1,425 research outputs found
A Research on the Effect of Retrogression and Re-Aging Heat Treatment on Hot Tensile Properties of AA7075 Aluminum Alloys
No full textAluminum 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
No full textIn 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
No full textPurpose: 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
Chinese Vaccine Diplomacy in the Eastern Mediterranean: Continuities and Rupture in Beijing’s Soft Power Prospects
No full text© The Author(s) 2023.This article examines China’s vaccine drive in Eastern Mediterranean countries of Türkiye, Egypt, Syria, Lebanon, and the Palestinian territories during 2020–2021 from a soft power angle. 1 Although Chinese COVID-19 era health diplomacy is presented as a major breakthrough in the West, this study argues that continuities are more visible in the Eastern Mediterranean context with regard to China’s discourse and diplomatic practices. Beijing invested in the existing notions of propaganda, such as solidarity with developing countries, anti-Americanism, and economic partnership. In assessing the impact of Chinese vaccine diplomacy in the Eastern Mediterranean, the study investigates major diplomatic events and concludes that China could not improve its image in Türkiye in the aftermath of the COVID-19 pandemic
The Psychology of Morality
No full textFive questions regarding the nature of the moral sense, the origin of conscience, the development of morality, variability in the moral sense, and the relation of morality to behavior are examined from the point of view of four theoretical approaches (psychoanalytic theory, social learning theory, cognitive-developmental theory, and evolutionary psychology). In addition, some concepts and findings from outside the four approaches are also touched upon. The moral sense is shown to be complex, comprising cognitions, feelings, and behaviors. The theoretical approaches disagree regarding the issues of whether conscience directly reflects social teaching, or is constructed by the developing individual. They also disagree on whether moral development is incremental or stagewise. Explanations of individual, gender, and cultural differences in morality differ across the four approaches. None of the approaches explains the relation of behavior to morality; rather, application of social psychological theories is suggested. More recent developments are briefly reviewed, supporting the view that the evolutionary approach and its extensions have become dominant in the field in recent years. Focus on social relations rather than individuals, emphasis on emotions rather than reason or action, pluralist views of the bases of morality, and functions of morality in group competition are highlighted as aspects of the newer approaches
Transitioning from “traditional” to the “new normal” - what is in between? An editorial to BRIDGES symposium proceedings Vipava, Slovenia
No full textThe COVID-19 medical emergency resulted in a similar educational
emergency as educators and learners at all levels were rapidly required to
transition into online digital spaces, use digital tools and services that they may
not have been familiar with, and adopt digital pedagogies that they may not have
been used to. This created uncertainties bringing challenges and opportunities,
and shed light on the affordances and constraints of digital tools. The Erasmus+
BRIDGES project has taken a research-led approach to understand the
experiences of educators during the emergency remote teaching (ERT) period in
order to inform practices, professional development and support needs in the
post-lockdown, post-digital higher educational (HE) landscape. The BRIDGES
Symposium has therefore brought together HE practitioners worldwide to reflect
on the lessons learned. This editorial will briefly report on the findings of this
project, and the emergent themes of the symposium and pose critical questions
on lessons learned and the possible futures of digital education in multinational
settings
Transitioning from “traditional” to the “new normal” - what is in between? An editorial to BRIDGES symposium proceedings Vipava, Slovenia
No full textThe COVID-19 medical emergency resulted in a similar educational
emergency as educators and learners at all levels were rapidly required to
transition into online digital spaces, use digital tools and services that they may
not have been familiar with, and adopt digital pedagogies that they may not have
been used to. This created uncertainties bringing challenges and opportunities,
and shed light on the affordances and constraints of digital tools. The Erasmus+
BRIDGES project has taken a research-led approach to understand the
experiences of educators during the emergency remote teaching (ERT) period in
order to inform practices, professional development and support needs in the
post-lockdown, post-digital higher educational (HE) landscape. The BRIDGES
Symposium has therefore brought together HE practitioners worldwide to reflect
on the lessons learned. This editorial will briefly report on the findings of this
project, and the emergent themes of the symposium and pose critical questions
on lessons learned and the possible futures of digital education in multinational
settings
Investigation of Mechanical Properties of AA7075 Alloys Aged by Various Heat Treatments
No full textAbstract: 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
Effects of Mold Cavity Geometry on Flow Rate and Mechanical Properties in Al-Si-Mg Alloy
No full textIn 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
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