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The effects of rotational and welding speed on the mechanical properties and thermal behavior in friction stir welded joints of high-density polyethylene using a non-rotational shoulder have been investigated experimentally. Tensile properties and hardness were measured to determine the mechanical properties, and the effect of the welding parameters. Heating and cooling cycles of differential scanning calorimetry were used to establish thermal properties. Microstructure observations complemented experimental observations. Results showed that tensile strength, hardness, and crystallinity decreased when rotational speed was increased, while the welding speed effect was weak. Deleterious phenomena on molecular structure of the stir region were explained by means combination of selected welding parameters and the material flow during the process.

The technique of surface modification using electrolytic oxidation, called micro-arc oxidation (MAO), has been used in altering the surface properties of titanium alloys for biomedical purposes, enhancing their characteristics as an implant (biocompatibility, corrosion, and wear resistance). The layer formed by the micro-arc oxidation process induces the formation of ceramic oxides, which can improve the corrosion resistance of titanium alloys from the elements in the substrate, enabling the incorporation of bioactive components such as calcium, phosphorus, and magnesium. This study aims to modify the surfaces of Ti-25Ta-10Zr-15Nb (TTZN1) and Ti-25Ta-20Zr-30Nb (TTZN2) alloys via micro-arc oxidation incorporating Ca, P, and Mg elements. The chemical composition results indicated that the MAO treatment was effective in incorporating the elements Ca (9.5 ± 0.4 %atm), P (5.7 ± 0.1 %atm), and Mg (1.1 ± 0.1 %atm), as well as the oxidized layer formed by micropores that increases the surface roughness (1160 nm for the MAO layer of TTZN1, 585 nm for the substrate of TTZN1, 1428 nm for the MAO layer of TTZN2, and 661 nm for the substrate of TTZN2). Regarding the phases formed, the films are amorphous, with low crystallinity (4 and 25% for TTZN2 and TTZN1, respectively). Small amounts of anatase, zirconia, and calcium carbonate were detected in the Ti-25Ta-10Zr-15Nb alloy.

Ternary Al–15 wt% Cu–7 wt% Si and Al–22 wt% Cu–7 wt% Si alloy specimens were generated by transient directional solidification (DS) and rapid solidification (RS) techniques. The microstructures are constituted by an α-Al dendritic matrix surrounded by two eutectic, that is, a binary eutectic (Si + α-Al) and a bimodal eutectic, consisting of cellular-type binary eutectic colonies (α-Al + Al2Cu) in a ternary eutectic matrix consisting of α-Al + Al2Cu + Si. The bimodal eutectic exists at cooling rates from 0.5 to 250 K/s. The secondary dendritic spacing, λ2, of the DS samples varied from 5 to 20 μm and from 10 to 18 μm for both examined alloys. The λ2 from 2.7 to 4.0 μm characterized the RS samples. Mechanical properties have been determined for various samples related to different dendritic spacing values. Based on the evaluation of the rapidly solidified microstructures, it was possible to assess the cooling rates.

Titanium and its alloys currently are used as implants, possessing excellent mechanical properties (more suited than stainless steel and Co-Cr alloys), good corrosion resistance and good biocompatibility. The titanium alloy used for most biomedical applications is Ti-6Al-4V, however, studies showed that vanadium and aluminum cause allergic reactions in human tissues and neurological disorders. New titanium alloys without the presence of these elements are being studied. The objective of this study was to analyze the influence of thermomechanical treatments, such as hot-rolling, annealing and solution treatment in the structure, microstructure and mechanical properties of the Ti-25Ta-Zr ternary alloy system. The structural and microstructural analyses were performed using X-ray diffraction, as well as optical, scanning and transmission electron microscopy. The mechanical properties were analyzed using microhardness and Young’s modulus measurements. The results showed that the structure of the materials and the mechanical properties are influenced by the different thermal treatments: rapid cooling treatments (hot-rolling and solubilization) induced the formation of α” and β phases, while the treatments with slow cooling (annealing) induced the formation of martensite phases. Alloys in the hot-rolled and solubilized conditions have better mechanical properties results, such as low elastic modulus, due to retention of the β phase in these alloys.

