The Experts below are selected from a list of 843 Experts worldwide ranked by ideXlab platform
C. G. Kang - One of the best experts on this subject based on the ideXlab platform.
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The effect of solid fraction and indirect forging pressure on mechanical properties of wrought aluminum alloy fabricated by electromagnetic stirring
The International Journal of Advanced Manufacturing Technology, 2009Co-Authors: C. G. KangAbstract:This study demonstrated the effect of solid fraction and forging pressure on mechanical properties of the product of wrought aluminum alloys fabricated by the indirect rheoforging through electromagnetic stirring (EMS). In addition to EMS, the rheological material was examined for its response to various pouring temperatures as the rheo-material was forged into a sample which consisted parts that were directly and indirectly subjected to forge pressure. As results of investigating the relationship between microstructural features and mechanical properties of the product through microscopic inspection, the EMS rheo-forged materials revealed a fine and Globular Microstructure. Microstructures of Al6061 wrought aluminum alloy with uniform solid and liquid phase distributions (no segregation) demonstrated good mechanical properties with tensile strengths of up to 341 MPa.
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The effect of forging pressure on liquid segregation during direct rheoforging process of wrought aluminium alloys fabricated by electromagnetic stirring
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2008Co-Authors: C. G. KangAbstract:This study demonstrated rheoforging of wrought aluminium alloys fabricated by means of electromagnetic stirring (EMS) and characterization of the rheoforged products. When EMS was applied under a stirring current of 60 A, infusion of surface oxides into the bulk material and porosities within the bulk material were both prevented and dendrites were crushed. Material rheoforged at a densification pressure of 150 MPa exhibited good mechanical strength and surface quality. The temperature of the rheological material during forging influences the formability of the material. When the solid fraction is below 70 per cent, the rheological material completely fills the die cavity and the pressure applied by the punch is transferred to the material at the bottom of the die cavity. Investigating the microstructural features and mechanical properties of the material, it is shown that the rheoforged material following EMS yields a fine and Globular Microstructure.
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Development of a new rheology forming process with a vertical-type sleeve with electromagnetic stirring
The International Journal of Advanced Manufacturing Technology, 2008Co-Authors: C. G. KangAbstract:In this paper, a rheology forming process using a mid-pressure caster and incorporating an electromagnetic stirring system (EMS) has been demonstrated and adapted to the forming processes used to manufacture engineering components such as knuckles. After using the new rheological forming process to produce the knuckle, we investigated the Microstructures and mechanical properties of the part by image analysis. Comparing this part to one fabricated by a process that did not use EMS revealed that this part was 30% better. In addition, it had a Globular Microstructure. Furthermore, this research provided a foundation for improving recycling and die life. The new forming process also provided energy savings because of low pressure die-casting conditions. The mid pressure die-casting process also improves productivity because of its shorter cycle times.
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A study on reheating characteristics for thixo die casting process with electromagnetic stirring and extruded aluminum alloys and their mechanical properties
The International Journal of Advanced Manufacturing Technology, 2008Co-Authors: C. G. KangAbstract:In this paper, the reheating process and mechanical properties of thixo die cast A356 alloy, using electromagnetic stirring (EMS) and extrusion before thixo die casting, were discussed. The EMS is used mainly to manufacture raw materials with a Globular Microstructure. If relevant reheating is carried out, products with excellent mechanical properties can be manufactured by EMS. Contrarily, extruded material has a fine dendrite Microstructure and has rarely been assumed to be suitable for the thixo die casting process. This study demonstrated that the Microstructure of extruded material could be Globularized and applied to the thixo die casting process only with the relevant reheating parameters. This applicability was estimated through image analysis obtaining the solid fraction, the mean equivalent diameter, and roundness under various reheating conditions. After thixo die casting experiments using three materials, which were EMS, low-extrusion material (LER), and high-extrusion ratio materials (HER), mechanical properties were comparatively analyzed. EMS and HER materials show better mechanical properties than LER.
