The effect of friction stir welding (FSW) on the resultant microstructures in the welded nugget (WN), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and base metal (BM) of a TRIP-780 steel was investigated in this work. Color tint etching was used in the welded regions to disclose the exhibited microstructural constituents. In addition, significant fine grain size material was found in the WN regions. It was found that is considered to have experienced severe plastic deformation due to interaction with the welding tool pin lead to a drop in mechanical properties. Lap shear tensile testing indicated that the steel shear tension strength in the welded condition dropped compared with the BM. Microhardness profiles of the welded regions indicated that the hardness in both the WN and TMAZ were relatively elevated suggesting the development of martensite in these regions. In particular, the WN was found to shear fracture with uniformly distributed elongation shear dimples.

Arsenic is one of the most toxic elements that can be found. Arsenic is mainly emitted by the copper, lead and zinc production, in agriculture as pesticides and herbicides. Two forms of arsenic are common in natural waters: arsenite (AsO33−) and arseniate (AsO43−), referred to as As(III) and As(V). The nano-Mg/Al-hydrotalcites present ionic exchange and adsorbent capacities. In this work, the physic-chemical characterization of nano-Mg/Al-hydrotalcites and his arsenic removal capacityis described. The solids were synthesized by the sol-gel method with Mg/Al=2 and 3 ratio. The solids and their thermal treated products were characterized by XRD, FTIR, DTA, TGA and N2 adsorption. The solids were used as adsorbents As(III) in aqueous solutions. Adsorption isotherm studies of As(III) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin–Radushkevich adsorption isotherm models. The As(III) adsorption isotherm data fit best to the isotherm Freundlich model. The maximum As(III) uptake capacity by nano-Mg/Al-hydrotalcites and the heated solids were determined using the Freundlich equation and were found to 547.46, 660.15, 799.88 and 739.12 mg As(III)/g HT-Mg/Al=2, HT-Mg/Al=3, HT-Mg/Al=2 at 350°C and HT-Mg/Al=3 at 350°C respectively. In the kinetic studies using 40 mg/L concentration of As(III) solutions was obtained an excellent removal capacity in contact times less at one minute.

Duplex stainless steels (DSS) have good mechanical and corrosion resistance properties which allow their application in very aggressive environments. However, their aging at 600–1000 °C causes the precipitation of dangerous intermetallic phases, resulting in serious detrimental effects on their interesting properties. These secondary phases are structural discontinuities which act as preferential cracks initiation sites and their negative effect is especially highlighted on toughness. For these reasons, many standards related to the manufacturing of DSS require the microstructure of these steels "free from intermetallics". In this paper, the effect of isothermal heat treatments on the impact toughness in two Duplex steels (SAF 2205 and Zeron®100) has been investigated, in order to study the influence of different amount of secondary phases on the toughness response.

Recognition of material structures, particularly, identification of electrical properties of materials by Electrical Tomography is very important in different applied problems. In a plane case Electrical Tomography can be mathematically described as a coefficient inverse problem for the Laplace type equation, written in the divergent form. The General Ray (GR) Principle, proposed by the author, reduces the Laplace type equation to the family of ordinary differential equations with respect the traces of the potential function and the permittivity function on the lines, which intersect the plane domain. General Ray Principle was realized as General Ray method and fast algorithm for the plane domains. In presented investigation we apply the plane scheme of GR-method for some space domains to identify distribution of structure characteristics inside it. For this we consider the space domain as assemblage of plane slices. Reconstructing desired distribution in each plane slice we obtain then the space internal distribution of electrical characteristics by 3D spline approximation. We consider here specific variant of the measurement scheme for the 3D Electrical Tomography (ET), based on the variant, proposed by the author for the plane domain. Proposed approach gives, in principle, the possibility to use a large number of electrodes, obtain more values of the input data and reconstruct the desired space structure more perfectly. Computer simulation of this 3D scheme is realized as MATLAB software and justified by numerical experiments on simulated examples.

Recently they have discovered a large number of oil wells, however these are found in deeper waters. So it is necessary to develop a repair's methodology and inspection for this type of system to prove its operation. This research was focused to establish a methodology for evaluating residual stress generated from the application of solder in a subsea environment, in order to establish whether there is a relationship between residual stress and the depth of the sea. For this purpose was used underwater electrodes (UW -CS- 1) and an API 5L X65 steel to the development of underwater welds, which was welded at 10 and 15 meters depth by a diver welder on site. The measurement of residual stress is developed using non-destructive techniques, the first one was ultrasound technique (UT) which was the technique proposed by viability to being applied in site and as a second option, was applied X-ray diffraction (XRD), with the objective to validate the results obtained by ultrasound technician. The results showed a similar behavior between both non-destructive techniques. In this study was observed the tendency to increase the level of residual stress with increasing the work depth.

This study evaluates the behavior of the adherence layers - sawn flat iron boride formed on the surface of steels used in manufacturing industry in Mexico. In steels AISI 1018, AISI 8620 and AISI 316 was characterized this behavior, boriding thermochemical treatment with box technique, with a processing temperature of 1273 °K, with an exposure time of 8 hours. Furthermore the adherence is assessed by the Rockwell C hardness technique prescribed by the German standard VDI 3198 of traction, this impact test qualitatively determine the type of adherence formed three thermochemical steels treated by the technique of boriding. Moreover optical microscopy determines the type of film morphology FeB/ Fe2B of each of the materials exposed to a boriding, also shows the thicknesses of the phases generated in the surface type in all three steels boriding. Phase presence boride FeB/Fe2B was determined by X -ray diffraction (XRD). Technique for scanning electron microscopy (EDS) was evaluated qualitatively the presence of FeB/Fe2B of boronizing. Otherwise determines the hardness and elastic modulus by nanoindentation technique of the phases present in the three steels. Lastly, AISI 1018 and AISI 8620 are bounding scale H1 to H3, the AISI 316 steel has an adherence of H3 to H6 under German standard VDI 3198.

