The paper present selected results of the research conducted for elimination of toxic cadmium from silver based brazing alloys of Ag-Cu-Zn-Cd type. The investigations were conducted with nine new alloys of constant, low silver content (25%) and diversified copper (38.8-46%), zinc (19-32%) and tin (3-10%) contents. Tin was selected as potentially the best cadmium substitute basing on literature review and analysis of equilibrium systems.For examinations and tests a series of ingots in laboratory scale was manufactured, as well as some ingots in pilot scale for the selected, most promising alloys. Complex metallographic examinations of the brazing alloys samples produced in various conditions were made as well as analyses of their phase composition. Also mechanical properties of the samples both in ambient and in elevated temperatures were examined, and physical and technological properties and usability of the alloys were determined. The last stage of the study covered laboratory trials of brazing using the selected alloys.Basing on the results it can be said that there is a possibility to substitute selected cadmium containing silver-based alloys with environmentally friendly alloys of Ag-Cu-Zn-Sn type of relatively low silver content. Low range of melting point was reached, as preliminary assumed. Mechanical properties of the studied alloys strongly depend on temperature, and present limited plasticity in room temperature, while at high temperature (over 500• C) present superplasticity. The examined alloys show good spreadability and the brazing tests confirmed their good reactions both with copper and brass base in a wide temperature range.Keywords: cadmium, silver, environmentally friendly alloys, brazing alloys, mechanical properties, microstructure, phase composition W niniejszym artykule przedstawiono wybrane wyniki prac, których celem jest wyeliminowanie toksycznego kadmu ze srebrowych spoiw twardych typu Ag-Cu-Zn-Cd. Badaniami objęto 9 nowych gatunków stopów o stałej, niskiej zawartości srebra (25%) oraz zróżnicowanej zawartości miedzi (38,8-46%), cynku (19-32%) oraz cyny (3-10%). Cyna została wytypowana, na podstawie analizy literaturowej oraz układów równowagowych, jako potencjalnie najlepszy zamiennik kadmu.Wytworzono szereg wlewków w skali laboratoryjnej oraz dla wybranych, najbardziej obiecujących gatunków spoiw, wlewki w skali półtechnicznej przeznaczone do badań i prób. Przeprowadzono kompleksowe badania metalograficzne próbek spoiw wytworzonych w różnych warunkach oraz dokonano analizy składu fazowego. Wykonano także badania właściwości mechanicznych próbek zarówno w temperaturze otoczenia jak i podwyższonej oraz badania właściwości fizycznych, technologicznych i użytkowych. W ostatnim etapie pracy przeprowadzono laboratoryjne próby lutowanie przy zastosowaniu wybranych spoiw.Uzyskane wyniki badań pozwalają stwierdzić, że możliwe jest zastąpienie wybranych gatunków spoiw srebrowych kadmowych stopami ekologicznymi z grupy Ag-Cu-Zn-Sn o stosunkowo niskiej zawartości srebra. Uzyskano, zakładany we w...

The paper shows results of the study into influence of chemical composition and consolidation process conditions on changes of physical and electrical properties of silver-based composites used in production of electric contacts. The investigations addressed influence of content of zinc oxide (ZnO) and modifying additions in a form of silver tungstate (Ag 2 WO 4 ) and silver molybdate (Ag 2 MoO 4 ) on changes in density, porosity and electrical conductivity. Density of the produced compacts was established by geometric method. The results of density measurements were used in determination of total porosity of sinters. Also arc erosion was examined to determine applicability of the produced composites for production of electric contacts. The erosion was measured as mass loss of individual materials after specific number of connections. The studies were conducted at current intensity of 10 A and voltage of 500V. The scope of the studies covered also evaluation of kinetics of sintering of the examined composites and determination of the mechanisms of mass transport in the process. Studies into kinetics of sintering were conducted in the air atmosphere at constant temperature of 900• C. Production of the examined composite materials consisted of mechanical synthesis of powders of silver, zinc oxide and silver tungstate and molybdate, and then their consolidation by two-sided pressing and subsequent sintering. In cold pressing various pressures were applied 200, 300 and 400 MPa. Sintering was performed with a partial participation of liquid phase in temperature of 900• C. Also additional two-sided pressing was applied under pressure of 500 MPa and stress-relieving recrystallization annealing was performed as the final operation.Keywords: Contact materials, compaction, sintering, physical properties, arc erosion W pracy przedstawiono wyniki badań wpływu składu chemicznego oraz parametrów procesu konsolidacji na zmiany właściwości fizycznych oraz elektrycznych materiałów kompozytowych na osnowie srebra przeznaczonych na styki elektryczne. Analizie poddano wpływ zawartości tlenku cynku (ZnO) oraz dodatków modyfikujących w postaci wolframianu srebra (Ag 2 WO 4 ) oraz molibdenianu srebra (Ag 2 MoO 4 ) na zmiany gęstości, porowatości oraz przewodności elektrycznej. Gęstość uzyskanych wyprasek wyznaczono metodą geometryczną. Na podstawie uzyskanych wyników gęstości wyznaczono porowatość całkowitą spieków. Wykonano również badania erozji łukowej jako parametru określającego przydatność wytworzonych materiałów kompozytowych do zastosowania na styki elektryczne. Miarą erozji był ubytek masy poszczególnych materiałów po określonej liczbie łączeń. Badania zostały przeprowadzone przy natężeniu 10 A i napięciu 500 V. W ramach badań dokonano również oceny kinetyki spiekania badanych materiałów kompozytowych oraz podjęto próbę określenia mechanizmów transportu masy jakie występują podczas tego procesu. Badania kinetyki spiekania prowadzono w atmosferze powietrza w stałej temperaturze wynoszącej 900• C. Proces wytwarzania badanych ma...

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The article presents the influence of mechanical alloying and plastic consolidation on the resistance to arc erosion of the composite Ag–Re material against the selected contact materials. The following composites were selected for the tests: Ag90Re10, Ag95Re5, Ag99Re1 (bulk chemical composition). Ag–Re materials were made using two methods. In the first, the materials were obtained by mixing powders, pressing, sintering, extrusion, drawing, and die forging, whereas, in the second, the process of mechanical alloying was additionally used. The widely available Ag(SnO2)10 and AgNi10 contact materials were used as reference materials. The reference AgNi10 material was made by powder metallurgy in the process of mixing, pressing, sintering, extrusion, drawing, and die forging, while the Ag(SnO2)10 composite was obtained by spraying AgSniBi alloy with water, and then the powder was pressed, oxidized internally, sintered, extruded into wire, and drawn and die forged. The tests of electric arc resistance were carried out for loads with direct current (DC) and alternating current (AC). For alternating current (I = 60 A, U = 230 V), 15,000 switching cycles were made, while, for constant current 50,000 (I = 10 A, U = 550 V). A positive effect of the mechanical alloying process and the addition of a small amount of rhenium (1% by mass) on the spark erosion properties of the Ag–Re contact material was found. When DC current of 10 A was used, AgRe1 composite was found to be more resistant than commonly used contact materials (AgNi10 and Ag(SnO2)10).