• Korean Journal of Materials Research
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• v.22 no.2
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• pp.97-102
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• 2012

The microstructure and tensile properties of Al-Mn/Al-Si hybrid aluminum alloys prepared by electromagnetic duocasting were investigated. Only the Al-Mn alloy showed the typical cast microstructure of columnar and equiaxed crystals. The primary dendrites and eutectic structure were clearly observed in the Al-Si alloy. There existed a macro-interface of Al-Mn/Al-Si alloys in the hybrid aluminum alloys. The macro-interface was well bonded, and the growth of primary dendrites in Al-Si alloy occurred from the macro-interface. The Al-Mn/Al-Si hybrid aluminum alloys with a well-bonded macro-interface showed excellent tensile strength and 0.2% proof stress, both of which are comparable to those values for binary Al-Mn alloy, indicating that the strength is preferentially dominated by the deformation of the Al-Mn alloy side. However, the degree of elongation was between that of binary Al-Mn and Al-Si alloys. The Al-Mn/Al-Si hybrid aluminum alloys were fractured on the Al-Mn alloy side. This was considered to have resulted from the limited deformation in the Al-Mn alloy side, which led to relatively low elongation compared to the binary Al-Mn alloy.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.4
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• pp.770-783
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• 2015

Lately, high production rate welding processes for Al alloys, which are used as LNG FPSO cargo containment system material, have been developed to overcome the limit of installation and high rework rates. In particular, plasma-metal inert gas (MIG) hybrid (PMH) welding can be used to obtain a higher deposition rate and lower porosity, while facilitating a cleaning effect by preheating and post heating the wire and the base metal. However, an asymmetric undercut and a black-colored deposit are created on the surface of PMH weld in Al alloys. For controlling the surface defect formation, the wire feeding speed and nozzle diameter in the PMH weld was investigated through arc phenomena with high-speed imaging and metallurgical analysis.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.160-166
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• 2011

Weight reduction while maintaining functional requirements is one of the major goals in the automotive industry. The use of lightweight magnesium alloys offers great potential for reducing weight because of the low density of these alloys. However, the formability and the surface quality of the final magnesium alloy product for auto-body structures are not acceptable without a careful optimization of the design parameters. In order to overcome some of the main formability limitations in the stamping of magnesium alloys, a new approach, the so-called "hybrid technology", has been recently proposed for body-in-white structural components. Within this approach, necessary level of mechanical joining can be obtained through the use of lightweight material-steel adhesion promoters. This paper presents the development process of an automotive hybrid hood assembly using magnesium alloy sheets. In the first set of material pairs, the selected materials are magnesium alloy AZ31B alloy and steel(SGCEN) as inner and outer panels, respectively. In order to optimize the design of the inner panel, the stamping process was analyzed with the finite element method (FEM). Laser welding by CW Nd:YAG were used to join the magnesium alloy sheets. Based on the simulation results and mechanical test results of the joints, the determination of die design variables and their influence on formability were discussed. Furthermore, a prototype based on the proposed design was manufactured and the static stiffness test was carried out. The results demonstrate the feasibility of the proposed hybrid hood with a weight reduction of 25.7%.

• Journal of Magnetics
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• v.20 no.4
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• pp.336-341
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• 2015

MnBi alloys were fabricated by arc melting and annealing at 573 K. The heat treatment enhanced the content of the low-temperature phase (LTP) of MnBi up to 83 wt%. The Bi-excess assisted LTP MnBi alloys were used in the hybridization with the Nd-Fe-B commercial Magnequench ribbons to form the hybrid magnets (100-x)NdFeB/xMnBi, x = 20, 30, 40, 50, and 80 wt%. The as-milled powder mixtures of Nd-Fe-B and MnBi were aligned in a magnetic field of 18 kOe and warm-compacted to anisotropic and dense bulk magnets at 573 K by 2,000 psi for 10 min. The magnetic ordering of two hard phase components strengthened by the exchange coupling enhanced the Curie temperature ($T_c$) of the magnet in comparison to that of the powder mixture sample. The prepared hybrid magnets were highly anisotropic with the ratio $M_r/M_s$ > 0.8. The exchange coupling was high, and the coercivity $_iH_c$ of the magnets was ~11-13 kOe. The maximum value of the energy product $(BH)_{max}$ was 8.4 MGOe for the magnet with x = 30%. The preparation of MnBi alloys and hybrid magnets are discussed in details.