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The effect of Globular Microstructure size on the mechanical properties in reheating process of aluminum alloys
Journal of Materials Engineering and Performance, 2004Co-Authors: C. G. Kang, S. W. YounAbstract:One of the important steps in semi-solid forming is the process of reheating raw materials to the semi-solid state. This process is not only necessary to achieve the required semi-solid state of the billet, but also to control the Microstructure of the billet. In the reheating process, the globule size is determined by the holding time of the final reheating step. Therefore, some experiments to investigate the relationship between the mechanical properties and the holding time in the last heating step were performed. The alloys used in this experiment were 357, 319, and A390 alloys. The experiments of reheating were performed using an induction heating system with a capacity of 50 kW. This article shows the evolution of the Microstructure according to the holding time of the last reheating stage. Furthermore, to evaluate the effect of globule size as determined by holding time of the final reheating step, uniaxial tension tests were performed. The stress-strain curves were plotted according to the holding time, and a relationship between the Microstructure and the flow stress of semi-solid material was formulated.
H. K. Jung - One of the best experts on this subject based on the ideXlab platform.
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Numerical analysis by new proposed coil design method in induction heating process for semi-solid forming and its experimental verification with globalization evaluation
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003Co-Authors: C. G. Kang, H. K. JungAbstract:Abstract In this paper, four procedures for optimizing inductive coil design are presented to reduce computational time and lead time. First, a theoretical coil design is proposed by defining the quantitative relationship between billet length and coil length. Second, the numerical simulation of the induction heating process using a general purpose finite element analysis code, ansys , is carried out to predict the temperature distribution. Third, an objective function on the basis of the optimization process for the coil design is proposed by introducing an optimization technique. Finally, the results of the optimal coil design are also applied to the induction heating process to obtain a fine Globular Microstructure. The proposed objective function based on the computational techniques and numerical simulation model would contribute to producing thixoformed parts with good mechanical properties and reducing lead time.
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Induction heating process of an Al–Si aluminum alloy for semi-solid die casting and its resulting Microstructure
Journal of Materials Processing Technology, 2002Co-Authors: H. K. Jung, C. G. KangAbstract:Abstract During induction heating, the relationship between time and temperature must be controlled exactly to obtain a homogeneous temperature distribution over the entire cross-sectional area. Because the initial solid fraction in the semi-solid die casting (SDC) process is the main parameter to achieve a homogeneous flow behavior of the liquid and solid phases and to prevent macro-segregation effects in the SDC process, an accurately controllable induction heating method must be selected for the reheating process. The purpose of this work is not just to obtain the desire solid fraction, generally about 50%, but also to ensure the optimal induction heating conditions of A356 alloy to reduce the temperature gradient of a 76 mm diameter ×90 mm length billet and to obtain a fine Globular Microstructure without grain coarsening (resulting Microstructure). This work shows that, in the case of a three-step reheating process for the SDC process, the final holding time is the most important factor to maintain a fine Globular Microstructure without grain coarsening.
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The induction heating process of semi-solid aluminium alloys for thixoforming and their Microstructure evaluation
Journal of Materials Processing Technology, 2000Co-Authors: H. K. JungAbstract:Abstract The optimal inductive coil design in the induction heating process of A356 (ALTHIX) alloy billets of 76 mm diameter and 90 mm length to reduce the temperature gradient of the billet and to obtain a Globular Microstructure was theoretically proposed and tested by reheating experiments. The optimal reheating conditions to apply the thixoforming process were investigated by changing the reheating time, holding time, holding temperatures, capacity of the induction heating system, and adiabatic material size. This study shows that, the larger the billet size, the better the multi-step reheating, and the heating time and the capacity of the induction heating system must be increased. In case of the three-step reheating process, the final holding time is most important factor and 2 min is suitable to maintain a Globular Microstructure.
