| A new thermal analysis technique was developed and tested. It makes use of the improvements in heat transfer characteristics associated with recent advances in heat pipe technology. Heat is extracted from a liquid sample of a melt taken in-situ from within a vessel or furnace. The rate of heat extraction is such as to cause the sample to solidify. The technique was tested both in the laboratory and on an industrial scale (Grenville Castings, Perth, Ontario). Aluminum alloys including 356, 319, Al-xSi, Al-Si-Cu-xMg, and 6063 were subjected to various melt treatments and were used to carry out the tests. Classical thermal analysis was also carried out simultaneously under the same melt conditions using a preheated graphite cup.; The comparison showed that the new technique has great potential over classical thermal analysis. The major advantages of the new method are that it conducts the analysis inside the melt (since it is no longer necessary for a physical sample to be removed from the melt itself), it consumes less time and the cooling rate can be precisely controlled during the solidification process. Moreover, it produces curves of greater detail and of better resolution than conventional techniques. In fact, the detail is of such resolution that, in some cases, the cooling curves may be used to infer the chemical composition of certain components of the melt, a fact which equates to a form of rapid chemical analysis. The peaks in the signal which refer to intermetallic formation are of better resolution and more identifiable when the new technique is used. The size of the peaks obtained using the new probe is about three times greater than that obtained by the classical method. With this new technique it becomes possible to correlate the area below the intermetallic peak to the concentration of iron or copper in the melt. This is a feature which makes the new thermal analysis probe act as a rapid chemical analyzer for selected constituents. |
