Materials Science Forum Vol. 1135

Abstract: This study investigates the careful investigation of cutting parameters to improve machining effectiveness and increase tool life while milling Nickel-Titanium Shape Memory alloy (NiTiNOL). The NiTiNOL material is employed to manufacture components such as, dental braces, seismic dampers and medical implants. Using Finite Element (FE) simulation, the research closely examines the intricate interactions among parameters, such as feed rate (f_r), depth of cut (D), and cutting speed (V_c). The use of Response Surface Methodology (RSM) and Taguchi has been used to determine the most optimal settings for tool longevity and machining efficiency. The FE simulation model provides a strong framework to investigate how cutting parameters affect necessary reactions. The present study examines interactions among parameters like cutting speed, depth of cut, and feed rate. Moderate cutting speed, lower depth of cut, and the highest feed rate has induced lower stress in the workpiece. This study adds to understanding NiTiNOL alloy machining fundamentals and offers useful information for industry applications. To attain better machining results while milling NiTiNOL alloy, the results are intended to guide an optimization technique

Abstract: Diffusion bonded joint of Commercially Pure Aluminum (CpAl) with Inconel 718 (IN718) superalloy was investigated for its mechanical and microstructural characteristics. Diffusion Bonding (DB) of CpAl/IN718 was performed at 500 °C for 60 minutes using vacuum tube furnace in the presence Argon (Ar) gas under pressure at a heating rate of 10 °C/minutes followed by furnace cooled. The resultant joint interface was investigated by using Optical and Scanning Electron Microscopy (OM and SEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), microhardness and shear strength. The microstructural analysis shows the formation of various Intermetallic Compounds (IMCs) at the bonding interface, such as NiAl_3, FeAl₂, FeAl₃, Fe₂Al₅ along with austenitic matrix, which was confirmed by XRD. Additionally, the hardness of the bonding interface was 15% and 255 higher as compared to BM of IN718 and CpAl respectively. Lastly, an average lap shear strength of 61 MPa was achieved with a joint efficiency of 84%.

Abstract: Ti-6Al-4V, renowned for its high strength and corrosion resistance, is a preferred material in aerospace and marine applications for lightweight structures due to its durability in challenging environments. Typically, GTAW welding is used for it’s fabrication. The residual tensile stresses produced after welding are known to worsen the corrosion and mechanical properties of welds. However, these properties can be improved by introducing near surface residual compressive stress by shot peening. When compared to the traditional shot peening treatment, the surface roughness that results from multiple shot peening with varying ball sizes and intensities can be significantly reduced. In the present work, Ti-6Al-4V plates were welded using conventional GTAW technique. Six different combinations of multiple shot peening treatments were applied to the welded specimens. Surface morphology and surface roughness were analysed. Surface residual stresses measurement were performed using by X-ray stress analyzer. Domain size and microstrain were measured using X-ray diffraction technique. Micro-hardness measurements were made along the weld thickness. Corrosion studies were carried out using potentiodynamic polarization test in 3.5% NaCl solution. The SP4 parameter comes out to have the best combination among all the multiple shot peened samples. It results in lowered surface roughness, higher compressive residual stress, better grain refinement, increased surface hardness, and enhanced corrosion resistance.

Abstract: This work presents the finite element modelling of porosity in super alloys coatings, developed with cobalt-base/chromium/molybdenum/silicon metallic powders, which were thermally sprayed on oil & gas steel pipeline substrates, with the aim to protect the steel against H₂S and CO₂ corrosive environments. Therefore, in the developed finite element models, a small level of porosity, identified and analysed on the cross-section of the developed coatings, was incorporated in the developed models in order to perform a more realistic analysis of the structural response of the coating with some level of porosity by the local damage modelling technique. The porosity was incorporated in the developed finite element models with the micromechanical Gurson-Tvergaard-Needleman damage model, consequently the damage model parameters of Gurson-Tvergaard-Needleman model were calibrated against the true stress-strain material curve of the coating. The damage model was applied only on the finite elements subjected to higher bending loads. The values of and damage parameters are in the range of those published in the literature, for different type of steels, however value was lower, showing that for super alloy coatings, is quite lower than for steels. For the case of the initial and critical void volume fraction, the best calibrate values are higher compared to steels values reported in the literature. The relative density was similar compared to data published in the literature. Once the damage model parameters were properly calibrated, the modelling was employed to evaluate the stresses and strain states in the coating/substrate structure and in coating-substrates interface. The developed models were able to properly simulate the hardening material response of the coating with good agreement with material data. The results showed that Gurson-Tvergaard-Needleman damage modelling technique was able to model porosity damage in cobalt-base/chromium/molybdenum/silicon hard coatings, since numerical results agree well with true stress-strain material curve of coating material.

