Ferritic stainless steels are widely used in transportation industry due to their exceptional performance regarding mechanical and corrosion properties. However, after a welding process, joints feature the sensitizing phenomenon because of the heat exchange from the torch affecting mechanical properties and corrosion resistance. This work describes the behavior firstly of mechanical properties of weld joints of ferritic stainless steel as base material without and with filler material (AISI 308L) by gas tungsten arc welding (GTAW). Operating parameters such as arc voltage, welding currrent, welding speed, feed speed, shielding gas flow were evaluated. Secondly, samples of weld joints were coated by flame spraying of composite particles in order to reduce the weight loss induced by corrosion in a salt spray (fog) apparatus. Changes induced from GTAW on the heat affected zone and Thermal Spraying on corrosion resistance, were monitored by optical and scanning electron microscopy, microhardness and longitudinal tensile testing. Results show that GTAW helps to control the size and the microstructure of heat affected zone improving simultaneously the mechanical properties. Meanwhile, welded joints covered by composite coatings feature a lower damage provided that the ceramic phase has been homogeneously dispersed.

The aim of this research was to work out the technology of ceramics for finding optimal sintering temperatures and to study their mechanical properties. Samples were prepared from powders with different volumetric ratio of the components. The powders underwent a prolonged co-milling in a vibratory mill, followed by uniaxial pressing, cold isostatic pressing (CIP) and pressureless sintering in a vacuum furnace under an argon atmosphere. Hot pressing (HP) was applied to some powder formulations. This study showed that it is advisable to carry out the first stage of the heat treatment up to 1550 ̊C under vacuum, with the aim of refining the grain surface from the oxygen-containing impurities due to their dissociation and evaporation. The studied area of formulations has a very narrow range of sintering (1940-1945 ̊C). It was established that the sinterability of the materials is affected by the amount of silicon carbide in the ternary system. Under pressureless sintering, the relative density of the material directly depended on the volume fraction of SiC. However, a change in the concentration of B4C had no appreciable effect on the sinterability of the materials. The application of HP helped us to reduce the negative impact of large amounts of SiC. Under HP at temperatures close to Teut, a certain decompaction of materials was observed with a significant amount of B4C (3-5% loss in density).

In this work it was conducted a pre heat treatment of a number of samples of alumina with organic binder in order to remove most of the organic phase. The treatment showed no effect on the physical properties of test specimens; green bodies remained stable during sintering process. Preheating at 100 °C for 4 h followed by heating at 300 °C for 4 h were the most favorable conditions to avoid formation of defects in the sintered pieces.

A metallurgical by product mostly constituted of Wustita (FeO) was transformed to Magnetite (Fe3O4) spheres using a flame treatment. Then magnetite spheres surface was modified by cold plasma treatment with ethylene, where a thin polyethylene film was deposited on the spheres surface. Finally, HDPE composites with modified spheres were obtained by melt mixing and its thermal conductivity was determined by MDSC. It was found that spheres surface modification helps to increase composites thermal conductivity.

This work shows a cost effective process to prepare carbon-carbon nanostructured composites using mechanical milling (MM) and a new manufacturing method based on rapid induction sintering. Here we use commercially and cost effective amorphous sources of carbon. The nature of the raw carbon is characterized by means of XRD and Raman, and after MM and sintering we observe a clear evolution of the phases of carbon in situ into more complex structures, including but not limited to graphene, graphitic carbon, and nanodiamond. The raw soot transforms in situ into graphitic particles after 1 hour of MM. Further milling (10 hours) induces the formation of nano-diamond particles. Milling times between 1 and 10 h are ideal to prepare intermediate phases between graphene and nanodiamond. In other words MM is capable of inducing the formation of nearly amorphous carbon soot into complex structures that are ideal for structural composite materials. The sintering process is a novel method involving a “pressureless” process and rapid induction heating. Furthermore, the carbon nanostructures that are produced during milling serve as seeds to grow larger particles that can easily reach micrometric sizes. This process achieved high densification as that proposed in commercial methods such as Spark Plasma Sintering.

A protective coating was built and assessed in order to reduce the degradation of metallic substrates caused by corrosion damage. Hence, a set of coatings with different configurations, in terms of layer arrangement, was produced by flame-spraying of composite powder (AISI 316L stainless steel coated with an α-alumina layer) onto an AISI 1018 steel substrate. In order to ensure a homogeneous dispersion of phases, a correlation was established between the operating parameters of thermal spraying (roughness and surface temperature of substrate, spraying distance, passing speed) and the splat formation. Then, corrosion damage caused in the coated samples by exposure to a salt spray was monitored through weight measurements and observations with optical and scanning electron microscopy. The results show that corrosion still remains in all cases; however, it proceeds at lower rates for coatings made with composite particles plus an α-alumina layer. The weight loss due to corrosion damage was reduced in approximately 94% as compared with the substrate without protection. Coating adhesion was also improved by an increased substrate roughness, with no need for an intermediate layer.

