Quality assessment of artificially aged A357 aluminum alloy cast ingots by introducing approximate expressions of the qu
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I. INTRODUCTION
PRECISION casting is currently attracting considerable attention as a reliable manufacturing process for producing aeronautical and automotive aluminum components of complex shape cost efficiently. Inferior mechanical properties, specifically in terms of ductility, and increased scatter in mechanical properties as compared to the wrought materials with similar chemical composition, represent serious drawbacks for the increased exploitation of cast aluminum alloys in aircraft and automotive structural parts. The tighter controls currently applied during the casting process of premium quality castings, e.g., References 1 and 2, the advancements on the casting processes, e.g., References 1 through 3, and a better understanding of the background physical metallurgy of the age-hardened aluminum alloys, e.g., References 4 through 8, led to an appreciable improvement of the material quality and, hence, to an appreciable increase of the competitiveness of aluminum casting products. Yet, assessment of the quality of a casting material involves an essential amount of interpretation and finally relies heavily on subjective engineering judgment. Classically, the quality of a cast alloy is related to microstructural features such as porosity, inclusions, and intermetallic compounds. On the other hand, in the production line, the easiest and most common method for a fast assessment of the quality of a cast alloy is the hardness test. Impact and tensile tests are also involved to characterize the quality of the alloy in terms of mechanical performance. The final decision about the involvement of a cast alloy for a certain engineering application is met at the design office on the basis of the technological features of the material, that are required for the considered application. These technological features are application dependent. In aircraft and N.D. ALEXOPOULOS, Research Associate, and S.G. PANTELAKIS, Professor, are with the Laboratory of Technology and Strength of Materials, Department of Mechanical and Aeronautical Engineering, University of Patras, 26500 Patras, Greece. Contact e-mail: [email protected] Manuscript submitted January 27, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS A
automotive industry, certain minimum values in tensile strength and ductility are prerequisite for considering a material as a candidate for structural applications. The recent advancements in understanding the background physical metallurgy of the age-hardened aluminum alloys[4–8] allow, by the proper selection of chemical composition, solidification rate, and heat treatment, balance of tensile strength against ductility, such as to “tailor,” within certain material dependent ranges, the material’s mechanical properties to the design office requirements. From a structural engineering viewpoint, the quality of an alloy may be understood as a combination of tensile strength and ductility values that meet the design prerequisites for using it in a certain application. Yet, in a broader interpretation, the quality of
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