1,720,966 research outputs found
A Research on the Effect of Retrogression and Re-Aging Heat Treatment on Hot Tensile Properties of AA7075 Aluminum Alloys
Full text linkAluminum alloys are preferred in most industries due to the functional properties they provide. It is known that alloys that can be processed with heat treatments show better mechanical properties. 7xxx series alloys can be processed via heat treatments and are often used in environmental conditions such as extreme temperatures and corrosive environments. Corrosive sensitivities such as stress corrosion cracking can be observed with the effect of working conditions. It is known that retrogression and re-aging heat treatment provide corrosion resistance and decrease the stress corrosion cracking velocity. The purpose of this study is to examine the tensile behavior of annealed and retrogression-re-aging heat-treated AA7075 alloys at elevated temperatures. The mechanical properties of the alloys were investigated by conducting tensile tests at room temperature, 100, 200, and 300 °C. Hardness tests were performed at room temperature on the samples that were taken from tensile test specimens after tensile tests. The potential effects of test temperature on mechanical and microstructural properties were examined. The annealed and RRA heat-treated alloys were characterized by scanning electron microscope and X-ray diffraction analysis. As a result, an increase in strength and hardness of the retrogression-re-aging treated AA7075 alloys was observed. The ductility of the retrogression-re-aging treated alloy was lower compared to the annealed AA7075 alloy. Fracture surface examinations showed that there was a semi-ductile fracture below 200 °C and ductile fracture at temperatures of 200 and 300 °C. Ductility was observed to increase with increasing temperature
Effect of Al2O3Nanoparticles as Reinforcement on the Wear Properties of A356/Al2O3Nanocomposites Produced by Powder Metallurgy
Full text linkIn this study, microstructure and wear properties of A356 aluminum matrix nanocomposites reinforced with nano-Al2O3 particles were investigated. The powder metallurgy method was used for the production of 1 wt% and 2 wt% nano-Al2O3 particle reinforced nanocomposites. After 1 h of mechanical milling of A356 and nano-Al2O3 powders, green compacts were obtained by cold pressing. Green compacts were sintered at 550 °C in a vacuum environment (10-6 mbar) for 1 h. Samples were characterized by density, hardness measurements, scanning electron microscopy investigations, and wear tests. As the reinforcement ratio increased, there was a decrease in the densities of the nanocomposites, as well as an increase in the porosity. The highest hardness and the lowest weight loss values were obtained in 1 wt% Al2O3 reinforced nanocomposites. A decrease in hardness was measured at 2 wt% Al2O3 reinforced nanocomposites
Mechanical and wear performance of A356/Al2O3 aluminum nanocomposites by considering the mechanical milling time and microstructural properties
Full text linkPurpose: The paper aims to examine the mechanical and wear performance of A356/Al2O3 (alumina) nanocomposites. The correlation between wear performance and the microstructural properties that result from various mechanical milling periods was investigated. Design/methodology/approach: The production of nano alumina reinforced (1 Wt.%) A356 aluminum nanocomposite specimens was carried out using the traditional powder metallurgy method, incorporating three different mechanical milling times (1, 2 and 4 h). Subsequently, mechanical and wear performance assessments were conducted using hardness, compression and pin-on-disc wear tests. Findings: Although the specimens subjected to the most prolonged mechanical milling (4 h) demonstrated superior hardness and compressive strength properties, they exhibited a remarkable weight loss during the wear tests. The traditional evaluation, which supports that the wear performance is generally correlated with hardness, does not consider the microstructural properties. Since the sample milled for 1 h has a moderate microstructure, it showed better wear performance than the sample with higher hardness. Originality/value: The originality of the paper is demonstrated through its evaluation of wear performance, incorporating not only hardness but also the consideration of microstructural properties resulted from mechanical milling. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2023-0031
Manufacturing of B4C particle reinforced A360 aluminium cellular composite materials by the integration of stir casting and space holder methods
Full text linkStir casting method has become prominent for fabrication of metal matrix composites in recent years. This method can be adjusted for casting around space holding particles to obtain cellular composite materials. In this study, a specific method which is a combination of stir casting and space holder techniques were used to produce open-celled A360 aluminium-B4C composite foams with regular sized and distributed pores. Weight ratios of reinforcement particles determined as 0.5, 1, 1.5 and 2%. The influences of particle reinforcement on the microstructure and the mechanical behaviour of composite foams were investigated. Microstructures were analysed with optical microscope (OM), scanning electron microscope (SEM). Compression and hardness tests were carried out to observe the effects of reinforcement on mechanical properties. Compression strength properties and hardness of composites increased with the ceramic reinforcement, however the plastic strength of the composite foams showed worsening trend after a certain reinforcement ratio (0.5 wt.%). Energy absorption properties of the composite foams showed parallel trends with compressive strength properties
