Influence of reduced pressure on density of aluminium extrusion alloy

Hydrogen has high solubility in molten aluminium during solidification, causing porosity, low tensile strength, low elongation and poor surface finish. Porosity is enhanced by inclusions and particles suspended in the melt. The popularity of the reduced pressure test (RPT) stems from its simplicity....

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Bibliographic Details
Published in:International journal of cast metals research (Online) 2012-01, Vol.25 (1), p.59-64
Main Authors: Velasco, E, Montalvo, F
Format: Article
Language:English
Subjects:
Aluminium
Aluminum base alloys
Density
Extrusion
Hydrogen gas content
Melts
Porosity
Reduced pressure test
Solidification
Solubility
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Summary:Hydrogen has high solubility in molten aluminium during solidification, causing porosity, low tensile strength, low elongation and poor surface finish. Porosity is enhanced by inclusions and particles suspended in the melt. The popularity of the reduced pressure test (RPT) stems from its simplicity. It is basically a comparative and semiquantitative test. The reduced pressure encourages pore formation and lower density than if obtained under atmospheric conditions of solidification. The RPT samples of 6063 aluminium alloy were solidified under different vacuum conditions and correlated to its specific gravity. Visual examination of the samples shows that the standard RPT is less sensitive to hydrogen concentration when used with the 6063 alloy than in the case of aluminium foundry alloys. The results reveal that the use of a reduced pressure of 28″Hg (−95 kPa) instead of the suggested standard vacuum of 25″Hg (−84·5 kPa) gives a better visual assessment of the gas content in the melt.
ISSN:1364-0461
1743-1336
DOI:10.1179/1743133611Y.0000000017