• Proceedings of the KWS Conference
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• 2007.11a
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• pp.121-123
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• 2007

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.672.2-672.2
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• 2006

• Journal of Korea Foundry Society
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• v.22 no.4
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• pp.174-183
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• 2002

Twin-roll process is a relatively new continuous casting process which can produce high-quality strip products directly, and solidification rate can reach $10^3$ to $10^4$ K/s, leading to fine and uniform microstructures with enhanced mechanical properties. The strip casting condition for producing fine Al-Sn alloy strip was obtained experimentally, and defects appearing on the strip was examined. Crack formation and surface quality of the strip was found to depend mainly on process parameters such as melt temperature, roller gap and rolling speed. Sn structure of network type was observed in Al-20Sn and Al-40Sn alloy strips, and cell spacing of Al-40Sn alloy was smaller than that of Al-20Sn. Banding strength of the heat treated specimens increased with increasing of soaking time and temperature, and bonding strength of Al-20Sn alloy was more superior than that of Al-40Sn alloy. However wear resistance of Al-40Sn alloy contained large amount of soft Sn which possess good anti-friction characteristics was superior than that of Al-20Sn alloy.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.21-24
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• 2000

Ultra-fine grains were produced in pure Al using an Accumulative Rolling-Bonding (ARB) process. After several cycles of the ARB process, pure Al sheets were filled with the ultra-fine grains whose diameters were several hundred nano-meters. With ARB cycles, the nature of grain boundaries of the ultra-fine grains changed from diffusive sub-boundaries to well-defined high angle boundaries. After 7 cycles, ultra-fine polycrystals with large misorientations between neighboring grains were obtained. Sliding wear tests using a pin-on-disk type wear tester were co ducted on the ultra-fine grained pure Al. Wear rates of pure Al increased with the increase of ARB cycle numbers in spite of the increase in hardness. Worn surfaces and cross-sections were examined with optical microscopy (OM) and scanning electron microscopy (SEM) In investigate the wear mechanism of the ultra-fine grained pure Al.

• Journal of Korea Foundry Society
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• v.30 no.5
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• pp.187-195
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• 2010

In this study, in order to obtain a useful guide line for design and production of automotive heat exchanger components made of 4343/3003/4343 aluminum clad sheets, it was aimed to improve the understanding about the grain refinement effect on brazing characteristic of the clad sheets. Al-10Ti master alloy was used for grain refinement of 3003 core alloy, and the Ti inoculation level was systematically changed up to 0.1 wt%. The three-layer aluminum clad sheets were fabricated by hot roll bonding process. The effect of grain refinement on brazing characteristic of the clad sheets was investigated by evaluating wettability, bonding strength and sagging resistance.

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.316-323
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• 2012

The aim of this study is to investigate the effect of post heat treatment on bonding properties of roll cladded Ti/MS/Ti materials. First grade Ti sheets and SPCC mild steel sheets were prepared and then Ti/MS/Ti clad materials were fabricated by a cold rolling and post heat treatment process. Microstructure and point analysis of the Ti/MS interfaces were performed using the SEM and EDX Analyser. Diffusion bonding was observed at the interfaces of Ti/MS. The thickness of the diffusion layer increased with post heat treatment temperature and the diffusion layer was verified as having $({\epsilon}+{\zeta})+({\zeta}+{\beta}-Ti)$ intermetallic compounds at $700^{\circ}C$ and an $({\zeta}+{\beta}-Ti)$ intermetallic compound at $800^{\circ}C$, respectively. The micro Knoop hardness of mild steel decreased with post heat treatment temperature; however, those of Ti decreased at a range of $500{\sim}600^{\circ}C$ and showed a uniform value until $800^{\circ}C$ and then increased rapidly up to $900^{\circ}C$. The micro Knoop hardness value of the diffusion layer increased up to $700^{\circ}C$ and then saturated with post heat treatment. A T-type peel test was used to estimate the bonding forces of Ti/Mild steel interfaces. The bonding forces decreased up to $800^{\circ}C$ and then increased slightly with post heat treatment. The optimized temperature ranges for post heat treatment were $500{\sim}600^{\circ}C$ to obtain the proper formability for an additional plastic deformation process.

