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Microstructure and phase composition characterization of a Ti–Al intermetallic alloy

Frocisz Ł., Krawczyk J., Dziurka R., Górecki K., Cios G., Gondek Ł.

Inżynieria Materiałowa

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2016

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Vol. 37, nr 6

322--327

EN

Intermetallic Ti–Al alloys are characterized by the unique set of properties which makes these alloys a prospective material for the energy, automotive and aviation industries. The mechanical properties of a intermetallic alloys are strictly related to the microstructure. The refinement of the microstructure can be obtained by the manufacturing process, alloying additions and heat treatment. Microstructure characterization and knowledge about phase transformation mechanisms and their temperature ranges allows to change properties of the bulk material. The aim of this study was the microstructure and phase composition characterization of intermetallic Ti48Al2Cr2Nb alloy. The microstructure was examined using the light and scanning electron microscopy. Identification of phases and their temperature stability were determined by X-ray diffraction, differential dilatometry and calorimetry investigation. The oxidation process was determined by high temperature X-ray diffraction and the thermogravimetric method. The alloy after annealing has a duplex microstructure with precipitations of α2 phase in the γ matrix. Dilatometry and calorimetry allowed us to define the stability of each phase. At first the enriched in chromium α2 phase dissolved, after that the regions depleted in chromium were transformed, and above 775°C the microstructure was only the γ phase. Gamma phase was transformed above 1100°C, the end of transformation γ → α was evaluated as 1250°C. The oxidation investigations allowed us to show that the oxidation process started at 700°C by the oxide layer formation, which was stable till 900°C. Above this temperature the oxide layer started to grow.

PL

Stopy tytanu na osnowie faz międzymetalicznych ze względu na swoje unikatowe właściwości mogą znaleźć szerokie zastosowanie w różnych dziedzinach przemysłu. Metody wytwarzania w znaczący sposób wpływają na mikrostrukturę tych stopów, podobnie jak zabiegi obróbki cieplnej czy zmiany składu chemicznego [1÷13]. Celem pracy była charakterystyka mikrostruktury, składu fazowego oraz przemian zachodzących w stopie Ti48Al2Cr2Nb podczas nagrzewania. Badano również utlenianie tego stopu. Wyniki badań mogą prowadzić do opracowania nowych zabiegów obróbki cieplnej i kształtowania struktury tego stopu.

2

Structural, magnetic, and Mössbauer effect studies of bornite

Przewoźnik J., Żukrowski J., Gondek Ł., Lemański A., Kapusta C., Piestrzyński A.

Nukleonika

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2013

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Vol. 58, No. 1

43-46

EN

The results of a combined study of bornite with Mossbauer spectroscopy, X-ray diffraction and DC magnetometry are reported. The orthorhombic crystallographic structure of the mineral is observed at 15 K and 300 K. It exhibits an increase of the orthorhombic distortion with decreasing temperature. Magnetic susceptibility shows a Curie-Weiss like behaviour between 230 K and 380 K corresponding to the effective magnetic moment of 7.2(3) mi B per formula unit. The material undergoes a transition to an antiferromagnetic-like state at 75 K. Mossbauer spectra at the paramagnetic range are doublets with a small quadrupole splitting and the isomer shift corresponding to a high spin Fe3+ state. Upon magnetic ordering, a coexistence of the paramagnetic doublet with a broadened magnetic sextet is observed indicating an inhomogeneous character of the magnetic transition. The hyperfine field of 350 kOe at 4.2 K is much lower than that observed for a high spin Fe3+ in oxides (510 kOe) which is attributed to covalence effects and a possible copper contribution to the effective magnetic moment of the compound.

3

Anomalous structural properties of some RCu2Ge2 compounds (R = La, Gd-Tm)

Rusinek D., Niewolski J., Czub J., Gondek Ł, Szytuła A.

Materials Science Poland

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2013

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Vol. 31, No. 4

495--500

EN

In this paper, we address the issue of possible quadrupole ordering in RCu2Ge2 compounds. In the literature, there are reports on anomalous behaviour of lattice parameters, however, lack of high quality data makes the relevant analysis dubious. Therefore, we attempt to perform precise, non-ambient XRD measurements within 12 – 300 K temperature range. Our results confirm peculiar temperature behaviour of the c-lattice parameter that exhibits a well defined minimum at about 60 – 120 K for majority of investigated compounds. However, in contrast to the literature, the anomalous behaviour does not exhibit discontinuities. On the other hand, such behaviour has been evidenced for La-based compounds (LaCu2Ge2 and LaNi2Ge2), where the 4f orbitals are unoccupied.

4

Znaczenie mikroporowatych materiałów metaloorganicznych (MOF ) dla potrzeb magazynowania wodoru

Czub J., Gondek Ł, Figiel H.

Wiadomości Chemiczne

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2012

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[Z] 66, 3-4

227-247

EN

Currently, the metal-organic frameworks (MOF s) are considered among the most promising materials for hydrogen storage. In this paper, the properties of MOF s that are particularly important for application purposes are presented. Examples include simplicity of their syntheses on an industrial scale, low synthesis costs, high thermal stability and durability, an excellent repeatability and very low degree of degradation during cyclic hydrogen loading and recovery. On the other hand, the potential use of MOF s as hydrogen reservoirs is to some extent limited due to the fact that the low temperatures of 77 K are required for effective adsorption of hydrogen in the microporous structures of MOF s. Nowadays, the research on MOF s is carried in two directions. In particular, there are intensive studies on increasing of the concentration of hydrogen adsorbed at low temperatures in order to determine the limiting value for which maintaining the reservoir at the temperature of liquid hydrogen would be economically viable. It seems that the limiting concentration is being currently reached. The second direction of research is to increase the limiting value of temperature at which the concentration of adsorbed hydrogen is acceptable.

5

Magnetism and electronic structure of hexagonal 1:1:1 rare earth-based intermetallic compounds

Gondek Ł, Żukrowski J, Bałanda M, Kaczorowski D, Szytuła A

Materials Science Poland

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2008

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Vol. 26, No. 4

815--820

EN

Correlations between magnetic properties and electronic structure of rare earth based intermetallics of the ZrNiAl-type crystal structure have been analysed. The analysis has been supported by results of magnetometric, neutron diffraction and photoelectron spectroscopy measurements. It has been demonstrated that structure of the valence band and crystal electric field effects are the most important factors affecting the magnetic behaviour of the discussed compounds.