Cylindrical nanowires made of Co2FeSn Heusler alloy with high spin polarization have been synthetized via template-assisted electrochemical deposition in nanoporous anodic alumina membranes. Their microstructure and morphology have been characterized by in situ studies of X-ray diffraction, together with scanning and transmission electron microscopy techniques. The basic structural and magnetic characterization revealed a B2-type cubic ordered Heusler structure with a lattice parameter of around 5.8 Å and the [110] direction, preferably aligned with the longitudinal axis of the polycrystalline nanowires. The easy magnetization axis is parallel to the nanowire’s axis too. The point-contact Andreev reflection spectroscopic measurements performed on the nanowire’s fresh surface released high polarization values, that is, P = 0.85–1, and prove that the high spin polarization or half-metallicity will be preserved in the nanoscale regime. The presented results open the possibilities toward future exploration of Heusler nanowires with high spin polarization, which are promising materials for applications in spintronics and high-density magnetic data recording.

In this paper the dissimilar welded joints between the ferritic (tempered martensitic) steel T92 and the non-stabilised austenitic steel TP316H were investigated in terms of microstructure and creep rupture behaviour characterisation. The welded joints were prepared by the TIG method using the Ni-based filler metal Nirod 600 (Inconel-type). After the welding, the individual weldments were subjected to the two different regimes of post-weld heat treatment (PWHT), either the "classical" PWHT (i.e. subcritical tempering -below Ac1 temperature) or the so-called "full" PWHT including the re-normalisation. The use of "classical" PWHT preserved microstructural gradient in the ferritic steel heat-affected zone (HAZ), which led to a premature creep failure by the "type IV cracking" mode. In contrast, the application of "full" PWHT eliminated the critical HAZ region of T92 steel and changed the creep failure mode to the "interfacial cracking" between the ferritic steel and the Ni-based weld metal. Consequently, this suppression of the "type IV cracking" failure led to a significant creep life increase of the studied ferritic/austenitic welded joints. K e y w o r d s : dissimilar weldment T92/TP316H, post-weld heat treatment (PWHT), microstructure, creep, type IV cracking, interfacial cracking

The chemical composition of standard Inconel 740 superalloy was modified by changes in the Al/Ti ratio (0.7, 1.5, 3.4) and addition of Ta (2.0, 3.0, 4.0%). Remelted Inconel 740 (A0) and nine variants with various chemical compositions were fabricated by lost-wax casting. The microstructure, microsegregation, phase transformation temperatures, thermal expansion coefficients and hardness of the superalloys were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, differential scanning calorimetry, dilatometry and Vickers measurements. Typical dendritic microstructure was revealed with microsegregation of the alloying elements. Segregation coefficient ki for Ti, Nb and Ta did not exceed unity, and so precipitates enriched mainly in these elements were found in interdendritic spaces. The Nb-rich blocky precipitates, MC carbides, MN nitrides, oxides, and fine γ’ was in all modified castings. Presence of other microstructural features, such as Ti-rich needles, eutectic γ-γ’ islands, small Al-rich and Cr-rich precipitates depended on the casting composition. The lowest solidus and liquidus temperatures were observed in superalloys with a high Al/Ti ratio. Consequently, in A7–A9 variants, the solidification range did not exceed 100 °C. In the A0 variant the difference between liquidus and solidus temperature was 138 °C. Hardness of all modified superalloys was at least 50% higher than for the remelted Inconel 740 (209 HV10).

The main goal of this study was to develop a new processing technology for a high-strength low-alloy (HSLA) steel in order to maximize the mechanical properties attainable at its low alloy levels. Samples of the steel were processed using thermal deformation schedules carried out in single-phase (γ) and dual-phase (γ + α) regions. The samples were rolled at unconventional finishing temperatures, their final mechanical properties were measured, and their strength and plasticity behavior was analyzed. The resulting microstructures were observed using optical and transmission electron microscopy (TEM). They consisted of martensite, ferrite and (NbV)CN precipitates. The study also explored the process of ferrite formation and its influence on the mechanical properties of the material.

In situ X-ray diffraction and transmission electron microscopy has been used to investigate René 108 Ni-based superalloy after short-term annealing at high-homologous temperatures. Current work is focused on characterisation of γ′ precipitates, their volume fraction, evolution of the lattice parameter of γ and γ′ phases and misfit parameter of γ′ in the matrix. Material in the initial condition is characterised by a high-volume fraction (over 63%) of γ′ precipitates. Irregular distribution of alloying elements was observed. Matrix channels were strongly enriched in Cr, Co, W and Mo, whereas precipitates contain large amount of Al, Ti, Ta and Hf. Exposure to high-homologous temperatures in the range 1100–1250 °C led to the dissolution of the precipitates, which influenced the change of lattice parameter of both γ and γ′ phases. The lattice parameter of the matrix continuously grew during holding at high temperatures, which had a dominant influence on the more negative misfit coefficient.

Influence of SPD process realized by ECAP on structural formation and mechanical properties was searched. Samples after ECAP were heat treated at various temperature and time conditions. Investigation material bases were high purity aluminium and aluminium alloys EN AW 6082, EN AW 2014. The best material properties are describing in dependence on experimental conditions.

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