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Reheating process of cast and wrought aluminum alloys for thixoforging and their Globularization mechanism
Journal of Materials Processing Technology, 2000Co-Authors: H. K. Jung, C. G. KangAbstract:Abstract A thixoforging process has numerous advantages compared to die casting, squeeze casting, and conventional forging. For the thixoforging process, beside a co-existing solidus–liquidus interval, the reheating conditions to obtain a fine Globular Microstructure are very important. During reheating, the eutectic must be remelted completely in order to obtain good mechanical properties. The solid fraction distribution over temperature, the phase distribution and the morphology of structure are important for the reheatability of SSM. Moreover, the reheating of the billet in the semi-solid state as quickly and homogeneously as possible is one of the most decisive aspect. To obtain the Globular Microstructure in the cross-section of the billet, the optimal design of the induction coil for variations of alloys and specimen sizes is necessary. Thus in this study, the optimal coil design of A356 (ALTHIX) and Al2024 with d×l=60 mm×90 mm to reduce the temperature gradient of the billet and to obtain a Globular Microstructure was theoretically proposed, and then the coil was manufactured. The suitability of the coil design will be demonstrated by reheating experiments. The Microstructure characteristics were investigated by changing the heating time, the heating temperature, the holding time, and the heating capacity.
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Induction heating of semisolid billet and control of Globular Microstructure to prevent coarsening phenomena
Journal of Materials Engineering and Performance, 2000Co-Authors: H. K. Jung, C. G. Kang, Y. H. MoonAbstract:An important step in the thixoforming process is the induction heating of the raw materials to the semisolid state. Using this technology, the process behavior is satisfactory from the point of view of reproducibility and temperature control. Therefore, the objectives of this study are to define the correct relationship between coil length and billet length for uniform induction heating and to present the optimal reheating conditions suitable for the thixoforming process (or to secure a fine Globular Microstructure without liquid segregation). The optimal inductive coil on the induction heating process of semisolid billet machined to 76 mm diameter and 90 mm length to reduce the temperature gradient of the billet and to obtain the Globular Microstructure was theoretically designed and the suitability of the designed coil dimensions verified by reheating experiments. The Globular Microstructures of semisolid billet in heating and holding processes were controlled to prevent the coarsening phenomena of Al-7%Si-0.3%Mg alloy and to apply to the thixoforming process. In addition, the effects of the history of processing and induction heating parameters such as reheating time, holding time, holding temperatures, capacity of the induction heating system, and adiabatic material size on the Globularization were investigated. It was concluded that in the case of a three-step reheating process, the final holding time is the most important factor and 2 min is suitable to maintain a Globular Microstructure.
Hussain Alawadhi - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and optical properties of electrodeposited crystalline Cu2O in the Vis–NIR range for solar selective absorbers
Renewable Energy, 2015Co-Authors: Abdul Hai Alami, Anis Allagui, Hussain AlawadhiAbstract:This paper reports on the thermal oxidation of electrodeposited copper Microstructures from a 0.2 M H2SO4 + 0.4 M CuSO4 aqueous solution on a copper substrate for selective solar thermal absorbers applications. A study of the morphological properties and crystalline structure of the deposited/annealed layer through SEM-EDS and powder XRD revealed the formation of self-assembled cubic Cu2O Microstructures. The copper oxide layer was optically examined by virtue of a spectrometer in the spectral Vis–NIR range. The surface roughness induced by the existence of the Globular Microstructure has been seen to enhance the absorptance of the material. Around two to three-fold enhancement of optical surface absorption is achieved in the wavelength range of 400–1000 nm versus an air-grown copper oxide.
