Surface engineering of Ti-6Al-4V by nitriding and powder alloying using a CW CO2 laser

A comparison has been made of the laser processing of Ti-6Al-4V (IMI-318) alloy by (a) nitriding under a dilute atmosphere, (b) preplaced 6 µm SiC powder and (c) a combination of (a) and (b). At least six laser tracks were overlapped. Microhardness maps allowed details of the variation in hardness with both melt depth and track number to be determined. The microstructure was characterised and related to the processing parameters, melt track dimensions, hardness and roughness data. It was found that the preheat generated due to the overlapping, influenced the individual track dimensions, microstructure and properties, which were also affected by the laser energy density and the nitrogen concentration in the nitriding atmosphere used in processing. Process (b) was shown to produce the smoothest surfaces, with Ra values <2μm, whilst (c) gave the highest Ra, value, 8.6 μm. These results are considered together with a wide range of data in the literature on laser processed Ti-6Al-4V

XRD and XPS studies of surface MMC layers developed by laser alloying Ti6Al4V using a combination of a dilute nitrogen environment and SiC powder

Using a continuous-wave CO2 laser, surface engineering of a Ti-6Al-4V alloy through a combined treatment of laser nitriding and SiC preplacement was undertaken. Under spinning laser beam conditions, a surface alloyed / metal matrix composite (MMC) layer over 300μm in depth and 24mm wide was produced in the alloy by the overlapping of 12 tracks. Microstructural and chemical changes were studied as a function of (a) depth in the laser formed composite layer and (b) of the track position. Using X- ray diffraction (XRD) and X-ray photospectrographic (XPS) techniques, it was shown that the composite layer contained a complex microstructure which changed with depth. At the surface, a non-stoichiometric, cubic TiNx solid solution ( possibly a carbonitride) containing C and Si , where x ≈ 0.65-0.8, was prominent, but was replaced by α′-Ti with increasing depth to 300μm. TiC phase was also identified, and the presence of TiN0.3 and Ti5Si3 phases considered a distinct possibility.

Single sided single pass submerged arc welding of austenitic stainless steel

The weld metal produced from a series of high productivity welds of 316LN austenitic stainless steel plate was examined to evaluate the effects of the use of a higher heat input process (> 2.5kJ/mm).This high heat input process was aimed at maximising single sided weld metal penetration in a single pass using simple square edge preparations and minimising time consuming handling operations. The evaluation was undertaken by correlating the local microstructure with the local toughness and microhardness of the cap, middle and root of the weld. It was established that the intermetallic phases / carbides present did not appear to have a significantly adverse effect on either corrosion or toughness. The phases observed and confirmed by the use of SAED were predominantly chi (χ) with some sigma( σ). No identifications were made of M23C6 which was observed in other studies of 316LN welds. A series of impact tests with variations in the notch positions showed that the thickness of the delta ferrite had an effect on the weld metal toughness. As a result of this work it was established that similar volume fractions of delta ferrite did not necessarily produce similar levels of weld metal toughness, but ferrite thickness did appear to have a contributory effect. Welding of 316LN stainless steel with a single sided single pass submerged arc welding process was satisfactorily undertaken up to 20mm plate thickness without preheat or post weld heat treatment. The ability to achieve this resulted in significant economic savings within the process for ship panel production combined with satisfactory weld metal properties

The Effects of Sulfuric Acid on the Mechanical Properties of Ice Single Crystals

Ice single crystals of various orientations containing various concentrations of H2SO4 up to 11.5 ppm were cut from large pucks of laboratory-grown ice. Constant-strain-rate compression tests were performed on the doped ice crystals both at −20°C at an axial strain rate of 1 × 10−5 s−1 and at −10°C at 1 × 106 s−1. The stress–strain curves showed a linearly rising stress with increasing strain, followed by a sharply declining stress after reaching a peak. With further strain, the sharp decline in stress slowed. The tests clearly showed, for the first time, that this naturally occurring impurity dramatically decreases both the peak stress and the subsequent flow stress of ice single crystals. The decrease in the peak strength was related to the square root of the concentration of H2SO4 up to 11.5 ppm, suggesting that the solubility limit of H2SO4 in ice is at least 11.5 ppm. The sulfuric acid also appeared to increase the ductility of the ice. Preliminary examination of a doped ice single crystal by synchrotron X-ray topography suggested that sulfuric acid dramatically increases the grown-in dislocation density

Metamorphosis & the Therapeutic Function of Storytelling: The Arabian Nights Vs. Franz Kafka’s Animal Stories

Abstract Story telling in the book of A Thousand and One Nights , functions as a way sublimating Shahrayar’s desire for murdering Sharazad and releasing it through catharsis. i.e. the stories function as a therapy for Sharayar and as a brain-washing mechanism through which Shahrazad hopes to cure Sharayar from his murderous desire that has led to the deaths of many women because of his wife’s act of infidelity. In this article, I will highlight the similarities between some of the stories in the book of A Thousand and One Nights which focus on ingratitude and metamorphosis as dominant themes and some of Franz Kafka’s animal stories (The Metamorphosis , A Hunger Artist, and A Report to An Academy) which share the aforementioned themes. By doing so, I hope to prove that there is a good reason to assume that Kafka was, at least indirectly, influenced by the book of A Thousand and One Nights which, to the best of my knowledge, is something that haven’t been done before. Key words: Arabian Nights; Franz Kafka; Storytelling & Therapy; Postcolonial Criticism Résumé Raconter des histoires dans le livre de Mille et Une Nuits, les fonctions sont comme un moyen de sublimer le désir de Shahrayar pour le meurtre de Sharazad et de la libérer par la catharsis. à savoir la fonction des histoires comme une thérapie pour Sharayar et comme un mécanisme de lavage de cerveau à travers lequel Shahrazad espoirs de guérir Sharayar de son désir meurtrier qui a conduit à la mort de nombreuses femmes en raison d'un acte de sa femme d'infidélité. Dans cet article, je vais souligner les similitudes entre certaines des histoires dans le livre des Mille et Une Nuits qui se concentrent sur l'ingratitude et de la métamorphose comme thèmes dominants et certains des histoires d'animaux de Franz Kafka (La métamorphose, un artiste faim, et un rapport une académie) qui partagent les thèmes susmentionnés. En faisant cela, je l'espère, pour prouver qu'il ya une bonne raison de supposer que Kafka était, au moins indirectement, influencé par le livre des Mille et Une Nuits qui, au meilleur de ma connaissance, c'est quelque chose qui n'ont pas été fait auparavant. Mots-clés: Mille et Une Nuits; Franz Kafka; Contes & Therapie; Critique post-colonial