Abstract: Friction Stir Welding (FSW) is a novel solid-phase welding process, which has proved to have a great potential for the realization of welded joints in materials with poor weldability such as heat-treatable aluminum alloys. However, the thermal cycles generated during FSW change the mechanical properties in heat affected zone (HAZ) due to two effects: over-age and re-dissolution of hardening precipitates. In other hand, the re-dissolved precipitates produce a evolution of both the microstructure and mechanical properties due to the natural aging phenomenon. The aim of this paper was to analyze the microstructural evolution in the HAZ of FSW joints in AA7075-T651 alloy. For this purpose samples FSW welded butt plate 4 mm in thickness. On the welded joint microstructural characterization was performed by light microscopy (LM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) and Vickers microhardness profiles (HV) after different elapsed times post welding. It was observed that the hardness increases with time after welding, due to the evolution of the phases present.

Abstract: This research studies the metallurgical transformations happening during the SMAW welding of AISI 316L austenitic stainless steel with AISI 430 ferritic stainless steel. Two different electrodes, AWS E309L austenitic and AWS E2209-16 duplex stainless steels 3.2 mm diameter, were used to perform the study. The joining was made with a single pass welding and keeping a low heat input ranging from 700 - 1000 J/mm. The influence of the type of electrode and the heat input on the microstructural evolution of the heat affected and the fusion zone was evaluated. Differences between δ ferrite morphology were found for both weld metals. The heat affected zone of the ferritic side showed grain coarsening and grain refinement with martensite at the grain boundaries. Tensile strength was similar for both welding conditions. Microhardness and δ ferrite percent were measured as well.

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Abstract: Sugarcane bagasse (SCB) is abundantly available agro-waste world-wide and has been used in different applications and its utilization as a source of cellulose attracting attention in the area of biomedical and other applications. The present study investigates the surface morphology, topography, structural, elemental and thermal properties of cellulose nanocrystals (CNCs) extracted by acid-hydrolysis from sugarcane bagasse as agro-waste. Morphological (field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM)), structural (fourier transformed infrared (FTIR) spectroscopy, X-ray diffraction (XRD)), elemental analysis (energy dispersive x-ray diffraction (EDX)) and thermal characterization (TG-DTG-DTA) of CNCs was carried out. Morphological characterization clearly showed the formation of rod-shaped CNCs having size in the range of 250-480 nm (length) and 20-60 nm (diameter). Elemental analysis (EDX) showed 0.72 wt% sulfur impurity in CNCs along with other main components. X-ray diffraction and thermal analysis revealed that CNCs have higher crystallinity (72.5%) than that of chemically purified cellulose (CPC) (63.5%) but have lower thermal stability. These lab extracted CNCs supposed to have a high potential as nano-reinforcement into bionanocomposite for biomedical and other value-added products in industrial applications.

Abstract: Single crystals of Cd_1-xZn_xTe (0 ≤ x ≤ 0.1) (CZT/CdZnTe) are used in manufacture of gamma and X-ray detectors and as substrates for epitaxial growth of HgCdTe. Computer simulation for the solidification of CZT was performed using finite elements. The simulation results indicate that a lower translation speed of the quartz ampoule within the Bridgman furnace determines a lower concavity of the liquid interface which assures a good crystalline quality. When the rate is 3.32 mm/h the concavity is 58% greater than for a speed of 0.50 mm/h. It was experimentally found that when growing at low speed, 1.66 mm/h, the process is more stable and improves the crystalline quality due that only two grains were generated in CZT ingots. Meanwhile a faster growth speed- 3.32 mm/h- generates a large amount of grains in the CZT ingot.