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Ma Lai Ching = 利用熱壓法制備塊体非晶態Pd₄₀Ni₄₀P₂₀合金 / 馬勵貞. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 51). / Text in English; abstracts in English and Chinese. / Ma Lai Ching = Li yong re ya fa zhi bei kuai ti fei jing tai Pd₄₀Ni₄₀P₂₀ he jin / Ma Lizhen. / Acknowledgements --- p.i / Abstract --- p.ii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Introduction to Metallic Glass --- p.1 / Chapter 1.2 --- Applications of Metallic Glass --- p.2 / Chapter 1.3 --- Solidification Process --- p.3 / Chapter 1.4 --- Some Production Methods of Bulk Glassy Alloys --- p.10 / Chapter 1.5 --- Another Production Methods: Powder Consolidation --- p.11 / Chapter 1.6 --- Flaws of the as-Compacted Materials --- p.16 / Chapter 1.7 --- A Solution --- p.17 / References --- p.20 / Figures --- p.22 / Chapter Chapter 2 --- Experimental --- p.31 / Chapter 2.1 --- Production of Pre-Compacted Bulk Metallic Glass --- p.31 / Chapter 2.2 --- Handling of Bulk Glass Before Compaction --- p.34 / Chapter 2.3 --- Compaction Process --- p.35 / Chapter 2.1 --- Sample Analysis --- p.37 / Figures --- p.40 / Chapter Chapter 3 --- Mechanism of fusion of bulk metallic glasses --- p.45 / Abstract --- p.45 / References --- p.51 / Table --- p.52 / Figures --- p.53

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Cheung, Hoi Cheung = Fe₈₁C₁₄Si₅旋節合金的變形 / 張凱翔. / "December 2010" / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Abstracts in English and Chinese. / Cheung, Hoi Cheung = Fe₈₁C₁₄Si₅ xuan jie he jin de bian xing / Zhang Kaixiang. / Abstract --- p.i / Acknowledgements --- p.iii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Spinodal Decomposition --- p.1 / Chapter 1.3 --- Theory of Elasticity --- p.5 / Chapter 1.4 --- Deformation of Metals --- p.9 / Chapter 1.5 --- Fracture Mechanics --- p.10 / Chapter 1.6 --- Contact Mechanics --- p.12 / Chapter 1.7 --- Indentation Fracture --- p.16 / Chapter 1.8 --- Deformation and Failure of Tungsten Carbide --- p.20 / References --- p.22 / Figures --- p.25 / Chapter Chapter 2 --- Experiment / Chapter 2.1 --- Sample Preparation --- p.40 / Chapter 2.2 --- Indentation --- p.42 / Chapter 2.3 --- Analysis Method --- p.43 / References --- p.46 / Figures --- p.47 / Chapter Chapter 3 --- Result and Discussion / Chapter 3.1 --- Introduction --- p.50 / Chapter 3.2 --- Deformation on the Top Surfaces --- p.50 / Chapter 3.3 --- Deformation on the Side Surfaces --- p.52 / Chapter 3.4 --- A comparison with Tungsten Carbide (WC/Co) --- p.59 / Chapter 3.5 --- Discussion --- p.60 / Chapter 3.6 --- Conclusion --- p.63 / References --- p.64 / Figures --- p.67

The aim of this thesis is to propose a more general understanding of the influence of the thickness of the plate and of the microstructural and mechanical properties of the material on the resistance to ductile tearing in thin metallic plates. The objective is to attempt unifying different observations made in the literature together with the results of a new extensive experimental campaign. The final goal is to develop predictive simulation tools with a micromechanics-based foundation. In order to reach this objective, a detailed experimental campaign has been performed concerning the fracture behavior of the aluminium alloy 6082, complemented by experiments on a stainless steel A316L and on a set of 14 other materials. In a first modelling effort, we propose very simple closed-form models in order to separate the different contributions to the total work of fracture in thin plates: the work of necking and the work of damage and material separation. The respective contributions are compared and an unique explanation of the different behaviors observed experimentally is proposed. In a second modelling step, we develop a full 3D numerical tool based on cohesive elements for simulating crack propagation in thin ductile plates. Three different methods are proposed to calibrate the parameters of the model in order to reproduce the experimental data and to extrapolate the results to other material properties or geometric conditions. Finally, the parameters of the cohesive zone model are justified using micromechanics-based arguments. / Le but de cette thèse est de proposer un modèle général à base micromécanique permettant de comprendre l’influence de l’épaisseur de la tôle ainsi que de la microstructure et des propriétés mécaniques du matériau sur la résistance à la rupture ductile de plaques minces métalliques. L’objectif est d’essayer d’unifier les différentes observations de la littérature ainsi que les résultats d’une nouvelle campagne expérimentale afin d’aboutir au développement d’outils numériques prédictifs. Pour atteindre cet objectif, nous avons réalisé une campagne d’essais concernant le comportement à la rupture de différents matériaux. Cette campagne a été menée en profondeur sur l’alliage d’aluminium 6082 et de manière moins approfondie sur un acier inoxydable A316L ainsi que sur 14 autres matériaux. Dans un premier temps, nous présentons une série de modèles semi-analytiques simples dont le but est de séparer les différentes contributions au travail de rupture total dans les tôles minces : le travail de striction et le travail d’endommagement du matériau. Ces deux contributions sont ensuite comparées et nous proposons une explication qui reprend les différents comportements observés expérimentalement. Dans un deuxième temps, nous développons un outil numérique 3D complet destiné à simuler la propagation de fissures dans les tôles minces ductiles et qui utilise des éléments cohésifs. Trois méthodes différentes sont proposées pour calibrer les paramètres du modèle de manière à reproduire les données expérimentales et à permettre l’extrapolation des résultats à d’autres matériaux ou d’autres épaisseurs de tôles. Finalement, les paramètres du modèle de zone cohésive sont justifiés grâce à des arguments à fondement micromécanique.

