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Analysis of the Effect of Rolling Speed on the Capability to Produce Bimodal-Structure AZ31 Alloy Bars in the Three-High Skew Rolling Mill

Stefanik A., Szota P., Mróz S.

Archives of Metallurgy and Materials

2020

Vol. 65, iss. 1

329--335

A numerical analysis of the process of single-pass rolling of AZ31 magnesium alloy bars in the three-high skew rolling mill has been carried out in the study. Based on the obtained investigation results, the effect of rolling speed on the band twist and the state of stress and strain occurring in the rolled band has been determined. From the obtained results of the numerical studies it has been found that with the increase in rolling speed the unit band twist angle θ, increase, which translates into an increase in the value of tangential stress in the axial zone of the rolled bar. This contributes directly to an increase in redundant strain in the rolled bar axial zone, which brings about a structure refinement. To verify the effect of rolling speed on the flow pattern and the stress and strain state, experimental tests were carried out. It has been found from the tests that the band twist (flow pattern) contributes to obtaining a bimodal structure in the bar cross-section.

Microstructure evolution and property analysis of commercial pure Al alloy processed by radial-shear rolling

Gamin Yu. V., Akopyan T. K., Koshmin A. N., Dolbachev A. P., Goncharuk A. V.

Archives of Civil and Mechanical Engineering

2020

Vol. 20, no. 4

674--683

The features of microstructure formation and properties of commercial pure aluminum alloy (Al 99.5%) obtained by radial-shear rolling (RSR) method at the different heating temperatures of 25, 200, 250, 300 and 350 °C were examined. In this paper, the rods with diameter of 14 mm were obtained from initial billet with diameter of 60 mm in five passes. The microstructure analysis with electron backscatter diffraction (EBSD), measurements of microhardness HV over cross-section, and tension test for determination of mechanical properties were carried out for these rods. The FEM simulation of RSR process and calculation of Zener–Hollomon parameter (Z) were carried out with Software QFORM. The obtained rods have the gradient microstructure typical of RSR characterized by surface layer with ultrafine grain structure (UFG) and grain size from 0.3 to 5 µm. In the central part of rod, the fiber deformed structure with minimal fraction of recrystallized grains (< 5%) is formed. This combination is optimal for simultaneous achievement of high strength (UTS ~ 107–110 MPa; YS ~ 100–109 MPa; ~ 35–40 HV) and ductility (El ~ 15–30%). The most intensive growth of plastic properties is observed at rolling temperatures close to the temperature of the onset of recrystallization, it is associated with additional deformational heating of surface layers and the formation of partially recrystallized structure. The obtained distribution dependences of average size of dynamic recrystallized grain on Zener–Hollomon parameter showed that the decrease in parameter Z leads to the increase in size of recrystallized grain for RSR process.

Study of Technology for Ultrafine-Grained Materials for Usage as Materials in Nuclear Power

Naizabekov Abdrakhman, Arbuz Alexandr, Lezhnev Sergey, Panin Evgeniy, Knapiński Marcin

New Trends in Production Engineering

2019

Vol. 2, Iss. 2

114-125

Nuclear power is associated with great environmental risks. In many cases, the problem of accidents of nuclear power plants is related to the use of materials that do not fully meet the following requirements: high corrosion resistance; high temperature resistance; creep resistance; fracture toughness; stability of structure and properties under irradiation. Therefore, studies aimed at finding materials that can withstand long-term loads at high temperatures, aggressive environment and gradual structural degradation under the influence of radiation are relevant. One of the structural materials, which has high resistance to radiation, is austenitic stainless steel. And one of the ways to increase the radiation resistance of parts made of this steel grade is to grind its microstructure to ultra-fine-grained state. Such structures provide a combination of a high level of strength characteristics with high plasticity, which distinguishes such materials from their coarse-grained counterparts. Also, numerous grain boundaries serve as runoff surfaces for radiation defects, preserving the structure, which causes their increased radiation resistance. From all methods for producing sub-ultra-fine grained materials the most promising is the severe plastic deformation (SPD), which can be implemented in the metal in various ways, including radial-shear rolling. This paper presents the results of studies of the process of radial-shear rolling on the mill SVP-08 and its effect on the microstructure and properties of austenitic stainless steel. During the study, bars with a diameter of 13 mm from AISI-321 steel with a grain size of 300-600 nm were obtained, while the mechanical properties increased more than 2 times compared to the initial values.