Abstract: In order to increase and extend the usage of mild steel in a range of applications, critical research needs are extremely interested in corrosion studies, including corrosion inhibitor performance. The goal of this study is to look at the corrosion-inhibiting capabilities of ammonium benzoate in a 0.5 M HCl solution for mild steel, with solanum tuberosum (potato) extract serving as a surfactant. Mild steel samples were cut into corrosion coupons and submerged in 0.5 M HCl media to investigate the inhibitory effects at room temperature for various concentrations of ammonium benzoate using polarisation and weight loss techniques. A scanning electron microscopy fitted with electron dispersion spectroscopy (SEM-EDS) was used to investigate the morphology of the corroded samples. The results obtained indicated that ammonium benzoate performed better when combined with solanum tuberosum (potato) extract as a surfactant that inhibits mild steel corrosion in 0.5 M HCl by lowering the rate of corrosion. As the concentration rises, ammonium benzoate becomes more effective. From the weight loss test and polarisation analysis, a maximum inhibition efficiency of 99.94% at the 1.0 M concentration of inhibitor was achieved. It was observed that the ammonium benzoate adsorption mechanism isotherm fit with the Langmuir absorption isotherm when it was adsorbed on mild steel. Furthermore, adding solanum tuberosum (potato) extract to the inhibitor significantly reduces the rate of mild steel corrosion in HCl solution. The SEM micrographs confirm the presence of an absorbed protective film layer on the mild steel surface.

Abstract: Polymer blends, particularly those containing Polybutylene terephthalate (PBT) and Polycarbonate (PC), are extensively utilized in various industrial applications due to their favorable mechanical and thermal properties. Enhancing the performance of such blends necessitates an understanding of the relationship between their crystalline structure and wear behavior. This study investigates the correlation between wear characteristics and structural aspects of PBT/PC blends having varying PC content. Additionally, techniques such as X-ray diffraction (XRD) and optical microscopy of the worn-out surface are employed. The findings reveal a strong connection between the wear behavior of PBT/PC blends and their crystallographic structure. This study provides useful insights into the wear mechanism and crystallization behavior of PBT/PC blends. Specifically, it is observed that with increasing PC content in the blends, the wear resistance is influenced by the size of crystallites, wherein smaller crystallites demonstrate a greater ability to withstand abrasive action-induced damage. The wear performance of the PBT/PC blend with 70% PC improves by ~37% as a result of the formation of a semi-orderly chain structure with a smaller crystallite size. A mechanism is also explained herein related to the change in the nature of crystallization of PBT/PC blends with increasing PC content. In conclusion, this study underscores the importance of considering crystallographic structure when assessing the wear behavior of polymer blends such as PBT/PC.

Abstract: This article addresses the burning test conducted on two different configuration of composite sandwich panel. Same flame-retardant material core but different face sheet material. The aim is to identify the heat resistance capability of plant fiber sandwich panel with flame-retardant core compare with traditional carbon fiber sandwich. There are researches of heat resistance behavior for carbon fiber sandwich panel with flame-retardant core [1] [2], but few on plant fiber. As plant fiber has been take a role in composite field, the heat resistance behavior of flame-retardant plant fiber sandwich panel deserves further investigated [3]. The test result indicates that, plant fiber with flame-retardant core sandwich has similar heat resistance behavior in the first stage of burning test with carbon fiber sandwich. However, after burning for 40 seconds, the heat resistance of plant fiber specimen attenuated dramatically than carbon fiber specimen. In addition, the heat induced delamination of two different specimens were also observed. Hence, decided the residual mechanical properties of the burnt specimens.

