Severe Plastic Deformation: SPD HPT[1], ECAP[1,2], ARB[3] HPT High-Pressure Torsion [4-6] [7-10] [10,11] HPT IF [12] IF 11C, <30Si, <30Mn, <20P, <3S,

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1 Severe Plastic Deformation: SPD HPT[1], ECAP[1,2], ARB[3] HPT High-Pressure Torsion [4-6] [7-10] [10,11] HPT IF [12] IF 11C, <30Si, <30Mn, <20P, <3S, <2B, 8N, 14O, 300Al, <20Ti, <30Cr, <30Cu, mass ppm Ar 1000, 3.6 ks 10 mm, 0.85 mm Fig mm, 0.25 mm 2 5 GPa, 0.2 rpm, HPT (a) Thermocouple (K-type) Load (b) Lubricant Fig. 1 (a) Schematic illustration of a set up for HPT-straining and (b) overview of anvil. Upper anvil Lower anvil Rotation Load 1mm Specimen Initial shape: 10mm t0.85 mm

2 HPT eq = / 3, = 2 NHPT r / t :, NHPT:, r:, t: 0.6 mm 1 mm 40 MoS2 Fig mm NHPT = 5 HPT 200, 3.6 ks NHPT =5+A 90 % 90%CR NHPT = 5+A NHPT = 5 Hv 3.6 ks 200 [7] 90%CR 1 10 ~ 20 % 90 % # vol% HClO vol% C2H5OH 2 FESEM-EBSP JEOL JSM-6500F - OXFORD INCA Crystal, HKL CHANNEL5 software, TEM HITACHI H-800, SHIMADZU EHF-LV020k1, SHIMADZU HMV-1ADW 0.5 mm Fig. 3a s -1 L Fig. 3b CCD KEYENCE CV-200MCCD 2 m 0.5 mm Fig. 4 R = 0.1,, 20 Hz 0.5 mm 0.98 N, 10 s (a) (b) 2mm Fig. 2 Surface morphologies of disks (a) without / (b) with slip between disk and anvil during HPT-straining. (a) 1050 Al, HPT condition: 5 GPa, 5 rpm, NHPT = 1, R.T. and (b) Fe mass%si steel, 3 GPa, 1 rpm, NHPT = 10, R.T.

3 (a) R0.2 (b) Upper die Load 7.4 L Unit: mm Fig. 3 Schematic illustrations of (a) tensile specimen shape and (b) a set up for tensile test. Miniature tensile specimen was cut from the off-center position of HPT-processed disk. Tensile specimen Lower Load die R R Unit: mm 6.0 Fig. 4 Schematic illustration of fatigue specimen shape. Miniature fatigue specimen was cut from the off-center position of HPT-processed disk. Fig. 5 NHPT = 5 FESEM-EBSP r = 1.5mm eq = nm, 600 nm GN Fig. 5 A, B TEM Fig. 6a HPT NHPT = 5 200, 3.6 ks NHPT = 5+A TEM Fig. 6b NHPT = 5 Fig. 7 HPT NHPT = 5 HPT 1.9 GPa TS Hv TS = Hv/3 NHPT = 5 NHPT = 10 NHPT = 5 HPT NHPT = 10

6 TEM micrographs at the region of r = 3.

4 Orientation map Local misorientation map A >15 Subgrain angle 0 3 Fig. 5 EBSD maps at the region of r = 1.5 mm after HPT-straining for NHPT = 5 ( eq = 45). (a) N HPT = 5 (b) N HPT = 5+A B 1 m Fig. 6 TEM micrographs at the region of r = 3.2 mm after (a) HPT-straining for NHPT = 5 ( eq = 97) and (b) subsequent annealing at 200 for 3.6 ks. 500nm HPT NHPT = 5+A Fig. 7b NHPT = 5, NHPT = 10, NHPT = 5+A NHPT = 5+A Fig. 7b Al [13,14] [14] [15] NHPT = 10 [16] IF

5 (a) 2000 (b) 2000 N HPT =5+A ( eq =45, Hv3.6GPa) Engineering stress, / MPa %CR ( eq =2.7, Hv2.1GPa) N HPT =5 ( eq =45, Hv3.6GPa) N HPT =2 ( eq =18) N HPT =10 ( eq =91, Hv3.6GPa) N HPT =1 ( eq =9, Hv2.8~3.2GPa) Engineering stress, / MPa %CR ( eq =2.7, Hv2.1GPa) N HPT =5 ( eq =45, Hv3.6GPa) N HPT =2 ( eq =18) N HPT =10 ( eq =91, Hv3.6GPa) N HPT =1 ( eq =9, Hv2.8~3.2GPa) As-prepared (Hv0.6GPa) Engineering strain, As-prepared (Hv0.6GPa) Engineering strain, Fig. 7 Engineering tensile stress-strain curves of (a) HPT-processed specimens after various turns and (b) subsequent annealing at 200 for 3.6 ks. Vickers microhardness, Hv, was measured under an applied load of 4.9 N for 10 s. Fig. 8 90%CR, NHPT = 5 Fig. 9 NHPT = 5, 10, 5+A 90%CR 2 [11] [17] NHPT = 5, 10, 5+A NHPT = 5, 10, 5+A 90%CR Nf = % Fig. 9 NHPT = 10 NHPT = 5, 5+A Fig. 10 NHPT = 10 90%CR, NHPT = 5, 5+A NHPT = 10 HPT