Tumors of the distal and proximal femur are treated by total femur resection. A hip disarticulation sometimes is a result of massive trauma with crush injuries to the lower extremity. This article discusses a system designed for patient rehabilitation with bilateral hip disarticulations. The prosthetics designed allowed a patient to attain natural gait suspended between parallel articulate crutches with the body weight supported between the crutches. The design is patent pending and it could be used in people with a simple ankle sprain, people with partial immobilizations in inferior members, or people with bilateral hip disarticulation. The final design system allows patients with bilateral hip replacement or partial immobilizations to attain mobility in a natural way.

The present paper shows the applicability of the Dual Boundary Element Method to analyze plastic, visco-plastic and creep behavior in fracture mechanics problems. Several models with a crack, including a square plate, a holed plate and a notched plate are analyzed. Special attention is taken when the discretization of the domain is done. In Fact, for the plasticity and viscoplasticity cases only the region susceptible to yielding was discretized, whereas, the creep case required the discretization of the whole domain. The proposed formulation is presented as an alternative technique to study this kind of non-linear problems. Results from the present formulation are compared to those of the well-established Finite Element Technique, and they are in good agreement. Important fracture mechanic parameters such as KI, KII, J- and C- integrals are also included. In general, the results, for the plastic, visco-plastic and creep cases, show that the highest stress concentrations are in the vicinity of the crack tip and they decrease as the distance from the crack tip is increased.

High-Mn austenitic twinning induced plasticity (TWIP) steels are the object of intense worldwide scientific study due to the promising combination of strength and ductility of these alloys. Mechanical behavior of this family of new generation steels has been extensively studied recently. However, limited information regarding their tribological properties is available in the literature. The aim of this research work is to study the wear behavior of a high-Mn austenitic Fe–20Mn–1.5Si–1.5Al–0.4C TWIP steel microalloyed with Ti. The wear behavior was evaluated under dry sliding condition by the ‘‘pin-on-ring’’ method. For this purpose, solution-treated samples were worn for 10 km against a counterface disc made of hardened AISI M2 steel, under loads of 52, 103 and 154 N, and at speeds of 0.20, 0.60 and 0.86 m/s. The wear resistance was evaluated from the average wear rate. Wear debris and worn surfaces were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (SEM-EDS). The Ti addition to TWIP steel slightly improved the wear resistance particularly at a speed of 0.86 m/s and at loads of 52 and 103 N. Results show that the wear resistance increases with increasing sliding speed. This is attributed to the formation of an oxide layer acting as a protective layer against wear, which suggests that the main wear mechanism for the studied TWIP steel under these conditions is oxidative.

Small-angle light scattering (SALS) and wide-angle X-ray scattering (WAXS) were used to study the influence of heat treatment on the texture and microstructure of extruded films of high-performance thermotropic liquid crystal polymers (LCPs). The microstructure was correlated with tensile mechanical properties. LCPs based on random units of hydroxybenzoic acid (B), hydroxynaphthoic acid (N), terephthalic acid (TA) and biphenol (BP) were supplied by the former Hoechst Celanese Corp. as 50 μm thick extruded films. The LCPs, denoted B-N, COTBP and RD1000, have B and N as common co-monomers and vary the other co-monomers. Thus, this study also enabled the investigation of the influence of monomer composition on microstructure and mechanical properties. Heat treatments were carried out at temperatures close to the solid-to-nematic transition (Ts→n) for periods up to 5 h, under dry air conditions. The thermal treatment produced either two endotherms or a small increase of Ts→n (B-N and RD1000), or Ts→n increased significantly (COTBP). Moreover, when heat treatment was carried out approximately 40°C below the respective Ts→n, the mechanical Young’s modulus, E, along the extrusion axis increased for all LCPs. Strikingly, for COTBP, E increased over 100% relative to the as-extruded film. The results also showed that the optimum treatment time for improving the Young modulus was between 3 and 4 h. Wide-angle X-ray scattering showed a significant sharpening of crystalline reflections and concentration of the 002 meridional reflection as a result of thermal treatment, suggesting the elimination of defects and a better alignment of the molecular chains along the extrusion axis. This would explain the increase in tensile modulus.

