Abstract The evolutions of microstructure and texture in 2205 duplex stainless steel (DSS) welds produced by two high energy density (HED) processes, CO2 laser beam welding (LBW) and electron beam welding (EBW) were investigated. A variety of analytical techniques were applied for the study on microstructure and texture of the welds. In which, optical microscopy and electron microscopy were used to evaluate the detailed microstructure. X-ray diffraction (XRD) was put to investigate the crystallographic textures among the base metal, heat affected zone and fusion zone. Particular attention was focused on the determination of microtexture in HED welds by using electron backscatter diffraction (EBSD) technique. After that, an effort was put to compare the results by both of X-ray macro-texture and EBSD-microtexture. The recorded micrographs illustrates that the HED welds are mainly composed of d-ferrite grained structure, which is further decorated with allotriomorphic and Widmanst&#x00E4;tten austenite (g) at grain boundaries. With preheating treatment, the volume fraction of austenite in LB weld is gradually increased, and then leading to a completely different morphology. An apparent amount of transformation twins are found in g phase under TEM observations. No matter that they are Widmanst&#x00E4;tten austenite in nonpreheated welds or blocky austenite in preheated welds, all of the transformation twins have the same {111} twin boundary. Furthermore, modulated fringes composed of ferrite, secondary austenite and amorphous phase are also found in the nonpreheated LB weld. It is ascribed to the rapid cooling effect occurred in the nonpreheated LB weld. Two chromium nitrides (CrN and Cr2N) are also identified and attributed to their different driving forces. A remarkable texture gradient is found in the base metal along the thickness direction for both of austenite and ferrite phases in 2205 duplex stainless steel. The texture is governed separately by the {001}//ND-fibre, a-fibre, Goss and rotated cube components. Despite the analogous local texture evolutions revealing in both LB and EB welds, the global solidification textures in the two processes are considerably different. For which, the texture of LB weld is predominantly evolved with the Goss component. However, the texture of EB weld is mainly composed of the pronounced cube {001}<100>, while the Goss {011}<100> and rotated cube {001}<110> are weakened. The microtexture analysis shows that the centre region of the weld is dominated by oriented nucleation mechanism. Whereas, regions near the fusion boundaries are governed by oriented growth mechanism. The texture feature from EBSD does consist well with the XRD measured result. Moreover, the measurement of local texture from EB weld clearly indicates that a high percentage of high angle grain boundaries distributed in the crown. By contrary, a high percentage of low angle grain boundaries distributed in the root. Both of them again reflect the cooling effect of weld on the solidification mechanism. Throughout this study, the key factors to be responsible for the evolution of solidification texture of HED welded DSS are summarized. Those are thermal conductivity of the weld, turbulent flow in the molten pool, parent textures and the orientation relationship between ferrite and austenite.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references. Also available on the World Wide Web.

D. Tech. Chemical, Metallurgical and Materials Engineering / Corrosion is the chemical or electrochemical interaction between a material, especially metals, and their environment resulting in mild to severe deterioration of the material and its properties. The economic impact and problems resulting from corrosion has drawn strong attention from scientists and engineers worldwide. Stainless steel is the most important engineering metal worldwide, and industrially stainless steel is used extensively due to its resistance to corrosion e.g. in acid pickling, industrial acid cleaning, acid descaling, oil well acidizing and the petroleum industry. The corrosion resistance of stainless steels is due to the formation of a protective film which covers the steel surface instantaneously when exposed to mild operational conditions in the presence of oxygen; however, the oxide is most often porous and insufficient to protect the steel from further oxidation and corrosion attack in harsh environments. It is hypothesized that: In-depth understanding of the electrochemical behaviour of ferrous alloys in interaction with selected organic compounds in acidic environments will enhance inhibitor application for corrosion control; Failure and poor performance of most inhibitor admixtures can be eliminated with comprehensive knowledge of electrochemical interaction at the metal-inhibitor interface, passive film formation, duration and breakdown, adsorption characteristics, bond formation and molecular structure effect; Optimization of the current electroanalytical method will enhance effective pitting corrosion detection, analysis and control with the use of organic inhibiting compounds. The primary aim of this research is to develop the science required for the effective assessment, development and confident use of organic compounds (heterocyclic compound, organosulphur compound, simple alcohol, aromatic amine compound, aromatic amine derivative and aminoalcohol) and tested alloys (austenitic stainless steel type 304 and mild steel) for applications in astringent environments through conventional and optimized corrosion monitoring techniques.

No description available.

Thesis (M.S.)--Ohio University, March, 1984. / Title from PDF t.p.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Thesis (doctoral)--Lappeenranta University of Technology, 2004. / Includes bibliographical references (p. 115-120). Also available on the World Wide Web.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 25, 2009) Includes bibliographical references.

Thesis (M.Applied Science(Metallurgical Engineering))--University of Pretoria, 2008. / Abstract in English. Includes bibliographical references.

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 179-186).