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Synthesis and optical properties of electrodeposited crystalline Cu2O in the Vis-NIR range for solar selective absorbers
Renewable Energy, 2015Co-Authors: Abdul Hai Alami, Anis Allagui, Hussain AlawadhiAbstract:This paper reports on the thermal oxidation of electrodeposited copper Microstructures from a 0.2M H2SO4+0.4M CuSO4aqueous solution on a copper substrate for selective solar thermal absorbers applications. A study of the morphological properties and crystalline structure of the deposited/annealed layer through SEM-EDS and powder XRD revealed the formation of self-assembled cubic Cu2O Microstructures. The copper oxide layer was optically examined by virtue of a spectrometer in the spectral Vis-NIR range. The surface roughness induced by the existence of the Globular Microstructure has been seen to enhance the absorptance of the material. Around two to three-fold enhancement of optical surface absorption is achieved in the wavelength range of 400-1000nm versus an air-grown copper oxide.
Y. H. Moon - One of the best experts on this subject based on the ideXlab platform.
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Induction heating of semisolid billet and control of Globular Microstructure to prevent coarsening phenomena
Journal of Materials Engineering and Performance, 2000Co-Authors: H. K. Jung, C. G. Kang, Y. H. MoonAbstract:An important step in the thixoforming process is the induction heating of the raw materials to the semisolid state. Using this technology, the process behavior is satisfactory from the point of view of reproducibility and temperature control. Therefore, the objectives of this study are to define the correct relationship between coil length and billet length for uniform induction heating and to present the optimal reheating conditions suitable for the thixoforming process (or to secure a fine Globular Microstructure without liquid segregation). The optimal inductive coil on the induction heating process of semisolid billet machined to 76 mm diameter and 90 mm length to reduce the temperature gradient of the billet and to obtain the Globular Microstructure was theoretically designed and the suitability of the designed coil dimensions verified by reheating experiments. The Globular Microstructures of semisolid billet in heating and holding processes were controlled to prevent the coarsening phenomena of Al-7%Si-0.3%Mg alloy and to apply to the thixoforming process. In addition, the effects of the history of processing and induction heating parameters such as reheating time, holding time, holding temperatures, capacity of the induction heating system, and adiabatic material size on the Globularization were investigated. It was concluded that in the case of a three-step reheating process, the final holding time is the most important factor and 2 min is suitable to maintain a Globular Microstructure.
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induction heating of semisolid billet and control of Globular Microstructure to prevent coarsening phenomena
Journal of Materials Engineering and Performance, 2000Co-Authors: H. K. Jung, C. G. Kang, Y. H. MoonAbstract:An important step in the thixoforming process is the induction heating of the raw materials to the semisolid state. Using this technology, the process behavior is satisfactory from the point of view of reproducibility and temperature control. Therefore, the objectives of this study are to define the correct relationship between coil length and billet length for uniform induction heating and to present the optimal reheating conditions suitable for the thixoforming process (or to secure a fine Globular Microstructure without liquid segregation).
Masoud Emamy - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the effect of Al-8B master alloy and strain-induced melt activation process on dry sliding wear behavior of an Al–Zn–Mg–Cu alloy
Materials & Design, 2020Co-Authors: Seyed Sajad Mirjavadi, Mohammad Alipour, A. M. S. Hamouda, M.k. Besharati Givi, Masoud EmamyAbstract:Abstract This study was undertaken to investigate the influence of Al–8B master alloy and modified strain-induced melt activation process on the structural characteristics and dry sliding wear behavior of Al–12Zn–3Mg–2.5Cu aluminum alloy. The optimum amount of B containing master alloy for proper grain refining was selected as 3.75 wt.%. The alloy was produced by modified strain-induced melt activation (SIMA) process. Reheating condition to obtain a fine Globular Microstructure was optimized. The optimum temperature and time in strain-induced melt activation process are 590 °C and 10 min, respectively. T6 heat treatment was applied for all specimens before wear testing. Significant improvements in wear properties were obtained with the addition of grain refiner combined with T6 heat treatment. Dry sliding wear performance of the alloy was examined in normal atmospheric conditions. The experimental results showed that the T6 heat treatment considerably improved the resistance of Al–12Zn–3 Mg–2.5Cu aluminum alloy to the dry sliding wear. The results showed that dry sliding wear performance of Globular Microstructure specimens was a lower value than that of B-refined specimens without strain-induced melt activation process.
