This paper aims to analyze the structure of the Ti-25Ta-xZr system alloys (x = 0, 10, 20, 30, and 40% wt.) after melting and hot-rolling by Rietveld's technique. The results confirm that zirconium acts as a β phase stabilizer (in which the Ti-25Ta-40Zr alloy is fully β in the as-cast condition), increases the lattice parameters of the phases, decreases the c/a ratio of the α phase, consequently, decreases the elastic modulus values (86 to 72GPa) and decreases the atomic packing factor (APF) of the alloys (60% reduction compared to alloys with and without zirconium in the as-cast condition and 50% reduction in the hot-rolled condition). Concerning hot-rolling, this mechanical process induces the α phase formation and increases the atomic packing factor of the alloys (APF). By the William-Hall technique, it was possible to calculate the average crystalline size and the micro-strain of the structures.

In recent years, there has been a growing interest in the search for metallic alloys with favorable mechanical and chemical characteristics that elicit a positive biological response. Among these alloys, β-Ti alloys have attracted significant attention due to their low elastic modulus and excellent biocompatibility. The addition of Nb contributes to stabilizing the β phase at room temperatures, leading to the transformation of β into β + α (β-isomorph). Additionally, despite Zr being commonly considered a neutral element, it can exhibit a β-stabilizing characteristic when combined with betagenic elements. Both Nb and Zr have been shown to effectively increase the lattice parameter of the β phase, which is advantageous for reducing the elastic modulus. The primary objective of this study was to characterize β-Ti alloys within the Ti-Nb-Zr system, specifically Ti-40Nb-20Zr, Ti-40Nb-30Zr, and Ti-40Nb-40Zr (wt.%) produced via arc furnace casting. The study aimed to investigate the influence of the proportion of β-stabilizing or betagenic elements on the microstructure and properties of the alloys, including Vickers microhardness and elastic modulus.

With increasing life expectancy, revision surgeries have become more frequent in implanted people. This is due to the biological and biomechanical incompatibility that generates, among others, problems such as stress shielding. This works aims to analyze the influence of the hot rolling process (HR sample) on the microstructure and, consequently, the properties of β-Ti multiprincipal alloys: Ti-27Nb-39Zr (39Zr), Ti-30Nb-50Zr (50Zr), and Ti-20Nb-30Zr-13Ta (30Zr) (wt. %.) (equimassic and with high content of β-stabilizer elements). All samples were subjected to characterization through X-ray diffraction (XRD) to determine the phases present, and optical microscopy (OM) and scanning electronic microscopy (SEM) were realized to characterize the microstructure and confirm the phases obtained through XRD. Before hot rolling, only the β phase was identified, but in the HR condition, the α and β phases were identified. Consequently, it did not observe significant changes in microhardness for all alloys, while the elastic modulus was observed with a reduction of 23% for 39Zr, 46% for 40Zr, and 13% for 30Zr. The hot rolling processing was confirmed to be a helpful route to reduce the elastic modulus for β Ti multiprincipal alloys opening perspectives for applying such alloys as metallic implant materials.

MoS2 powder has been used to form "self-lubricating" composite coatings, which are very useful to increase the lifetime of machines where liquid lubricants cannot be used. In this work, amorphous overspray powder of Fe60Cr8Nb8B24 (at%) alloy was mixed with 5wt.% MoS2 powder and it was used to produce single tracks on AISI 1020 steel substrates by laser cladding. The tracks were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Vickers microhardness. It was observed α-Fe, an Nb-rich intermetallic and MoS2 particles in the tracks, regardless of laser parameter used. DSC analyses proved the presence of amorphous phase for samples produced with parameters 200W/33.3mm/s, 600W/100mm/s, 800W/100mm/s and 800W/150mm/s. The tracks produced with larger power (800W) and higher scanning speeds (100 and 150mm/s) exhibited a better integrity and homogeneity, lower dilution and presence of amorphous phase, being these parameters considered the most appropriate to produce composite coatings of Fe60Cr8Nb8B24 (at%)/5wt% MoS2 containing amorphous phase. Hardness tests showed that the single tracks produced are harder than the substrate, for example, the track produced with 800W/150mm/s exhibits hardness six times higher than the steel substrate, 1200 HV0.3 and 200 HV0.3, respectively.

