336 Nanomaterials by Severe Plastic Deformation Note that experiments done on Al-Mg-Sc-Zr alloys shown quite homogeneous distribution of grain size and microhardness within the billet cross-section [4]. Third,TE (unlike ECAP)is characterized by intense flows of material being deformed within cross-sections of the billet.This is very important when deforming powder materials since it intensifies consolidation processes. Finally,TE is also characterized by a significant nonmonotone change of specimen surface while the specimen goes through the die:Upon entering the twisted region,the surface expands (by 70- 80%),and it returns to its original size upon exiting the region.Such changes affect metal structure and could allow one to insert various alloying elements into surface layers of the billet. From the technological viewpoint,TE has the following properties: First,the size of terminating,distorted areas of the specimen is much smaller under TE than under ECAP [2],which is especially important when doing repeated runs. Second,TE can handle profile billets including those with the axial channel [1]. Third,TE can easily be performed on any standard extrusion equipment by putting a twist die in place of the standard die. Finally,TE (unlike ECAP)does not change the direction of the billet moving which allows one to embed TE into already existing industrial lines. The last two properties of TE were pointed out to us by Dr.Rack.We would like to thank Dr. Rack for valuable comments about TE. Due to the properties of mentioned above,TE seems very promising for obtaining UFG materials,both via metals'grain refinement and via powder consolidation.We have previously described(see,for example,[1-9])grain refinement under twist extrusion.In this paper,we show that twist extrusion allows one to refine strong coarse particles without fracture of metals.We also give examples of consolidation of powder with amorphous and nano-crystalline structure. Materials and Experimental procedure First material used for these experiments was Al-3 wt.%Mg-0,3 wt.%Sc-0,15 wt.%Zr alloy! poured into a water-cooled copper mold and machined in 18x28x80 mm'bars.No thermal treatments or other processing were used before the TE processing.The TE was performed at elevated (280-300C)temperatures.The additional forced backpressure during the processing was about 200 MPa.It was performed 5 TE passes through 60 die for all the billets (accumulated equivalent strain e~5.8). Second material was oxygen-free high-purity copper powder2.The powder was produced via Plasma Rotating Electrode Process (PREP)in inert gas medium.Its fractional size was about 200 um;grain size (measured by X-ray diffraction technique)in the powder was 60-80 nm.The powder was pre-pressed in a copper can to 70%density.And twist extruded with the following parameters:temperature of deformation is 473 K;backpressure is about 200 MPa;true strain per pass is about 1.2 [2].Maximal pressure during the processing was about 1000-1300 MPa.It was performed the following processing of the billets: Billet I:Circle 28 mm in diameter>rectangle 18x28 mm2+1 TE pass; Billet II:Circle 28 mm in diameter>rectangle 18x28 mm2+2 TE passes; I The study was performed jointly with research group of Professor Milman from Frantcevich Institute for Problems of Materials Science,Kiev,Ukraine.Results of this research reported more in detail in paper [D.Orlov,A.Reshetov, A.Synkov,V.Varyukhin,D.Lotsko,O.Sirko,N.Zakharova,A.Sharovsky,V.Voropaiev,Yu.Milman and S.Synkov "Twist Extrusion as the Tool for Grain Refining in Al-Mg-Sc-Zr Alloys"//Proceedings of NATO ARW 'Nanostructured materials by high pressure severe plastic deformation',September 22-26,2004,Donetsk,Ukraine]. 2 The powder was supplied by group of Professor Firstov from Frantcevich Institute for Problems of Materials Science, Kiev,UkraineNote that experiments done on Al-Mg-Sc-Zr alloys shown quite homogeneous distribution of grain size and microhardness within the billet cross-section [4]. Third, TE (unlike ECAP) is characterized by intense flows of material being deformed within cross-sections of the billet. This is very important when deforming powder materials since it intensifies consolidation processes. Finally, TE is also characterized by a significant nonmonotone change of specimen surface while the specimen goes through the die: Upon entering the twisted region, the surface expands (by 70- 80%), and it returns to its original size upon exiting the region. Such changes affect metal structure and could allow one to insert various alloying elements into surface layers of the billet. From the technological viewpoint, TE has the following properties: First, the size of terminating, distorted areas of the specimen is much smaller under TE than under ECAP [2], which is especially important when doing repeated runs. Second, TE can handle profile billets including those with the axial channel [1]. Third, TE can easily be performed on any standard extrusion equipment by putting a twist die in place of the standard die. Finally, TE (unlike ECAP) does not change the direction of the billet moving which allows one to embed TE into already existing industrial lines. The last two properties of TE were pointed out to us by Dr. Rack. We would like to thank Dr. Rack for valuable comments about TE. Due to the properties of mentioned above, TE seems very promising for obtaining UFG materials, both via metals’ grain refinement and via powder consolidation. We have previously described (see, for example, [1-9]) grain refinement under twist extrusion. In this paper, we show that twist extrusion allows one to refine strong coarse particles without fracture of metals. We also give examples of consolidation of powder with amorphous and nano-crystalline structure. Materials and Experimental procedure First material used for these experiments was Al – 3 wt.%Mg – 0,3 wt.%Sc – 0,15 wt.%Zr alloy1 poured into a water-cooled copper mold and machined in 18x28x80 mm3 bars. No thermal treatments or other processing were used before the TE processing. The TE was performed at elevated (280-300ºC) temperatures. The additional forced backpressure during the processing was about 200 MPa. It was performed 5 TE passes through 60º die for all the billets (accumulated equivalent strain е≈5.8). Second material was oxygen-free high-purity copper powder2 . The powder was produced via Plasma Rotating Electrode Process (PREP) in inert gas medium. Its fractional size was about 200 µm; grain size (measured by X-ray diffraction technique) in the powder was 60-80 nm. The powder was pre-pressed in a copper can to 70% density. And twist extruded with the following parameters: temperature of deformation is 473 K; backpressure is about 200 MPa; true strain per pass is about 1.2 [2]. Maximal pressure during the processing was about 1000-1300 MPa. It was performed the following processing of the billets: Billet I: Circle 28 mm in diameter → rectangle 18x28 mm2 + 1 TE pass; Billet II: Circle 28 mm in diameter → rectangle 18x28 mm2 + 2 TE passes; 1 The study was performed jointly with research group of Professor Milman from Frantcevich Institute for Problems of Materials Science, Kiev, Ukraine. Results of this research reported more in detail in paper [D. Orlov, A. Reshetov, A. Synkov, V. Varyukhin, D. Lotsko, O. Sirko, N. Zakharova, A. Sharovsky, V. Voropaiev, Yu. Milman and S. Synkov “Twist Extrusion as the Tool for Grain Refining in Al-Mg-Sc-Zr Alloys” // Proceedings of NATO ARW ‘Nanostructured materials by high pressure severe plastic deformation’, September 22-26, 2004, Donetsk, Ukraine]. 2 The powder was supplied by group of Professor Firstov from Frantcevich Institute for Problems of Materials Science, Kiev, Ukraine. 336 Nanomaterials by Severe Plastic Deformation