The effect of the heat input on the mechanical and metallurgical properties of the welds has been investigated in the heat affected zone (HAZ) of welds joined with gas metal arc welding (GMAW), using normal production welding parameters. The thermal effect in the HAZ of the welds is important for the optimization of the welding parameters used when weld transformed induced plasticity (TRIP) steels, because this will have a great influence in the mechanical and metallurgical properties of the weld. In this work 3 samples was welded a high, average and low heat input, with the variation of welding parameters to obtain different thermal affectation to investigate the variations in different parts of weld joint: weld, HAZ and base metal, due the heat applied for the welding process used. Mechanical properties were evaluated by tension test, microhardness and fatigue testing and metallurgical evaluation with optical metallograpy, scanning electron microscopy (SEM), fractograpy and X-Ray diffraction (XRD).The results obtained shows that the mechanical properties of the tension test decrease when the heat input increase and the microhardness exhibit a softening zone in the HAZ with lower hardness and the fatigue life were similar for all heat inputs for the high stress levels, but only in low stress there is a difference. For metallurgical properties the metallographic evaluation shows ferrite, bainite - martensite and retained austenite, and the fractography analysis exhibit a ductile fracture in all cases and the content in volume fraction of retained austenite increases in the HAZ of welds when increasing heat input in to the base metal due the thermal effect.

Gas metal arc welding (GMAW) of a sub-frame automotive industry was studied, applying a design of experiment (DOE) in Minitab and Matlab software. Voltages, welding speed and wire feed speed was defined as input variables; legs and throats of welding were output variables in millimeters dimension. The requirement for GMAW process was to achieve complete penetration, minimum values acceptable of legs and throat indicated in AWS D8.8M:2007 “Specification for automotive weld quality-arc welding” without any discontinuity, like undercutting or porosity. The required of quality were difficult to achieve due to the materials have microstructural and mechanical properties different, the SAE 1008 has 279MPa for ultimate tensile strength (UTS) and the microstructure consist of ferrite matrix with some small areas of cementite, while SAE 2340 has 456MPa of UTS with a combination of perlite and ferrite. It was possible obtain good quality welds with proper geometry and defect free with help to design of experiment. The conditions needed were a combination of parameters to not obtained significant change microestructural characterized by optical microscopy, stereoscopy and scanning electron microscopy.

Today, stainless steel is widely used in automotive industry due to its high impact resistance, corrosion resistance and light weight. This paper present the research carried out to study the differences between microstructure and mechanical properties of 409 and 308 stainless steel sheets, each joints by gas tungsten arc welding (GTAW). For each of weldments, detailed analysis was conducted on the chemical composition, microstructure characteristics and mechanical properties of base metal (BM), heat affected zone (HAZ) and fusion zone (FZ). Scanning electron microscopy (SEM) and optical microscopy were used to analyze microstructural changes and mechanical properties, including microhardness and tensile test. This study can be a practical guide in the selection of other materials in order to determine the important to use in structural automotive industry.

Effect of residual stresses of multiple welding repairs on API 5L X52 pipeline steel on stress corrosion cracking (SCC) in a simulated acidic soil solution was studied. Four conditions of repairs of the girth weld were evaluated. The residual stresses were measured through X-ray diffraction (XRD) on the internal side of the pipe in longitudinal and circumferential direction. The circumferential and longitudinal residual stresses values are compressive on the inner surface of the welding joints. The highest residual stresses were measured in the hoop direction reaching values of about 98% of the yielding strength (360 MPa). It was observed that its magnitude increases as move away from weld center line. The effect of residuals stresses in the SCC susceptibility of X52 pipeline steel was evaluated through slow strain rate tests (SSRT) in a simulated acidic soil solution. Relation between mechanical properties obtained from SSRT and residual stresses on the SCC susceptibility was analyzed. Results of SCC index taking account the ratios obtained from the mechanical properties of the welding joints evaluate, showed good SCC resistance in acidic soil solution at low pH. Scanning electron microscopy (SEM) observations showed that the region with high residual stresses prior to generate cracks in the steel due to the combination of soil solution and the strain exerted, should favor pitting formation and not cracking.

The massive crystal growth of single crystal semiconductors materials has been of fundamental importance for the actual electronic devices industry. As a consequence of this one, we can obtain easily a large variety of low cost devices almost as made ones of silicon. Nowadays, the III-V semiconductors compounds and their alloys have been proved to be very important because of their optical properties and applications. It is the case of the elements In, Ga, As, Sb, which can be utilized for the fabrication of radiation sensors. In this work we present the results obtained from the ingots grown by the Czochralski method, using a growth system made in home. These results include anisotropic chemical attacks in order to reveal the crystallographic orientation and the possible polycrystallinity. Isotropic chemical attacks were made to evaluate the etch pit density. Metallographic pictures of the chemical attacks are presented in this work. Among the results of these measurements, the best samples presented in this work showed mobilities of 62.000 cm2/V*s at room temperature and 99.000 cm2/V*s at liquid nitrogen temperature. Typical pit density was 10,000/cm2. The Raman spectra present two dominant peaks associated at Transversal Optical (TO)- and Longitudinal Optical (LO)-InSb, the first vibrational mode is dominant due to the crystalline direction of the ingots and second one is associated to high defects density.