Materials Science Forum Vols.503-504(2006)pp.335-339 online at http://www.scientific.net C(2006)Trans Tech Publications,Switzerland Application of Twist Extrusion Viktor Varyukhin Yan Beygelzimer,Sergey Synkov and Dmitry Orlove Donetsk Physics Technology Institute of the NAS of Ukraine,72 R.Luxembourg St.,Donetsk, 83114,Ukraine. var@hpress.dipt.donetsk.ua,tean@an.dn.ua,orlov@donec.net Keywords:Twist Extrusion,powder,nanostructured materials,fragmentation,consolidation. Abstract.Twist Extrusion (TE)is a process of severe plastic deformation(SPD)being developed by us during recent 5 years.Upon this time we published few papers on mechanics of the process and influence of the TE processing on materials structure and properties.Here we reported some results on application of the twist extrusion processing and made few general conclusions. Peculiarities of Twist Extrusion Mode of TE functioning is obvious from the Fig.1. Fig.1.Scheme explains basic principle of twist extrusion processing In [1,2]it was shown that in first approximation each physical cross-section of a billet is deformed at the same way as thin disk under high pressure torsion(HPT)processing.At that,at the beginning it is realized torsion at some angle in one direction,and then re-torsion at the same angle in the opposite direction.I.e.the deformation is cyclic with amplitude of quasi-monotone part equals to a half of the full strain.For dies we use usually,the accumulated strain per pass is about 1.2 [2].Follow the billet's form does not changes during the treatment,it is possible to deform it over and over again in order to accumulate strain like this is done under ECAP processing. It is followed from the previous paragraph that TE is three-dimensional option of the HPT,in some terms.On the other hand,per se TE is equal channel extrusion,i.e.similar to ECAP.It is arisen the following question:what new this process can give and why one needs to concern oneself with it?From our point of view TE has a number of peculiarities in both stress-strain state and technological implementation which do this process attractive for both investigation and application. From the viewpoint of the stress-strain state of the specimen,there are four important properties: First,the simple shear plane in TE is perpendicular to the axis of the specimen,instead of being at 45-60 degrees as in ECAP.This allows us to obtain new structures and textures.Moreover, deformation by ECAP and TE in various combinations and regimes increases the number of possible deformation paths:besides paths achievable by ECAP only,one can obtain different combinations with paths achievable by TE (deformations in the same die and pipelined deformations through a die with oppositely twisted channels). Second,TE has the property that the deformation gradient is quite steep in the cross-section area, which makes TE similar to HPT.Note that this is not true for ECAP.There are still very few results about the effects of the deformation gradient on the structure and properties of materials,but there is enough evidence pointing to the fact that by increasing the gradient one can intensify grain refinement in metals and increase their ductility [3].Application of Twist Extrusion Viktor Varyukhina , Yan Beygelzimerb , Sergey Synkov and Dmitry Orlovc 1 Donetsk Physics & Technology Institute of the NAS of Ukraine, 72 R. Luxembourg St., Donetsk, 83114, Ukraine. a var@hpress.dipt.donetsk.ua, b tean@an.dn.ua, c orlov@donec.net Keywords: Twist Extrusion, powder, nanostructured materials, fragmentation, consolidation. Abstract. Twist Extrusion (TE) is a process of severe plastic deformation (SPD) being developed by us during recent 5 years. Upon this time we published few papers on mechanics of the process and influence of the TE processing on materials structure and properties. Here we reported some results on application of the twist extrusion processing and made few general conclusions. Peculiarities of Twist Extrusion Mode of TE functioning is obvious from the Fig. 1. Fig. 1. Scheme explains basic principle of twist extrusion processing In [1,2] it was shown that in first approximation each physical cross-section of a billet is deformed at the same way as thin disk under high pressure torsion (HPT) processing. At that, at the beginning it is realized torsion at some angle in one direction, and then re-torsion at the same angle in the opposite direction. I.e. the deformation is cyclic with amplitude of quasi-monotone part equals to a half of the full strain. For dies we use usually, the accumulated strain per pass is about 1.2 [2]. Follow the billet’s form does not changes during the treatment, it is possible to deform it over and over again in order to accumulate strain like this is done under ECAP processing. It is followed from the previous paragraph that TE is three-dimensional option of the HPT, in some terms. On the other hand, per se TE is equal channel extrusion, i.e. similar to ECAP. It is arisen the following question: what new this process can give and why one needs to concern oneself with it? From our point of view TE has a number of peculiarities in both stress-strain state and technological implementation which do this process attractive for both investigation and application. From the viewpoint of the stress-strain state of the specimen, there are four important properties: First, the simple shear plane in TE is perpendicular to the axis of the specimen, instead of being at 45-60 degrees as in ECAP. This allows us to obtain new structures and textures. Moreover, deformation by ECAP and TE in various combinations and regimes increases the number of possible deformation paths: besides paths achievable by ECAP only, one can obtain different combinations with paths achievable by TE (deformations in the same die and pipelined deformations through a die with oppositely twisted channels). Second, TE has the property that the deformation gradient is quite steep in the cross-section area, which makes TE similar to HPT. Note that this is not true for ECAP. There are still very few results about the effects of the deformation gradient on the structure and properties of materials, but there is enough evidence pointing to the fact that by increasing the gradient one can intensify grain refinement in metals and increase their ductility [3]. Materials Science Forum Vols. 503-504 (2006) pp. 335-339 online at http://www.scientific.net © (2006) Trans Tech Publications, Switzerland All rights reserved. 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