Experimental and theoretical investigation of ultrasonic cavitation processing of Al-based alloys and nanocomposites

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Date
2018
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University of Alabama Libraries
Abstract

Ultrasonic Treatment (UST) is one of the most promising manufacturing methods to refine the microstructure of casting alloys by transforming the morphology of the grains from dendritic to globular, decreasing the grain size, and modifying the precipitates. The applied temperature and/or temperature range during the ultrasonic and solidification processing are the key parameters that will influence the grain refinement. In this study, the effects of the temperature and/or temperature range applied during the ultrasonic and solidification processing on the microstructure and nano-particles distribution of the metal-matrix-nano-composites (MMNCs) have been investigated in detail. Aluminum alloy A356 and Al2O3/SiC nano-particles are used as the matrix alloy and the reinforcement, respectively. UST is applied during the solidification of the molten alloy. Experimental results indicated that the application of UST during solidification has positive effects on the microstructure of the as-cast ingots. Different UST application temperature/temperature range causes different refinement results. Moreover, the added nanoparticles refined the microstructure of the ingot section that is located adjacent to the immersed cylindrical face of the probe. Al-Si-Cu alloys have been widely used in the automotive industry. Fe-rich intermetallics are regarded as the most detrimental impurities that diminish the mechanical properties of alloys. In this study, the effect of ultrasound application temperature/temperature range on the pre-dendritic Fe-rich intermetallics (i.e, sludge) has been also investigated. Aluminum alloy A383 is used as the base alloy. Experimental results indicated that by applying UST on the melt highly influences the morphology and distribution of the precipitated Fe-rich intermetallics. Different UST application temperature/temperature range causes different modification and distribution results of the Fe-rich intermetallics. To create various temperature gradients in the laboratory scale ingot, an innovative two-zone furnace -ultrasound system has been set up in this study. A numerical model for simulation of the temperature-output power correlation that was validated by using experimental measurements has been built as well. The specific ultrasonic zone that will strongly affect the ingot microstructure has been identified and the ultrasonic attenuation coefficient of aluminum A356 melt has been determined.

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Electronic Thesis or Dissertation
Keywords
Materials science
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