목차

Chapter 1 Introduction ······························································· 1
1.1. Research background ································································ 1
1.2. Objective of the study································································ 4
1.3. Reference ·············································································· 5
Chapter 2 Theoretical background ················································ 8
2.1. Hydrogen embrittlement of HSLA steels ········································· 8
2.2. Theories of HE ·······································································10
2.2.1. Internal pressure ·······························································10
2.2.2. Hydrogen Enhanced Decohesion············································10
2.2.3. Hydrogen Enhanced Localized Plasticity ··································11
2.2.4. Hydrogen Enhanced Strain-induced Vacancy·····························12
2.3. Theories for hydrogen diffusion and trapping···································14
2.4. Effect of microstructure on HE ····················································15
2.5. Methods to evaluate and detect HE ···············································16
2.5.1. Slow Strain Rate testing ······················································16
2.5.2. Electro chemical hydrogen permeation technique ························17
2.5.3. Thermal desorption spectroscopy ···········································19
2.6. References ············································································21
Chapter 3 Experimental procedure ···············································24
3.1. Heat treatment and preparation of materials. ····································24
3.2. Sample preparation for microstructure observation ····························27
3.3. In-situ Slow Strain Rate Test ······················································28
3.4. Hydrogen permeation Test ·························································30
3.5. Thermal Desorption Spectroscopy ················································32
3.6. Numerical Analysis of Hydrogen Desorption in Ferritic steel ················35
3.7. References ············································································38
Chapter 4 Effect of grain size on HE············································39
4.1. Effect of grain size on HE with in-situ SSRT and TDS························39
4.1.1. Microstructure and grain size with respect to annealing treatment·····39
4.1.2. Effects of hydrogen and grain size on tensile properties·················41
4.1.3. Effects of grain size on diffusible hydrogen ·······························49
4.1.4. Summary········································································59
4.2. References ············································································61
Chapter 5 Effect of prestrain on HE ·············································63
5.1. Effect of prestrain on hydrogen diffusion and trapping ························63
5.1.1. Microstructure and strain maps with respect to prestrain················63
5.1.2. Permeation behavior for repeated charging and decay···················65
5.1.3. Influence of a pre-strain on the permeation behavior ····················68
5.1.4. Summary········································································71
5.2. Effect of pre-strain on HE with in-situ SSRT and TDS························72
5.2.1. Microstructure and prestrain with respect to annealing treatment······72
5.2.2. Effects of hydrogen and prestrain on in situ SSRT properties ··········74
5.2.3. Effects of prestrain on diffusible hydrogen before and after SSRT ····83
5.2.4. Summary········································································90
5.3. References ············································································91
Abstract in Korean ·········································································93