This paper describes a study of the effect of solution heat treatment temperature (500, 750 and 1000 °C) on the phase transformations, microstructure, microhardness and Young’s modulus of Ti-25Ta-xZr alloys, aimed at biomedical applications. The Ti-25Ta-xZr alloys ingots were melted in an arc furnace with five different compositions (x = 0, 10, 20 30 and 40 wt.%) in order to produce samples with α″, β + α″ and β phase. The results showed that both the microstructure and mechanical properties of the studied alloys can be tailored according to the temperatures used for solution in the Ti-25Ta-xZr system. Usually, higher solution heat treatment temperatures increase hardness due to the higher phase stabilization in single-phase alloys, while in the α″ + β alloys or predominantly β, hardness decreases due to the suppression of phase α″. However, the elastic modulus of the alloys decreases when solution heat treatment is performed at 1000 °C. In general, solution heat treatment performed at higher temperatures stabilizes more the β phase, optimizing the lower modulus of the alloys.

Maraging 300 is an ultrahigh strength steel with significant alloy addition, resulting in a martensitic matrix hardened by precipitation through aging treatment. In these steels, intercritical tempering can provide reverted austenite and precipitation of intermetallic products, increasing the ductility of additively manufactured parts due to austenite presence. Studies deal with postprocessing of additive manufactured parts of maraging steel; however, few focused on phases evolution during the heat treatments and their mechanical response. In the present work, a maraging 300 steel processed by laser-based powder-bed fusion was studied with a focus on microstructural and mechanical properties after applying several postprocessing heat treatments. Tensile tests assessed the mechanical properties, and the microstructure was analyzed by scanning and transmission electron microscopy. A synchrotron beamline with x-ray diffraction was used to conduct in situ measurements of martensite and austenite evolution. The in situ phase evolution revealed that isothermal heat treatments were efficient in promoting martensite-to-austenite reversion. Likewise, the presence of austenite significantly enhanced the ductility, however, at some mechanical strength expense.

This handbook presents contemporary research on public administration in Latin America. The first section explores the range of administrative systems in existence across the region. The second portion of the book discusses important topics such as public personnel management, accountability and policy coordination in Latin America.

The influence of open vessels during milling for 12, 24, 40 and 60 h on microstructure homogeneity and oxygen content effect in the β Ti–Nb–Mo system microstructure were studied. The β phase increased with longer milling times and the strain hardening on particles was verified at 60 h when agglomeration was greater and was also noticed after 40 h in the continuous mode. Oxygen content dropped slightly until 40 h and increased after 60 h, a result linked with the observed hardening. For 40 h in the continuous mode, the oxygen content was noted near 12 h, 24 h and 40 h with high hardness values. For the sintered parts, the α phase and oxygen content significantly increased in all samples. Microhardness-sintered samples decreased compared to sample powders due to grain growth during the sintering. Bending strength was higher at 60 h with more oxygen and α phase content. After 40 h in the continuous mode, more suitable mechanical properties were reached because hardness and bending strength were closer to bone tissue, which was associated with strain hardening and a small crystallite size.

The high contents of noble refractory elements of Ti35Nb10Ta (wt.%) alloy difficult the diffusion of them. The stabilization of the β phase can be favored by the addition of Fe in β-Ti alloys. In this work, elemental powders mixture with different contents of Fe (0, 1.5, 3.0 and 4.5 wt.%) were used. These powders were compacted with uniaxial pressure of 600MPa and sintered at 1250°C in high vacuum. The porosity obtained after sintering shows a dependence on the particle size of iron used, and homogeneous pores distribution was observed. The analyzed microstructure mainly corresponds to β-Ti phase, with small fractions of α phase appearing at grain boundaries, which decreases with increasing of Fe content. The microstructure showed good compositional homogeneity of Fe and Ta and some lack of diffusion related to large amount of undissolved Nb particles. Addition of Fe lead to a decrease in bending strength of Ti35Nb10Ta alloy.

Glassy overspray powders of Ni59Nb35Sn6 (at%) bulk metallic glass (BMG) obtained by spray forming were used in order to produce coatings on AISI 1020 mild steel substrate by laser cladding of the pre-placed powders. Different laser parameters, resulting in a variation of the power density, PD (J/mm2), were tested with a Yb fiber laser (up to 500 W). Gas atomized powders, suction cast sample trough copper mold casting and the laser clad tracks were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and coatings were subjected to measurements of Vickers microhardness. Atomized powder obtained showed no crystalline phases formation up to 425 μm, indicating good glass forming ability (GFA) of Ni59Nb35Sn6 (at%) alloy. Microstructure characterization confirmed maximum glassy dimension of tc =1mm for the Ni59Nb35Sn6 (at%). Laser cladding track showed nanocrystalline phases embedded in a glassy matrix with Vickers microhardness ranging from 336 to 1184 HV.