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Correlation of Mechanical and Microstructural Properties in As-Cast Condition of EN AW-5083 Aluminium Alloy Using Statistical Analysis

In the frame of this investigation, six (6) ingots of EN AW-5083 alloy have been casted by semicontinuous vertical Direct Chill process (DC). The idea behind the process was correlating mechanical properties (tensile strength) with microstructure of ingots (number of grains per unit area) in as-cast state using statistical analysis. The Latin square experimental design was used for statistical analysis. The ingot cross-sectional grain sizes and the mean grain number per unit area were determined at precise, statistically defined locations in the slice by means of semi-automatic method for measuring mean lineal intercept lengths. Additionally, determination of the ultimate tensile strength across the cross-sectioned slices of ingots was made. It revealed differences between ingots’ fronts and rears for both microstructure and ultimate tensile strength. Comparison of obtained differences enabled the correlation between ultimate tensile strength and number of grains per unit and hypothesis was based on impact of disposition and number of grains on ultimate tensile strength. The results were processed using the StatSoft® STATISTICA 13.2. software package using charge, slice height and slice width as sources of variability. Comparison of obtained statistical results for both number of grains per unit and tensile strength in respect to the sampling position enabled further correlation between these two properties and it explained how casting process has direct impact on microstructure and, ultimately, on mechanical properties.

aluminium alloy EN AW-5083 ; direct chill casting ; statistical analysis ; microstructure ; tensile strength

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