6 Maximum stress, / MPa %CR EP 90%CR #4000 N HPT=5 EP N HPT=5 # Cycles to failure, N f Fig. 8 Effect of surface roughness on the fatigue property in the HPT-processed (NHPT = 5) and the cold-rolled (90% reduction) specimens. EP: electrical polishing, #4000: mechanical polishing by using emery paper with # Maximum stress, / MPa %CR N HPT=5 N HPT=10 N HPT=5+A Cycles to failure, N f Fig. 9 S-N diagram of the electrical polished specimens after cold-rolling, HPT-straining and annealing. Arrows indicate that no fracture has been observed at a given stress and number of cycles.

66 10 3 N HPT = 5+A N HPT = 10 =600MPa, N f =2.

$10 Morphologies of fracture surface at the final$ 1 m (1) HPT 300 nm, 600 nm Hv 3.

7 90%CR N HPT = 5 =550MPa, N f = =1000MPa, N f = N HPT = 5+A N HPT = 10 =600MPa, N f = =700MPa, N f = Fig. 10 Morphologies of fracture surface at the final fracture areas after fatigue tests. 1 m (1) HPT 300 nm, 600 nm Hv 3.6 GPa (2) NHPT = > 5 eq = > 45 HPT 1.9 GPa NHPT = > 5 eq = > 45 HPT (3) HPT HPT (4) 90%CR NHPT = 5 (5) 90%CR NHPT = 5, 10, 5+A 2

8 JFE [1] R.Z. Valiev, R.K. Islamgaliev, I.V. Alexandrov: Prog. Mater. Sci. 45 (2000) 103. [2] V.M. Segal, V.I. Reznikov, A.E. Drobyshevskiy, V.I. Kopylov: Russ. Metall. 1 (1981) 99. [3] Y. Saito, N. Tsuji, H. Utsunomiya, T. Sakai, R.G. Hong: Scr. Mater. 39 (1998) [4] J.G. Sevillano: Proc. of 25th Riso Int. Symp. on Mater. Sci., ed. by C. Gundlach, K. Haldrup, N. Hansen, X. Huang, D.J. Jensen, T. Leffers, Z.J. Li, S.F. Nielsen, W. Pantleon, J.A. Wert and G. Winther, (Riso Natl Lab., Roskilde, Denmark, 2004), 1. [5] Y. Todaka, M. Umemoto, Y. Watanabe, A. Yamazaki, C. Wang and K. Tsuchiya: ISIJ Int., 47 (2007) 157. [6] Y. Todaka, M. Umemoto, J. Yin, Z. Liu and K. Tsuchiya: Mater. Sci. Eng. A, 462 (2007) 264. [7] Y. Todaka, M. Yoshii, M. Umemoto, C. Wang, K. Tsuchiya: Mater. Sci. Forum (2008) 597. [8] V.M. Segal: Mater. Sci. Eng. A 197 (1995) 157. [9] J.T. Wang, C. Xu, Z.Z. Du, G.Z. Qu, T.G. Langdon: Mater. Sci. Eng. A (2005) 312. [10] A. Vinogradov, S. Hashimoto, V.I. Kopylov: Mater. Sci. Eng. A 355 (2003) 277. [11] W.-J. Kim, C.-Y. Hyun, H.-K. Kim: Scr. Mater. 54 (2006) [12] Submitted to Int. J. Mater. Res. [13] N. Tsuji, Y. Ito, Y. Saito, Y. Minamino: Scr. Mater. 47 (2002) 893. [14] P.L. Sun, C.Y. Yu, P.W. Kao, C.P. Chang: Scr. Mater. 52 (2005) 265. [15] Y.H. Zhao, Y.Z. Guo, Q. Wei, A.M. Dangelewicz, C. Xu, Y.T. Zhu, T.G. Langdon, Y.Z. Zhoua, E.J. Lavernia: Scr. Mater. 59 (2008) 627. [16],,,, : 14 (2209) 14. [17] H.W. Hoppel, Z.M. Zhou, H. Mughrabi, R.Z. Valiev: Phil. Mag. A 82 (2002) 1781.

TestNian

TestNian Fatigue Damage Mechanism in Very High Cycle Regime Nian Zhou 2012.5.24 Fatigue Low cycle fatigue N f 10 5 cycles Strain-controlled fatigue High cycle fatigue N f f 10 5 cycles Stress-based fatigue Endurance