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Combined Effect of Zr and Si on Isothermal Oxidation of Ti

Ha S.-H., Kim B.-H., Yoon Y.-O., Lim H.-K., Kim S. K.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1493--1495

EN

In this study, the combined effect of Zr and Si on isothermal oxidation of Ti for 25 and 50h at 820°C, which is the temperature related to exhaust valves operation, was investigated. Si addition into Ti-5mass%Zr alloy led to a distribution of silicide Ti5Si3 phase formed by a eutectic reaction. The Ti sample containing only Zr showed more retarded oxidation rate than Ti-6Al-4V, the most prevalent Ti alloy, at the same condition. However, while a simultaneous addition of Zr and Si resulted in greater increase of oxidation resistance. The oxide layer formed after the addition of Zr and Si comprised TiO2, ZrO2, and SiO2.

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Wytwarzanie prętów do produkcji elektrod do zgrzewania punktowego za pomocą wyciskania metodą KOBO

Heyduk F., Ziółkiewicz S., Bochniak W., Korbel A.

Obróbka Plastyczna Metali

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2015

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T. 26, nr 4

325--334

PL

Zgrzewanie punktowe jest najpopularniejszą metodą łączenia blach, szczególnie w przemyśle motoryzacyjnym i kolejowym. W artykule przedstawiono wyniki wstępnych badań wytwarzania prętów, będących półwyrobem elektrod przeznaczonych do zgrzewania punktowego. Do badań wykorzystano pręty o średnicy 40 mm ze stopu miedzi Cu-Cr-Zr, które poddano przesycaniu przy dwóch wariantach temperatur: 900°C i 1030°C, a następnie wyciskano na zimno metodą KOBO i starzono. Wyciskanie metodą KOBO prowadzono przy dwóch wartościach siły wyciskania: 400 i 650 kN. W badaniach wykazano, że po tak przeprowadzonym procesie nastąpił wzrost twardości próbek, dochodzący do 10% przy wyciskaniu z siłą 650 kN w stosunku do materiału wyjściowego. W obu przypadkach próbek wyciskanych metodą KOBO obserwuje się ultra drobne ziarna w warstwie przypowierzchniowej na grubości ok. 200 μm, niezależnie od przyjętej siły wyciskania. Półwyroby po procesie KOBO i starzeniu mają inną strukturę przy powierzchni, w porównani do struktury rdzenia, niezależnie od wielkości siły wyciskania. Widać również układ pofalowanych pasm będących efektem płynięcia metalu w procesie wyciskania KOBO. W obu przypadkach próbek wyciskanych metodą KOBO i starzonych obserwuje się równomierne rozmieszczenie wydzieleń dyspersyjnych na tle rozdrobnionej struktury, przy czym rozdrobnienie jest większe dla próbki wyciskanej z większą siłą (650 kN). Uzyskane wyniki stanowią bazę umożliwiającą podjęcie w Instytucie Obróbki Plastycznej dalszych badań nad kształtowaniem plastycznym elektrod o wysokiej twardości, co pozwoli na zmniejszenie stopnia odpadu w stosunku do technologii obróbki skrawania o ok. 30%.

EN

Spot welding is the most popular method of joining sheets, particularly in the motorization and railway industries. This article presents the results of preliminary research on manufacturing rods as components used in the production of electrodes intended for spot welding. Rods with a diameter of 40 mm made of Cu-Cr-Zr copper alloy, hyperquenched at two different temperatures: 900°C and 1030°C, cold-extruded using the KOBO method and aged, were used in tests. KOBO extrusion was performed using two different extrusion force values: 400 and 650 kN. Tests prove that the hardness of specimens increased after this process, by up to 10% at extrusion with 650 kN of force compared to the starting material. In both cases of specimens extruded using the KOBO method, ultra-fine grains are observed in the near-surface layer over a thickness of approx. 200 μm, regardless of the accepted extrusion force. Semi-finished products after the KOBO process and ageing have a different structure near the surface than in the core, regardless of the extrusion force value. A wavy arrangement of bands can also be seen, the effect of metal flow during the KOBO extrusion process. In both cases of specimens extruded using the KOBO method and aged, uniform distribution of dispersive precipitates is observed on the background of the refined structure, where refinement is greater in the specimen extruded with greater force (650 kN). Obtained results constitute the foundations making it possible to undertake further research of plastic forming of electrodes of high hardness at the Metal Forming Institute, enabling reduction of waste by 30% compared to machining technology.

3

Structure characteristics of intermetallic NiAlZr based compound

Malcharcziková J., Kursa M., Pohludka M.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2010

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z. 97

19-19

EN

Observations were made in orientated state of inter-metallic Ni3Al based compound alloyed by zirconium. Zirconium in the form of wire or plasma melted foundry alloy Ni-Zr were used for preparation of the samples. The samples were cast by induction vacuum casting into the shape of cylinders. These castings were then directionally solidified in corundum tubes with the specified apex angle in a two-zone crystallisation furnace. Used rate of directional solidification was 50 mm/h. Cross sections and longitudinal sections of individual samples were used for determination of porosity, micro-hardness and for evaluation of character of created structures. It was established that the basic matrix contained formations of Ni3Al and elongated formations of Ni5Al3. Inter-dendritic regions contain eutectics with lamellar structure, which is formed by the Ni3Al phase and by the Zr-rich phase. Microhardness in the samples was determined in detail on the surface of the scratch pattern in polished state in accordance with precisely defined procedure, both in longitudinal and cross section. The scratch patterns were afterwards slightly etched in order to determine microhardness in individual phases and on grain boundaries. Microhardness was measured on microhardness tester FM-100 with use of the measuring unit "automatic microhardness testing system FM-ARS". It is very interesting that no big differences were found between the values of microhardness in the basic phase of Ni3Al rich in zirconium and grain boundaries, where this value varied approx. within the interval from 360š40 HV 0.05. Only eutectics formed by the Ni3Al phase and by the Zr-rich phase showed an increased microhardness. Evaluation of structure has been further completed with determination of porosity. Porosity in these samples was not too high and its value is of the order of hundreths of percent.

4

Electrolytic extractions obtained from Cu-Zr and Cu-Ce alloys and their X-ray phase analysis

Ozgowicz W., Nawrat G.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 20, nr 1-2

171-174

EN

Purpose: The aim of the investigations is the formation of electrolytic extractions from Cu-Zr and Cu-Ce model alloys containing microadditions of Zr and Ce amounting to about 0.1% by weight and their identification by X-ray diffraction analysis. Design/methodology/approach: Electrolytic extractions were obtained by the anodic dissolution of the alloys. In the X-ray analysis the comparative method was applied. Findings: The activity of anodic dissolution of the investigated alloys was determined basing on the mass of the electrolytic extraction and the time of dissolution of the alloy in solutions of the electrolytes with different chemical compositions and a different complexive effect to copper and different pH. Research limitations/implications: The qualitative X-ray phase analysis permits to identify the main intermetallic phases of the investigated alloys in a limited range, mainly due to experimental reasons. Practical implications: The results of these investigations indicate a distinct relation between the mass and the kind of the dissolved phase and the value of the electrochemical potential of the active dissolution of the alloys. Originality/value: The revealing of this relation is of practical importance in regard to the accuracy of the results of the phase and crystal analysis carried out by X-ray diffraction examination.