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The relation between time-dependent corrosion behaviors and microstructural characteristics of Sr modified and unmodified AlSi9 alloy was studied. The melted alloys were cast into the permanent mold at 700 °C casting temperature. The Effect of holding time in the furnace on chemical compositions of alloys was determined. Sr content of the modified alloys was 200 ± 5 ppm after 4 h and 50 ± 2 ppm after 17 h holding time. Microstructural properties were analyzed after casting. The corrosion behavior of AlSi9 depending on Sr content was investigated by means of electrochemical impedance spectroscopy technique and potentiodynamic polarization plots in 3.5 wt% NaCl solution at 25 °C. The effect of immersion time was examined at 1, 24, 72 and 120 h. The results indicated that high Sr content in AlSi9 alloy contributes to the formation of a finer eutectic phase and more stable corrosion behavior during immersion time. • The effect of Sr modification on the AlSi9 is investigated. • The relation between corrosion and microstructural characteristics are evaluated. • 50 ppm Sr is enough to obtain fine and fibrous eutectic morphology. • Sr Modification contributes to formation of stable and less defective oxide layer. • The protective effect of denser oxide/hydroxide layer is evident up to 120 h. [ABSTRACT FROM AUTHOR]

Abstract In this study, it aimed to produce carbon fiber (CF) reinforced aluminum metal matrix composite by squeeze casting method. In order to overcome the wetting problem between the aluminum matrix and the reinforcing agent, carbon fibers were coated with Ni coating with electroless technique. Different bath pH values and hypophosphite (HP), coating durations and bath temperature were investigated. SEM, EDS and XRD methods used to determine the characterize the layers. It has been observed that increasing the pH of the bath, coating time, bath temperature and amount of hypophosphite increases the thickness of the Ni coatings on the carbon fibers. Two different thicknesses of coatings were used with different volume fractions of fiber used to reinforce the 6063 aluminum as matrix alloy. Squeeze casting process was used for the production of the composites to increase the connection between the matrix and the carbon fibers. After achieving a good bonding, three-point bending, Charpy impact, and Vickers hardness tests were carried out to investigate the difference of at the mechanical properties. It was observed from the mechanical tests that while the hardness and the three-point bending strength was increasing the impact strength was decreasing after the carbon fiber addition. Also coating, in general, helping the mechanical properties, mechanical properties of composites are badly affected by higher coating thicknesses. Highlights • Carbon fiber reinforced 6063 alloy was produced by squeeze casting method. • Ni−P were coated on carbon fibers by electroless technique to enhance the wettability. • Ni coated CF addition increased mechanical properties of 6063 alloy. • Ni thickness and distribution of fibers in the matrix affect the mechanical properties. • Incorporation of carbon fibers resulted in increased bending strength in 6063 alloy. [ABSTRACT FROM AUTHOR]

3XX series Al–Si alloys are generally used in corrosive environments open for oxidation such as rainwater and seawater. The dendrite size and characteristics of the eutectic Si are important factors determining the properties of A356 alloy. In this study, the microstructure of Sr modified A356 aluminum alloy and the changes in corrosion properties were investigated. The alloy was cast into die and sand molds to examine the effect of cooling parameters on the microstructure. Sr modification was carried out by adding four different weight percentages (0, 120, 170 and 250 ppm). Corrosion behavior of the produced alloys was investigated by two ways. One of them was electrochemical impedance spectroscopy technique and the other is potentiodynamic polarization plots that was carried out in 3.5 wt.% NaCl solution at 25 °C. The corrosion resistance of the alloy was found to be increasing as Sr content was increased which modified the morphology of the silicon in the alloy. [ABSTRACT FROM AUTHOR]