Thesis (Ph.D.)--University of Hong Kong, 1999. / Includes bibliographical references. Also available in print.

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The cleanliness of high strength low alloy (HSLA) steel was assessed qualitatively and quantitatively. The determination of inclusion type and inclusion morphology were carried out using Selective Potentiostatic Etching by Electrolytic Dissolution (SPEED) method allowing in-situ examination of inclusion morphology by analytical techniques such as SEM/EDS. Inclusion size analysis mainly involved a combination of an analytical technique to provide images of the sample surface and an image analysis system to accurately measure the inclusion size. Four analytical methods were compared in order to evaluate their suitability for subsequent quantitative analysis. It was found that images taken with backscattered electron imaging mode from the scanning electron microscope provides the most accurate representation of inclusion distribution. The various techniques were used to evaluate HSLA steel grades of similar chemistry produced with and without gas shrouding. The results confirmed that with reoxidation minimized by gas shrouding between ladle and tundish, the steel cleanliness was significantly improved.

The cleanliness of high strength low alloy (HSLA) steel was assessed qualitatively and quantitatively. The determination of inclusion type and inclusion morphology were carried out using Selective Potentiostatic Etching by Electrolytic Dissolution (SPEED) method allowing in-situ examination of inclusion morphology by analytical techniques such as SEM/EDS. Inclusion size analysis mainly involved a combination of an analytical technique to provide images of the sample surface and an image analysis system to accurately measure the inclusion size. Four analytical methods were compared in order to evaluate their suitability for subsequent quantitative analysis. It was found that images taken with backscattered electron imaging mode from the scanning electron microscope provides the most accurate representation of inclusion distribution. The various techniques were used to evaluate HSLA steel grades of similar chemistry produced with and without gas shrouding. The results confirmed that with reoxidation minimized by gas shrouding between ladle and tundish, the steel cleanliness was significantly improved.

The irradiation of metallic glasses to induce nanocrystallization was studied in two metallic glass compositions, Cu50Zr45Ti5 and Zr55Cu30Al10Ni5. Atomic mobility was described using a model based on localized excess free volume due to displace- ment cascades created by energetic particle irradiation. Due to the di erence in cascade size among di erent masses of projectiles, a mass-dependent study was per- formed. Metallic glass ribbon samples produced by melt-spinning were bombarded with electron, He, Ar, and Cu particles. Electron irradiation and characterization was performed "in-situ" by means of transmission electron microscopy. The di erent metallic glasses showed dissimilar levels of radiation stability under electron irradi- ation by Cu50Zr45Ti5 forming crystals 1-10 nm in diameter embedded in the amor- phous matrix after about 30 minutes of irradiation, while Zr55Cu30Al10Ni5 showed no such crystallization. Increasing projectile mass caused an increase in the maximum nanocrystal diameter up to approximately 100 nm in Cu irradiated Zr55Cu30Al10Ni5. Studies of di raction patterns of irradiated specimens showed nucleation of Cu10Zr7 phases in both specimens, as well as evidence of CuZr2 in Cu50Zr45Ti5 and both CuZr2 and NiZr2 in Zr55Cu30Al10Ni5. Crystal sizes in irradiated Zr55Cu30Al10Ni5 specimens showed bimodal distribution with many large (50-100 nm) crystals and many small (1-5 nm) crystals. The small crystals in irradiated Zr55Cu30Al10Ni5 were determined to be NiZr2 phase because of the low abundance of Ni. After exposure to 2 keV Ar ions, areas of composition roughly Cu10Zr7 were found by energy-dispersive X-ray spectroscopy but no crystallization was found. Further crystallization was achieved in decomposed specimens after electron irradiation. This shows that atomic segregation is a necessary step before nucleation in metallic glasses.