Computer aided cooling curve analysis of aluminum alloys

Abstract

Computer aided cooling curve analysis (CA-CCA) is very helpful in foundry industry for an easy and fast evaluation of many properties. Typical applications include the prediction of the temperatures and amounts of different phases appearing during solidification and monitoring the quality of melt in terms of Si-modification, grain refinement, inoculation, graphite spheoridization etc. The use of cooling curve analysis can be extended to many other areas of solidification also, only if the calculated values are reasonably accurate. Thermophysical properties (latent heat and solid fraction) measurement by CA-CCA is relatively a new field and only few papers discussed this methodology. The fundamental basics for these calculations lie in Fourier and Newtonian heat transfer methods. The calculation of zero curve, which is vital in cooling curve analysis, offers many problems. In this study, an attempt was made to investigate the problems of zero curve calculation and a new method is suggested to minimize the errors in zero curve calculation. An in-house developed computer program was used for the complete analysis of cooling curves to find latent heat, solid fraction and inflection points. The data selection was made easier by reducing the data points to liquidus and solidification end point and linear fitting was applied. Hypoeutectic and eutectic aluminum silicon alloys were analyzed and the results were encouraging and reproducible by this method, and it can be deduced that zero curve calculation by linear fitting, using liquidus and solidification end points improved the calculation accuracy, reliability and reproducibility.