Nickel-based single-crystal superalloys are widely used for production of high pressure turbine blades. The studied blades were obtained in an ALD Vacuum Technologies furnace by the Bridgman technique. Crystallization process was carried out with drawing rates of 3 mm/min and 5 mm/min. The dendrite microstructure based on the γ/γ’ phases and their defects was characterized using X-Ray topography, Laue diffraction, transmission electron microscopy. The defect structure samples were examined with the positron annihilation lifetime spectroscopy. It was found that crystal orientation, lattice parameter of γ’ phase and concentration of defects are correlated. The defect concentration increases in some areas which was the result of deviation of the primary dendrite arm from crystallization direction . Only one type of point defects was detected.

Vacancies occupying different sub-lattices of D03 structure of Fe3Al alloy were investigated by the full potential linearized augmented plane wave method. The calculations basing on the super-cell approach have been performed for the vacancy concentrations of 1.6 and 3 at.%. For both concentrations the sub-lattice preference for vacancy location was determined. The dependence of vacancy formation energy on magnetic state of structure has been found. The positron lifetimes for the annihilation in the bulk (Fe3Al) and in vacancies have been investigated basing on the ab initio results for the electron density. The effect of vacancies on spin magnetic moment and hy-perfine parameters of Fe atoms neighboring the vacancy was examined. The results are discussed and compared with the data available.

Positron lifetime spectroscopy (PALS) is employed to study retained vacancies in Fe75Al25 and Fe70Al25X5 X= (Cr, Ni) after various thermal treatments. The PALS spectra were analyzed with the two states trapping model. The positron lifetime in defects suggests that they are Fe-monovacancies. The vacancy concentration, determined by the rates of trapping positrons to vacancies, strongly depends on the cooling rate of the sample and the ternary addition. An addition of Cr lowers, whereas an addition of Ni increases the concentration of the retained vacancies in relation to Fe75Al25 samples after the same heat treatment.

The paper discusses a theoretical model that associates the shape of the Mössbauer spectrum with the con guration of atoms in local surroundings of the Mössbauer nuclide. Using the model we analyse the Mössbauer spectra of Fe72Al28 alloys after various heat treatments. Basing on the model calculations the hyper ne structure parameters describing an e ect of an Al atom in the rst and the second coordination shell of Fe atom are evaluated. Using these parameters the values of hyper ne magnetic eld and isomers shift for the atomic con gurations present in stoichiometric Fe3Al are estimated and compared with the results of ab initio calculations.

The paper discusses a theoretical model that associates the shape of the Mossbauer spectrum with the configuration of atoms in local surroundings of the Mossbauer nuclide. Using the model we analyse the Mossbauer spectra of Fe72Al28 alloys after various heat treatments. Basing on the model calculations the hyperfine structure parameters describing an effect of an Al atom in the first and the second coordination shell of Fe-57 atom are evaluated. Using these parameters the values of hyperfine magnetic field and isomers shift for the atomic configurations present in stoichiometric Fe3Al are estimated and compared with the results of ab initio calculations.

The paper discusses a theoretical model that associates the shape of the Mössbauer spectrum with the conguration of atoms in local surroundings of the Mössbauer nuclide.Using the model we analyse the Mössbauer spectra of Fe72Al28 alloys after various heat treatments.Basing on the model calculations the hyperne structure parameters describing an eect of an Al atom in the rst and the second coordination shell of 57 Fe atom are evaluated.Using these parameters the values of hyperne magnetic eld and isomers shift for the atomic congurations present in stoichiometric Fe3Al are estimated and compared with the results of ab initio calculations.

It was shown that soft magnetic properties of Fe78Nb2B20 amorphous alloy can be significantly improved by applying 1-h annealing at temperature 623 K (permeability increases even about 8 times). The Mössbauer Spectroscopy technique indicated that the optimized microstructure (corresponding to the maximum magnetic permeability) is free of iron nanograins and should be attributed to annealing out of free volume and a reduction of internal stresses i.e. to the relaxed amorphous phase.

Magnetic properties of the Fe76.2Nb5.7B13.3Gd4.8, Fe69.6Nb5.2B12.2Gd13, Fe76.2Nb5.7B13.3Y4.8, Fe69.6Nb5.2B12.2Y13 bulk nanocrystalline alloys (mould casting technique) are presented and discussed. Measurements were carried out by the means of SQUID magnetometer (temperature range 2 K – 400 K, field up to 7 T) and magnetic balance (temperatures up to 1100 K). Microstructure was studied by the Mössbauer spectroscopy at room temperature. It was shown that the samples are nonocrystalline with α-Fe and different Fe-B, Y/Gd-Fe or Y/Gd-Fe-B compounds. The preparation method as well as the Gd addition causes a magnetic hardening of the studied alloys.

