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Chandan Choudhary,H. N. Bar,A. K. Pramanick,K. L. Sahoo,Durbadal Mandal 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10
In this study, simultaneous effects of modified strain induced melt activation (M-SIMA) process and addition of Al-5Ti-1Bchemical grain refiner on the casting defects, microstructural features, and mechanical properties of hypoeutectic Al-7Sialloys are investigated. The traditional melting and casting techniques were used to develop cast ingots of unrefined andgrain refined structures of Al-7Si alloy. Addition of chemical refiner Al-5Ti-1B to Al-7Si melt could significantly changethe secondary dendritic arm spacing and eutectic Si particle size to 31% and 28%, respectively. In the M-SIMA process, castingots were 60% warm deformed and heat-treated at mushy zone at temperature 585 °C for 30 min. Spherical morphology ofα-Al grain and fine fibrous type eutectic Si are observed after M-SIMA process. Grain size of α-Al and eutectic Si are furtherreduced to 56% and 40% after M-SIMA process of grain refined Al-7Si alloy. Porosity and micro-cracks are also minimizedafter M-SIMA process. Microstructural features of cast and M-SIMA processed alloys were characterized through opticaland scanning electron microscopy. X-ray diffraction techniques reveal the different phases present in the developed alloy. TEM analysis further confirms the presence of TiAl3and Ti7Al5Si14precipitates in grain refined Al-7Si alloy. A significantimprovement of 132% in hardness (HV), 76% in yield strength, 120% in ultimate tensile strength, 125% in elongation tofracture, and 116% in specific ultimate tensile strength are obtained in M-SIMA processed grain refined Al-7Si alloy. Fractographyanalysis reveals the mixed mode of fracture in M-SIMA processed Al-7Si alloy with refined structure comparedto brittle fracture of unrefined cast alloy.