Date of Award

8-17-2009

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

Supervisor

Sumanth Shankar

Language

English

Abstract

Increased efforts have been undertaken to develop advanced casting (near-net shaped) processes and materials to attain high-integrity cast components with improved mechanical properties and performances. Semi-Solid Metal (SSM) process is one such process route where in typical binary eutectic alloys with suitable alloying additions could be cast from a two phase (solid and liquid) state into a near net shaped component. The SSM technology has been feverishly developed globally via two fundamental processing routes, namely, thixocasting and rheocasting. The use of the former process has been diminishing in recent years due to economic disadvantages inherent to the process and the development of rheocasting route has been dominant. In this process the new SSM processing route in Controlled Diffusion Solidification (CDS) has been validated by carrying out shaped casting in a tilt-pour casting process. Additionally, the project has shown for the first time that it is viable to shape cast Al wrought alloys which have been traditionally impossible to do so. In CDS technology two precursor alloys with specific chemical composition and melt temperatures are mixed in a controlled manner and subsequently cast into a shaped component. The process yields components with a non-dendritic morphology of the primary phase during solidification in the resultant microstructure. Further, CDS circumvents the problems of hot tearing during casting which has been the primary deterrent in casting Al wrought alloys into shaped castings. The project has shown that CDS technology can be used for commercial casting of sound components with Al wrought alloys by using three alloys, namely, 2024, 6082, 7075 Al alloys. The objectives of the project were achieved by designing, manufacturing and validating a tilt-pour casting equipment along with a standard metal mould to shape cast test bars for tensile and fatigue properties assessment. Alloy compositions, melt temperatures and several process conditions were optimized by laboratory experiments and industrial tilt-pour casting trials. The project was successful in establishing a viable method to shape cast Al wrought alloys, specifically the three example alloys considered and it has been shown that the shaped casting of these alloys were visually sound with good casting integrity, heat treatable and showed reasonable tensile properties. Further, a viable scrap recycling methodology for shape casting AI wrought alloys by CDS has been formulated and validated in this project with 2024 Al alloy.

McMaster University Library

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