Features of Twist Extrusion: Method, Structures & Material Properties

Yan Y. Beygelzimer ,  Dmitry Orlov ,  Sergey Synkov ,  Victor M. Varyukhin ,  Alexey Reshetov ,  Alexandr Synkov 

Donetsk Physics & Technology Institute of the National Academy of Sciences of Ukraine (DonPhTI NASU), 72 R. Luxembourg St., Donetsk 83114, Ukraine

Abstract

As it was shown during last decade, severe plastic deformation (SPD) is very effective method of grain refinement aimed to ultra-fine grained and nanostructured materials obtaining.The basic SPD techniques are High Pressure Torsion (HPT) and Equal Channel Angular Extrusion (ECAE).Recently they were developed several new techniques: 3D forging, Accumulative Roll Bonding, Twist Extrusion (TE), Constrained Groove Pressing, Repetitive Corrugation and Straightening, etc. Twist extrusion was proposed by Prof.Beygelzimer in 1999 and is being developed by all the authors during last 5 years.Under TE each billet's cross-section is deformed similarly to thin disk under HPT.But unlike it, the deformation is cyclic: at first billet becomes twisted at some angle in one direction, and then - re-twisted at the same angle in opposite direction.In comparison with other SPD techniques, TE has few essential features.Plane of simple shear is perpendicular to a billet axis (in contrast to 45-60 degrees in ECAE).Intense flows of material being deformed within cross-section of a billet.During the processing billet's surface expands by ~80% in twisted part and shrinks to original size upon exiting it.Size of distorted areas of a billet is smaller than under ECAE.Possibility to handle profile billets including those with axial channel.Relative simplicity of TE installation into standard tool due to constant extrusion axis.Our experiments on primary and recycled Al alloys, Cu, Ti, and Ni-base superalloys showed effectiveness of TE in both grain refinement and mechanical properties improving.So, we obtained in the above metals ultra-fine grained structure quite homogeneously distributed in a billet cross-section and length.The mechanical properties are also uniform.This is confirmed by Microhardness and tension tests data.For Ti alloys we observed anisotropic (in longitudinal and transversal directions) mechanical properties.But this anisotropy was eliminated by following rolling.

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Presentation: invited oral at E-MRS Fall Meeting 2005, Symposium I, by Dmitry Orlov
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-04-30 17:19
Revised:   2009-06-07 00:44
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