SEMI-SOLID ALUMINUM DIE CASTING PROCESS DESIGN FOR PREVENTING DEFECTS: POROSITY

1,2 SUSLU Yekta Berk
Co-authors:
2 ACAR Mehmet Sirac 2 MUTLU Muammer 1 KELES Ozgul
Institutions:
1 Istanbul Technical University, Faculty of Chemical and Metallurgical Engineering, Istanbul, Turkey, ozgulkeles@itu.edu.tr
2 Mita Mold and Casting Inc., Istanbul, Turkey
Conference:
28th International Conference on Metallurgy and Materials, Hotel Voronez I, Brno, Czech Republic, EU, May 22nd - 24th 2019
Proceedings:
Proceedings 28th International Conference on Metallurgy and Materials
Pages:
1222-1229
ISBN:
978-80-87294-92-5
ISSN:
2694-9296
Published:
4th November 2019
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
42 views / 5 downloads
Abstract

Gas porosity is one of the most common casting defect in die cast parts and it has an undeniable effect on strength, leakage and heat treatability. Reducing and even preventing porosity level can be achieved by the integrative design of mold, vacuum system and optimized process parameters. Applying semi-solid processing also helps to improve quality; not only by preventing defects but also modifying microstructure to have stronger products. In semi-solid casting, generated globular primary phases cause reduction in apparent viscosity under increased shear stress in thixotropic behaviour. This leads to planar flow instead of turbulent, which helps reducing air entrapment during injection and mold filling. In this study, GISS (Gas Induced Semi-Solid) adapted high pressure die casting technique is used for producing AlSi9Cu3 alloy die cast parts. The effects of semi-solid processing temperature, rheo-casting time, changeover position and fast shot velocity are investigated on microstructural changes and porosity levels by using Taguchi method. Radiographic analysis is used for non-destructive testing for determining porosity state. Optic and field emission scanning electron microscope (FE-SEM) are used for microstructural and morphological characterization. Energy-dispersive X-ray spectroscopy (EDS) is also applied for chemical analyses of the phases involved. As results, fast shot velocity and rheo-casting time are found to be the most effective parameters on the porosity level and globular microstructure, by increased shear stress.

Keywords: High pressure die casting, semi-solid, aluminum, Taguchi method, characterization
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