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Advanced Processing and Characterization of Al- Based Composites Containing Aｌ3X Intermetallics Platelets
No full textMetallurgical investigation of early failure of heater pipes in a gas complex
No full textAbstract An early corrosion failure of the piping system of a gas heater was reported by a gas complex company. Local corrosion rates of 0.90 and 0.66 mm/year were observed in the heater piping system. An investigation including visual examination, macrostructure, microstructure (SEM, EDS and XRD), thickness gauging, chemical analysis, and mechanical testing, was performed. The results showed that corrosion damage occurred on the external surface of the pipes. Corrosion occurred at the cold sides of the pipes and elbows. The corrosion pattern is broad and shallow pitting. Some elbows showed an early stage of carbide spheroidization and pearlite decomposition. The EDS microanalysis revealed that the level of sulfur, chlorine, and nitrogen was substantially high in the rust samples. The XRD of the corrosion products showed that the main oxyhydroxide was Akaganeite. The analysis of results showed that the flue gas dew point corrosion was the mechanism of damage, and the root cause was the operation of the heater at low temperatures and the frequent outings of service, combined with evident material drawbacks including low levels of Si, Cu, Ni, Cr, and Mo. These elements should be at their maximum allowable limits of the SA 105 and SA 106 to improve the corrosion resistance of the steel piping components
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Surface Modification Effects on Microstructure and Mechanical Properties of Bio-Titanium Alloys
No full textTi-6Al-7Nb (Ti67) alloy has recently been developed to replace the commercial Ti6Al4V (Ti64) alloy because of the reported cytoxicity of vanadium. Surface modification by thermal oxidation is used to enhance the hardness and wear resistance of such titanium alloys. Since Ti67 alloy contains Nb as β phase stabilizer instead of V in Ti64, it is expected to behave differently upon processing by thermal oxidation. Therefore, it is of interest to compare the response of the two alloys to thermal oxidation in terms of hardness and wear resistance. Forged and cast samples were used to study the influence of the microstructure on the surface properties after oxidation. The forged samples with their equiaxed microstructure showed a well developed sub-surface hard layer (α-case) compared to the cast structure for the two alloys. The thickness of this case in Ti64 after oxidation at (900-1100 °C) was greater than in Ti67. This resulted in higher wear resistance of the Ti64 alloy relative to Ti67. These results are worth considering when designing implants for joints replacement.</jats:p
Microstructure and Wear Behavior of Solidification Sonoprocessed B390 Hypereutectic Al-Si Alloy
No full textWear of Al/Al3Zr functionally graded materials fabricated by centrifugal solid-particle method
No full textVariations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Assessment of Tribological Properties of Cast and Forged Ti-6Al-7Nb and Ti-6Al-4V Alloys for Dental Applications
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