• 한국주조공학회지
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• 제31권5호
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• pp.274-283
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• 2011

The vacuum die casting is a promising candidate of the stamping process for fabrication of fuel cell bipolar plate due to its advantages, such as precision casting, mass production and short production time. This study proposes vacuum die casting process to fabricate bipolar plates in fuel cell. Bipolar plates were fabricated under various injection conditions such as molten metal temperature and injection velocity. Also, according to injection velocity conditions, simulation results of MAGMA soft were compared to the experimental results. In case of melt temperature $650^{\circ}C$, misrun occurred. When the melt temperature was $730^{\circ}C$, mechanical properties were low due to dendrite microstructure. Injection velocity has to set at more than 2.0 m/s to fabricate the sound sample. When melt temperature, injection velocity (Fast shot), and vacuum pressure are $700^{\circ}C$, 2.5 m/s and 30 kPa respectively, sample had good formability and few casting defects. Simulation results are mostly in agreement with experimental results.

• 열처리공학회지
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• 제37권3호
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• pp.121-127
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• 2024

We investigate the effect of T6 heat treatment on the microstructure and mechanical properties of AA365 (Al-10.3Si-0.37Mg-0.6Mn-0.11Fe, wt.%) alloy fabricated by vacuum-assisted high pressure die casting by means of thermodynamic calculation, X-ray diffraction, scanning and transmission electron microscopy, and tensile tests. The as-cast alloy consists of primary Al (with dendrite arm spacing of 10~15 ㎛), needle-like eutectic Si, and blocky α-AlFeMnSi phases. The solution treatment at 490 ℃ induces the spheroidization of eutectic Si and increase in the fraction of eutectic Si and α-AlFeMnSi phases. While as-cast alloy does not contain nano-sized precipitates, the T6-treated alloy contains fine β' and β' precipitates less than 20 nm that formed during aging at 190℃. T6 heat treatment improves the yield strength from 165 to 186 MPa due to the strengthening effect of β' and β' precipitates. However, the β' and β' precipitates reduce the strain hardening rate and accelerate the necking phenomenon, degrading the tensile strength (from 290 to 244 MPa) and fracture elongation (from 6.6 to 5.0%). Fractography reveals that the coarse α-AlFeMnSi and eutectic Si phases act as crack sites in both the as-cast and T6 treated alloys.

• 한국주조공학회지
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• 제27권4호
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• pp.153-158
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• 2007

Molten metal flow in vacuum die casting was characterized by a numerical analysis. The VOF method was used to simulate the filling behaviors of molten metal during filling process. The various vacuum degrees of no vacuum(760 mmHg), 650, 500, 250 and 60mmHg were artificially applied in cavity. And the filling behaviors of molten metal with the applied vacuum conditions were simulated and compared with those of experiment. The results showed that molten metal was partially filled into cavity when vacuum was applied and the filling length of molten metal in cavity was increased with increasing applied reduced pressure in cavity. Also, the simulated filling behaviors of molten metal were apparently similar to those of experiment, indicating the numerical analysis developed in this study was highly effective. Through the result of fluid flow simulation, both relation equations of filling length and filling velocity with the variation of pressure conditions in cavity were calculated respectively and the internal gas contents of casting was significantly reduced by the modification of vacuum gate system.