Torsional severe plastic deformation method for metal bar, employing surface polishing to improve mechanical properties of metal bar

Abstract

The present invention relates to a torsional severe plastic deformation method for a metal bar to which surface polishing is applied to the metal bar to improve the mechanical properties of the metal bar. According to an embodiment of the present invention, there is provided a torsional severe plastic deformation method for a metal bar, which includes: applying torsion to a metal bar; and removing a surface defect on the surface of the metal bar, the surface defect being caused by the applying of torsion, wherein the removing of the surface defect is carried out in a continuous manner in which the removing of the surface defect is performed together with the applying of torsion or in a discontinuous manner in which the applying of torsion is temporarily stopped and then the applying of torsion is performed, and the removing of a surface defect increases the amount of torsional rotation or the shear strain applied to the metal bar.

Description

TECHNICAL FIELD[0001]The present invention relates to a torsional severe plastic deformation method for a metal bar, to which surface polishing is applied, and more particularly, to a torsional severe plastic deformation method for a metal bar that is capable of improving the mechanical properties of a material by forming a gradient structure through shear deformation formed by applying a huge shear stress through torsion while substantially maintaining the shape of the metal bar, and by ultrafine crystallization or nano-crystallization of fine structures of a metal pipe material.BACKGROUND ART[0002]When plastic deformation is applied to a metal material, a dislocation cell structure having a small boundary angle is formed, and a phenomenon occurs in which the greater the amount of plastic deformation, the greater the crystal grain boundary angles of dislocation cell sub-grains, and the finer crystal grains gradually become. Using this, when a large plastic deformation is applied to...

AI Technical Summary

Benefits of technology

The present invention provides a torsional severe plastic deformation method that can form a gradient structure of crystal grain sizes, ultrafine crystallize fine structures, and improve the mechanical properties of materials. This method can also adjust torsional deformation and mechanical properties by adjusting a rotation speed, making it easy to reinforce the physical properties of metal bars and adjust fine structures of the metal bars. Additionally, this method can apply a more amount of deformation than existing torsional deformation through surface polishing, thus increasing the degree of gradient and fine crystallization of fine structures.

Problems solved by technology

A gradient structure may be formed through a high-pressure torsion (HPT) process among the existing sever plastic processing methods, but this processing method has a disadvantage that the size of the produced material is limited because of requiring high pressure.

Thus, a defect is caused on the surface to which the largest amount of deformation is applied, and a shear fracture phenomenon proceeds at the point at which the defect occurs while a process proceeds.

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