The paper presents the results of finite element analysis of plastic deformation in the contact zone of dissimilar superalloys subjected to pressure welding. The results are compared for the two cases: with and without relief on the surfaces of parts to be welded. It is shown that the relief made on the surface can either decrease or increase the area of deformation stagnant zones, depending on the relief shape. The results of simulations are compared with the experimental test results.

Pressure welding (PW) is an advanced method for obtaining solid phase joints (SPJs). Using physical and finite element modelling (FEM) it is shown that PW under superplasticity conditions provides SPJs between dissimilar cast single-crystal intermetallic and deformed polycrystalline heat-resistant Ni-based superalloys. Special attention is paid to exclude the stagnant zones in the solid phase joining region using surface relief. The results of physical modelling and FEM are in qualitative agreement. It is revealed that the surface relief can decrease the stagnant zone and increase localisation of deformation in the joining region, which helps to improve the joining quality. A monotonous change in microhardness in the joint zone is shown.

Studies on the process of multiple isothermal forging of high-temperature nickel-based EK61 superalloy using computer simulation in the DEFORM-3D software package in a three-dimensional formulation and a comparison with experimental data were carried out. Based on the simulation results, it is shown that with each subsequent stage of forging, the maximum strain values become higher, and the strain differences in the central and peripheral regions become smaller. Such a strain distribution leads to the formation of a homogeneous ultrafine-grained (UFG) microstructure. The initial coarsegrained microstructure is gradually transformed into a fine-grained microduplex type microstructure at 0.77T melt and with a further decrease in the processing temperature to 0.73T melt , it is transformed into a submicroduplex type (γ + δ) UFG microstructure.

The work is devoted to a study of the microstructure and microhardness of the heat-resistant nickel-based superalloy 58Ni-Cr-Mo-B-Al-Cu after radial-shear rolling. The radial-shear rolling was carried out at a temperature of 925°С in three stages. It was found that the grain size of γ-phase after all rolling stages decreased in the radial direction from the center to the periphery from 62 ± 2 to 2.5 ± 0.2 µm. At the third rolling stage, the grains size was reduced twice in the billet center in a comparison to the initial state. At the same time, individual grains with a size of 100 μm in the billet surface are observed, and grains with a size of 1±0.1 μm are present at the periphery. The microhardness changes in inverse proportion to the grain size, the values increase in the radius direction. The maximum microhardness value is achieved in the peripheral part of the sample and is equal to 5.4 ± 0.6 GPa. According to the EBSD analysis, there is no texture at the billet periphery, but at the middle of the radius there is a two-component axial texture of the <001> + <111> type along the billet axis. The billet center is characterized by the presence of a more pronounced two-component axial texture of the <001> + <111> type along the billet axis. The obtained results indicate the possibility of the gradient structure formation by radial-shear rolling in the heat-resistant nickelbased superalloy 58Ni-Cr-Mo-B-Al-Cu with the initial coarse-grained structure.

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