Quantitative Characterization of Hypoeutectic Aluminum Silicon Copper As Cast Alloy Microstructures
There are only two kinds of qualitative methods for the estimation of aluminum alloy structures: (1) bar charts (degree of eutectic fineness, porosity content, etc. and (2) atlases of microstructures, mainly for rejection (overheating, for example) In this paper, the development of quantitative methods for the characterization of hypoeutectic Al Si Cu as cast alloy microstructures using panoramic image analysis is described. As cast and solution annealed Al 6Si 2Cu alloy microstructures were studied. Parameters for monitoring the quality of the structure of this alloy were proposed. New algorithms for automatic estimation of eutectic fineness and its volume fraction were developed. Correlations among different microstructural parameters were found and interpreted using thermodynamic simulation. The grade of porosity according to GOST 1583 93 versus pore volume fraction, calculated by ASTM E1245, was defined. Bar charts for estimation of the average length of eutectic silicon particles were proposed. The eutectic modification grade, according to the American Foundry Society chart for microstructure control of hypoeutectic alloys, versus both the length and the elongation of eutectic silicon particles was determined. The relationships between alloy hardness and tensile elongation versus the proposed microstructural parameters for Al 6Si 2Cu alloy were defined. These relationships describe various grades of hypoeutectic Al Si Cu alloys in both the as cast and as solution annealed conditions.