Fe60Cr8Nb8B24 (at%) amorphous powder and ingot were submitted to LASER cladding and remelting process, respectively. Fe-based coatings were produced using different LASER processing parameters and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Vickers microhardness. All coatings obtained by LASER cladding (LC) and layers obtained by LASER surface remelting (LSR) with shorter and median interaction times (scanning speeds of 16.7 and 66.7mm/s), irrespective of overlap value, presented peaks of the crystalline phases α-Fe, Fe2B and the FeNbB intermetallic. In addition, layers obtained by LSR with shorter interaction time (150mm/s), in general, presented only peaks of the α-Fe and Fe2B phases, except that produced with overlap value of 20%, more amorphous. SEM results showed that, regardless of LASER process, the coatings presented cracks, some pores and FeNbB intermetallic phase. All coatings obtained by LC and that obtained with shorter interaction time, by LSR, showed a Vickers microhardness, 1086 to 1329HV and 2161 to 2294HV, respectively, significantly higher than the substrates, AISI steel: 170HV and Fe-Cr-Nb-B: 1921HV.

A structural and mechanical characterization of pure aluminum and 2124 T6 aluminum alloy reinforced with quasicrystalline phases of composition Al65Cu20Fe15 and Al70.5Pd21Mn8.5 (%at.) were performed. The quasicrystalline phases were synthesized by arc melting and then milled to produce powder of the alloys, which were then mechanical mixed with the starting powders of aluminum and 2124 aluminum alloy. The composites were produced by hot extrusion of a mechanical mixture containing 20% (%wt.) of the reinforcing phases on the metallic matrix. The structural characterization of the composites was carried out by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Mechanical characterization was carried out by Vickers hardness measurements and torsion tests at room temperature. The pure aluminum/quasicrystal composite showed the presence of the same phases from the starting powder mixture while for the 2124 aluminum alloy/Al65Cu20Fe15 the quasicrystalline phase transformed to the tetragonal ω-Al7Cu2Fe during the solution heat treatment. Mechanical strength of the composites presented a substantial increase in comparison to the original matrix metal. While the equivalent ultimate tensile strength of the Al/quasicrystal composites reached values up to 215MPa and Vickers hardness up to 60HV, the 2124/quasicrystal composites reached values up to 670MPa and Vickers hardness up to 190HV.

An experimental investigation was conducted using laboratory-processed low carbon Mn-Mo-Nb-Ti-B dual phase steel with additions of 0.2Cr or 0.6%Cr. This study investigates the effect of Cr additions on ferrite recrystallization and austenite formation during continuous annealing in the intercritical temperature range. It was found that moderate additions of Cr (0.2%) accelerates the ferrite recrystallization (nucleation and growth) resulting in coarse ferrite grains. An increase in Cr content up to 0.6% also accelerates the ferrite recrystallization which in addition to the presence of Cr-rich carbides facilitates the austenitization predominantly through the nucleation process resulted in finer austenite grains. Thereby, the higher Cr content increases the volume of homogenized and refined martensite in the final quenched structure.

