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Porous Titanium Niobium (Ti-6Al-7Nb) are widely found in biomedical applications due to their excellent mechanical characteristics and biocompatibility with human bone. In this study, porous Ti-6Al-7Nb were produced with powder metallurgy process together with space holder technique. Magnesium (Mg) was used as spacer to generate pores with porosity range 20-40 vol.%. The production of porous samples started with the spherical Ti-6Al-7Nb powders with average size of 20 µm were mixed with Mg powders with different weight percentage and Polyvinyl Alcohol (PVA) as binder. The mixtures then were compacted using Hydraulic Hand Press under pressure of 600 MPa with double-ended steel die. The green compacts produced sintered for 2 hours under high purity argon gas atmosphere at temperature 1300°C to remove the Mg. The calculated porosity in range ~25-37 % of sintered samples achieved desired porosity content. Compression test with speed 0.001mm/sec were conducted to figure out the mechanical characterization resulting in Elastic modulus, E in the range ~0.0651-0.9375 GPa and yield strength, σy ~3.9-47.0 MPa which sufficient for implantations with human bone. The sintered samples were observed under Scanning Electron Microscope (SEM) where spherical, interconnected macropores and irregular shape of micropores were identified. [ABSTRACT FROM AUTHOR]

Porous Nickel-Titanium (NiTi) alloy has been developed especially in the biomedical sector due to its shape memory ability and its mechanical properties which is comparable to human bones. However, NiTi alloy carries the risk of Nickel (Ni) ions leaching when implanted in the human body making it less favourable for biomedical use forlong term. Therefore, the goal of this research is to passivate the porous NiTi by oxidizing the surface via annealing treatment. Initially, the porous NiTi alloy was fabricated via powder metallurgy technique with addition of Calcium Hydride (CaH2) as a pore forming agent. Here, the degree of porosity was measured and the pore morphology, phase identification and transformation behavior were characterized by Scanning Electron Microscope (SEM), X-Ray Diffractometer (XRD), and Differential Scanning Calorimeter (DSC), respectively. Then, the surface treatment was performed by varying annealing temperatures where the oxide layer formation was characterized by using SEM and Energy Dispersive Spectrometer (EDS). The result shows that the sample's porosity increased by up to 42% from its theoretical density, demonstrating that the weight percentage of the pore-forming agent has a significant effect on theporosity of the NiTi alloy. For surface treatment, at higher annealing temperature i.e. 500°C, it produced a thicker oxide layer of TiO2 as compared to samples annealed at 300°C and 400°C. This indicates that the annealing temperature highly affects the formation of oxide layers on the surface. This oxide layer adheres well to the NiTi alloysurface and is expected to prevent the Ni ion from releasing, thus making this porous NiTi biocompatible metal. [ABSTRACT FROM AUTHOR]

In this research work, binary Al-25Zn and ternary Al-25Zn-3Cu alloys were fabricated using stir casting process. Microstructure and mechanical properties of as-cast alloys were foundout and the composition of the alloys was validated using energy dispersive X-ray analysis (EDX). The fabricated alloys were solution treated at 450 °C for 10 hours and then artificially aged at different temperatures (100 °C, 150 °C and 200 °C), each at 1 hour, 2 hours, 3 hours and4 hours. The microstructure after heat treatment was compared with the as-cast microstructure. Hardness and tensile properties were investigated for both as-cast and heat-treated alloys. Al-25Zn-3Cu alloy exhibits superior strength (hardness and tensile) when compared to Al-25Zn alloy in both as-cast and heat-treated conditions. Higher hardness and tensile strength were obtained at the aging temperature of 100 °C for 1 hour, for both alloys. The results were validatedusing scanning electron microscope (SEM) microstructures and X-ray diffraction (XRD). [ABSTRACT FROM AUTHOR]

Ti-6Al-4V is the most common titanium alloy for implant application. However, Ti-6Al-4V has disadvantages that this alloy's vanadium element. Vanadium is a toxic element and may cause potentially serious health problems. In this study, Vanadium was substituted with Niobium to obtain an alpha/beta titanium alloy which is safe for use in the human body as an orthopedic material. The Hot Rolling process carried out Ti-6Al-6Nb to improve its mechanical properties. Hot rolling is carried out at 900, 1000, and 1100 °C temperatures. Microstructural observations with optical microscopy (OM), scanning electron microscope (SEM), and hard tests were carried out to observe changes in microstructure and hardness after melting, homogenization, and hot rolling processes. The study revealed that hot rolling at 1000 °C has the lowest hardness, and rolling at 900 °C has the highest hardness value. The finer grain size most influenced to the increasing hardness value of hot rolled Ti-6Al-6Nb. [ABSTRACT FROM AUTHOR]

