A. E. Shelest

Effect of the quasi-continuous equal-channel angular pressing on the structure and functional properties of Ti–Ni-based shape-memory alloys

The effect of severe plastic deformation by equal-channel angular pressing (ECAP) under normal and quasi-continuous regimes on the structure and the mechanical and functional properties of a Ti–50.2 at % Ni shape-memory alloy (SMA) has been studied. ECAP was carried out at an angle of intersection of channels of 120° in the normal regime with heating between passes at 450°C for 20 passes and in the quasi-continuous regime at the temperature of 400°C for three, five, and seven passes. The hot screw rolling with subsequent annealing at 750°C for 30 min and cooling in water was used as a control treatment (CT). A mixed submicrocrystalline and nanosubgrained structure was formed. The increase in the number of passes from three to seven led to a decrease in the average size of structural elements from 115 ± 5 to 103 ± 5 nm and to an increase in the fraction of grains/subgrains having a size less than 100 nm. After ECAP (seven passes) and post-deformation annealing at the temperature of 400°C for 1 h, a completely recoverable strain was 9.5%; after normal ECAP, 7.2%; after CT, 4.0%.

Effect of copper additions on the mechanical properties of iron

The effect of copper alloying on the mechanical properties of iron is studied. Alloying of a model material (armco-iron) with 0.2–2.0% Cu is shown to increase the strength characteristics by a factor of 1.5–2.5 and to decrease the ductility by 8–60%.

Forming index for metal forming

An index that takes into account the deformation-kinematic and thermomechanical parameters of metal forming is proposed to estimate and compare metal forming processes. This index represents the product of the strain resistance and the cumulative shear strain. The values of this index are calculated for real piercing processes in various tube rolling mills, and the deformation conditions of the mills located at the OAO Pervoural’sk Novotrubnyi Plant are compared.

Stampability Parameters of Automotive Steel

The methods of estimating the plasticity of sheet metals subjected to standard and nonstandard tests of their mechanical and technological properties have been analyzed and compared. A strain-hardening exponent and a coefficient of normal plastic anisotropy are found to adequately characterize the stampability of metals. It is demonstrated that a plastic stability criterion can be used to estimate the energy required for metal forming at the stage of uniform deformation.

Refinement of the technique of plotting the flow curves of a metal to predict its hardening in alternating cold plastic deformation

The technique of plotting the flow curves of a metal, which describe the true strain as a function of the true principal strain intensity, is refined. The forms of analytical representation of these curves are substantiated. Using copper as an example, we show that the flow curves of a metal in a softened state can be used to predict its hardening in cold deformation. The alternating deformation of commercial-purity copper on a mangle is shown to increase its conventional yield strength substantially.

Mechanical and functional properties of commercial alloy TN-1 semiproducts fabricated by warm rotary forging and ECAP

The influence of various thermomechanical treatment schemes, which include rotary forging and severe plastic deformation by equal-channel angular pressing, on the structure and the mechanical and functional properties of TiNi alloys is studied. Treatment according to these schemes is shown to result in the formation of a mixed nano- and submicrocrystalline structure with a high dislocation density, which ensures high mechanical (σ0.2 = 760–954 MPa, σu = 917–1097 MPa, δ = 21–51%) and functional (maximum completely recoverable strain of 6.8–8%) properties.

Plastic deformation nonuniformity and localization during metal forming

The nonuniformity of deformation of metallic materials during metal forming, the causes of its appearance, its mechanisms, the effect of the deformation nonuniformity on the limiting strain of a billet, the loss of stability and its causes during plastic deformation are discussed. Experimental results are given for the loss of stability during longitudinal flat rolling. These results are important for understanding metal flowing under various loading conditions.

Work during screw rolling

A new technique is proposed to determine the specific volume work of deformation during screw rolling. Methods for determining the work of deformation in various sections of the deformation zone in a piercing mill are considered. The dependence of the work of deformation on the reduction in the deformation zone is obtained. A new approach is proposed to calculate the fracture sensitivity and the working of the structure of continuously cast round billets. The effect of the reduction ratio on the work of deformation in similar piercing mills located at OAO Pervoural’sk Nonvotrubnyi Plant and the Yuzhnotrubnyi Plant is estimated.