M.Sc. Tezi Görüntüleme | |||||||||||||||||||||
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| Summary: In this study, Zn-60Al and Zn-60Al-2Cu alloys were produced by permanent mould casting. After casting, equal channel angular extrusion (ECAE) was applied by using Route-A and Route-Bc up to four passes. Effect of ECAE parameters (Route and pass number) on structural, mechanical and wear properties were examined systematically. Microstructure of Zn-60Al consists of Al-rich (alpha)dendrites and Zn-rich eutectoid (alpha+eta) phase. Microstructure of Zn-60Al-2Cu alloy composed of the same phases of Zn-60Al alloy and also Cu-rich (theta)phase due to copper addition precipitated inter-dendritic regions. The ECAE led to elimination of dendritic structure and elongated and fragmented microconstituents occurred depending on processing route and number of passes.Strength values of the alloys after one-pass ECAE increased and then decreased by increasing the number of passes. This effect is more pronounced in binary Zn-60Al alloy. After four-pass-ECAE in both routes, the strength values obtained from ternary Zn-60Al-2Cu alloy are higher than those obtained from the alloy in the as-cast sate. Ductility and toughness of the alloys increased with increasing the number of ECAE passes in both processing routes due to the elimination of dendritic structure and structural defects, structural refinement and strain induced homogenization. The ECAE process generally improved the wear behavior of the Zn-60Al-2Cu alloy and this effect was found to be more effective in operation conditions of higher applied pressure and longer sliding distance. Brittleness which is the major drawback of as-cast alloys was overcame by applied ECAE process without considerable decrease in strength values of Zn-60Al alloy and with increase in strength values of Zn-60Al-2Cu alloy.
Key Words: Equal Channel Angular Extrusion, Severe Plastic Deformation, Zn-Al Based Alloys, Mechanical Properties, Wear | |||||||||||||||||||||