Solid State Phenomena Vol. 357

Abstract: Ti₄₈Al₄₈Cr₂Nb₂ intermetallic alloy was studied for its tribological properties. The as-received TiAl alloy was prepared by spark plasma sintering (SPS) at 1200 °C for 5 and 7 min using 50 and 100 °C/min heating rates. Wear tests were done on the sintered TiAl under 10 N at room temperature in air. Results showed that an increase in relative density and superior microhardness led to a reduced material loss in the sample sintered for 7.5 min using a 100 °C/min heating rate. Scanning electron microscopy (SEM) images of the worn surface showed the wear widths and wear marks on the surface of TiAl alloy. The wear track width indicated the degree of wear, and the samples sintered for 7.5 min using a 100 °C/min heating rate showed improvement in wear resistance.

Abstract: Materials are a core part of the development in mechanical turbines, where there is always potential for life-improvement. The demand for alloys with durability, low cost, and long service cycles are evergreen. The materials used in turbomachinery must have excellent resistance to thermal fatigue, as well as high temperature oxidation and corrosion resistance. Good creep resistance is also an important consideration, especially for large blades and multi-airfoil latter stage nozzles. Development of new alloy compositions and material characterization plays a critical role in advanced machinery evolution. In this work, some of the available characterization methods are applied to analyze and study the effect of heat treatment, service effect and aging on alloys.

Abstract: A family of Al_xCu_yCrFeMnNi (x=0, 0.15, 0.3, 0.6, 0.9 and y=0, 0.07, 0.14) high entropy alloys (HEA) were arc cast and then heat treated for 24h at 1100֯C-1150֯C followed by water quench. The microstructure of low Al alloys (Al₀Cu_x and Al_0.15Cu_x) consisted of FCC and BCC phases. Al_0.3Cu_x showed an additional ordered precipitate phase. High Al alloys (Al_0.6Cu_x and Al_0.9Cu_x) consisted of two BCC phases rich in Cr-Fe and Ni-Al. In the present study, the phases formed in the microstructures were evaluated in light of valence electron concentration (VEC), Hume-Rothery (H-R) and degree of partitioning. Although VEC successfully predicts the impact of Al and Cu on the trend of FCC-BCC phase formation, the parameter does not accurately predict the structure of high Al alloys. A good agreement was observed between H-R rules prediction and the experiments which might be ascribed to the high temperature equilibrium phases developed by the heat treatment. As per these criteria, increasing Cu (up to 3at.%) and decreasing Al promote formation of solid solution phases. Adding minor amounts of Cu avoids the Cu partitioning that besets high Cu HEAs.

Abstract: Additive Manufacturing (AM) is a product creation method done layer-by-layer. This process tends to create an unwanted feature known as staircase effect. Vapor smoothing is considered a viable solution for polymer-based AM products to minimized surface roughness. Research literature concerning vapor smoothing of polylactic acid (PLA) parts generally limited unlike its ABS counterpart. This research aims to identify optimum level for both chamber temperature and exposure time of the AM product. Two methods were used to compare their outputs with one another. The two methods are surface roughness tester and optical microscopy. The results provided an impressive 50.88 and 62.72% improvement based on the two test methods. Lastly, a contour-plot was generated to provide future users a guideline if they want to conduct research similar study.

Abstract: Additive manufacturing (AM) was developed to cope with the demand for manufacturing goods. It ensures faster production and high waste reduction but is limited by material compatibility. One of the technologies in AM is Vat Photopolymerization (VP). It is a type of AM that uses photopolymer resin and UV light for polymerization. Various materials had been studied to improve the mechanical properties of the photopolymer resin by adding additives from indigenous sources. This study extracted cellulose from abaca and modified it by cross-linking it with Polyethylene Glycol (PEG). The cross-linked abaca cellulose (CAC) was investigated as an additive in the photopolymer resin with fiber loading of 3 wt.%, 6 wt.% and 9 wt.%. Fourier Transform-Infrared Spectroscopy (FT-IR) shows that the presence of the oxygenated functional groups in resin and CAC can interact to form hydrogen bonds. Thermogravimetric Analysis (TGA) showed better thermal stability with the addition of 9 wt.% CAC compared to pure UDMA. Furthermore, the glass transition (Tg) decreased with the addition of CAC by 8.29 °C. The Tensile Test showed that 3 wt.% of CAC resulted in the highest value for tensile strength and toughness with an 11.27% increase for tensile strength and 133.46% for toughness. The elastic modulus increased with fiber loadings and had increased by 48.51% at 9 wt.% of CAC. Based on the results, the effect of adding abaca cellulose into a UDMA based resin had improved the thermal stability and mechanical properties of the composites.