In this work, we studied the dissolution of three different refractory compositions belonging to the ternary system SiO2-CaO-MgO into two Simulated Lung Fluids (SLF). The initial powder mixtures were uniaxially pressed and then sintered at 1300-1400 °C. The sintered samples were immersed for times from 1 to 21 days into a given SLF at 37 °C. The samples were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The dissolution of Ca2+, Mg2+ and Si4+ into the SLF was quantified by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The in vitro studies suggested that all the considered materials had a potential to show a diminished biopersistence in vivo, due to reasons that depended on their chemical and phase composition.

The main objective of this research work was to study the influence of glassy additives on the formation of crystalline phases in sintered red ceramic bodies used for the fabrication of ceramic floor tiles, whose composition is a mixture of quartz (SiO2), kaolinite [Al2Si2O5(OH)4], albite (NaAlSi3O8), muscovite [KAl2(Si3Al)O10(OH)2] and calcite (CaCO3). The additives used were: fly ash, soda-lime glass, borosilicate glass, glass frit, Na2P3O10 and cryolite (Na3AlF6). These were added in variable proportions to the nominal composition of the red ceramic bodies, either as single or as combined additions, aiming to accelerate the densification of the materials during their sintering process. For all the additive types used, the crystalline phases formed in the samples sintered using a peak temperature ranging from 950 to 1030 °C were: quartz (SiO2), anorthite (CaAl2Si2O8), and hematite (Fe2O3). It is known that the presence of anorthite is particularly beneficial for the mechanical properties, chemical stability and densification of the sintered red ceramic bodies. However, some of the considered additions tended to be detrimental for the formation of this phase in the studied materials, especially at the lowest peak sintering temperature employed. This was verified by means of XRD and SEM analysis.

It was established that at selective laser sintering of Al2O3 - Al compacted mixtures oxidation of the Al particles took place due to diffusion of oxygen into the volume of the workpieces. Depending on the content of aluminum, composite ceramics of various types were formed.

In the present work, the stress relaxation method was employed to determine the influence of B addition on the kinetics of strain-induced precipitation and its interaction with the static austenite recrystallization. For this purpose, the behavior of two low carbon advanced ultra-high strength steels was analyzed during stress relaxation tests at different temperatures and constant pre-strain rate. The precipitation start (Ps) and finish (Pf) times were determined from the relaxation curves and then the corresponding precipitation-time-temperature diagrams were constructed for each steel. Transmission Electron Microscopy was used to determine the chemical nature and evolution of precipitation. In general, the results show that the addition of B retards the austenite recrystallization, tends to accelerate the precipitation kinetics of carbonitrides and leads to a finer and denser distribution of precipitates. These results are discussed in terms of the driving force for the nucleation of precipitation, which in turn is controlled by the degree of supersaturation of microalloying element and as a function of B segregation and B-vacancy complexes to dislocations and grain boundaries.

Advanced ultra-high strength steels (A-UHSS) are revolutionizing both the steel and automotive industries, therefore it is imperative to study their hot plastic deformation behavior and modeling. The flow characteristics of all hot forming processes consist basically of two competitive phenomena: strain hardening and softening due to dynamic mechanisms (recovery and/or recrystallization). In this research work, the softening parameter was determined in a low carbon A-UHSS microalloyed steel with different amounts of boron (0, 14 and 214 ppm). Experimental stress–strain data of uniaxial hot-compression tests at different temperatures (950, 1000, 1050 and 1100 °C) and strain rates (10–3, 10–2 and 10–1 s–1) were used. The stress–strain relationships as a function of temperature and strain rate were described on the basis of the Estrin, Mecking, and Bergström model. The experimental values of the softening parameter Ω were adjusted using the least-squares method. In general, the results reveal that the softening parameter increases with increasing boron content.

Nowadays, there are limited referenced data on the hot deformation of twinning induced plasticity (TWIP) steels, particularly on the crystallographic preferred orientation (crystallographic texture). It is well know that texture is one of the most important factors affecting sheet metal forming performance. The aim of this research work is to determine the influence of microalloying elements on the microstructure and texture of high-Mn austenitic TWIP steels deformed under uniaxial hot-tensile conditions. For this purpose, one non-microalloyed and other single microalloyed with Ti, V and Mo TWIP steels were melted in an induction furnace and cast into metal and sand molds. Samples with average austenitic grain size between 400 and 2000 µm were deformed in the temperature range between 800 and 900 °C at a constant true strain rate of 10-3 s-1. The evolution of the microstructure and texture near to the fracture tip were characterized using electron back-scattering diffraction (EBSD) technique. The results show that the TWIP steels microalloyed with V and Mo and the non-microalloyed one, solidified in metal mold, exhibit dynamically recrystallized grains oriented in the [012] preferential direction, which was corroborated by local misorientation measurements, indicating low dislocation density. On the other hand, most TWIP steels solidified in sand molds do not show dynamically recrystallized grains, having the largest austenitic grains oriented in the [001]/[101] preferred directions. In general, weak textural Cube {001}<100> combined with <111> fiber, namely γ-fiber, spread from E {111}<110> to Y {111}<112> as major texture components were detected.

