Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Mechanical and Materials Engineering

Supervisor

Dr Jeffrey Wood

Abstract

The primary goal of this study was to conduct experiments and simulation modeling to determine the relevant filling and solidification process parameters that influence microstructural features of the high-pressure die-cast magnesium alloy AM60. This work continues from the previous research that has been carried out by Dr. Jeff Wood’s research group over the last sixteen years.

Metallographic and spherical microindentation were used to analyze the influence of microstructural features on the flow stress for both skin (finer grain sizes) and core (larger grain sizes) of high pressure die castings (HPDC), as well as different regions of gravity cast stepped-plate. It was observed that the local yield stress and flow stress of magnesium alloys depend on grain size.

Multiple runs of the commercial casting simulation package, ProCAST™, were used to model the mold filling and solidification events employing a range of interfacial heat transfer coefficient (IHTC) values. The simulation results were used to estimate the centreline cooling curve at various locations through the casting. In this contribution, a new method was developed which employs the knowledge of local cooling rates to predict the grain size and the skin thickness of HPDC magnesium. The local cooling rate was used to calculate the resulting grain size and skin thickness via the established relationships.

A new casting instrument to simulate the important aspects of the HPDC process was designed. The heat flux and IHTC profiles at the metal-die interface in that casting process have been successfully predicted by solving the inverse thermal problem.

Available for download on Friday, June 01, 2018


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