Development Of A Rapid Thermal Analysis System For Aluminum Alloy Melt

The quality of aluminum alloy melt such as modification effect determines factors to the integrity of aluminum alloy parts and their mechanical properties. By use of thermal analysis method evaluating quality of aluminum alloy melt has both theoretical and practical significance. A multi-channel, high precision aluminum alloy thermal analysis system based on PC machine has been designed in this paper, which can measure modification level of ZL101 alloy inside five minutes.Finally a compensating circuit for temperature and a low drift signal amplifying circuit were designed, and then a data acquisition card suit to thermal analysis was chosen. A new pattern of thermocouple structure sensitive to temperature was designed. It was no need to replace thermocouple from time to time, therefore material was saved and it was convenient to operate. A ceramic sample cup was designed, which can be used permanently. Through analysis on the cooling curves of three sample cups, which have different kind of dimension, the cup's size was determined.The software part of thermal analysis system was developed using Visual C++. High speed, sixteen-channels acquisition was available by interrupt. The acquisition process could be monitored and the signal was stored applying three levels storing mechanism. Filtering was implemented by calculating average and medial value. The segmental least square linear fitting for thermocouple index saved memory space and improved the conversion speed between thermal electric potential and temperature. The derivative curve was calculated using three points central difference method and smoothed using adjacent averaging method. Therefore the curve had high accuracy and was continuous and smooth. The characteristic values were identified by both means of math model and artificial cognition, which helped each other. The performance was avail to identification accuracy.The factors affecting system's accuracy were investigated, and system accuracy was tested according to the experiments of thermal analysis with pure aluminum. The results indicated that the repetitiveness of data measuring and anti-noise ability were high.The random pouring method was taken to find thermal analysis characteristic values of ZL101 alloy with no refinement or modification. The modification effect of strontium modified ZL101 alloy melt under different amount of modificator and different modification holding time was investigated. Human elements was reduced by inserting intermediate levels between AFS six levels while evaluating modification effect. The results showed that the depression of the eutectic growth temperature between modified and unmodified melt and modification levels agreed with S-style curve relationship. With the help of the eutectic undercooling temperature, the relationship can be used to evaluate ZL101 alloy modification effect.