Materials Science Forum Vols. 537-538

Abstract: The TIG welding has a high disadvantage against the substantially high productivity welding procedures. This is why there were continuously going on several trials to improve the productivity of the TIG welding. The Activated Tungsten Inert Gas welding (ATIG welding) is one of these trials. Application experiments of ATIG welding on austenitic stainless steel plates will be presented. The main problems which appear when using the ATIG welding are the choosing of tungsten electrode, the suggested fitting of parts for the joining, portioning of the activating flux and the sensitivity for the measure of flux. They are extremely important to apply the ATIG welding and the results will be presented by this work. In the second half of this paper the comparison of the productivity differences between TIG and ATIG welding; mechanical properties, microstructure and corrosion resistance of welded joints will continue. Finally the evaluating the results and trying to classify the ATIG welding amongst the modern and most productive welding procedures is detailed. Furthermore advises for using the ATIG welding for suitable applications are represented.

Abstract: The effect of span-to-thickness ratio (L/h) on the bending modulus was investigated in warp, 45°, 67.5° and weft directions in woven glass fiber reinforced polyester laminates. Using classical beam theory the results of the bending tests carried out for L/h = 5,..,50 were extended to the total range of definition (0≤L/h<∞) by applying rational fractional and exponential fractional functions. The extensions take the asymptotic behavior of the bending test for L/h = 0 and L/h = ∞ in account while providing the best fitting to the measured data. It has been shown that the exponential fractional estimations give better results regarding the form of functions that is independent from the directions.

Abstract: The selected dihydroxamic acid derivatives, namely oxalyl-dihydroxamic acid (C2) and pimeloyl-1,5-di-hydroxamic acid (C7) have been synthesized and evaluated as corrosion inhibitors for carbon steel in neutral aqueous solution by potentiodynamic polarization and ac impedance methods. C2 molecule acts as good inhibitor with inhibition efficiency value reached 91%; it is well adsorbed most likely throughout the two hydrophilic groups, and forms a protective film on the metal surface. C7 has moderate inhibition efficiency probably due to the presence of long single hydrocarbon chain in the molecule, negatively affect the adsorption process. Addition of Ni2+ to C7 significantly improve the inhibition efficiency, throughout the formation of a dense compact layer of complexes between Ni2+ and C7.

Abstract: Surface coatings of Al-Si/SiC metal-matrix composites were deposited on Al-7 wt. % Si alloy substrates by laser cladding. The microstructure of the coatings was characterized by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The microstructure of the coating material is profoundly influenced by the processing parameters used, in particular by the particle injection velocity and by the specific energy. When the injection velocity is low or specific energy is high excessive dissolution of SiC in the melt pool occurs. The microstructure of the coatings presents partially dissolved SiC particles, and considerable proportions of Al4SiC4 plates and faceted Si equiaxed crystals dispersed in a α-Al+Si eutectic matrix. On the contrary for high injection velocity or low specific energy dissolution of SiC is very limited and the microstructure of the coatings consists essentially of undissolved SiC particles in a matrix consisting of primary α-Al dendrites and α-Al+Si eutectic. Abrasive wear tests were performed on the coatings using a ball cratering device and a 35 wt. % suspension of 4.25 μm average diameter SiC particles in water as abrasive. Coatings prepared with a high specific energy present an average hardness of 248 HV and an average abrasive wear rate of 17.4x10-5 mm3/m. Coatings deposited with a low specific energy exhibit an average hardness of 117 HV and an average abrasive wear rate of 4.3 x10-5 mm3/m.

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Abstract: Highly oriented polypropylene fiber reinforced random PP copolymer composites were produced by film-stacking method. The reinforcing fibers were carded and needle punched and the film-stacked packages were compression molded at different processing temperatures (T=150…170°C) and holding times (t=90…600 s). For characterization of the consolidation of the composite sheets interlaminar strength was determined and further the polished sections were studied by light microscopy. Static tensile and dynamic impact (instrumented falling weight impact - IFWI) tests were performed on the specimens cut from the sheets. It was established that the best properties can be achieved when the processing conditions are 165°C and 90s. Increasing temperature and improving consolidation reduced perforation impact energy owning to better fiber/matrix adhesion and the smaller extent of delamination between the film-stacked layers.

Abstract: The ageing phenomena and its effect on the thermoelastic martensitic transformation was investigated in three Cu-base SMAs. The transformation temperatures shifted to higher temperatures due to aging in the beta-phase. To increase the alloy’s ductility, a definite amount of Mn (4 wt%) and Fe (2 wt%) were added to the ternary alloy. The thermoelastic martensitic transformation was found in the not-aged samples of the CuAlNiMn and CuAlNiMnFe alloys. This transformation was destroyed due to ageing heat treatments by a fairly unknown exothermic process. The thermoelastic martensitic transformation appeared again in the aged CuAlNiMn and CuAlNiMnFe samples after keeping them on room temperature for a few months. This phenomena was investigated by DSC, SEM, TEM, and XRD.

Abstract: Different properties (tensile strength, elongation, modulus, impact strength) of rice husk (RH) reinforced polypropylene (PP) coupled by Maleic-Anhydride grafted Polypropylene (MAgPP) have been investigated. MAgPP is an effective coupling agent, not only in cellulosic-fibre filled polyolefine composites, but in rice husk flour filled polypropylene composite systems as well. It gives a utilizable construction polymer matrix composite (PMC) material even at a 40 wt.% RH filling degree. The strength and modulus increases by adding the rice husk but the elongation decreases in a non-monotonic way. Micrographs shows weak coupling in between RH and PP without MAgPP.