On-line control of heat extraction during thermal analysis of aluminium alloys

Abstract

Thermal analysis is a non-destructive and quantitative technique used to assess the quality of liquid metal prior to casting. Conventional thermal analysis is carried out by pouring a relatively small sample of the melt into a sampling cup. The liquid metal is then allowed to solidify, and its temperature is recorded as a function of time. One of the shortcomings associated with this method is that the physical and thermal characteristics of the sampling cup in any one given test determine the effective cooling rate. Moreover, the method is a batch operation which is difficult to automate and to computerise. To overcome these shortcomings, a new technique of performing thermal analysis has been devised. This new technique, which is based on heat pipe technology, is in-situ, semi-continuous, easy to use, dependable, and most importantly, capable of performing thermal analysis tests at controlled and variable cooling rates throughout the entire solidification process. In the present paper, the characteristics of the new system, as well as the technique of controlling the cooling rate (heat extraction) during thermal analysis of aluminium alloys are described.