Document Type thesis Author Name Deshpande, Jayesh U URN etd-092106-151830 Title The Effect of Mechanical Mold Vibration On the Characteristics of Aluminum Alloys Degree MS Department Manufacturing Engineering Advisors Dr. Makhlouf M. Makhlouf, Advisor Dr. Diran Apelian, Committee Member Dr. Richard D. Sisson Jr.,, Department Head Keywords hot tearing microstructure Aluminum casting Date of Presentation/Defense 2006-09-15 Availability unrestricted
Aluminum-Silicon and Aluminum-Copper alloys are important non-ferrous casting alloys. Different methods have been applied to improve their casting characteristics, their microstructure and consequently, their mechanical properties. Application of mechanical vibrations to the mold during solidification of the alloy is one of these methods. In this study, the effect of controlled mechanical vibrations on the dendrite coherency point, the hot tearing tendency, and the microstructure of B206, B390, and binary Al-7%Si alloys was evaluated. The dendrite coherency point was determined using the two-thermocouple method. The hot tearing tendency was evaluated using the crack susceptibility criterion (CSCb) and by means of measurements using a specially designed ring mold. Microstructure characterization was performed using optical and scanning electron microscopy coupled with image analysis. It was found that mechanical vibrations refine the microstructure of the alloys; and, in the case of B390 alloy, it resulted in significant improvement in the distribution of the primary silicon particles. In the case of B206 and Al-7%Si alloys, where aluminum is the primary phase, mechanical vibrations caused the dendrite coherency point to shift towards lower temperature, i.e., towards higher fraction solid. This shift, together with the refinement of the grain structure, manifested itself in significant reduction in the incidence of hot tearing in B206 castings.
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