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1

The study of properties TiAl-Nb alloys

Juřica J., Losertová M., Petlák D.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2010

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z. 97

8-8

EN

Subject of this work is an intermetallic alloy based on TiAl and doped with Nb with high creep resistance and good mechanical properties. The experimental Ti-Al-Nb material with two compositions of Ti-45Al-10Nb and Ti-40Al-15Nb was prepared from master alloy TiNb (55/45 wt. %) and Al pieces by plasma melting, vacuum induction remelting and casting into the rod shape. The samples were homogenisation annealed at 1100°C for 12 hours in Ar atmosphere and water quenched from 700°C. Heat treatment at 700 °C for 8 hours in Ar atmosphere as well as in hydrogen flowing gas was realised to prepare experimental material for hydrogen effect study. Microstructure of the specimens was studied by light and scanning electron microscopies, microhardness measurement and phase microanalysis were performed. The lamellar microstructure of the samples in as-cast and heat treated conditions formed of the ? (45 at.% Al) and ?2 (41 at.% Al) phases resulted from metallographic observation and EDS phase analysis. Microhardness values of the samples decreased after annealing and quenching. Effect of hydrogen on lamellar microstructure and microhardness values was studied on the hydrogen-charged and hydrogen-free specimens. X-ray diffraction analyses were performed on Ti-Al-Nb specimens.

2

The study of microstructure TiNb based alloys with different heat treatment

Štěpán P., Losertová M., Petlák D.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2010

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z. 97

33-33

EN

The study of TiNb-based alloys that are suitable candidates for substitution of TiNi in many biocompatible applications was performed. The experimental alloys with two nominal compositions Ti22Nb and Ti25Nb (at.%) were prepared by plasma melting of TiNb master alloy (55/45 wt.%) and Ti pieces. Different conditions of heat treatment were performed and consisted of homogenisation annealing at 1100°C for 12 hours in flowing Ar gas and water quenching and solution annealing at 900°C for 1 hour in flowing Ar gas and water quenching followed by precipitation aging at different temperatures (200, 400 and 600°C) for 1 hour. The metallographic observation and phase microanalysis of the alloys proved the composition homogeneity. The microstructure of Ti22Nb and Ti25Nb samples after plasma melting was dendritic with very fine martensite needles. After solid solution annealing of plasma melted alloys, the presence of ? phase and " martensite in the microstructure was observed. The microhardness values showed obvious relation with heat treatment and aging. The annealing at 1100°C and quenching increased microhardness because the dendritic and martensite microstructure changed to lamellar one. Furthermore, the higher Nb content in Ti25Nb alloy decreased microhardness of the samples in plasma melted as well as annealed conditions by reason of increasing amount of beta phase.

3

Quantitative description of Kirkendall's effect in bonded joints of Ni3Al alloy and nickel

Adamiec J., Sozańska M., Losertová M., Hyspecká L.

Inżynieria Materiałowa

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2004

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R. XXV, nr 3

698-701

EN

Performed are the qualitative and quantitative metallographic examinations of bonded joints of the Ni3Al alloy on intermetallic phase matrix with pure Ni executed by means of electron beam. To simulate the working conditions for joints of this type, the samples were annealed at temperature of 1140°C for 48 h, 96 h and 192 h. There were observed structures typical for bonded joints: a polycrystalline native material, narrow heat affected zone and a weld area. An equiaxial polycrystalline structure of joint was disclosed after annealing. In the joint area was discovered occurrence of voids (i.e. Kirkendall's Effect), what confirms a vacancy nature of atomic diffusion in Ni3Al-Ni joints. Changes of shape and size of Kirkenadall's voids in the weld area are described by means of stereological parameters.

PL

Przeprowadzono badania metalograficzne jakościowe i ilościowe połączeń spajanych ze stopu na osnowie fazy międzymetalicznej Ni3Al z czystym Ni wykonanych za pomocą wiązki elektronowej. W celu symulacji warunków pracy tego typu połączeń próbki były wyżarzane w temperaturze 1140 °C przez 48 h, 96 h 192 h. Obserwowano struktury typowe dla połączeń spajanych: polikrystaliczny materiał rodzimy, wąską strefę wpływu ciepła oraz obszar spoiny. Po wyżarzaniu ujawniono równoosiową strukturę polikrystaliczną złącza. Stwierdzono, również występowanie pustek w obszarze złącza (tzw. Efekt Kirkendall'a), co potwierdza wakansowy charakter dyfuzji atomów w połączeniu Ni3Al-Ni. Za pomocą parametrów stereologicznych opisano zmiany kształtu i wielkości pustek Kirkendall'a w obszarze spajania.

4

Makro- i mikrostruktura połączeń spajanych stopu Ni3AI z niklem wykonanych wiązką elektronową

Adamiec J., Sozańska M., Losertová M., Hyspecká L.

Inżynieria Materiałowa

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2004

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R. XXV, nr 4

751-755

PL

Celem pracy było określenie makro- i mikrostruktury połączeń stopu na osnowie fazy międzymetalicznej Ni3Al z niklem. Wykonano złącze poprzez stapianie wiązką elektronową stopu Ni3Al, a następnie mechaniczne połączenie z prętem Ni. Tak przygotowane połączenia były wyżarzane w temperaturze 1140°C przez 48 h, 96 h i 192 h. Przeprowadzono badania metalograficzne makro- i mikrostruktury oraz mikroanalizę składu chemicznego połączenia. W połączeniu obserwowano struktury typowe dla połączeń spawanych: polikrystaliczny materiał rodzimy, wąską strefę wpływu ciepła oraz obszar spoiny. Po wyżarzaniu ujawniono równoosiową strukturę polikrystaliczną złącza. Stwierdzono również występowanie pustek w obszarze złącza (tzw. efekt Kirkendalla), co potwierdziło wakansowy charakter dyfuzji atomów w połączeniu Ni3AI-Ni. Zjawiska dyfuzji potwierdziła również liniowa mikroanaliza składu chemicznego Al i Ni wykonana za pomocą energetycznego spektrometru rentgenowskiego EDS. Wraz ze wzrostem czasu wyżarzania obserwowano koagulację pustek. Przeprowadzone badania makro- i mikrostruktury złącza Ni3AI-Ni należy uzupełnić badaniami własności mechanicznych otrzymanych połączeń, co umożliwi ocenę przydatności technologicznej łączenia stopów na osnowie faz międzymetalicznych za pomocą wiązki elektronowej.

EN

The purpose of the study was to determine the macro- and microstructure of joints of an intermetallic phase based alloy, Ni3Al, with nickel. A joint was made by melting Ni3Al with an electron beam and connecting it afterwards mechanically with a Ni rod. So prepared joints were annealed at a temperature of 1140°C for 48 h, 96 h and 192 h. Metallographic investigations of the macro- and microstructure of the joint as well as a microanalysis of the its chemical composition were carried out. In the joint, structures typical of welded joints were observed, i.e. a polycrystalline native material, a narrow heat affected zone and a fusion weld region. After annealing, an equiaxial polycrystalline structure of the joint was revealed. Also, some voids were found in the joint region (so called "Kirkendall effect"), which corroborated the vacancy nature of atoms diffusion in the Ni3Al-Ni joint. The occurrence of diffusion was confirmed by a linear microanalysis of the chemical composition performed by the X-ray energy dispersive spectroscopy (EDS) method. With an increase of the annealing time, voids coagulation was observed. The investigations of the Ni3Al-Ni joint macro- and microstructure should be supplemented by investigations of the obtained joints mechanical properties, which would facilitate an assessment of technological usefulness of joining intermetallic phase based alloys by means of an electron beam.