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Thermal profiles and fraction solid of aluminium 7075 at different cooling rate conditons

Ahmad, Asnul Hadi, Naher, Sumsun and Brabazon, Dermot (2013) Thermal profiles and fraction solid of aluminium 7075 at different cooling rate conditons. Key Engineering Materials, 554-55 . pp. 582-595. ISSN 1013-9826

In order to determine suitable processing conditions for semi-solid aluminium 7075 thermal analysis (TA) was performed in order to obtain the relationship between fraction solid and temperature. During experimental work, the alloy was heated to 750°C by resistance heated box furnace and solidified at various cooling rates. Cooling curves for the metal were recorded with two thermocouples, one at the centre of the melt volume and one beside the containing crucible wall. A specially designed chamber with kaowool blanket was used to achieve the slowest cooling rate. The faster cooling rate was achieved with the crucible in open atmosphere with a set air flow rate over the crucible. A Data Acquisition (DAQ) system controlled by LabVIEW software was used to record the temperature-time profiles. From these cooling curves, the phase change at any corresponding time and temperature was estimated. The temperature difference between centre and wall of crucible was used to determine dendritic coherency point (DCP). Results show that, the slowest cooling rate with the kaowool blanket was at 0.03°C/s. An intermediate cooling rate of 0.21°C/s was achieved by leaving the melt to cool without kaowool blanket or forced air flow, and the fastest cooling rate was 0.43°C/s. The change in cooling rate altered the temperatures at which phase changes occurred, including those for eutectic and solidus. It was found that for lower the cooling rates that the DCP occurred at lower temperatures. The DCP for the cooling rate of 0.03°C/s was found to be 574°C (corresponding to 0.85 fraction solid) whereas the DCP for 0.43°C/s was found to be 623°C (corresponding to 0.55 fraction solid).
Item Type:Article (Published)
Uncontrolled Keywords:Thermal analysis; fraction solid; aluminium 7075; dendritic coherency point
Subjects:Engineering > Materials
Engineering > Mechanical engineering
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Engineering and Computing > School of Mechanical and Manufacturing Engineering
Publisher:Trans Tech Puclications
Official URL:http://dx.doi.org/10.4028/www.scientific.net/KEM.5...
Copyright Information:© 2013 Transtech
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 3.0 License. View License
ID Code:18043
Deposited On:13 Aug 2013 10:55 by Fran Callaghan . Last Modified 19 Jul 2018 14:59

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