• Korean Journal of Metals and Materials
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• v.50 no.12
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• pp.939-948
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• 2012

A 3-ply clad metal consisting of aluminum and copper was fabricated by roll bonding process and the microstructures and mechanical properties of the roll-bonded and post-roll-bonding heat treated Cu/Al/Cu clad metal were investigated. A brittle interfacial reaction layer formed at the Cu/Al interfaces at and above $400^{\circ}C$. The thickness of the reaction layer increased from $12{\mu}m$ at $400^{\circ}C$ to $28{\mu}m$ at $500^{\circ}C$. The stress-strain curves demonstrated that the strength decreased and the ductility increased with heat treatment up to $400^{\circ}C$. The clad metal heat treated at $300^{\circ}C$ with no indication of a reaction layer exhibited an excellent combination of the strength and ductility and no delamination of layers up to final fracture in the tensile testing. Above $400^{\circ}C$, the ductility decreased rasxpidly with little change of strength, reflecting the brittle nature of the intermetallic interlayers. In Cu/Al/Cu clad heat treated above $400^{\circ}C$, periodic parallel cracks perpendicular to the stress axis were observed at the interfacial reaction layer. In-situ optical microscopic observation revealed that cracks were formed in the Cu layer due to the strain concentration in the vicinity of horizontal cracks in the intermetallic layer, promoting the premature fracture of Cu layer. Vertical cracks parallel to the stress axis were also formed at 15% strain at $500^{\circ}C$, leading to the delamination of the Cu and Al layers.

• Transactions of Materials Processing
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• v.27 no.5
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• pp.267-275
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• 2018

The clad sheet material is produced by a roll-bonding process of one or more materials with different properties. Good formability of clad sheet material is an essential property in to deform a clad metal sheet into a part or component. Performance of the clad sheet material largely depends on interfacial bond strength between different materials. In this study, interfacial bond strength of STS/Al clad sheet was analyzed by varying experimental parameters using a blanking process. Experimental parameters are the punching speed, clearance, and stacking order of plate materials. In addition, blanking test results were compared with bond strengths measured by the T-peel test, that analyzes interface bonding strength of the standard clad sheet. The blanking process was analyzed by the finite element method under the sticking condition of interface of different materials, and experimental results and analysis results were compared.

• Journal of Welding and Joining
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• v.27 no.3
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• pp.92-96
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• 2009

Metallic sandwich plate has many good properties such as high specific stiffness, high specific strength, good impact absorptivity, effective thermal insulation and soundproofing. In our study, a new bonding method, 3-layer roll projection welding, is introduced to fabricate the metallic sandwich plate. The new method uses a pair of roll electrodes like the seam welding, and projection welding is made at two internal interfaces of the 3-layer weldment consisting of a structured inner sheet and a pair of skin sheets. During the welding process, skin sheet temperature are measured to produce metallic sandwich plate with uniform and good quality. But it is difficult to observe or measure the temperature at the welding points during welding process because the welding points exist at the internal interfaces. Therefore FEM numerical analysis using ABAQUS is conducted to estimate the generated heat at the welding points with different welding conditions.

• Journal of Welding and Joining
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• v.18 no.4
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• pp.38-47
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• 2000

Characteristics of the interface between tube and tube sheet which were formed by explosive expansion and roll expansion, have been studied in the research. The results are as follows: Optimum amounts of explosives for the expansion of Alloy 600 (19.05mm and 15.88mm) were found to be RDX 3.5-8.5g/m. Because explosive expansion caused les strain hardening and increased bounding strength, characteristics of the explosively expanded were better than those of mechanically expanded. As the transition region of the explosive expansion is inactive, the resistance to the stress corrosion cracking increases by 30∼40% compared to the roll and hydraulic expansion.