Effects of Al-Mg wire replacing Al-Cu wire on the properties of 2219 aluminum alloy TIG-welded joint

The effects of Al–Mg wire replacing Al–Cu wire on the microstructure, microhardness and tensile properties of 2219 aluminum alloy tungsten inert gas (TIG)-welded joints were studied. Comparing joints with Al–Cu wire, the capping welds of joints with Al–Mg wire can be strengthened by the introduction of Mg-containing strengthening phase and the hardness can be significantly improved. However, for joints with Al–Mg wire, both the solidification cracks caused by inappropriate control of alloying element content and the continuous brittle phases at grain boundaries around the weld zone (WZ) can result in the reduced tensile properties. The crack-free weld can be obtained by adjusting the alloying system of WZ. Furthermore, the geometry of WZ also affected the tensile properties of joints with Al–Mg wire.

Avials, history of creation and overview of future outlook

Scientific domestic and foreign literature touching the field of Al – Mg – Si wrought aluminum alloys are reviewed, the history of appearance of the most common brands is described. It is shown that the development of alloys was proceed gradually advancing their chemical composition along the quasi-binary Mg/Si = 1.73 сross -section in the direction of increasing concentration of just Mg and Si, and the strength of last modern brands was provided by additional alloying, primarily copper, the content of which can reach 1-1.4%. The influence of alloying elements on microstructure, mechanical and corrosion properties of alloys is described, features of their heat treatment, factors of maximum strengthening and susceptibility to intergranular corrosion are revealed. Attention is focused on the key role of the Mg/Si ratio, transition metals, Cu, Cr and Mn first of all, in the formation of balanced properties, since the positive effect of these elements on increasing the strength and the recrystallization temperature is often offset by the negative impact on intergranular corrosion and quench sensitivity. It is shown that in low-alloyed Al–Mg–Si alloys the strength premises Mg/Si≈1 and the premises for high-end corrosion resistance Mg/Si≈2 are occurred simultaneously. Alongside an increase of the absolute content of Mg and Si in alloys, alongside an increase of alloying degree with other strengthening elements, it is impossible to simultaneously fulfill both of these premises; therefore, one has to look for a reasonable compromise between strengthening, decreasing the technological plasticity and corrosion resistance of alloys. One of the effective ways to reach such a compromise is multi-stage regimes of artificial aging. The prospects of microalloying with Sc and Ca able to form with aluminum nanoscale intermetallic phases of hardening are outlined. Keywords: avials, semi - finished products, alloying system, transition metals, aging, mechanical properties, intergranular corrosion.

PREDICTION THERMO-PHYSICAL CHARACTERISTICS HEAT-RESISTANT NICKEL ALLOYS DIRECTIONAL CRYSTALLIZATION

The thermodynamic processes of phase separation are modeled, which significantly affect the temperature characteristics of heat-resistant nickel alloys of directional solidification. Using an empirical approach, new ratios of elements Kg¢ and Kg have been obtained for the first time, which take into account the combined effect of alloying elements on the temperature of multicomponent compositions of cast heat-resistant alloys. The calculated values of the critical temperatures for the Ni-6Al-9Co-8W-4Re-4Ta-1.5Nb-1Mo-0.15C system (ZhS32-VI, ZhS32B-VI, and ZhS32E-VI alloys) are in good agreement with the experimental ones. The dependences of the Kg ratio on the alloying system are constructed, and the effect of alloying on the liquidus temperature of alloys is investigated. The ratios of the content of alloying elements and regression models that can be used to predict the width of the temperature range of crystallization and the optimal temperature of homogenization for a particular alloy are presented.

Effects of TiO2 structure and Co addition as a second metal on Ru-based catalysts supported on TiO2 for selective hydrogenation of furfural to FA

The TiO2 supported Ru-based catalysts were prepared with 1.5 wt% Ru and 0–0.8 wt% Co on various TiO2 (anatase, rutile, P-25, and sol–gel TiO2) and studied in the liquid-phase selective hydrogenation of furfural to furfuryl alcohol (FA) under mild conditions (50 °C and 2 MPa H2). The presence of high anatase crystallographic composition on TiO2 support was favorable for enhancing hydrogenation activity, while the strong interaction between Ru and TiO2 (Ru–TiOx sites) was required for promoting the selectivity to FA. The catalytic performances of bimetallic Ru–Co catalysts were improved with increasing Co loading due to the synergistic effect of Ru–Co alloying system together with the strong interaction between Ru and Co as revealed by XPS, H2-TPR, and TEM–EDX results. The enhancement of reducibility of Co oxides in the bimetallic Ru–Co catalysts led to higher hydrogenation activity with the Ru–0.6Co/TiO2 catalyst exhibited the best performances in FA selective hydrogenation of furfural to FA under the reaction conditions used.

Effect of microstructure on corrosion-mechanical endurance of welded joints of aluminium alloy V1341T produced by manual argon-arc welding

The results of microstructure effect on corrosion-mechanical endurance of 1.2 mm thick alloy of Al-Mg-Si-Cu alloying system and its welded joints, depending on their condition due to different types of HT are presented. Change of microstructure of the welded joints during performance of various HT operations practically does not affect its resistance against intergranular and exfoliating corrosion. Effect of HT on corrosion-mechanical endurance of welded joint under the conditions of simultaneous action of continuous loading and corrosive environment is ambiguous. Resistance against intergranular corrosion and corrosion cracking will determine the fracture resistance of welded products of V1341T alloy in service.

