楊哲人臺灣大學：材料科學與工程學研究所翁光良Weng, Kuang-LiangKuang-LiangWeng2007-11-262018-06-282007-11-262018-06-282004http://ntur.lib.ntu.edu.tw//handle/246246/55281雙相不Duplex stainless steels have been widely used in the oil, chemical and nuclear industries due to their high strength, good weldability, and high resistance to stress corrosion and pitting. The superior properties of these duplex stainless steels come primarily from approximately equivalent amounts of austenite (γ) and δ-ferrite. However, these types of steels are intrinsically subject to embrittlement when exposed to temperatures above 300 ℃ because of solid-state reactions within the ferrite phase. It is well known that in Fe-Cr alloys there is a miscibility gap, where the ferrite phase may decompose into an iron-rich b.c.c. phase (Chapter One General introduction.......................................1 Chapter Two Literature survey..........................................3 2-1. Development and Microstructure of duplex stainless steels.....................................................3 2-1-1. Development of duplex stainless steels..............3 2-1-2. Microstructure of wrought duplex stainless steels...4 2-2. Phase transformation in duplex stainless steels.......5 2-2-1. Secondary austenite.................................5 2-2-2. σ phase............................................6 2-2-3. Chromium nitrides...................................6 2-2-4. Carbides (M7C3 and M23C6)...........................6 2-2-5. χ phase..........................................7 2-2-6. R phase.............................................7 2-2-7. τ phase............................................7 2-2-8. π phase............................................7 2-2-9. α΄ and G phases....................................8 2-3. Spinodal decomposition................................8 2-3-1. Theory of spinodal reactions........................8 2-3-2. Concentration fluctuations..........................9 2-3-3. Spinodal structure.................................10 2-4. Low temperature aging embrittlement..................11 2-4-1. Fracture mechanism.................................12 2-4-2. Embrittlement mechanism............................13 2-5. Crystallographic relationships.......................13 Chapter Three The low-temperature aging embrittlement in a 2205 duplex stainless steel 3-1. Introduction.........................................22 3-2. Experimental Procedure...............................23 3-3. Results and Discussion...............................24 3-4. Conclusions..........................................30 Chapter Four The dislocation character aged at 475 ℃ in a 2205 duplex stainless steel 4-1. Introduction.........................................50 4-2. Experimental Procedure...............................51 4-3. Results and Discussion...............................52 4-4. Conclusions..........................................55 Chapter Five Crystallography of secondary precipitates in 2205 duplex stainless steel 5-1. Introduction.........................................75 5-2. Experimental Procedure...............................76 5-3. Results and Discussion...............................77 5-4. Conclusions..........................................84 Chapter six General conclusions......................................117 Future works.............................................120 Appendix.................................................121 Reference................................................12212636439 bytesapplication/pdfen-US方位關係雙相不離相分解差排duplex stainless steelorientation relationshipspinodal decompositiondislocationthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/55281/1/ntu-93-D89542002-1.pdf