The paper discusses a theoretical model that associates the shape of Mossbauer spectrum with the configuration of atoms in local surroundings of the Mossbauer nuclide. The model has been implemented to a computer program which was used to analyse the Mossbauer spectra of Fe72Al28 alloys after various heat treatments. Basing on the determined configuration of atoms, the long range ordering parameter was estimated.

In the paper was studies the influence of chemical composition and temperature on the properties, microstructures, hardness and ordering process of intermetallics on the base closed to one of Fe3Al phase. The major problem restricting universal application of intermetallic phase base alloy from Fe-Al system is their low plasticity which leads to hampering their development as construction materials. The analysis were performed for two alloys i.e Fe28Al and Fe28Al-5Cr which were produced by casting and next were annealed for 8, 16 and 48 hours at 1000◦C. Both alloys is closed to one of Fe3Al phase. Mechanical properties were measured by the uniaxial tensile test at room temperature and at 600◦C. Some basic mechanical properties i.e. R0,2, Rm, A5, Z were determined. Were obtained increasing ductility with a increase the temperature test in air condition for both alloys. Structural examination was carried out using light microscopy and scanning electron microscopy. There observed that in Fe28Al alloy without Cr phases rich in Fe and Al, which can correspond to FeAlC0,5 were visible as well as phases rich in Zr. The precipitates rich in Cr and Zr were identified alloy with Cr which probably correspond to FeCr2 ZrC and Cr2Zr phases. The fractographs of destruction surfaces after tensile tests shown, that for both alloy at room temperature are brittleness and intergrannular. After the test at 600◦C character of the fractures were changed (different). Were observed transgrannular cleavage for both alloys. The ordering process was analyzed by X-ray diffraction, Mössbauer spectroscopy. The studied alloys were prepared by melting in induction furnace under vacuum and next were gravitatively casted into cylindrical graphite moulds. After then samples were annealed at 1000◦C for 8, 16 and 48 hours. Different behaviour of Fe-28Al and Fe-28Al-5Cr alloys after annealing were founded. Microstructures for both alloys was similar. Were indicated the presence of phases and precipitates in investigated alloys in the dendritic primary structure which wasn’t changes after the heat treatment process. Were observed the influence the time of annealing on the hardness alloys. Increasing time of annealing from 8h to 48h at 1000◦C influenced on the increasing of hardness in Fe-28Al alloy and decreasing of hardness in Fe-28Al-5Cr alloy. X-ray diffraction method were obtained that the Fe3Al phase of DO3 type structure was stated only in the sample of Fe28Al alloy annealed for 48 hours. The FeAl phase appeared to be the main phase in the other samples. All the informations including a some of mechanical properties, analysis of microstructure, long range ordering during the heat treatment of studied alloys could be helpfully for technological processing this materials.

The defect structure of Fe28Al samples is examined with the Positron Annihilation Lifetime Spectroscopy. The studies are carried out for samples in as-cast state and after heat treatments: annealing for 24 hours at 900 degrees C (or 1050 degrees C) and either slow cooling with furnace or quenching to oil. The PALS spectra are analyzed using two-state trapping model. Only one type of defects is detected. The positron lifetime in these defects (tau(V)) suggests that they are quenched-in Fe-monovacancies (V-Fe). The vacancy concentration strongly depends on the rate of cooling. Besides, tau(V) also depends slightly on the rate of cooling of the material. This fact suggests, according to the predictions of latest theoretical calculations, that tau(V) is sensitive to the atomic configuration in the nearest neighborhood of V-Fe, which give hope to estimate the degree of atomic ordering in alloys by the PALS technique.

Single phase materials with general formula CdxMeyCr2Se4 (where Me = Mn, Sn) were obtained using solid state synthesis method. Both compounds are ferromagnets with TC =115K (Sn) and 135K (Mn). The values of Curie-Weiss parameter ΘC-W = 135K (Sn) and 145K (Mn) are higher than respective values of TC indicating a presence of competing antiferromagnetic component. The values of lattice parameters are consistent with Sn and Mn replacing Cd. Slight cadmium deficiency has been also observed.

This work presents the results of investigations using Mössbauer spectroscopy technique and XRD, and their interpretation concerning precipitations and transformation of iron carbides and retained austenite stabilization. It also discusses changes in hardened matrix during tempering in relation to previously conducted dilatometric, microscopic and mechanical examinations. This research was carried out using a new high-carbon alloy 120MnCrMoV8-6-4-2 steel, which was designed in 1998, in Phase Transformations Research Group at the AGH UST. The influence of the tempering time on the mechanical and chemical stability of retained austenite and on the products of its transformation, nucleation and solubility of iron carbides and cementite nucleation and growth, was determined.

