Procedia Materials Science最新文献

Friction stir processing (FSP) was used to modify the microstructure in 316L austenitic stainless steel. FSP was successfully applied on 6 mm thick plate using a 16 mm diameter cylindrical WC-3%Co tool with rotating and traverse speeds of 315 rpm and 31.5 mm/min, respectively. Grain refinement, microstructural control and the related recrystallization mechanisms were characterized using optical microscopy and FE-SEM. The results indicated that the nanograins with 50-200 nm in size have been achieved from base material with grain sizes of 30-40 μm. The restoration mechanism responsible for the formation of nanostructure is likely to be discontinuous dynamic recrystallization (DDRX). Decreasing the grain size during FSP led to considerable improvement of surface mechanical properties such as twofold increase in wear resistance and threefold increase in surface hardness. There was a continuous decrease in hardness from the nanograin sized stir zone with 510 HV towards the base material with 180 HV.

In our daily life, the safety plays a vital role to safeguard many important things, which include money, gold, documents, etc. The most common form of security is the age old lock and key system. The diversity that exists in the world today among peoples professions raises the need for multiple duplicate keys. 3D printing, a rapidly growing innovative methodology of Additive Manufacturing Technology, allows the mass production of required profiles in a fast and cost-effective manner. MakerBot Replicator 2X Experimental 3D printer uses the Fused Deposition Melting (FDM) method to produce components with Acrylonitrile Butadiene Styrene (ABS) material. This paper presents an innovative methodology to create an accurate duplicate of a key. This methodology can be extended to print any component.

Effect of 0.05, 0.1, 0.5, 1 and 3 (wt. %) Ca addition and extrusion process on the microstructure and tensile properties of Mg-Mg₂Si metal matrix composite has been studied by the use of optical microscopy (OM) and standard tensile testing. The average size of primary Mg₂Si particles decreased from 34 μm to about 10 μm with the addition of 0.05 (wt.%) Ca and extrusion process and also the size of eutectic Mg₂Si decreased from 20 μm to about 2 μm. The morphology of Mg₂Si particles altered from octahedron to fine polygonal and more round shape and eutectic phases altered to well distuributed fragmented particles on the microstructure that was enhance the mechanical properties in comparison with as-cast specimens. Tensile test showed that UTS value increases with the addition of Ca. The maximum UTS value was achieved with 0.1 (wt.%) Ca addition.

The chemical reduction of graphene oxide (GO) typically involves highly toxic reducing agents that are harmful to human health and environment. Moreover, complicated surface modification is often needed to avoid aggregation of the reduced GO during reduction process. In this paper, GO was synthesized by modified Hummer's method. Modified hydrothermal method was utilized to prepare reduced GO in pH value of 11 adjusted by NaOH at 140 °C for 6 h under continuous stirring. FTIR, Raman, SEM and XRD analyses are performed, which reveal that the labile oxygen functional groups are progressively eliminated, thereby partially restoring the π-conjugated network. Raman spectra show G to D band progression. Furthermore, XRD results confirm proper GO reduction. Carbonyl, carboxyl, ether, and phenolic groups are found to be thermally stable, which hinders complete deoxygenation of GO and makes their dispersion in water stable. In modified hydrothermal method, pressure can be controlled efficiently and temperature is lower than simple hydrothermal method. Also, the final product has homogenous structure, thus facilitating the use of graphene-based materials for large-scale applications.

The MgO-C bricks are extensively used as lining work on different steel containers. Due to the high temperatures of the process, these refractories are subjected to severe wear and corrosion processes, principally in the area of contact with the slag. These slags have variable contents of CaO, SiO₂, Al₂O₃, MgO and FeO, varying in composition according to the process stage. In this paper, cup tests were performed at 1650 °C during 2 hours in air, using three kinds of commercial MgO-C bricks. They were put in contact with a high basicity slag. The corrosion degree and decarburization level sufferered by the refractories were analyzed and compared. Microstructural observations were performed in order to postulate the probable corrosion mechanisms acting on each material.

