International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

ECAP was carried out with a gradual decrease in temperature and an increase in the number of passes on two medical magnesium alloys: WE43 (Mg-3.56%Y-2.20%Nd-0.47%Zr) and ZX10 (Mg-1.0%Zn-0.3%Ca). It was shown that ECAP leads to a significant refinement of the alloys structure. For ZX10 alloy, the average grain size after ECAP decreased from ~ 105 μm in the initial state to 8 ± 0.18 μm in the longitudinal section and to 4 ± 0.19 μm in the transverse one. For the WE43 alloy, the average grain size was changed from 70 μm to 0.69 ± 0.13 μm and the precipitation of particles of the Mg41Nd5 phase with an average size of 0.45 ± 0.18 μm was also discovered. At the same time, the grain refinement led to an increase in the strength characteristics of the both alloys (including fatigue strength), and increased prismatic slip activity (along with the formation of an inclined basal texture in ZX10 alloy) led to an increase in their ductility. The alloy structure formed during the ECAP process does not lead to a decreasing in resistance to chemical corrosion.

Structural changes on the surface of R260Mn grade rails, developed during wheel/rail contact were investigated by optical microscopy, electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD) in scanning electron microscope (SEM) and transmission electron microscopy (TEM) The microstructures of the heavily deformed surface layer known as white etching layer (WEL) and the deformed under layer were characterized in different length scales. Ferrite grain fragmentations and grain alignment in normal direction, (perpendicular to traffic direction) are characterized by all applied methods. Substructures, having misorientations lower than 5°, are identified by analysing the local misorientation maps (kernel average misorientation (KAM)). Retained austenite was detected in the WEL by XRD, EBSD and TKD. Detection of retained austenite and ultrafine grain structure were considered as an indication for mixed mechanism of formation of the WEL where both martensitic transformation and severe plastic deformation take place.

The paper describes the metrological activity in D.I. Mendeleev Institute for Metrology (St.-Petersburg, Russia) in the field of dilatometric research of solids. The main attention is paid to standard reference materials and standard samples of Thermal Expansion.

The texture evolution in pipeline steel is studied as a function of the thermo-mechanical processing parameters –rolling tem- perature and cooling rate after the finish rolling stage carried out with equal rolling reduction per pass.. The austenite recrystallization and grain growth during thermo-mechanical control processing (TMCP) of a pipeline steel grade are described and analysed in terms of precipi- tation state progress. Two stage controlled rolling (roughing and finishing) was carried out on a laboratory rolling mill for a set of complet- ed and interrupted schedules. Subsequent to rolling, two different cooling routes were used water quenching and accelerated water cooling (ACC) together with coiling simulation. From the combination of transmission electron microscopy (TEM) observations, detailed texture analysis and inductively coupled plasma-mass spectroscopy (ICPMS) precipitates quantification, consistent correlations between precipita- tion state and microstructure at every stage of TMCP can be recognized. The formation of specific transformation textures was explained via appropriate texture models that describe both formation of transformation and recrystallization textures in the austenite.

Due to technological particularities of low carbon low alloy API 5L X80 steels producing they have strong texture and its inhomogeneity on plate thickness. Charpy impact tests at ambient and negative temperatures and investigation of texture of samples of API 5L X80 steel were performed. By the method of X-ray structural analysis DPF, IPF and ODF were obtained. Texture components and their volume fraction were determined. It was shown that correlation between volume fractions of main texture components, misoriented grains fraction and DBTT exists. As a result analysis of texture parameters allowed characterization of effect of texture on cold resistance of low carbon low alloy API 5L X80 steel.

In the present work, the magnesium alloy WE43 (Mg-Y-Nd-Zr) after high pressure torsion (HPT) was investigated. HPT was conducted at room temperature, 200 °C or 300 °C. As a result of HPT processing, a large number of twins with the twin size of 0.4 − 8.1 µm were formed. Furthermore, the HPT process led to the formation of a very fine grain structure with the average grain size of 30 – 100 nm. The deformation by HPT caused the formation of a displaced basal texture, which sharpens with an increase in the deformation temperature. The refinement of the microstructure brought about an improvement of the microhardness of the alloy over the as-received condition. The microhardness after HPT at the room temperature increased up to 1189 ± 33MPa compared with 774 ± 50 MPa in the initial state. A subsequent aging after HPT led to an additional strengthening to a level of 1411 ± 40 MPa. It was noted that thermal stability of strengthening caused by HPT did not depend on the deformation temperature and sustained up to 250 °C.