Real-time X-ray Radiography and Computational Modeling of Shrinkage Porosity Formation in Aluminum Alloy Castings

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 50; no. 2; pp. 757 - 771
• Main Authors: Khalajzadeh, Vahid, Goettsch, David D., Beckermann, Christoph
• Format: Journal Article
• Language: English
• Published: New York Springer US 15.02.2019; Springer Nature B.V
• Subjects: Aluminum alloys; Aluminum base alloys; Casting; Casting alloys; Castings; Characterization and Evaluation of Materials; Chemistry and Materials Science; Computation; Computer simulation; Image processing; Materials Science; Mathematical models; Metallic Materials; Nanotechnology; Parameter sensitivity; Porosity; Radiography; Real time; Shrinkage; Solidification; Solids; Structural Materials; Surfaces and Interfaces; Temperature distribution; Thin Films; Wedges; X-ray radiography
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-018-5018-0

The formation of shrinkage porosity in an A356 aluminum alloy wedge casting is investigated using real-time video radiography. An image processing technique is developed to quantify the amount of porosity observed in the video. The transient temperature field is obtained using casting simulation. The results show that initially, sinks develop in the low solid fraction regions on the surface of the wedge. Once the surface becomes sufficiently solid to be rigid, the subsequent solidification shrinkage is accommodated by internal porosity. The internal porosity is found to nucleate and grow in the central part of the wedge where the solid fraction is the lowest. A computational model is developed to predict the formation of the surface sinks and the internal porosity. The model is validated using the experimental measurements and a parametric study is performed to investigate the sensitivity of the predictions to changes in the model parameters.