F.Yan et al.:J.Mater.Sci.Technol.,2011,27(8),673-679 679 (1)The microstructures in the DS-region and SB- [7]F.Dalla Torre,R.Lapovok,J.Sandlin and P.Thom- region are characterized by extended boundaries,in- son:Acta Mater.,2004,52,4819. terconnecting dislocation boundaries and isolated dis- [8]A.P.Zhilyaev,S.Swaminathan,A.A.Gimazov,T.R. locations in the volume between the boundaries. McNelley and T.G.Langdon:J.Mater.Sci.,2008,43. (2)The DS-region microstructure in the LN-DPD 7451. Cu shows:i)a smaller boundary spacing(121 nm);ii) [9]X.Molodova,G.Gottstein,M.Winning and R. a lower misorientation angle (3.8).iii)a lower frac- Hellmig:Mater.Sci.Eng.A,2007,460-461,204. 10]N.Hansen:Scripta Mater.,2004,51,801. tion of high angle boundaries (~0)and iv)a higher dislocation density (5.6x1015 m-2)compared with Cu [11]D.A.Hughes and N.Hansen:Acta Mater.,2000,48, 2985. sample processed by low strain rate deformation at 12 L.Liu and I.Baker:Scripta Metall.,1993,28,197. room temperaturel12-15,18-22,24,25] [13]W.Q.Cao,C.F.Gu,E.V.Pereloma and C.H.J.Davies: (3)The boundaries in the NT-region are deviated Mater.Sci.Eng.A,2008,492,74. from the perfect 53 relationship (60/<111>)up to [14]J.Gubicza,L.Balogh,R.J.Hellmig,Y.Estrin and T. a maximum value of 9o.Based on the boundary pa- Ungar:Mater.Sci.Eng.A,2005,400-401,334. rameters and the deviation angles,the density of the [15]Y.Zhang,N.R.Tao and K.Lu:Acta Mater.,2008, excess dislocations in the boundaries was estimated 56.2429. tobe1.7×1016m-2 16]E.Orowan:Proc.Phys.Soc.,1940,52,8. (4)The boundaries in the SB-region are mainly [17 J.W.Christian and S.Mahajan:Prog.Mater.Sci., 1995.39.1. low angle dislocation boundaries that are spaced [18 S.C.Baik,R.J.Hellmig,Y.Estrin and H.S.Kim:Z. <50 nm.The dislocation density was estimated to Metallkd.,2003,94.754. be1.6×1016m-2. 19 F.Dalla Torre,A.Gazder,C.Gu,C.Davies and E. (5)The flow stress-structural parameters relation- Pereloma:Metall.Mater.Trans.A.2007,38.1080. ship has been established based on the linear additiv- [20]M.Shaarbaf and M.Toroghinejad:Metall.Mater. ity of the weighted contributions from three types of Trans.A.2009,40,1693. microstructures in the LN-DPD Cu sample. 21 B.L.Li,N.Shigeiri,N.Tsuji and Y.Minamino:Mater. Sci.Forum,2006,503-504,615. 22 A.Belyakov,T.Sakai,H.Miura and K.Tsuzaki:Phi- Acknowledgements los.Mag.A,2001,81,2629 The authors acknowledge the Danish National Re- [23]F.J.Humphreys,Y.Huang,I.Brough and C.Harris: J.Microsc.,1999,195,212 search Foundation and the National Natural Science Foundation of China (Grant No.50911130230)for the [24]O.V.Mishin and G.Gottstein:Philos.Mag.A,1998, Danish-Chinese center for Nanometals,within which this 78,373 study was performed.Thanks Dr.X.Huang and Dr. 25 O.V.Mishin,D.Juul Jensen and N.Hansen:Mater. W.Pantleon for constructive discussion.This project Sci.Emg.A,2003,342,320. was sponsored by MOST international S&T project [26]G.R.Canova,C.Fressengeas,A.Molinari and U.F. (2010DFB54010),SRF for ROCS,SEM,and the Young Kocks:Acta Metall.,1988.36.1961. Merit Scholar of Institute of Metal Research.Chinese [27]J.Weertman and S.S.Hecker:Mech.Mater.,1983,2, 89. Academy of Science,China. 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Technol., 2011, 27(8), 673–679 679 (1) The microstructures in the DS-region and SB￾region are characterized by extended boundaries, in￾terconnecting dislocation boundaries and isolated dis￾locations in the volume between the boundaries. (2) The DS-region microstructure in the LN-DPD Cu shows: i) a smaller boundary spacing (121 nm); ii) a lower misorientation angle (3.8◦), iii) a lower frac￾tion of high angle boundaries (∼0) and iv) a higher dislocation density (5.6×1015 m−2) compared with Cu sample processed by low strain rate deformation at room temperature[12–15,18–22,24,25]. (3) The boundaries in the NT-region are deviated from the perfect Σ3 relationship (60◦/<111>) up to a maximum value of 9◦. Based on the boundary pa￾rameters and the deviation angles, the density of the excess dislocations in the boundaries was estimated to be 1.7×1016 m−2. (4) The boundaries in the SB-region are mainly low angle dislocation boundaries that are spaced <50 nm. 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