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A step-by-step procedure to determine the quality of ingots has been developed. This procedure is built on the reduced pressure test and is designed to guide the foundrymen to decide (1) whether the lot of ingots should be accepted and/or (2) what remedial liquid metal processing should be done to bring the melt to the desired levels. A case study on two aluminum alloy A356 ingots is also presented. The results show wide variability in the initial quality of the ingots. Moreover, traditional metallographic techniques to characterize the quality from the slice of the reduced pressure test sample have been shown to provide similar results to those obtained from computerized tomography. [ABSTRACT FROM AUTHOR]

Corrosion behavior of A356 aluminum alloy with different grain refiners was evaluated. For this purpose, the Sr-modified A356 alloy was grain refined with Al5Ti1B and Al3B, and then, the corrosion characteristics were determined. For the mechanical properties, impact and Vickers hardness tests were carried out. To determine the corrosion behavior, both the electrochemical impedance spectroscopy technique and by potentiodynamic polarization plots were carried out in a 3.5 wt.% NaCl solution at 25 °C. The corrosion resistance of A356 alloy was dramatically improved in sequence with the following modifications compared to the unmodified castings: Sr, Ti and B additions. This situation applies to both different cooling rates, namely die and sand casting. The increase in corrosion rate was more than 80% for all alterations of the microstructure. Additionally, charge transfer resistance was increased ten times in die cast samples, while this value was 2.5 for sand cast samples compared to the unmodified alloy. It is important to note that sand casting of the unmodified alloy was improved four times with regard to the die cast unmodified A356. [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]