One of the most powerful techniques to extract physical and chemical information of a material is the light scattering. Opposite to x-ray scattering for instance, where an average of the sample properties is obtained, Raman scattering is a local probe which can be used to detect inhomogeneities, local strain, lack of crystallinity, anharmonicities or information on the electronic structure by means of resonant Raman scattering. In this work, we will analyze the main contributions of Raman scattering in Materials Sciences. After a brief introduction of the technique and the equipment needed for the physical measurements, we will give practical examples of Raman scattering measurements applied to a number of materials and the valuable information obtained in every example.

Friction stir welding (FSW) has produced a great impact in several industries due to the advantages that this process presents. In particular, the automotive industry has developed a variant of the original process, called Friction Stir Spot Welding (FSSW), which has a strong interest related to the welding of aluminum alloys and dissimilar materials in thin sheets. Aluminum-steel welding is an actual challenge, being FSSW an alternative to produce these joints. However, the information available related to the influence of process parameters on the characteristics of aluminum-steel joints is scarce. The aim of this work was to study the effect of the pin length of the welding tool and its penetration depth, during friction stir spot welding (FSSW) of overlaps joints of AA6063 with galvanized low carbon steel. FSSW was done by changing the pins length between 0.65 and 1.5 mm, and also by modifying the tool penetration depth in the welded joints. On the welded spots macro and microstructural characterization was performed, Vickers microhardness profiles were determined and Peel and Cross Tension Tests were also done. The maximum loads increased when the tool penetration depth goes up and the pin length decreased. The fracture mode was, at first, interfacial meanwhile it changed to a circumferential mode when the tool penetration depth increased and the pins length was reduced.

In the last 50 years in the worldwide market for power transmission cables, there has been a tendency to replace aluminium cables electrical grade (EC) with steel cables by fully aluminium alloy (AAAC). The advantage in using cable AAAC is mainly economic (least amount of support structures and maintenance), addition to the elimination of the problems of galvanic corrosion and improved abrasion resistance. In order to obtain better mechanical properties, respect to the pure aluminium, aluminium alloyed with magnesium and silicon (AA6XXX series) is used, which by a combination of cold working and heat treatment allows obtaining greater mechanical strength without affecting too much the electrical conductivity. In this development it has worked with AA6101/6101 M alloy. The manufacturing of aluminium alloy wire rods for such applications, using the conventional process Properzi, requires heat treatment of solubilized, continuous or discontinuous (batch). During the waiting time of two months or more, the wire coils are exposed to natural aging at room temperature, entering into the wiredrawing machines with different mechanical properties. The wires obtained by the traditional method of manufacture in Argentina, through the wiredrawing, result in significantly higher mechanical properties, not complying with the standards. Furthermore many breaks occur mainly when a high tensile strength wire is processed for wire 2 mm in diameter or less. In the proposed method, a part of the initial wiredrawing is replaced by cold rolling and a subsequent partial aging. The results obtained in this study allow us to conclude that in the proposed process better properties and mechanical integrity are achieved than the traditional process, maintaining the electrical conductivity.

It is true that nanotechnology has become one of the influential technologies in this century since it has been successful in fascinating all most all manifolds of technology, like that it has also embraced the field of Civil Engineering. More particularly the construction sector finds its advantage with nanotechnology, construction industry needs more material and energy resources. Among all the materials used in construction, concrete occupies nearly 70% of the materials by volume and shows significant impact. The advent of nanotechnology helped in producing more strong and durable material than conventional materials. Nanotechnology in making concrete refers to the production and addition of nanosized particles in to concrete at suitable proportions by appropriate methods. The basic purpose of using nanosized materials in concrete is to improve compressive and flexural strengths at early age, it is possible due to the high surface – to volume ratio. It also helps to improve the pore structure of concrete. Nanosized materials help to reduce porosity as they absorb less water compared to traditional cementitious materials. The presence of nanomaterials reduces the amount of cement content in concrete than the conventional concrete. This can be achieved without sacrificing strength characteristics, thereby it is possible to produce eco friendly concrete called green concrete. This paper tries to review how nanotechnology is used in civil engineering and its effects on various nanomaterials viz. steel, glass, wood and the paper also throws a special focus on concrete how does it affect various properties of materials.