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Powder Bed Fusion
Full text linkThis chapter presents the available powder bed fusion technologies for the processing of polymers. Selective laser sintering (SLS) is the most commonly used technique; the process involves the deposition of a powder layer and the use of a laser to selectively melt the region of interest. The 3D object is therefore produced with a layer-by-layer strategy. The increasing interest of both scientific and industrial communities for this technique has promoted its development, which nowadays is involved for the production of functional prototypes and a small series of components. An alternative and emerging technique is multi-jet fusion (MJF); differently from selective laser sintering, MJF uses an infrared (IR) radiation to promote the melting of thermoplastic polymers. Both these processes will be discussed in terms of required processing conditions, available materials and all the processing aspects which can influence the properties of the final component. Conclusively, some alternative technologies including selective mask sintering (SMS), high-speed sintering (HSS) and selective inhibition sintering (SIS) will be presented
High temperature hot corrosion and oxidation resistance of aluminized blade for aeroplane engine applications
No full textDissimilar friction stir welding of AA2198 and AA7475: Effect of solution treatment and aging on the microstructure and mechanical strength
Full text linkA post-weld heat treatment consisting of solution treatment and subsequent aging (STA) is widely applied to aluminum joints fabricated by friction stir welding (FSW) to improve the mechanical strength via precipitation hardening. In this study, aerospace aluminum alloys of AA2198 and AA7475 were FSWed in similar and dissimilar states. Differential scanning calorimetry (DSC) was used to trace the precipitation strengthening during the aging of welded specimens. The post-weld aging procedures were designed based on the DSC outputs. Accordingly, welded sheets were solution treated at 480 °C and 540 °C for 10–90 min, air-cooled and aged at 155 °C and 170 °C for 2–40 h, respectively. Optical micrographs revealed that due to the faster kinetics of the recrystallization, higher homogenizing temperature led to nucleation of the finer grains from highly stress localized points in the stir zone (SZ) and TMAZ by faster growth rate. Higher time and temperature of the solution-treatment eventuated in accumulation of Cu-enriched intermetallic phases in the grain boundaries at SZ and TMAZ of AA7475, attenuation of the grains adhesion and failure of the sample. Hardness test results showed that the hardness increased in AA7475 alloy while decreasing in AA2198 alloy in the as-welded state. Post weld heat treatment enhanced the hardness in AA2198 and reduced it in AA7475. However, it had no significant effect on the grain size
Effect of the mobility of active species on the soot-combustion kinetics of some Cs-V catalysts
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Cs-V catalyst for soot combustion produced by solution combustion synthesis: characterization and activity
No full text3D Printing of Low-Filled Basalt PA12 and PP Filaments for Automotive Components
Full text linkFused Deposition Modeling (FDM) enables many advantages compared to traditional manufacturing techniques, but the lower mechanical performance due to the higher porosity still hinders its industrial spread in key sectors like the automotive industry. PP and PA12 filaments filled with low amounts of basalt fibers were produced in the present work to improve the poor mechanical properties inherited from the additive manufacturing technique. For both matrices, the introduction of 5 wt.% of basalt fibers allows us to achieve stiffness values comparable to injection molding ones without modifying the final weight of the manufactured components. The increased filament density compared with the neat polymers, upon the introduction of basalt fibers, is counterbalanced by the intrinsic porosity of the manufacturing technique. In particular, the final components are characterized by a 0.88 g/cm3 density for PP and 1.01 g/cm3 for PA12 basalt-filled composites, which are comparable to the 0.91 g/cm3 and 1.01 g/cm3, respectively, of the related neat matrix used in injection molding. Some efforts are still needed to fill the gap of 15–28% for PP and of 26.5% for PA12 in tensile strength compared to injection-molded counterparts, but the improvement of the fiber/matrix interface by fiber surface modification or coupling agent employment could be a feasible solution
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