Abstract: In today's automotive, aerospace, and high-temperature applications, there is a pressing demand for lightweight, high-strength materials. Meeting these industry requirements necessitates the development of such materials through rigorous research efforts. This study is focused on synthesizing, characterizing, and exploring the mechanical and tribological properties of forged AA7075-based Hybrid Metal Matrix Composites (HMMCs) reinforced with TiB₂ (titanium boride) and ZrO₂ (zirconium oxide) particles. The composites were subjected to hot forging, and comprehensive analyses were conducted to assess their microstructural features, elemental composition, and phase distribution. Mechanical properties were evaluated to gauge the enhancements achieved by incorporating TiB₂ and ZrO₂ reinforcements. Tribological behavior was examined using a tribotester under diverse conditions to elucidate the influence of these particles on wear resistance and frictional characteristics, thereby shedding light on potential applications in demanding tribological environments. This investigation incorporates varying percentages of ZrO₂ (zirconium dioxide) by weight (4% and 6%) and TiB₂ particles at 5% by weight into an AA7075 matrix alloy to synthesize a composite material. Scanning Electron Microscope (SEM) micrographs illustrate the uniform distribution of ZrO₂ and TiB₂ particles achievable through the stir casting and grain refinement after the forging process. Experimental results demonstrate that the addition of ZrO₂ and TiB₂ particles enhances the hardness and tensile strength of the AA7075/ZrO₂/TiB₂ composite compared to the base matrix material, with the AA7075/5%TiB₂/4%ZrO₂ composite exhibiting the highest hardness and strength among all variants. At the same time, tribological evaluations underscored enhanced wear resistance and frictional performance, indicating suitability for applications where tribological stability and mechanical strength are paramount. This investigation contributes valuable insights to developing advanced MMCs for high-performance engineering applications, demonstrating that the forging technique facilitates fine grain refinement, enhancing the abovementioned properties. Furthermore, the study identifies notable property improvements achieved through the forging process.

Abstract: Nanoparticles' unique properties, such as their huge surface area, higher thermal conductivity, and increased dielectric strength, make them appealing candidates for high voltage insulation applications. The choice of a suitable surfactant is critical in the creation of nanofluids. The ratio of hydrophilic to lipophilic (HLB) values, which ratio up the hydrophilic and lipophilic structure of the surfactant, is normally considered in the selection of suitable surfactant for the nanofluid. Surfactant with HLB value less than 6 is said to be more suitable for oil base nanofluids. Recent research, however, indicated that the sediment generated by high and low HLB value surfactants is not significantly different. Tween 20 surfactant, while rarely used in this context due to its high HLB value, is an intriguing option due to its affordable cost and excellent properties. Its distinct features, such as low toxicity, and strong emulsification capacity, make it an appealing candidate for stabilizing and dispersing nanoparticles in nanofluid compositions. In this research, tween 20 was used in the preparation of palm oil (PO) and palm fatty acid ester oil (PFAE) based nanofluids. Iron (II,III) Oxide (Fe₃O₄) nanoparticle was introduced to the nanofluids at high, medium and low concentrations. The nanofluids were evaluated in terms of its breakdown strength and dielectric properties. The alternating current (AC) breakdown and dielectric properties were conducted based on the IEC 60156 and ASTM D924 Standard respectively. Tween 20 has positive impact on shortening down the sonication period by 10 % and 33.3 % for PO and PFAE based nanofluids, respectively, while elongating the sedimentation period for PO nanofluids. The breakdown voltage improved by 40% and 18% for PO based nanofluid and PFAE based nanofluid, respectively. Even at low concentrations, the inclusion of Fe₃O₄ nanoparticles improved breakdown strength, and breakdown voltage distributions offered useful information. The addition of nanoparticles slightly increases the relative permittivity of the base oils. Fe₃O₄ nanoparticle and tween 20 surfactant has successfully improved the dielectric loss of the base oil with the lowest value recorded at 0.05 g/L, with 72.4 % and 36.8 % improvement for PO and PFAE based nanofluids, respectively. These results proved that tween 20 is suitable for oil-based nanofluids applications.