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Tomita, Kohei; TANIYAMA, Hisanori; Imabayashi, Mamoru; Iwamura, Harero

doi:10.2464/jilm.31.186

Cited by 3 publications

(3 citation statements)

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“…for CO 2 ). 7 Since the solubility of N 2 and CO 2 gases in aluminium alloys is very low, the internal gas pressure values for the pre-existing pores were simply calculated based on the ideal gas law.…”

Section: D Image Based Numerical Simulationmentioning

confidence: 99%

“…It has been reported that in the case of aluminium alloys, nitrogen, carbon dioxide and hydrogen are the major gas species entrapped during die casting. 7 Since blistering usually occurs when die castings are heated to high temperatures, it is difficult to apply a solution heat treatment to ordinary die castings to improve their mechanical properties through age hardening. In addition, with respect to gas precipitation from solids, aluminium and its alloys are highly susceptible to supersaturation with hydrogen, after cooling from a molten to a solidus state, due to the large miscibility gap in hydrogen concentration between molten and solid aluminium.…”

Section: Introductionmentioning

confidence: 99%

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Formation behaviour of blister in cast aluminium alloy

Toda

Itô

et al. 2014

International Journal of Cast Metals Research

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The formation behaviour of a blister in a die cast aluminium alloy was observed by employing a combined methodology of in situ three-dimensional observation using X-ray microtomography and image based simulation. It has been revealed, via a reverse approach based on the simulation, that nitrogen and carbon dioxide gases fill the blister nucleus. Spontaneous growth of the blister nucleus occurs through creep deformation of the surrounding aluminium due to the blister nucleus' high internal gas pressure. This internal gas pressure also induces hydrogen precipitation in the form of micropores, which undergo steady growth in a spherical shell region around the blister nucleus. The selective growth of the micropores is attributable to the elevation of hydrostatic stress in directions parallel to the casting surface, thereby promoting the expansion of the blister, also parallel to the casting surface, through the absorption of surrounding micropores into the blister nucleus.

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Section: D Image Based Numerical Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Formation behaviour of blister in cast aluminium alloy

Toda

Itô

et al. 2014

International Journal of Cast Metals Research

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“…However, due to the high speed and high pressure mold filling of molten metal, die casting is generally disturbed by porosity defects arising from the entrapment of air or gases in the cavity of the mold. 1,2) It has been reported that the porosity defects can be reduced by increasing casting pressure in a number of researches.…”

Section: Introductionmentioning

confidence: 99%

Compression Behavior of Entrapped Gas in High Pressure Diecasting

et al. 2012

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Die castings generally contain a large quantity of porosities due to the entrapment of air or gas in molten metal during mold filling. Although the entrapped air or gas is compressed by high casting pressure during pressurization, it will eventually remain in the castings as defects after solidification. Therefore, it is important to clarify the relation between the volume of gas defects and the pressure applied to the molten metal so as to optimize the casting design.In this study, we investigated the compression behavior of entrapped gas during casting. We determined the volume of gas defects and gas content in die castings by density measurement and vacuum fusion extraction method respectively. Then we calculated the gas pressure in the defects from the above volume of defects and gas content, and compared with the die casting pressure. The calculated gas pressure in the defects was found to be not equal to the die casting pressure, but equal to the pressure of the molten metal just before it dropped abruptly due to the complete blocking of the liquid metal channel by solidification. From the experimental results, the behavior of the entrapped gas can be inferred as follows. Immediately after the mold was filled with molten metal, the entrapped gas was instantly compressed. After that, the pressure of molten metal decreased gradually with the progress of solidification of the molten metal channel, and the volume of entrapped gas increased correspondingly until the pressure of the molten metal dropped abruptly. Then the volume of the entrapped gas showed a slight expansion equal to the solidification shrinkage of the enclosed molten metal.The above inference was verified by measuring the volume of the entrapped gas defects in castings made with intentional depressurization carried out at the time when mold filling just finished or halfway through the solidification of the molten metal channel.

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