In this work, Na- and K-doped β-Li5AlO4 samples were synthesized, characterized and analyzed thermogravimetrically (dynamically and isothermally), under different CO2 conditions. Additionally, chemisorption/desorption cycles were performed for the best chemical compositions and thermal conditions determined. While the CO2 chemisorption of the Na- and K-doped β-Li5AlO4 samples was improved at high temperatures (450 -700 °C), the opposite effect was observed at lower temperatures as well as in the presence of water vapor.

Phase relations along the Li2O⋅2B2O3-Yb2O3⋅B2O3 polythermal section of the Li2O –B2O3–Yb2O3 system were investigated by differential thermal analysis, x-ray diffraction, and microstructural analysis. The state phase diagram of the Li2O⋅2B2O3-Yb2O3⋅B2O3 section is an eutectic system with invariant eutectic point corresponding to ∼0.2 mole fraction of Yb2O3⋅B2O3 and 800 °C. According to physico-chemical analysis, the Li2O⋅2B2O3-Yb2O3⋅B2O3 polythermal section is quasi-binary, allowing us to partially triangulate the Li2O-B2O3-Yb2O3 system. The borders of the glass formation region were defined in the Li2O⋅2B2O3-B2O3-Yb2O3⋅B2O3 concentration triangle. The vitreous samples showed a semiconducting nature.

Shape memory alloys (SMA) are metallic attractive engineering materials due to their capacity to store pre-defined shapes through a thermally induced phase transition from a solid state. This paper aims to evaluate the influence of solubilization thermal treatments on a NiTi shape memory alloy originally fabricated by vacuum induction melting and then reprocessed by plasma melting followed by injection molding (Plasma Skull Push Pull process) into different metal molds (steel, aluminum, brass and copper) in order to compare the thermal properties regarding to its raw state. The thermal treatments of solubilization were carried out at 850°C in different times (2n function, n = 0, 1, 2 and 3, in hours). The influence of solubilizing treatments in the NiTi shape memory alloy was analyzed using the following characterization techniques: Differential Scanning Calorimetry (DSC) and Electrical Resistance as a function of Temperature (ERT). The results demonstrate that the solubilization heat treatments applied on the reprocessed NiTi shape memory alloy through the plasma skull push pull process, provides important changes in the phase transformation of the material. Therefore, it was demonstrated that it is necessary to solubilize the material after melting or remelting the NiTi shape memory alloy via this process to obtain mini-actuators products with homogeneous properties.

The non-ferrous shape memory alloys have, normally, two problems that hinder its use in industrial scale: the natural aging and grains growth. The first degrades the memory effect, while the second, observed during the processing of alloy, modifies the temperatures which the transformations occur. Thus, the study of kynetic of recrystallization is important for enabling the control of hardened state in function of treatment time, without causing excessive grain growth. Therefore, the objective of this study is to determine the kinetics of recrystallization of Cu-14Al-4Ni shape memory alloy, based on an empirical law of the formation of Jonhson-Mehl-Avrami, as well as their activation energies for grain growth process according to the empirical Arrhenius law. The alloy was vacuum melted in an induction furnace. After casting, the bulk samples of the alloy were homogenized for 24 hours, solubilized and hot rolled followed by water-quenching to initiate the recrystallization. Then, different samples were annealed at temperatures close to the peak, start and end of the DSC curve. Following the heat treatments, the samples were submitted to mechanical tests and the values of the properties were correlated to the fraction transformed for determination of recrystallization’s kinetic. For the characterization of the grain growth process, analyses in optical microscopy were accomplished and all annealed samples were examined by statistical metallography and the grain sizes were measured. After measurements, the ln[-ln(1-Yrec)] x ln(t) and the ln [D-Do] x 1/T diagrams were plotted to determine the parameters of Jonhson-Mehl-Avrami equation and the activation energy of the process, respectively. The results showed that the equation of the recrystallized fraction follows the empiric law of the formation of Jonhson-Mehl-Avrami for the considered property, as well as, also showed that the alloy Cu-14Al-4Ni is extremely sensitive to temperature variation in which the alloy is treated, having a dual kinetics of grain growth. In the first domain, between 670 and 710°C, the diagram provides a value for the activation energy equal to 39.32 KJ/mol, in the second domain, between 710 and 790°C, the diagram provides a value for the activation energy equal to 9.01 KJ/mol.