Investigation of Mechanical Properties of AA7075 Alloys Aged by Various Heat Treatments
Full text linkAbstract: In this study, annealing (O), artificial aging (T6), retro-regression aging (RRA) and high temperature pre-precipitation (HTPP) heat treatments were applied to AA7075 aluminium alloys. The effects of these treatments on the mechanical properties of AA7075 alloy were investigated. The microstructures of the samples were examined by Optical Microscope (OM), Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) analysis. Then, X-ray diffraction analysis (XRD) was conducted to identify intermetallics formed in the microstructure of the samples. Tensile and hardness tests were carried out to investigate the mechanical properties. Results showed that secondary phase particles such as Al2Cu, Al2CuMg and MgZn2 are formed in the microstructures. In terms of the mechanical properties, T6 applied samples showed the best results. The HTPP applied alloy which presented optimum ductility behaviour among the other heat-treated samples. Dimples and some cleavage surfaces were observed on the fracture surfaces of the samples. Therefore, it is concluded that a ductile/semi-ductile fracture occurred on the samples
On the thermal impact during drilling operations in guided dental surgery: An experimental and numerical investigation
Full text linkIn recent years, a major development in dental implantology has been the introduction of patient-specific 3D-printed surgical guides. The utilization of dental guides offers advantages such as enhanced accuracy in locating the implant sites, greater simplicity, and reliability in performing bone drilling operations. However, it is important to note that the presence of such guides may contribute to a rise in cutting temperature, hence increasing the potential hazards of thermal injury to the patient's bone. The aim of this study is to examine the drilling temperature evolution in two distinct methods for 3D-printed surgical dental guides, one utilizing an internal metal bushing system and the other using external metal reducers. Cutting tests are done on synthetic polyurethane bone jaw models using a lab-scale automated Computer Numeric Control (CNC) machine to find out the temperature reached by different drilling techniques and compare them to traditional free cutting configurations. Thermal imaging and thermocouples, as well as the development of numerical simulations using finite element modeling, are used for the aim. The temperature of the tools' shanks experienced an average rise of 2.4 °C and 4.8 °C, but the tooltips exhibited an average increase of around 17 °C and 24 °C during traditional and guided dental surgery, respectively. This finding provides confirmation that both guided technologies have the capability to maintain temperatures below the critical limit for potential harm to bone and tissue. Numerical models were employed to validate and corroborate the findings, which exhibited identical outcomes when applied to genuine bone samples with distinct thermal characteristics
Effects of Mold Cavity Geometry on Flow Rate and Mechanical Properties in Al-Si-Mg Alloy
Full text linkIn this study, the effects of the oxide films formed by using different mold cavity geometries on the mechanical properties of the parts were investigated. The casting process was carried out using the same runner system with different mold geometries. The effect of liquid metal flow rate on bifilm formation and the mechanical properties of the cast material were examined. Eventually, oxide bifilms formed in the mold cavity when the flow rate is low (caused by folding). These oxide bifilms negatively affect the mechanical properties as much as the oxide bifilms formed in the runner system. When real-time liquid metal flow rates are examined in different casting cavities, flow irregularities such as turbulence, folding, and splashing were developed differently in the flow rate of the liquid metal. It was determined that the stability in the flow rate of the liquid metal directly affects the mechanical strength
Cutting Forces and 3D Surface Analysis of CFRP Milling with PCD Cutting Tools
Full text linkAbstractThis paper provides a study on the milling of carbon fiber reinforced laminated composites. A set of milling experiments were carried out under various conditions. Cutting force results were measured and analyzed (based on the cutting coefficients modelling). 3D surface topographies of machined areas were measured. The cutting forces and surface roughness results were analyzed and better average surface roughness values were obtained from the process conditions of high cutting velocity and low feed rate. The influences of fiber orientation on the surface quality were evaluated. The tool flank wear was measured by an optic microscope periodically and the results were interpreted
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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