Ph.D. Tezi Görüntüleme | |||||||||||||||||||||
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| Summary: In this study, five binary Zn-(5-25)Al, five ternary Zn-15Al-(1-5)Cu and six quaternary Zn-15Al-3Cu-(0,5-3)Si alloys were prepared by permanent mould casting. Their structural, mechanical and tribological properties were investigated in the as-cast and heat treated conditions. Friction and wear tests were carried out using a block-on-disc machine. The microstructure of the binary Zn-15Al alloy consisted of β dendrites, eutectic (β + η) and eutectoid (α + η) mixtures. Ternary Zn-15Al-(3-5)Cu alloys contained ε phase in addition to the phases present in the binary alloy and quaternary Zn-15Al-3Cu-(0,5-3)Si alloys revealed silicon particles in addition to the phases present in the ternary alloys. T5 heat treatment had no significant effect on the dendritic microstructures of Zn-15Al-3Cu and Zn-15Al-3Cu-1Si alloys. However, the dendritic microstructure of these alloys was completely removed after T7 heat treatment which also caused the formation of T’ phase by decomposition of ε phase. Among Zn-15Al based ternary and quaternary alloys the highest tensile strength and wear resistance were obtained with Zn-15Al-3Cu and Zn-15Al-3Cu-1Si alloys, respectively. T5 and T7 heat treatments reduced the hardness, strength and wear resistance of these alloys. In addition, the wear resistance of the Zn-15Al based alloys was observed to be dependent upon their tensile strength rather than their hardness. The wear resistance of Zn-15Al based ternary and quaternary alloys was found to be much higher than those of Al-12Si alloy and SAE 660 bronze especially in dry sliding condition.
Key Words: Zn-15Al Based Alloys, Zn-15Al-3Cu, Zn-15Al-3Cu-1Si, Microstructure, Mechanical Properties, Friction and Wear. | |||||||||||||||||||||