Reduction of oxides formation at surfact depositsitson of wear-resistant alloys

The article deals with the issues of reducing the content of harmful substances when surfacing alloyed wear-resistant alloys. Studies have been carried out to determine the possibility of reducing the formation of oxides during surfacing of high-alloy wear-resistant alloys of the sormite type using a closed filter-ventilation system, which ensures minimal losses of alloying elements during the formation of the deposited layer. The loss of alloying elements during surfacing is influenced by a number of metallurgical and technological factors, including the share of the base metal in the deposited, surfacing modes, oxidation processes during melting of the electrode material and in the melt of the weld pool when interacting with the surrounding gas environment. To reduce the oxygen content in the gas-air mixture formed during the surfacing process, special absorbent substances are used in a closed filtering and ventilation system, which reduce the course of oxidative processes with the formation of oxides of alloying elements. At the same time, the gas-air mixture is taken from the zone of arc burning and the weld pool, filtered through a system of special filters, in which solid and gaseous components of the welding aerosol are removed, after which the purified gas mixture is used as gas protection during surfacing. We used powder tapes containing a mechanical mixture of powder components and a complex-alloyed alloy in the core. A complex-alloyed alloy, an alloy previously melted in an induction furnace, containing the necessary alloying elements. Particles of the required sizes were obtained by hydrogranulation, which were then introduced into the core of a flux-cored tape. The indicated flux-cored strips provided the same chemical composition of one alloying system in the deposited layer. After surfacing, the chemical composition of the deposited metal was determined for the content of carbon, manganese, silicon, nickel. The use of a closed filtering and ventilation system makes it possible to reduce the formation of oxides of alloying elements, which requires the determination of specific parameters for each surfacing process. Creation and use of closed fil'tro vent system (CFVS), serve of the filtered air in area of surfacing and providing safe labour in the workplace of welder. It corresponds the international standard of ISO and norms of European Union. Therefore, to execute a requirement to impermissibility of hit of harmful questions in an atmosphere concordantly Kiotskomuo and to Parisian protocols.

Increasing the heat resistance of cast nickel-based complex alloyed alloys due to the influence of the redistribution of alloying elements between the γ-solid solution and the strengthening intermetallic γ'-phase

The analysis of alloying of the chemical and phase composition of domestic and foreign cast heat-resistant alloys with a nickel matrix is carried out; the tendency to increase the level of heat-resistant properties of cast nickel alloys due to more complex alloying is traced. Recently, expensive rhenium, ruthenium, hafnium, and dysprosium have increasingly been used as alloying elements. The positive effect of these elements on the thermal stability of the γ-matrix and the strengthening γ'-phase is established. The above elements inhibit diffusion processes, thereby increasing the creep resistance of alloys at high temperatures and loads. The evaluation of heatresistant nickel alloys obtained by directional crystallization is given. It is established that the most significant parameters of the phase composition of the studied alloys are the distribution coefficients of alloying elements between the γ' and γ-phases (Ki). The basic principles of balanced alloying, which are used to select the optimal chemical composition of heat-resistant nickel alloys, are formulated. To achieve the maximum heat resistance parameters in the selected heat-resistant nickel alloys alloying system, the calculated value γ/γ' defined by “misfit” was used, which is calculated by the formula: Δа = (аγ-аγ')/ аγ, where аγ and аγ' are the lattice periods of γ and γʹ-phases. Thus, the calculated Δа should be positive for аγ> аγ' and at least two to three times more than for single-crystal heat-resistant nickel alloys with a traditional alloying system, for which Δа = (0.1-0.2) or more. It is shown that misfit (γ/γ') is mainly determined by those alloying elements that increase the аγ most significantly. These elements are Re, Pu, Mo, W, Nb, and Ta in ascending order of influence on the lattice period (аγ) of the phase.

Reduction of Oxides Formation During Surfacing of Wear-resistant Alloys

The article deals with the issues of reducing the content of harmful substances when surfacing alloyed wear-resistant alloys. Studies have been carried out to determine the possibility of reducing the formation of oxides during surfacing of high-alloy wear-resistant alloys of the sormite type using a closed filter-ventilation system, which ensures minimal losses of alloying elements during the formation of the deposited layer. The loss of alloying elements during surfacing is influenced by a number of metallurgical and technological factors, including the share of the base metal in the deposited, surfacing modes, oxidation processes during melting of the electrode material and in the melt of the weld pool when interacting with the surrounding gas environment. To reduce the oxygen content in the gas-air mixture formed during the surfacing process, special absorbent substances are used in a closed filtering and ventilation system, which reduce the course of oxidative processes with the formation of oxides of alloying elements. At the same time, the gas-air mixture is taken from the zone of arc burning and the weld pool, filtered through a system of special filters, in which solid and gaseous components of the welding aerosol are removed, after which the purified gas mixture is used as gas protection during surfacing. We used powder tapes containing a mechanical mixture of powder components and a complex-alloyed alloy in the core. A complex-alloyed alloy, an alloy previously melted in an induction furnace, containing the necessary alloying elements. Particles of the required sizes were obtained by hydrogranulation, which were then introduced into the core of a flux-cored tape. The indicated flux-cored strips provided the same chemical composition of one alloying system in the deposited layer. After surfacing, the chemical composition of the deposited metal was determined for the content of carbon, manganese, silicon, nickel. The use of a closed filtering and ventilation system makes it possible to reduce the formation of oxides of alloying elements, which requires the determination of specific parameters for each surfacing process.