Diffusion-controlled growth of hydrogen pores in aluminum-silicon castings: In situ observation and modeling

Journal Article · Mon Jan 24 04:00:00 EST 2000 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(99)00363-8· OSTI ID:20015247

Atwood, R C; Sridhar, S; Zhang, W; Lee, P D

In situ observations were made of the nucleation and growth kinetics of hydrogen porosity during the directional solidification of aluminium-7 wt% silicon (Al7Si) with TiB{sub 2} grain refiner added, using an X-ray temperature gradient stage (XTGS). The effect of altering the solidification velocity on the growth rate and morphology of the porosity formed was characterized by tracking individual pores with digital analysis of the micro-focal video images. It was found that increasing the solidification velocity caused the pore radius to decrease and pore density to increase. Insight gained from the experimental results was used to develop a computational model of the evolution of hydrogen pores during solidification of aluminum-silicon cast alloys. The model solves for the diffusion-limited growth of the pores in spherical coordinates, using a deterministic solution of the grain nucleation and growth as a sub-model to calculate the parameters that depend upon the fraction solid. Sensitivity analysis was carried out to assess the effects of equiaxed grain density, pore density, initial hydrogen content and cooling rate. The model agrees with the experimental results within the resolution limits of the XTGS experiments performed.

• Research Organization: Imperial Coll., London (GB)
• OSTI ID: 20015247
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 2 Vol. 48; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
HYDROGEN
KINETICS
LIQUID METALS
MATHEMATICAL MODELS
NUCLEATION
PORE STRUCTURE
SILICON ALLOYS
SOLIDIFICATION
VALIDATION