced weld joint was post heat-treated in the temperature range from 500 to 800 °С. Microstructural characterizations were carried out using optical and scanning electron microscopy. The results of the analysis revealed the presence of 2 zones at the interface: mixing zone of bronze and stainless steel and a diffusion zone. The diffusion processes in the weld joint during heating were studied by the energy-dispersive analysis (EDX). EDX studies revealed that at 800 °С copper contained in bronze completely migrated from the diffusion layer to the mixing zone whereas iron concentration, on the contrary, increased in the diffusion layer. Voids appeared in the mixing zone of stainless steel and bronze due to the difference of diffusion coefficients of basic elements in the composite.

Explosive welding was used to form reliable joining between commercially pure titanium and stainless steel. To prevent cracking at the interface induced by brittle intermetallic bronze - tantalum interlayer was used. Microstructural characterization of produced composite was analyzed using optical and scanning electron microscopy as well as energy dispersive analysis. Determination of structure has revealed no micro defects such as cracks in the composite. Intermediate layer of 5 μm thick at the bronze - tantalum interface was formed. Structure of intermediate layer corresponds to highly dispersed mixture of tantalum and copper alloy particles. Ultimate strength of 4 layered composite is 1000 MPa that exceeds of ultimate strength of composite produced without interlayer. Analysis of fractograph indicates a high adhesion level between interactive materials.