Date of Award

Fall 2021

Publication Type

Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Magnesium (Mg) melting, Intermetallic formation in sludge, High pressure die casting

Supervisor

H. Hu

Supervisor

X. Nie

Rights

info:eu-repo/semantics/openAccess

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Abstract

Intermetallic formation in sludge during magnesium (Mg) melting, holding and high pressure die casting practices is a very important issue. But, very often it is overlooked by academia, original equipment manufacturers (OEM), metal ingot producers and even die casters. The aim of this study was to minimize the intermetallic formation in Mg sludge via the optimization of the chemistry and process parameters. Through the analyses of the commercial sludges, it was found that AZ91D recycling ingot sludge, and AZ91D, AM60B and AE44 die casting sludge contained intermetallic of 2.77wt.%, 10.33wt.%, 34.07wt.% and 44.81 wt.%, respectively. The Al8Mn5 intermetallic particles were identified by the microstructure analysis based on the Al and Mn ratio. The design of experiment (DOE) technique, Taguchi method, was employed to minimize the intermetallic formation in the sludge of Mg alloys with various chemical compositions of Al, Mn, Fe, and different process parameters, holding temperature and holding time. The sludge yield (SY) and intermetallic size (IS) was selected as two responses. The optimum combination of the levels in terms of minimizing the intermetallic formation were 9wt.% Al, 0.15wt.%Mn, 0.001wt.% (10 ppm) Fe, 690°C for the holding temperature and holding at 30 mins for the holding time, respectively. The best combination for smallest intermetallic size were 9wt.% Al, 0.15wt.%Mn, 0.001wt.% (10 ppm) Fe, 630°C for the holding temperature and holding at 60 mins for the holding time, respectively.

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