Effect of Large Shear Deformation on Rail Steels and Pure Metals

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3 3 Results and Discussion Figure 3.12: SEM micrographs <strong>of</strong> HPT-deformed Dobain 430 (a) ɛeq = 1, (b) ɛeq = 2, (c) ɛeq = 4 and (d) ɛeq = 8, all in radial direction, (e) ɛeq = 1, tangential direction and (f) ɛeq = 8, tangential direction. similar microstructure (and a similar mechanical strength) are much higher. Already after two cycles with ∆ɛ = 4 (ɛeq,total = 8) the lamellae are extremely deformed and fanfold structures 22
3.2 Structural Evolution <strong>of</strong> Rail Steels during Severe Plastic <strong>Deformation</strong> are present. After higher total strains, the lamellae are no longer clearly recognisable. Figure 3.13: SEM micrographs <strong>of</strong> CHPT deformed 900A (a) ∆ɛ = 0.25, ɛeq,total = 8 (b) ∆ɛ = 0.25, ɛeq,total = 32 (c) ∆ɛ = 4, ɛeq,total = 8 and (d) ∆ɛ = 4, ɛeq,total = 64. 3.2.3 Microstructure after additional heat treatment Deformed samples <strong>of</strong> the three steels (900A with ɛeq = 16, 350 LHT with ɛeq = 8 and Dobain 430 with ɛeq = 8) were head treated a different temperatures and for different times. As can be seen in Figure 3.14, only after temperatures larger than 600°, a markedly change in the microstructure has occurred. In etched samples round carbides with a size <strong>of</strong> ≈ 10nm are clearly visible. SEM micrographs using back scatterd electrons reveal that the ferritic matrix is recrystallized, the grain size grows with increasing temperature and increasing heat treatment time. In order to obtain ultra-short heat treatment times, samples <strong>of</strong> the rail steel 900A were heated by by a laser pulse. The pulse time was 10 - 50 µs, the temperature (average value, measured by a spectrometer) was varied between 600 and 750 degree. This heat treatment by a laser pulse resulted in a heat affected zone part <strong>of</strong> which is white in optical microscopy after 23 3
Page 1 and 2: University of Leob
Page 3: ASTRID, LÄTITIA
Page 7 and 8: Danksagung Die hier vorliegende Arb
Page 9 and 10: Summary The investigation o
Page 11 and 12: Kurzfassung Die Untersuchung der Au
Page 13 and 14: Sobald jemand in einer Sache Meiste
Page 15 and 16: Contents 1 Introduction 1 1.1 Motiv
Page 17 and 18: Contents E.3.2 Mechanical strengths
Page 19 and 20: 1.1 Motivation 1 Introduction Today
Page 21 and 22: 1.2 Objectives The aim of</
Page 23 and 24: 2 Methods of Sever
Page 25 and 26: 2.2 Equal Channel Angular Pressing
Page 27 and 28: 2.2 Equal Channel Angular Pressing
Page 29 and 30: 3 Results and Discussion In the fol
Page 31 and 32: 3.1 Structural Evolution of
Page 39: 3.2 Structural Evolution of
Page 45 and 46: 3.3 Mechanical Properties In contra
Page 47 and 48: 3.3 Mechanical Properties Figure 3.
Page 49 and 50: 3.3 Mechanical Properties Figure 3.
Page 51 and 52: 3.3 Mechanical Properties can be se
Page 53 and 54: 4 Conclusions The methods o
Page 55 and 56: [1] G. Baumann, H.-J. Fecht, and S.
Page 57 and 58: Bibliography [36] T. Hebesberger, H
Page 59 and 60: 5 List of appended
Page 61 and 62: A Structural Refinement of<
Page 63 and 64: A.1 Introduction A.1 Introduction K
Page 65 and 66: A.3 Results Figure A.2: Micrograph
Page 67 and 68: A.4 Discussion Figure A.3: Microgra
Page 69 and 70: Bibliography to paper A [1] W. Lojk
Page 71 and 72: B Structural Changes of</st
Page 73 and 74: B.1 Introduction B.1 Introduction D
Page 75 and 76: B.3 Results and Discussion after a
Page 77 and 78: Figure B.5: 2Θ scans of</s
Page 79 and 80: B.4 Conclusion B.4 Conclusion • T
Page 81 and 82: Bibliography to paper B [1] G. Baum
Page 83 and 84: C Strain Hardening during High Pres
Page 85 and 86: C.1 Introduction C.1 Introduction R
Page 87 and 88: C.3 Results With this equation it i
Page 89 and 90: C.4 Discussion Figure C.4: SEM micr
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Bibliography to paper C [1] T. Hebe
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D Formation of sur
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D.1 Introduction D.1 Introduction T
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D.3 Results D.3.1 Monotonic <strong
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D.3 Results Figure D.4: SEM microgr
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D.4 Discussion Figure D.6: SEM micr
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occurring on the surface of
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Bibliography to paper D [1] Y. K. C
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E High Pressure Torsion of<
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E.1 Introduction E.1 Introduction T
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E.3 Results Figure E.2: SEM microgr
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E.3.2 Mechanical strengths E.4 Disc
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Bibliography to paper E [1] L. Wang
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F TEM Investigation of</str
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F.1 Introduction F.1 Introduction C
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F.4 Discussion see Figure F.2b. The
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Figure F.3: In-situ measured torque
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F.4 Discussion Figure F.6: Comparis
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F.6 Appendix • Electron energy-lo
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[1] M. Zelin. Acta Mater., 50(17):4
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G Fracture Processes in Severe Plas
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G.2 Introduction G.2 Introduction T
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G.4 Results toughness test. It can
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G.5 Discussion Figure G.3: (a) Load
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G.5.2 Fracture G.5 Discussion Fract
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Bibliography to paper G [1] J. D. E
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H Cyclic High Pressure Torsion <str
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H.1 Introduction H.1 Introduction I
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Figure H.2: Sample preparation for
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H.3 Results With increasing ∆ɛ a
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H.3 Results Figure H.7: SEM microgr
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H.3 Results between 2°and 15°, th
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H.4 Discussion comparable to ECAP R
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H.5 Conclusions bon steels as a fun
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H.5 Conclusions • The steady stat
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Bibliography to paper H [1] Y. T. Z
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Bibliography to paper H [33] C. Buq
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I Structural Evolution during Cycli
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I.1 Introduction I.1 Introduction T
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I.3 Results Figure I.2: SEM microgr
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I.4 Discussion be seen that saturat
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I.5 Conclusions structure size is a
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[1] H. Mughrabi. Mater. Sci. Eng.,
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Effect of Large Shear Deformation on Rail Steels and Pure Metals

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