Seong-Seock Cho

Structure and properties of rapidly solidified Mg-Al alloys

Three binary Mg-Al alloys containing nominally 5, 15, and 30 at % Al were prepared in the ingot and rapidly solidified flake conditions using the twin roll technique. The microstructure, mechanical properties, and electrochemical behavior of the extruded alloys in both the conditions were investigated. The hardness, tensile strength, and corrosion resistance increased with increasing Al content. Further, the hardness, tensile strength, and corrosion resistance of the rapidly solidified alloys were superior to the ingot-metallurgy alloys and this is attributed to the microstructural refinement and increased homogeneity in the rapidly solidified alloys.

Demonstration of a high throughput on-board hydrogen generation reactor system using aluminum coil as fuel for a vehicle

ABSTRACT A novel on-board hydrogen generation concept using Al coil with NaOH was investigated. The reaction rate was successfully controlled by introducing a pumping system for the NaOH solution. The time for the flow to develop fully was mainly dependent on the solution temperature, and the fastest start time recorded was 60 sec at a solution temperature of 70°C. The maximum H2 generation rate was 200 L min–1 with a prototype design of the on-board hydrogen generation system 1/8 times the size of a full-size reactor. The H2 generation process coupled with the solution pumping system was simulated with three-dimensional fluid dynamic software, and the calculated H2 flow and temperature rise of the system were validated with experimental data.

Influence of Foaming Temperature and Time on the Hardness of Cellular Al-Si-Cu-Mg Alloys

ABSTRACT Micro Vickers hardness was measured on the cell wall of A1-Si-Cu-Mg alloy foams having different compositions and subjected to different foaming temperature and period of time during production. The powder metallurgical route was utilized to obtain aluminium alloy foam. A1-5%Si-4%Cu-4%Mg-l%TiH2 alloy precursor showed higher hardness value than A1-3%Si-2%Cu-2%Mg-l %TiH2 alloy because of higher alloying element. The hardness value was increased with the increase of foaming period of time at all foaming temperatures while foams having same composition but higher foaming temperature showed higher hardness value regardless of material. These might be due to the fine eutectic grain size effect. Local hardness of foams at α-A1 grain boundaries and junctions of multiple grains were found to be higher than that inside the α-A1 grains. Higher hardness value of eutectic phase and accumulation of eutectic phase near grain boundaries are responsible for this higher hardness value at α-A1 grain boundaries.

Bending Behaviors of Stainless Steel Tube Filled with Al5Si4Cu4Mg Closed Cell Aluminum Alloy Foam

The foam-filled tube beams can be used for the front rail and firewall structures to absorb impact energy during frontal or side collision of vehicles. In the case of side collision where bending is involved in the crushing mechanism, the foam filler would be effective in maintaining progressive crushing of the thin-walled structures so that much impact energy could be absorbed. In this study, bending behaviors of the closed-cell-aluminum-alloy-foam-filled stainless steel tube were investigated. The various foam-filled specimens including piecewise fillers were prepared and tested. The aluminum-alloy-foam filling offered the significant increase of bending resistance. Their suppression of the inward fold formation at the compression flange as well as the multiple propagating folds led to the increase of load carrying capacity of specimens. Moreover, the piecewise foams would provide the easier way to fill the thin-walled shell structures without the drawback of strength.

Development of RQ Al composites by new process

Abstract Ten volume percent of Al2O3–TiC ceramic particle reinforced Al 5083 and Al 6061 alloy composites were successfully fabricated with high strength by combining twin rolling, a newly devised stone mill type crushing and hot extruding. Crushing and composing procedures are enlightened in this work. Both composites showed high UTS, although Al 5083 alloy composites were effectively strengthened by the rapid solidification, whereas Al 6061 composite by heat treating. No reaction product was found to form between the matrix and reinforcement interfaces, due to no severe thermal exposure of this process.