Papers by Author: Je Sik Shin

Abstract: in this paper, it was aimed to improve understanding about the effects of physical melt treatment on the morphologies of eutectic silicon crystal size, and then the effects of these microstructural features on anodizing characteristics. A380 and A356 casting aluminum alloys were used in this experiment. A twin-screw melt-shearing process and an electro magnetic stirring process were utilized before high pressure die casting. In order to refine and homogenize the microstructure of the diecast Al-Si alloys, the melt-shearing process parameters were controlled and T6 heat treatment was carried out. A uniform microstructure over the whole thickness of the diecast specimens caused smaller difference in oxidation coating layer thickness between machined and non-machined surfaces. More uniform anodic coating layer was obtained by AC/DC coupled anodizing and PEO processes compared to conventional DC anodizing process.

Abstract: In this paper, it was aimed to develop a new Al-Zn-Mg base aluminum alloy having high electrical conductivity, strength, and formability simultaneously. As a result, Al-Zn-Mg base low aluminum alloy sheet can be effectively strengthened without significant thermal conductivity loss by multiply alloying precipitation hardening elements and properly controlling production process parameters.

Abstract: In this paper, it was aimed to develop a new interconnect material having high electrical conductivity and strength simultaneously. The Cu composite sheet, possessing mesh type Ag conduction paths on the surface of a high strength Cu alloy sheet, was manufactured by damascene electroplating. The peel strength of Cu composite sheet prepared by damascene electroplating increased by above 50 times compared to Cu composite sheet by conventional electroplating. Al wire wedge bonding was able to be successfully conducted without extra metal thin film coating.

Abstract: In this study, it was aimed to investigate the effects of grain refining of 3003 core alloy on forming and brazing characteristics of 4343/3003/4343 aluminum clad sheet. Ti inoculation level was changed up to 0.1wt% by adding Al-10Ti master alloy into 3003 aluminum melt as grain refiner. The three-layer aluminum clad sheets of 0.7 mm thickness were fabricated by hot roll bonding process. The forming and brazing characteristics were evaluated by measuring FLD (forming limit diagram), bonding strength and sagging resistance.

Abstract: In order to investigate the effects of physical melt treatment on microstructural feature and anodizing characteristics of Al-Si system casting alloys, A380 and A356 aluminum alloys were chosen and a twin-screw melt-shearing process was utilized before high pressure die casting. In order to refine and homogenize the microstructure of the diecast Al-Si alloys, the melt-shearing process parameters were controlled and T6 heat treatment was carried out.

Abstract: In this study, it was aimed to develop a novel interconnect material simultaneously possessing high electrical conductivity and strength. Combined structural Cu sheets were fabricated by forming the high electrical conduction paths of Ag on the surface of high strength Cu alloy substrate by damascene electroplating. As a result, the electrical conductivity increased by 40%, while the ultimate tensile strength decreased by only 20%. When the depth of Ag conduction path was deep, fracture zone ratio as well as roll-over zone increased.

Abstract: Eco-friendly grain refinement of A3003 alloy was studied by addition of non-toxic Al-Ti alloy because of toxic-fluorine in Al-Ti-B alloys which used as a representative grain refiner for aluminum and its alloys. TiAl3 phase in Al-Ti alloy bring to decrease grain size of A3003 alloy. But, grain growth occurred with prolonged holding time due to the solution of Ti into aluminum matrix. In contrast, lasting grain refinement of A3003 alloy was occurred in graphite crucible. It can be mentioned that carbon comes from graphite crucible was combined with Ti solute in aluminum melt and then TiC acts as a heterogeneous nucleation for A3003 alloy.

Abstract: The consolidation process of ultra fine Si powders, generated as by-product during the decomposition process of silane gases, was systematically investigated for use as economical solar-grade feedstock. Si powder compacts were tried to fabricate by a consolidation process without a binding agent and then their density ratio and strength were evaluated. The Si powders in as-received state were not pure enough to be used alone as solar grade feedstock material. After the adequate chemical treatments, a sufficiently high purity above solar-grade was able to be achieved.

Abstract: In order to investigate the feasibility of spray forming process for production of high Si steel sheets, 4.8~6.4%Si steels were prepared by spray forming process using N2 and Ar gases and their cold workability was compared with that of conventional ingot cast samples. Atomizing gas affected significant effect on deposit features, microstructural characteristics and mechanical properties of the spray formed high Si steels.

Abstract: A Mo-free high-Cr cast iron with superior impact-wear resistance was tried to develop for mill balls by alloy design and subsequent heat treatment. The Cr/C ratio was varied up to 7.7 in order to minimize and eventually eliminate Mo addition, still ensuring hardenability. For the proper balance between abrasion resistance and toughness, the combined effects of each heat treatment parameters on the mechanical properties were systematically investigated using Taguchi method and response surface method (RSM), well recognized as powerful tools of the designs of experiments (DOE). It was found that hardness and impact energy were mainly affected by tempering and destabilization conditions, respectively. It is noted that high impact energy of 5.2 J/cm2 was obtained without deteriorating hardness (54 HRc) during the verification experiments under the heat treatment condition optimized by the DOE analyses.