Effect of Process Parameters on the Microstructure and Mechanical Properties of Bars from Al-Cu-Mg Alloy Processed by Multipass Radial-Shear Rolling

The study of microstructure and mechanical properties formation of A2024 alloy obtained by the multipass radial-shear rolling (RSR) method is discussed in this article. FEM simulation was carried out that made it possible to evaluate the influence degree of rolling temperature-velocity parameters on the strain state of material. It has been found the increase in rotary velocity of rolls significantly influences on the deformation heating of bar after RSR (predominantly in its surface layer). The combination of rolling temperature-velocity conditions at selection of deformation regime has complex effect on structure and properties formation. The analysis of sizes and distribution of phase particles has shown that the rolling at lower temperatures allowed to increase the mechanical strength due to the more intensive refinement of undissolved Fe-containing phase. The gradual decrease in the rolling temperature in each pass makes possible to achieve the high strength (UTS~430 MPa and YS~255 MPa) while maintaining the ductility level ~15%, that are comparable to ones obtained at some severe plastic deformation (SPD) methods.

Development of Alternative Method for Manufacturing Structural Zirconium Elements for Nuclear Engineering

Zirconium is used as a structural material for use in aggressive environments, including the core of nuclear reactors. The traditional technology of manufacturing the structural elements of zirconium nuclear reactors is characterized by a long technological process and a significant amount of waste in the form of metal shavings. The paper presents the results of an alternative technology, spark plasma sintering, for manufacturing zirconium products. A complex of microstructural and mechanical studies of the obtained samples was carried out according to the ASTMB-351 standard. The sintering of zirconium powder and options for subsequent processing by various methods, including non-standard ones such as radial shear rolling, are justified.

Recycling of stainless steel bar scrap by radial-shear rolling to obtain an ultrafine-grained gradient structure

This work is devoted to the study of the possibility of recycling bar scrap of stainless metals using radial-shear rolling. In the course of studies on the deformation of bar scrap in the form of pins made of 12X18N9T stainless austenitic steel on a radial-shear rolling mill, the resulting bar was obtained microstructure of two different types: on the periphery an equiaxed ultrafine-grained structure with a grain size of 0.4–0.6 microns was formed; in the axial zone anoriented, banded texture was obtained. This discrepancy in the structure of the peripheral and axial zones, together with the results of cross-section microhardness measurements of samples made of 12X18N9T austenitic stainless steel with a total degree of deformation of 44.4 %, indicates the gradient nature of the resulting microstructure.

Formation of a Gradient Structure in Austenitic Stainless Steel AISI 321 by Radial-Shear Rolling

One of ways to increase the strength of a structural material is to grind its microstructure to an ultra-fine-grained state. But with the simultaneous increase in strength properties in ultrafine materials, there is an inevitable decrease in its plastic properties. The use of metal materials with a gradient structure is an effective way to solve the problem of increasing the plasticity of metal products in general. This work is devoted to the study of the possibility of a gradient structure forming in austenitic stainless steel AISI-321 using radial-shear rolling. The results of the studies showed that the UFG-structure extends in the bar from its surface to a depth of at least a quarter of the radius of the bar. The transition zone is in the region between 0.5 R and 0.25 R of the bar section. Anything deeper is rolling texture. Due to the structural heterogeneity of the cross-section of the bar, there is a smooth drop in the micro-hardness of the central zone of the bar by 10.2 %. All this testifies to the gradient character of the structure formed in bars of AISI-321 steel deformed on the radial-shear rolling mill.

Radial-shear rolling as a new technological solution for recycling bar scrap of ferrous metals

Waste recycling of both ferrous and non-ferrous metals is a useful process for the economy of any country. This paper proposes a new technology for recycling bar scrap of ferrous metals by rolling it in radial-shear rolling mills by producing a commercial product in the form of bars with an ultrafine-grained gradient structure. Studies have shown that the deformation of bar scrap in the form of pieces of reinforcement made of steel grade 18G2S in a radial-shear rolling mill makes it possible to significantly disperse its structure by producing a gradient ultrafine-grained structure, and this, in turn, leads to the elevating of the mechanical characteristics of this steel grade. Thus, the tensile limit of the 18G2S grade steel deformed on the radial-shear rolling mill was 620 MPa (at the initial value of 365 MPa).