Ph.D. Tezi Görüntüleme | |||||||||||||||||||||
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| Summary: The cooling curves of a series of zinc-aluminum, zinc-aluminum-copper and zinc-aluminum-copper-silicon alloys were plotted during casting at different poring and mould temperatures using thermocouples and an analog digital converter in a computer. The average cooling rates of these alloys were determined. The effect of cooling rate on the structure and properties of the alloys were investigated. In addition, the influence of porosity content, secondary dendrite arm spacing and copper content on some physical and mechanical properties of these alloys were examined. It was found that as the mould and pouring temperatures decreased the cooling rate of the alloys increased during solidification. It was also observed that as the cooling rate increased the percentage porosity and secondary dendrite arm spacing of the alloys decreased, but the density, hardness, tensile strength, percentage elongation and impact energy of the alloys increased. As the percentage porosity and secondary dendrite arm spacing decreased the density, hardness, tensile strength, percentage elongation and impact energy of the alloys increased. The hardness of the alloys was found to be increased with increasing copper content. However, as the copper content exceeded a certain level tensile strength and impact energy of the alloys decreased. It was also found that the silicon addition increased the hardness of ZnAl40Cu2 alloy, but decreased its tensile strength, percent elongation and impact energy. , Correlation of the experimental results showed that cooling rate of the alloys can be related to their density, percentage porosity, secondary dendrite arm spacing, hardness, tensile strength, percentage elongation and impact energy using mathematical equations. In addition, Skenazi equation was found to be applicable to these alloys. As a result of this work, the optimum cooling rate for zinc-aluminum alloys was found to between 3,90°C/s and 4,79°C/s. Keywords: : Zinc-Aluminum Based Alloys, Cooling Rate-Property Relationships, Secondary Dendrite Arm Spacing, Porosity
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