Key Engineering Materials Vol. 822

Abstract: The present research describes the comparison of numerical and physical simulation of hot high strain rate torsion tests for Al-based alloys in order to clarify the accuracy of calculations using basic grades of materials in Deform-3D^TM software. A comparative visual analysis of the results is presented. Obtained data on the distribution of temperatures, strains, stresses and strain rates during the torsion test are discussed.

Abstract: The paper devotes a new general experimental method for studying the anisotropy of conducting materials of various functional purposes. The difference between the presented method and the previously known one is in the high rate of anisotropy assessment, ensuring the possibility of anisotropy assessment of the properties of materials by the volume of the sample or product under investigation during their manufacture or operation. The procedure for measuring the anisotropy of electrophysical properties and the results of the study of some samples are presented.

Abstract: Specimens of pipe steel of increased strength grade type K56-K60, with different values of impact toughness (KCV) were investigated: a metallographic examination of the specimens’ structure was carried out by optical and electron scanning microscopy methods. The interrelation of the microstructure with mechanical properties, in particular with impact toughness and their influence on the nature of fracture pattern is established.

Abstract: Modern shipbuilding yards apply traditional aluminum alloys in production of high-speed vessels, ships with dynamic principles of support, other small vessels and vessel constructions. These alloys provide the low weight for the construction, but have definite disadvantages, which could be improved by application of the new generation Al-Sc-alloy with low concentration of scandium. The developed technology allows to increase durability and to improve other mechanical characteristics, decrease the vessels’ weight, decrease operational costs, increase the operational lifecycle of the production, as well as to achieve some indirect effects. The feasibility study was held to assess the economic effect of applying the new generation Al-Sc-alloy in shipbuilding, which proves its advantages comparing to traditionally used Al-alloys.

Abstract: The structure and properties of discs from cast coarse-grained D16 alloy have been investigated with the help of optical metallography and transmission electron microscopy, after the traditional heat treatment (HT) modes or subjected to high pressure torsion (HPT) under pressure in 6 GPa at room temperature. Standard HT modes included: Т4 (hardening 495°С + natural aging at room temperature for 5 days) and Т6 (hardening 495°С + artificial aging at 185°С for 10 hours). It is shown that after HT of alloy D16 according to modes T6 and Т4, the sizes of the structural elements, compared with the original, decreased by about 4,8 times and the microhardness increased by 1,6 times. It is shown that after one or ten rotates of HPT in D16 alloy the sizes of structural elements, in comparison with initial, decreased by 393 and 899 times, and microhardness increased by 2,4 and 2,9 times, respectively. Detection of hardening hard, brittle and high-alloy copper γ2- phases (Cu₉Al₄) indicates the passage in the HPT process of the decomposition of a supersaturated solid solution (dynamic aging) in the planes of a local shift.

Abstract: The tendency of the aluminum alloy D16 system Al-Cu-Mg to natural (NA) and artificial aging (AA) after hardening and high pressure torsion (HPT) under a pressure of 6 GPa at room temperature was studied using optical metallography, scanning electron microscopy, electrical conductivity tests. The dependences of microhardness and electrical conductivity were constructed depending on the exposure time. It is shown that heat treatment (HT) (hardening + HPT + NA) leads to an increase of hardening of the alloy D16 compared to standard HT (T4) in 2,3 times, at preservation of level of conductivity.

Abstract: This article is devoted to the study of the mechanism of formation of dissimilar welded joints Ti-2Al-1.5Mn, pure titanium (Ti35A) and aluminum (Аl (pure), Аl-6Mg-0.5Mn) alloys obtained by friction stir welding (FSW). The investigated microstructure of the weld joint nugget (WN), zones of thermo mechanically affected zone (TMAZ) and heat affected zone (HAZ) formed at FSW between Ti-2Al-1.5Mn, Ti35A and aluminum (Аl (pure), Аl-6Mg-0.5Mn) alloys. Zones of welded joints at FSW are formed in the mode of structural superplasticity (SP) with a specific shear-band layered structure with alternating layers. The achievement of superplastic state (SPS) in the formation of WN, TMAZ, HAZ is provided by the step–by–step transformation of various mechanisms of plastic deformation in the mode of simple, collective, abnormal dynamic recrystallization, prepared by the processes of dynamic return, polygonization with the transition to post-dynamic recrystallization by the mechanisms of Bailey–Hirsch, Kahn-Burgers-Taylor. At FSW aluminum and titanium alloys with polymorphism, SPS is supported additionally due to recrystallization by twinning and as a result of phase transformations of alpha-gamma or alpha-beta phases.

Abstract: Materials with high content of rare-earth elements can be used for the manufacture of structural elements of containers for the transport of spent nuclear fuel. The combination of methods of powder metallurgy and methods of intensive plastic deformation allows to introduce a greater number of additives into the composition of the material than in the classical metallurgical processes. The article shows the possibility of using a combination of friction stir welding and friction stir processing in order to create a layered composite with a high content of rare-earth elements.

Abstract: The temperature influence on the microstructure evolution and microhardness of the age-hardenable aluminium alloy 6082 T6 during friction stir welding was defined. In order to achieve this aim, the thermocycles calculated using the developed 3D Finite Element Model were physically simulated on the Gleeble-3800 in the points which located in the different zones of the weld. The microstructure in the chosen points after Gleeble testing was investigated as well as the microhardness was measured. The results were consequently compared with the relevant results obtained after friction stir welding. It was shown that the microstructure and microhardness profile are influenced not only by temperature but by deformation. The increase in hardness in different zones after FSW compared to Gleeble testing can be explained by the grain refinement in the nugget zone as well as the hardening precipitate distribution along the weld which can occur more rapidly due to the deformation influence.

Abstract: Welded metal porosity significantly influences the mechanical properties of dissimilar metal joints. In this study, the comparison of porosity evaluation methods was held using the sample of welded-brazed zinc coated steel and Al-Mg-alloy plates joint. Relative porosity was measured through cross-sections’ images area analysis, as well as it was evaluated through 3D-fitting of spotted on these images pores. Area and size of pores was measured, volume and distribution were evaluated. It was found that relative porosity values estimated by 2D and 3D methods are equal.