Date of Award
2024
Document Type
Open Access Dissertation
Degree Name
Doctor of Philosophy in Materials Science and Engineering (PhD)
Administrative Home Department
Department of Materials Science and Engineering
Advisor 1
Paul Sanders
Committee Member 1
Alexandra Glover
Committee Member 2
Walter Milligan
Committee Member 3
Gregory Odegard
Abstract
Die soldering, an adhesion defect in high pressure die casting (HPDC), is a symptom of localized sticking where a localized portion of the cast material is adhered to the tooling surface causing build up over time. This requires the tooling to be serviced which incurs additional costs to the process that gets passed on to the parts. Historically, soldering has been mitigated using lubricants, coatings, and alloy chemistry modifications but solder persists.
The Tresca friction thermomechanical model suggests soldering occurs when the local interfacial shear stress between the casting and die surface exceeds the local shear strength of the casting. The ratio of these shear strengths, as a function of temperature, has been shown to predict solder. Research up to this point has focused on reducing the friction coefficient, and in turn the interface shear strength, with no work done on the strengthening of the castings regarding solder. Chemistry of the alloy has been shown to influence soldering behavior, but for the wrong reason as Al-Fe intermetallics are the commonly accepted soldering mechanism.
High temperature strengthening mechanisms through chemistry modifications were investigated to support the Tresca friction model. First, the improvement of the solid solution and Orowan strengthening mechanisms was quantified for several aluminum HPDC alloys through the addition of magnesium, improving the hot shear strength of the alloys. Next, the improved alloy shear strength was applied to the Tresca model and tested using a laboratory scale permanent mold designed to solder along with a full scale HPDC production trial with results pointing towards a new soldering mechanism. Finally, the relationship between solder and the casting surface chill zone or “skin” is examined and discussed.
Recommended Citation
Belke, Jacob A., "High Temperature Strength Reduces Soldering In Aluminum High Pressure Die Casting", Open Access Dissertation, Michigan Technological University, 2024.