• Smart Structures and Systems
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• v.3 no.4
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• pp.405-422
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• 2007

A new hybrid damping technique for vibration reduction in flexible structures, wherein a combination of layers of hard passive damping alloys and active (smart) magnetostrictive material is used to reduce vibrations, is proposed. While most conventional vibration control treatments are based exclusively on either passive or active based systems, this technique aims to combine the advantages of these systems and simultaneously, to overcome the inherent disadvantages in the individual systems. Two types of combined damping systems are idealized and studied here, viz., the Noninteractive system and the Interactive system. Frequency domain studies are carried out to investigate their performance. Finite element simulations using previously developed smart beam elements are carried out on typical metallic and laminated composite cantilever beams treated with hybrid damping. The influence of various parameters like excitation levels, frequency (mode) and control gain on the damping performance is investigated. It is shown that the proposed system could be used effectively to dampen the structural vibration over a wide frequency range. The interaction between the active and passive damping layers is brought out by a comparative study of the combined systems. Illustrative comparisons with 'only passive' and 'only active' damping schemes are also made. The influence and the mode dependence of control gain in a hybrid system is clearly illustrated. This study also demonstrates the significance and the exploitation of strain dependency of passive damping on the overall damping of the hybrid system. Further, the influence of the depthwise location of damping layers in laminated structures is also investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.75.1-75.1
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• 2013

Atomic layer deposition (ALD) and molecular layer deposition (MLD) are based on sequential, self-limiting surface reactions that produce atomic layer controlled and conformal thin film growth. ALD can deposit inorganic films and MLD can deposit films containing organics. ALD and MLD can be used together to fabricate a wide range of hybrid organic-inorganic alloy films. The relative fraction of inorganic and organic constituents can be defined by controlling the ratio of the ALD and MLD reaction cycles used to grow the film. These hybrid films can be tuned to obtain desirable mechanical, electrical and optical properties. This talk will focus on the growth and properties of metal alkoxide films grown using metal precursors and various organic alcohols that are known as "metalcones". The talk will highlight the tunable mechanical properties of alucone alloys grown using Al2O3 ALD and alucone MLD and the tunable electrical conductivity of zincone alloys grown using ZnO ALD and zincone MLD with DEZ and hydroquinone as the reactants.

• Journal of Welding and Joining
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• v.34 no.4
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• pp.62-66
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• 2016

The trend of the fabrication technology of high strength, high toughness aluminum alloys by the severe plastic deformation(SPD) process and the welding technology of lightweight alloys in the automobile has been studied. The lightweight aluminum alloys can reduce vehicle weight, while stringently demanding the high quality and efficient welding techniques, to produce the best weldments. Among the production technologies, welding plays an important role in the fabrication of lightweight vehicle structure. This paper covers the scientometric analysis of the severe plastic deformations of lightweight alloys and the welding technology in the automobile which are based on the published research works in the 'HPT, ECAP and rolling', and 'welding technology of the automobile' obtained from Web of Science, and deals with the details of the background data of the HPT, ECAP, and rolling of lightweight alloys, and welding technology of the automobile technology.

• Proceedings of the Korean Magnestics Society Conference
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• 2006.06a
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• pp.70-71
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• 2006

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.5
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• pp.519-524
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• 2014

The use of light weight magnesium alloy offers significant potential towards improvement of the automotive fuel efficiency. However, the application of formed magnesium alloy components in auto-body structures is restricted due to the low formability at room temperature and lack of knowledge for processing magnesium alloys at elevated temperatures. In this study, a warm tensile test of magnesium alloys was performed to measure tensile strength and elongation. An improvement in formability was confirmed at increased temperatures above about $250^{\circ}C$. Car body warm forming technology was conducted for forming forming reinforced dash components of the magnesium alloy AZ31B sheet at elevated temperatures.

• Proceedings of the Korean Magnestics Society Conference
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• 2005.06a
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• pp.158-159
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• 2005