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. 1 10 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
HPT eq = / 3, = 2 NHPT r / t :, NHPT:, r:, t: 0.6 mm 1 mm 40 MoS2 Fig. 2 0.6 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 % #4000 10 vol% HClO4 + 90 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 1 10 3 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 - 3.3 mass%si steel, 3 GPa, 1 rpm, NHPT = 10, R.T.
(a) 3.0 1.5 3.0 1.8 1.0 1.0 R0.2 (b) Upper die Load 7.4 L Unit: mm 1.4 5.0 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 1.5 1.0 R1.0 9.4 4.0 1.4 R0.7 2.8 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 = 45 300 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
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
(a) 2000 (b) 2000 N HPT =5+A ( eq =45, Hv3.6GPa) Engineering stress, / MPa 1500 1000 500 90%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 1500 1000 500 90%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) 0 0 0.1 0.2 0.3 0.4 0.5 0.6 Engineering strain, As-prepared (Hv0.6GPa) 0 0 0.1 0.2 0.3 0.4 0.5 0.6 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 = 1.6 10 5 81 % Fig. 9 NHPT = 10 NHPT = 5, 5+A Fig. 10 NHPT = 10 90%CR, NHPT = 5, 5+A NHPT = 10 HPT
1600 1400 Maximum stress, / MPa 1200 1000 800 600 400 200 90%CR EP 90%CR #4000 N HPT=5 EP N HPT=5 #4000 0 10 2 10 3 10 4 10 5 10 6 10 7 10 8 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 #4000. 1600 1400 Maximum stress, / MPa 1200 1000 800 600 400 200 90%CR N HPT=5 N HPT=10 N HPT=5+A 0 10 2 10 3 10 4 10 5 10 6 10 7 10 8 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.
90%CR N HPT = 5 =550MPa, N f =1.63 10 5 =1000MPa, N f =2.66 10 3 N HPT = 5+A N HPT = 10 =600MPa, N f =2.02 10 6 =700MPa, N f =1.12 10 5 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
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