The intermetallic alloys basing on iron-aluminum ordered phases are characterized by low specific weight, high strength, low cost and good potential for industrial applications as a replacement for high-temperature oxidation resisting or corrosion resisting stainless steel [4]. On the other hand, the lack of ductility at room temperature and a decrease in strength of above 873 K limits the scope of their application as a construction material. However, the addition of alloying elements such as Cr can improve the room temperature ductility of Fe3Al [2]. The intermetallic materials from the Fe-Al system with the content of iron larger than 50% have two types of ordering structure, D03 structure below 550°C and B2 structure at temperatures between 550°C and 1250°C. The phases are based on the body-centred cubic (bcc) lattice and can exist in a wide range of compositions. The B2 entirely ordered phase relates to stoichiometric FeAl. The B2 structure can undergo ordering of second nearest neighbours to form a complex cubic D03 phase when the aluminium content ranges between 25 and approximately 37 at.%. This phase is based on a Fe3Al stoichiometry [8]. It is well established that physical and mechanical properties of Fe-Al alloys are related to the atomic ordering and the presence of point defects. As in most ordered materials, the defect structure in the B2 and D03 phases is substantially more complicated than in pure metals [4]. Besides single vacancies, one must The influence of heat treatment on point defect concentration in Fe-Al and Fe-Al-Cr systems Jerzy Kansy, Aneta Hanc, Dawid Giebel

We have observed that doping CuCr2Se4 with tin introduces and then increases the tetrahedral deformation of the spinel structure, which can be connected with the Jahn-Teller (JT) distortion due to Cr2+ ions in antiprismatic environment. The presence of Cr2+ is corroborated by the increase of the saturation magnetization above the 6μB value expected for the 2 Cr3+ ions. In the high limit of the high Sn doping the deformation is decreased, which we attribute to elimination of the JT condition by the increased local distortions. With the tin doping the magnetic structure evolves from the ferromagnet, through spin-glass like to the antiferromagnetic due to increased AF coupling in the system. This is corroborated by the decreasing transition temperature and the Curie-Weiss parameter.

Single phase materials with general formula CdxMeyCr2Se4 (where Me = Mn, Sn) were obtained using solid state synthesis method. Both compounds are ferromagnets with TC =115K (Sn) and 135K (Mn). The values of Curie-Weiss parameter ΘC-W = 135K (Sn) and 145K (Mn) are higher than respective values of TC indicating a presence of competing antiferromagnetic component. The values of lattice parameters are consistent with Sn and Mn replacing Cd. Slight cadmium deficiency has been also observed.

The aim of the work is to search possibility for preparation of the Mn2VSn and V2MnSn Heusler-type compounds. We have carried out the 119Sn-Mössbauer spectroscopy, scanning electron microscopy and X-ray diffraction studies on the some Mn0.5V0.25 Sn0.25 and V0.5Mn0.25Sn0.25 solid solutions prepared by arc melting of the constituent metals. Combining an independent information about atomic structure from X-ray diffraction and Mössbauer spectroscopy it was possible to identify main chemical environments responsible for the magnetic ordering observed in the samples. The studies revealed that investigated alloys are characterized by existence of the binary compounds, namely V2Sn3, V3Sn and Mn3Sn, with different extension in Mn and V atomic concentration, respectively. No ternary compounds were found in investigated systems.

In this work, we employed the Mössbauer spectroscopy in a study of point defect formation in intermetallic phases of the B2 structure from the Fe-Al system as a function of Al concentration. We present the values of the 57Fe isomer shift and quadruple splitting for the components describing the point defect in the local environment of a Mössbauer nuclide. The concentration of the Fe vacancies and Fe atoms substituting Al (Fe-AS) are determined. The results shown that an increase in Al content causes an increase in vacancy and Fe-AS

This work presents the results of investigations using Mössbauer spectroscopy technique and their interpretation concerning retained austenite (RA) and its transformation during tempering in relation to previously conducted dilatometric, microscopic and mechanical investigations. This research was conducted on a new high-carbon alloy steel 120 MnCrMoV8-6-4-2, which was designed in 1998, in Phase Transformations Research Group at the AGH UST. The influence of the tempering time on the mechanical and chemical stability of retained austenite and on the products of its transformation, nucleation and solubility of ε carbides and cementite nucleation and growth, was determined.