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Effects of the SIMA Process on the Microstructure of 6061 Al Alloy Refined by Al-5Ti-1B
Key Engineering Materials, 2013Co-Authors: R. Khorshidi, Masoud Emamy, M. AmueiAbstract:In current research the effect of the strain-induced melt activation (SIMA) process on the Microstructure of 6061 Al alloy has been investigated. The optimum amount of Ti for proper grain refining was found to be 0.03 wt.% in the alloy. In SIMA process, after hydraulic pressing, recrystallization and partial melting (RAP) were employed to obtain a fine Globular Microstructure. Certain amount of strain (40%), heat treatment time (30 min) and temperatures (605-645°C) were employed to find an optimized fine Globular Microstructure of the alloy. A microstructural study which was carried out by optical microscopy, exhibited the uniform equiaxed recrystallized grain structure.
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Effect of Titanium on Microstructure of Al2014 Alloy Prepared by SIMA Process
Key Engineering Materials, 2013Co-Authors: M. Amuei, Masoud Emamy, R. KhorshidiAbstract:Forming in semi-solid state to achieve Globular Microstructure has an effective influence on mechanical properties of aluminum alloys. In this research, the Al2014 alloy was prepared by a semi-solid strain-induced melt activated (SIMA) process. In order to analyze the effect of titanium content on the macrostructure of Al2014, the optimum amount of titanium according to its efficiency on reducing the grain size was obtained. Then, specimens with optimum titanium content were prepared by the SIMA process. Cold working was applied on specimens by an upsetting technique. Cold worked specimens were heat treated at 595, 605, 615, 625 and 635°C and were kept at these temperatures for 30 min to achieve a Globular structure. Observations through optical and scanning electron microscopy (SEM) revealed that by increasing the temperature, an increase in sphericity and grain size occurs. According to the results, optimum condition in order to achieve a fine and Globular Microstructure is keeping specimens at 625°C for 30 min.
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Investigation of the effect of Al–5Ti–1B grain refiner on dry sliding wear behavior of an Al–Zn–Mg–Cu alloy formed by strain-induced melt activation process
Materials & Design, 2013Co-Authors: Mohammad Alipour, Baharak Ghorbanian Aghdam, Hamid Ebrahimi Rahnoma, Masoud EmamyAbstract:Abstract This study was undertaken to investigate the influence of Al–5Ti–1B master alloy and modified strain-induced melt activation process on the structural characteristics, mechanical properties and dry sliding wear behavior of Al–12Zn–3Mg–2.5Cu aluminum alloy. The optimum amount of Ti containing master alloy for proper grain refining was selected as 2 wt.%. The alloy was produced by modified strain-induced melt activation (SIMA) process. Reheating condition to obtain a fine Globular Microstructure was optimized. The optimum temperature and time in strain-induced melt activation process are 575 °C and 20 min, respectively. T6 heat treatment was applied for all specimens before tensile testing. Significant improvements in mechanical properties were obtained with the addition of grain refiner combined with T6 heat treatment. After the T6 heat treatment, the average tensile strength increased from 283 MPa to 587 MPa and 252 MPa to 564 MPa for samples refined with 2 wt.% Al–5Ti–1B before and after strain-induced melt activation process, respectively. Dry sliding wear performance of the alloy was examined in normal atmospheric conditions. The experimental results showed that the T6 heat treatment considerably improved the resistance of Al–12Zn–3Mg–2.5Cu aluminum alloy to the dry sliding wear. The results showed that ultimate strength and dry sliding wear performance of Globular Microstructure specimens was a lower value than that of Ti-refined specimens without strain-induced melt activation process.