| Summary: | In this study, the effect of copper (Cu) and silicon (Si) additives on mechanical and machinability properties of Al-25Zn alloy was investigated experimentally. Binary Al-25Zn, ternary Al-25Zn3Cu and quaternary Al-25Zn-3Cu-3Si alloys were produced by induction melting and permanent mold casting method and microstructure and mechanical properties of these alloys were determined. Cutting tests were conducted using CVD Al2O3 coated cutting tool on CNC lathe with three different cutting speeds (250-350-450 m/min) and feed rate (0,05-0,1-0,15 mm/rev) and 1,5 mm constant depth of cut. The internal structure of Al-25Zn alloy was observed to be composed of aluminum-rich α dentrites and zinc-rich interdendritic η phase. In addition to intermetallic α and α+η phases, θ phase was formed with 3% Cu addition to this alloy and the eutectic and primary silicon particles were formed in addition to α, α + η, θ phases with the addition of 3% Si to the Al-25Zn-3Cu alloy. Al-25Zn and Al-25Zn-3Cu alloys by adding Cu and Si, respectively, hardness, yield and tensile strength increased while breaking elongation decreased. As a result of the machinability tests, it was observed that the cutting forces were measured at the highest Al-25Zn-3Cu-3Si and the lowest Al-25Zn-3Cu alloys. It was found that the lowest surface roughness values were measured in Al-25Zn alloy at all cutting speeds and feed rates of 0,05-0,1 mm/dev and in Al-25Zn-3Cu alloy at feed rate of 0,15 mm/rev. The highest surface roughness values were determined in Al-25Zn-3Cu-3Si alloy at all cutting speeds.
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