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Ali Paşa Hekimoğlu,Merve Çalış,Gizem Ayata 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.6
In this study, a binary Al–12Si, eight ternary Al–12Si–Sr, and six quaternary Al–12Si–0.1Sr–(0.2–1)Mg alloys were producedby permanent mold casting. It was observed that microstructure of the binary alloy consisted of the phases of aluminum richα grains (dendrites), primary silicon, plate like β and eutectic Al–Si containing needle like silicon particles. The ternaryalloys have fine and globular (modified) eutectic silicon particles and higher volume fraction of α (Al) dendrites than binaryalloys. They also contained Al4Srphase after 0.02 wt% Sr, in addition to the phases in the binary alloy. This phase got coarsewhen the strontium ratio exceeded 0.1%. It was observed that the plate like β phase seen in the binary alloys transformed intothe fibrous form δ phase in the ternary alloys. Magnesium addition resulted in transformation of δ phase into script like πphase, and the formation of lamellar like Mg2Siphase when the ratio of it in the quaternary alloys reached the 0.6 wt%. Thelamellar like form of Mg2Siphase changed to Chinese-script type after the 0.6 wt% Mg. The results showed that hardness,yield and tensile strength of the Al–12Si–Sr alloys increased with increasing strontium content up to 0.1 wt%. The resultsalso showed that hardness of the quaternary alloys increased with increasing magnesium content, while yield and tensilestrength increased only up to 0.6 wt% Mg.
Effect of Zinc Content and Cutting Tool Coating on the Machinability of the Al‑(5–35) Zn Alloys
Şenol Bayraktar,Ali Paşa Hekimoğlu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.4
In this study, Al-5Zn, Al-15Zn, Al-25Zn and Al-35Zn alloys containing 5, 15, 25 and 35 wt% Zn, respectively were producedby permanent mold casting. Their microstructures and mechanical properties were investigated using metallographyand universal hardness and tensile tests. Cutting tests of the alloys produced were carried out in a vertical machining center. During the tests, the cutting forces were continuously measured and saved by a software. The roughness of the machinedsurfaces of the alloy samples was measured accordance with the standard of ISO 4287. It was observed that Al-(5–15)Znalloys exhibit single phase (aluminum rich α) microstructure while Al-(25–35)Zn alloys exhibit two-phase microstructureconsisting of α and zinc rich η. As the zinc content increased the hardness and tensile strength of the alloys increased, buttheir elongation to fracture decreased. Cutting force, surface roughness, formation of built-up edge (BUE) and built-uplayer (BUL), and the size of the chip occurring in the machining of the alloys decreased with increasing zinc content. Themachining of the Al-(5-35)Zn alloys with uncoated WC tools results in both lower cutting forces and better surface qualitycompared to titanium-aluminum-nitride (TiAlN) coated tools. The changes in the cutting properties of the tested alloys withthe increasing zinc content were discussed in the based on changes in structural and mechanical properties.