Thermal analysis of AL-Si alloys

ABSTRACT One primary objective of this study is to specify a new method called dual cups-thermal analysis in which differences of cooling curves are plotted versus time. Also, to investigate the phases which occur during the solidification of Al-Si alloys and to find usage of other phases which are not possible to be determined through other methods. In addition, the effects of grain refinement of Al-Si alloys were examined. By this way, addition of l%Ti to Al-Si alloys, which have different compositions, was made by means of the addition of A1-5Tİ-1B master alloy. Finally,the investigation of metalografic structure, both not grain refined and grain refined samples were fulfilled and the relationship between the derivative and the differences of cooling curves from these samples were investigated. At the end of those researchs, it was recognized that the results of the new method comply with those of the derivative and it can be applied for the determination of new phases. However, another new phase was not found unexpectedly. Moreover, the new method satisfies the derivative usage in grain refinement. And, the outcomes the grain refinement on the cooling curves were observed as specified in the literature. The quantities of undercooling in the primary solidification region decreased and that's why caused solidification starting temperature to rise a further one. Morover, the undercooling in eutectic region decreased and starting solidification temperature in it increased. A comprise was written between the obtained metalografic structures and the phases formed at cooling curve derivatives and the new method. It was observed that the phases displayed a one to match with structures. The effects of grain refinement at the metalografic structures was obviously shown. The importance of used method at the end is coming from its new approach. Also obtained data shows that results. However, for the future research,the method should be developed. Key Words: Thermal Analysis, Dual-Cups Method, Al-Si Alloys, Grain Refinement VI