Abstract: Mild steels were the most frequently used materials in industries and factories since it possesses unique properties but due to weak environmental changes, these cause deterioration and corrosion to the materials’ surface. To prevent such, protective coatings were applied to protect against corrosion in which by incorporating titanium nanoparticles in polyurethane coatings. Titanium nanoparticles were synthesized using titanium butoxide as a precursor. The obtained nanoparticles were used as an inhibitor mixed with coconut oil-based polyurethane polyol blend against the corrosion on mild steel of 3.5% of sodium chloride solution which has been investigated using the Tafel polarization technique. The polarization curves of the corrosion potential for bare mild steel, along with different amounts of titanium nanoparticles coating, exhibit a positive shift. This shift indicates that the coating film effectively reduces the transport path for the corrosive solution, providing a protective barrier against corrosion. This observation is further supported by the results of the adhesive strength test, which demonstrates that the attachment of the coating films to the metal increases with higher amounts of titanium nanoparticles. This indicates improved adhesion and a stronger bond between the coating and the substrate, enhancing the overall corrosion resistance. The increase of contact angle test confirms the improvement of the coating’s hydrophobicity with the addition of titanium nanoparticles. This suggests that the coating repels water more effectively, further contributing to its protective properties against corrosion. Results also show that the addition of 4wt% of titanium nanoparticles has better anti-corrosion properties than the PU CCP alone, and 0.5, 1.0, and 2.0wt% of titanium added.

Abstract: Lightweight metallic alloys in the transport sector are the essential choice to reduce carbon monoxide emissions. Magnesium (Mg) can serve this purpose appreciably because it has a low density compared to other metallic metals and a high strength in a small portion of metals. The reason behind this is having very low weight. Notwithstanding the alloys exhibit high susceptibility to corrosion especially galvanic corrosion, which impedes it from its various applications. The corrosion resistance of magnesium alloy depends largely on the surface film whether it can protect well and the corrosion due to galvanic effect between the second phase particles or microstructures and the magnesium matrix. Role of second phase particles eventually improves the corrosion property by enhancing its resistance to corrosion. Mg-4Zn being a promising alloy, 3 wt% Gd has been added further to investigate the corrosion resistant properties of Mg-4Zn-3Gd alloy. After preparing the alloys by casting method in induction furnace followed by homogenization at 410°C, the sample was hot rolled at 400°C. Preparation of the samples has been verified by EDS, XRF and XRD analysis. Corrosion study has been done for 1 hour, 24 hours and 72 hours. Microstructures have been taken for as cast, homogenized, and as rolled condition before corrosion test. The analysis shows a large difference in the grain size and phase distribution. Due to dynamic recrystallization during rolling hardness also shows differences compared to as cast and homogenized sample. The corrosion test is performed by weight loss test, electrochemical measurement, and immersion test. In the results, it has been seen an increase in corrosion rate at the initial stage, however it came to a constant rate after some time. After corrosion test, optical micrographs (OM) and scanning electron microstructures (SEM) images show typical morphology of corroded surface with some micro cracks. The presence of Gd in Mg-4Zn alloy enhanced the corrosion performance when it is done for longer time.

Abstract: Researchers continue to be concerned about corrosion of materials, which motivates them to start projects to address the harmful impacts of this phenomena that affects the desired function of our materials, especially in industries where acid is used in the process of cleaning machines. The purpose of this study is to reduce the corrosion rate of brass in 5M solution of H₂SO₄ acid using orange juice as inhibitor. The study was conducted using weight loss method. It was observed that for 24 hours the corrosion rate was higher for acid and decreased as the inhibitor was added. In all samples the corrosion rate decreases as the inhibitor were added, however improves over time. For 24 hours the efficiency was higher for acid + 100mil at 14% and it became constant after 48hrs at 32,7%. However, for 72 – 96 hours acid + inhibitor of 60mil there efficiency reported to be 54.3 and 56.4%. Keywords-orange juice, inhibitor, corrosion, acid, efficiency.

Abstract: Investigators used Potentiodynamic Polarization, Spectroscopy of Electrochemical Impedance (EIS), Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX), Spectroscopy of X-Ray Photoelectron (XPS), and chemical studies to examine the inhibitory effect of Theobroma cacao peel extract (TCPE) on mild steel (MS) corrosion in 1.5M HCl. Studies of electrochemical data indicate that, TCPE reduces MS corrosion through adsorption using a mixed inhibition mechanism. As the inhibitor concentration grows and temperatures lowers, TCPE becomes more protective. The adsorption of TCPE molecules on the MS surface is controlled by the Langmuir adsorption isotherm. To determine the correlation between the hampers effect and the structure of TCPE molecular, a number of chemical characteristics were computed.