Персона: Абрамов, Антон Владиславович
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Development of rapidly-quenched al-ge-si filler alloys for the joining of stainless steel aisi 304 and aluminum alloy aa6082
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.Aluminum alloys based on the Al-Ge-Si system with a germanium content of up to 40 wt.%, promising for the brazing of aluminum alloy AA6082 with the stainless steel AISI 304, were studied. The temperature characteristics and microstructural and mechanical properties of the filler alloys were systematically investigated. Differential scanning calorimetry showed that with an increase in the germanium content from 28.0 to 40.0 wt.%, the liquidus temperature of the filler alloys decreased from 514.8 to 474.3◦ C. X-ray diffraction analysis and electron microscopy data showed that the foil of the filler alloys reveals a homogeneous structure. The ingots of the alloys contain two eutectics, the first of which consists of a solid solution of (Al, Ge) with a solid solution of (Ge, Si), and the second consists of a solid solution of (Al, Ge) with a solid solution based on (Ge). When the content of germanium increases from 28.0 to 40.0 wt.%, a separation of the faceted solid solution particles (Ge, Si) and an increase in their number could be observed. Nanohardness measurements showed that the (Ge, Si) and (Ge) solid solutions had similar nanohardness, with values of 11.6 and 10.2 GPa, respectively. Simultaneously, the Al solid solution and the intermetallic Al7 Ge2 Fe phase exhibited significantly lower nanohardness values of 0.7 and 6.7 GPa, respectively. Brinell hardness measurements showed that the ingots of the filler alloys were sufficiently ductile and had a hardness comparable to that of AA6082, which is used for brazing with AISI 304 stainless steel. The obtained results for the studied ingots and the rapidly quenched foils can be used to predict the forming structure of the seam after brazing and adjusted for diffusion processes occurring between the brazed materials and the studied filler alloys.
Microstructure Evolution of Vacuum-Brazed Ti/Mo Joints with Ti- and Zr-Based Filler Metals
EFFECT OF HEAT TREATMENT ON THE PROPERTIES OF RAPIDLY QUENCHED Al – Ge – Si ALLOYS
This paper examines Al – Ge – Si alloys containing up to 40 wt. % germanium that can potentially be used for brazing corrosion resistant steels to high-strength aluminium alloys. Using ultrarapid quenching, ingots of the above alloys were converted into 55±5 μm thick bands. Properties of both ingots and bands were methodically studied, and effect of heat treatment on the properties of ingots and bands – determined. Optimal regimes of heat treatment for bands were tested that help achieve the required plasticity. Homogenous and heterogenous materials were brazed together. X-ray phase analysis and electron microscopy showed that rapidly quenched bands have a homogenous structure and contain a eutectic comprised of solid solutions (Al, Ge) and (Si, Ge) and a metastable compound Al6Ge5. The ingots of the alloys consist of two eutectics. The first one consists of solid solutions (Al, Ge) and (Si, Ge), while the second one comprises a solid solution (Al, Ge) and a Ge-based solid solution. The bands have a nanocrystalline structure. Having measured microhardness and plasticity of the bands, the authors identified the best regime of heat treatment, which is 300oC/10 min. A series of pilot tests was conducted to analyze the applicability of the studied alloys as filler metals. For this, aluminium alloy AA6082 was brazed to corrosion resistant steel AISI 304 and a heterogenous joint was made. A metallographic study revealed no compromized integrity or defects in any of the brazed joints. © 2022, Ore and Metals Publishing house. All rights reserved.
Joining Stainless-Steel AISI 304 and High-Strength Aluminum Alloy AA 6082 by Brazing Using Al-Ge-Si Foils
An Al-40.0Ge-3.4Si wt.% alloy foil with a thickness of 50 ± 5 μm, obtained via an ultrafast solidification method, is described in this work. A complete wetting of the aluminum alloy substrate with a wetting angle of 0° is observed, and the formation of a drop with a wetting angle of 30 ± 5° is observed on the steel substrate. Similar and dissimilar brazed joints of aluminum alloy AA 6082 and stainless-steel AISI 304 are obtained. The microstructure of the AA 6082/AA 6082 brazed seam is homogeneous and contains particles of an Al7Fe2Si system intermetallic compound and particles of an Al-Ge eutectic composition. The brazed seam of the AISI 304/AISI 304 joint is formed due to the formation of the Al8Fe2(Si, Cr) intermetallic compound reaction layer on the steel surface. The proposed scheme for the AISI 304/AA 6082 brazed joint formation is given. The brazed seam represents the Al8Fe2(Si, Cr) reaction layer on the steel surface, the thickness of which depends on the holding time during brazing, and the aluminum matrix of which has particles of a composition close to an Al-Ge eutectic. The obtained results could be used for the optimization of time–temperature brazing modes in order to improve the mechanical characteristics of AISI 304/AA 6082 dissimilar joints.