Materials Science Forum Vol. 805

Abstract: In this work was carried out the microstructural characterization and evaluation of mechanical properties of steel with different microstructures. The intercritical region and the existing phases in function of temperature were determined using the THERMOCALC software. The samples of steel were quenched at different temperatures to obtain differents microstructures consisting of ferrite, pearlite and martensite. The microstructural characterization of the samples was performed by qualitative and quantitative metallography. The determination of volume was performed with the "Image J" software. The mechanical properties were determined by uniaxial stress test, which determined the parameters: yield strength, tensile strength, breaking point and total elongation.

Abstract: In this work it was analyzed the evolution of mechanical properties of Dual-Phase steel as a function of volume fractions of ferrite and martensite, obtained from steel type LNE 380. The intercritical region and the existing phases in function of temperature were determined using the THERMOCALC software. The samples of steel were quenched at different temperatures to obtain differents microstructures consisting of ferrite, pearlite and martensite. The microstructural characterization of the samples was performed by qualitative and quantitative metallography. The mechanical properties were determined by hardness and impact tests. It was concluded that the volume fraction of ferrite and martensite calculated experimentally agrees with the simulation and the variation of these fractions affects significantly the hardness of the steel, but does not significantly affect the results of fracture toughness.

Abstract: In the second half of the last century, the automobile industries were affected from the petroleum crisis caused mainly by the wars in the Middle East. These crises led the automakers reconsider their vehicles. One of the most important events after that was the adoption of new steels by the industry. One example is the TRIP steels (Transformation-induced plasticity). In this work, a specimen of TRIP steels was etched using LePera reagent. The obtained images were analyzed using digital processing. Using the ImageJ software the methods threshold and watershed were studied. The methods were compared: the morphological characteristics and volumetric fraction of the retained austenite and martensite phases were analyzed. The results showed that the threshold led to a higher number of identified grains with lower mean area and total area fraction than the watershed method.

Abstract: A modified SAE 4118H steel was subjected to isothermal treatments between 700 °C and 400 oC every 50 °C range, with the intention of evaluating the decomposition of austenite at constant temperature. It was varied time of stay in the isothermal treatment between 15 and 28800 seconds depending on the treatment temperature. After each isothermal treatment and standard metallographic preparation, the samples were etched with color metallography reagents for revealing the microstructure obtained. At temperatures of 700oC to 550°C the steel showed microstructure composed of ferrite and pearlite. Between 500oC and 400°C bainitic microstructure was quickly formed. The reduction of treatment temperature provided finer microstructures, which increased the hardness of steel. With the use of color metallography reagents, excellent contrast for determining the volume fraction of microstructural constituents formed isothermally was obtained, helping the study of isothermal decomposition of austenite.

Abstract: A comprehensive set of experiments used to study the temperature distribution inside the chamber of a heat treatment furnace is presented, considering the surface and the core of steel SAE 8640 samples. The objective is to evaluate the best control strategy in order to achieve a better uniformity between the temperature of the core and the surface of the part with the desired temperature of treatment.

Abstract: Cobalt and cobalt-manganese spinel ferrites have magnetostrictive properties suitable for application in magneto-electric and magneto-mechanical transducers. In this work, copper-substituted ferrites of these compositions were processed by means of the ceramic method and their sinterabilities were evaluated by dilatometric thermal analyses. The results obtained suggest that copper affects the solid-state reactions for the spinel formation and lowers the required sintering temperature for the ferrites. However, the densification obtained with sintering of the copper-substituted ferrites at 950 ^oC for 6h was only 64%, which indicates that further adjustments on the processing route must be made in order to obtain higher densities.

Abstract: Open pit mine design and production scheduling deals with the quest for most profitable mining sequence over the life of a mine. The dynamics of mining ore and waste, and spatial grade uncertainty make predictions of the optimal mining sequence a challenging task. Valuation and related decision-making in surface mining require the assessment and management of orebody risk in the generation of a pit design and long term production scheduling. As the most profitable mining sequence over de life of a mine determines both economic outcome of a project and the technical plan to be followed from mine development to mine closure, the adverse effects of orebody risk on performance is critical and are documented in various studies. Ignoring such a consequential source of risk and uncertainty may lead to unrealistic production plans. This paper presented a set of procedures that enable mine planning engineers to carry out a series of analysis, which can be used to evaluate the sensitivity of incremental pit shells and pit designs to grade uncertainty. The results obtained from the analysis have shown to provide valuable information, which can be used to develop mining strategies that are risk resilient in relation to grade uncertainty. A real life application at Sossego copper mine ensure that such procedures are technically implementable, supporting decision-making as (a) in-fill drilling programs; (b) review of mining sequence; (c) identification of areas of upside potential and downside risk and (d) ore blending between mining areas in order to minimize the impact of high risk areas. The goal of this work is to provide an approach for clear risk analysis and management in mine planning cycle to various aspects of pit optimisation and design, resulting in more technically and economically sustainable life-of-mine production plans and mineral reserve depletion.

Abstract: Much interest has been aroused in the application in industrial processes using zeolite membrane, due to its crystalline structure, and narrow pore diameters. These features enable the continuous separation of mixtures based on differences in molecular size and shape and also based on different adsorption properties. This paper reports the synthesis of MCM-22 zeolite membrane, using the method of secondary growth. The MCM-22 zeolite was synthesized by the hydrothermal method and characterized by spectroscopy Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM).The ceramic support (α-alumina) was prepared using the technique of forming powder and then subjected to the sintering temperature of 1400 °C/1h and characterized by XRD. The zeolite membrane preparation was performed by the method of secondary growth and characterized by XRD, SEM and mercury porosimetry. The obtained zeolite membrane could be confirmed by X-ray diffraction. From, the obtained SEM pictures it was possible to observe the formation of a homogeneous film on the zeolite surface of the ceramic support (α-alumina).

Abstract: Environmental problems caused by the presence of toxic metals in effluents emitted by various industries are contaminating surface water and subsoil and this has generated much discussion.

Abstract: As minimization process control pollution by heavy metals, adsorption can play an important environmental role. Therefore, many adsorbents can be used as effective alternatives. This work presents a study that aims to evaluate the removal of lead in liquid effluent through adsorption process using a finite bath system and with the adsorbent clay Chocobofe. The clay in its natural form was characterized by the techniques of X-Ray Diffraction (XRD), Cation Exchange Capacity (CEC), Chemical Analysis by X-Ray Spectrometry by Energy Dispersive (EDX), moreover, the natural clay was subjected to test adsorption capacity to analyze the behavior the same in certain organic solvents. Was performed to assess the effectiveness of the natural clay in the process of removal of Pb²⁺ present in solutions based on a factorial design 2³ + 3 replicates at the central point, with the analysis variables solution pH (3.0, 4.0 and 5.0) and the initial concentration of lead (10, 30 and 50 ppm). The studies showed this material as promising in the removal of Pb²⁺ ions in synthetic wastewater and that the adsorption capacity showed that the organic solvents tested.