Recently, intermetallic compounds have attracted much attention due to their potential technological applications as high-temperature materials. In particular the intermetallic compounds, associated with the Al-Ni binary system stand out as promising candidates for high-temperature materials for the use in harsh environments. It is expected that a bulk Al-Ni alloy may exceed the strength of many commercial materials. The great challenge in developing these alloys is to manipulate the solidification thermal parameters in order to obtain the desired microstructural features. One of the indicated routes to obtain very refined intermetallic phases dispersed in the microstructure is the spray forming process. The dendritic and eutectic growth dependences on cooling rate are already known for directionally solidified (DS) hypoeutectic Al-Ni alloys. In the case of rapidly solidified (RS) samples, extrapolations of such experimental laws are needed, which can be very helpful to estimate realistic values of high cooling rates imposed during the spray forming process. The present study aims to compare directionally solidified and spray-formed Al-5wt. (%)Ni alloy samples with a view to providing a basis for understanding how to control solidification parameters and the as-cast microstructure. The Al-5.0wt. (%)Ni alloy was shown to have a cellular morphology for the overspray powder size range examined (up to 500 µm). The mean cell spacing decreased from 5.0 to 1.1 µm with the decrease in the powder average diameter. It was found that the experimental cooling rates imposed during the atomization step of the overspray powder solidification varied from 10³ to 2.10(4) K/s. The DSC trace depicted a crystallization peak of an amorphous structure fraction in the smallest Al-5.0wt. (%)Ni alloy powder size range (<32 µm) estimating a 15 µm critical diameter of amorphous powder in the binary Al97.5Ni2.5 (at%) alloy.

Prolongar a vida útil e aumentar a confiabilidade de equipamentos e tubulações de plantas de produção e processamento de petróleo é uma busca constante no setor de petróleo e gás. Tais aspectos dependem essencialmente do uso de ligas resistentes à corrosão. Neste contexto, a soldagem de revestimento com superligas à base de níquel tem sido uma alternativa interessante, pois confere aos equipamentos uma alta resistência à corrosão com um custo inferior, se comparado à fabricação de componentes ou tubulações maciças com superligas. Assim, o objetivo do presente trabalho foi investigar o comportamento metalúrgico de revestimento de superliga à base de níquel do tipo Inconel 625 depositados pelo processo TIG com alimentação de arame frio. As soldagens foram realizadas em uma bancada robotizada, empregando uma fonte eletrônica de soldagem com sistema de aquisição de dados para o monitoramento dos sinais de corrente e tensão. A caracterização microestrutural foi realizada através das técnicas de microscopia eletrônica de varredura (MEV) e transmissão (MET), espectroscopia de energia dispersiva de raios-X (EDS). Os resultados mostraram que a microestrutura do metal de solda foi constituída por uma matriz γ com fases secundárias ricas em Nb. Foi encontrada a formação de precipitados complexos de carbonetos/nitretos de Ti e Nb.

To extend the life and reliability of pipes and equipment in oil & gas production and processing settings is a continuous demand. These aspects are essentially dependent on corrosion resistant alloys used. In this context, the weld overlay with Ni-based superalloys is a great interesting alternative, since improve the corrosion resistance without increase the cost of manufacture when compared to massive equipment. Thus, the objective of this study was to evaluate the metallurgical aspects of Inconel 625 weld overlays deposited by GTAW cold wire feed process. The welds were performed using a robotic workbench, an electronic power supply and a data acquisition system. The microstructural characterization was carried out using scanning electron microscopy (SEM), transmission electron microscopy (MET), electron dispersive spectroscopy (EDS) and X-ray diffraction. The results shown that the microstructure of overlays was formed by a gamma matrix and secondary phases rich in Nb. These precipitates were identified as Nb-rich Laves phase and a complex TiN/NbC.

Based on electrical and magnetic properties, such as saturation magnetization, initial permeability, and coercivity, in this work are presented some considerations about the possibilities of applications of nanocrystalline alloys in toroidal cores for current transformers. It is discussed how the magnetic characteristics of the core material affect the performance of the current transformer. From the magnetic characterization and the computational simulations, using the finite element method (FEM), it has been verified that, at the typical CT operation value of flux density, the nanocrystalline alloys properties reinforce the hypothesis that the use of these materials in measurement CT cores can reduce the ratio and phase errors and can also improve its accuracy class.