Defect band characteristics in Mg-Al and Al-Si high-pressure die castings

Bands of positive macrosegregation and porosity commonly follow the surface contour of components produced by high-pressure die casting (HPDC). In this article, Al alloy AlSi7Mg and Mg alloys AZ91 and AM60 were cast into tensile test bars using cold-chamber (cc) HPDC. Microstructural characterizatio...

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Bibliographic Details
Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2007-08, Vol.38 (8), p.1833-1844
Main Authors: GOURLAY, C. M, LAUKLI, H. I, DAHLE, A. K
Format: Article
Language:English
Subjects:
Alloys
Applied sciences
Exact sciences and technology
Foundry engineering
Metallurgy
Metals. Metallurgy
Microstructure
Pressure before casting
Production techniques
Studies
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Summary:Bands of positive macrosegregation and porosity commonly follow the surface contour of components produced by high-pressure die casting (HPDC). In this article, Al alloy AlSi7Mg and Mg alloys AZ91 and AM60 were cast into tensile test bars using cold-chamber (cc) HPDC. Microstructural characterization revealed that externally solidified crystals (ESCs) are not necessary for defect band formation, and that defect bands can form both near to and relatively far from any surface layer of different microstructure. The defect bands were 140 to 240 µm thick. In addition to defect-band-related macrosegregation, the castings also contained inverse segregation and surface segregation. Defect bands are shown to have the characteristics of the dilatant shear bands reported in past rheology studies, indicating that defect bands form due to strain localization in partially solid material during the HPDC process. [PUBLICATION ABSTRACT]
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-007-9243-1