Ferum-nickel-chromium (Fe-Ni-Cr) alloy is a family of Ni-based alloy which is generally utilized in elevated temperature applications with excellent oxidation resistance properties. In this study, Fe-33Ni-19Cr alloy underwent a heat treatment procedure at 1000°C and 1100°C for 3 hours soaking time, and then rapidly cooled by water quench. The heat- treated alloys were then subjected to a cyclic oxidation test at 900°C for 150 cycles in air. The oxidized alloys were characterized in terms of weight change per surface area as a function of cycles and oxide scale behavior in plan and cross- sectional view using a scanning electron microscope outfitted with an energy dispersive x-ray spectrometer. It was found that the low heat treatment temperature, which is 1000°C, produced fine grain structure. Whereas, heat-treated alloy at 1100°C produced coarse grain structure. On the other hand, cyclic oxidation of both heat-treated oxidized alloys recorded a weight gain pattern. Various oxide phases were formed on the oxidized alloys surface, namely Cr-rich and Cr-Mn rich oxides. The surface morphology analysis exhibited an uninterrupted oxide layer established on the oxidized alloys surface, with fine grain heat-treated alloy forming a uniform oxide layer. However, oxide exfoliation has been recorded on coarse grain heat-treated alloys. [ABSTRACT FROM AUTHOR]

Ni-based Fe-Ni-Cr alloy is an important engineering material for a variety of applications especially at high temperature conditions. However, during service, this alloy experienced an oxide exfoliation that may reduce the material lifetime and its potential applications. To enhance the protective properties of this alloy at high temperature application, the modification on the alloy surface was done to introduce the subsurface region of refined grain that will induce diffusion. This project is to study the effect of different surface preparation on the isothermal oxidation behavior of Fe-Ni-Cr alloy. Different grit of SiC papers were used during grinding processes, namely P180, P600 and P1000 in order to achieve different surface roughness of the samples. The ground samples were exposed to oxidizing temperature at 700°C in air for 150 hours. The isothermally oxidized alloys were analyzed using kinetics of oxidation and scanning electron microscope equipped with energy dispersive x-ray spectrometer. Oxides layers were formed on the alloy surface which act as a protective layer at the isothermal temperature condition. As a result, all samples exhibited a weight gain pattern, following a parabolic rate law showing diffusion-controlled oxide growth mechanism. P180 sample recorded the lowest parabolic rate constant, showing the lowest oxidation rate. In addition, P180 sample also displayed a uniform and incessant oxide layer without evidence of oxide exfoliation. [ABSTRACT FROM AUTHOR]

The effect of mechanical treatment of powder on the structure and phase composition of hard alloys has been studied. It is shown that the average size of agglomerated particles measured by scanning electron microscope decreased from 350 to 15 µm within up to 300 s of mechanical activation. In samples mechanically treated for more than 100 s, the detected peaks belonged to the carbide phase Co3W3C. The lattice parameter of the WC-phase correlates well with the literature data. The minimum porosity of the sintered sample was 7.8 ± 1% that corresponds to that of the sample subjected to mechanical pre-treatment for 30 s. It is shown that hardness depends on the grain size, porosity and second carbide content. Thus, mechanical activation can effectively improve physical and mechanical properties and inhibit grain growth, but in this case, mechanical treatment should be performed in the time interval of 60–100 s. [ABSTRACT FROM AUTHOR]

When choosing a grade of hard alloy for the production of button of roller-cone drill bits, they are guided by the nature of the loads experienced by a hard-alloy bit during drilling and the mechanism of its destruction. The mechanism of rock destruction when drilling with bits is based on the principle of crushing the rock with some slippage, i.e. with abrasion. Uniform abrasion of the teeth along the height is considered a normal mechanism for the wear of the teeth. Therefore, the alloy for the production of button is subject to increased requirements in terms of compressive strength, abrasion resistance and fracture toughness KIc (impact toughness). The influence of different modes of sintering of hard-alloy bits of drill bits on the physical and mechanical characteristics and microstructure of the alloy has been investigated. The relationship between exposure time and crack resistance, hardness and coercivity is shown. The photographs of the microstructure of the samples taken on a Jeol JSM-6390A scanning electron microscope are presented. The ways for further work to improve the quality and microstructure of the carbide cutting structure of drill bits at the production of JSC "Volgaburmash" are considered. [ABSTRACT FROM AUTHOR]