Effect of Temperature and phase transformation on the Characteristics of Al-Mg alloy | ||||
| Egyptian Journal of Solids | ||||
| Article 3, Volume 34, Issue 2, 2011, Page 29-40 PDF (623.6 K) | ||||
| DOI: 10.21608/ejs.2011.148869 | ||||
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| Abstract | ||||
| Samples of Al-5wt.%Mg alloy used as sheets, for internal friction Q-1 , dynamic elastic modulus Y and wires for stress-strain measurements, were heated at 823K for 2 hours then one group of the samples was slowly furnace cooled to room temperature and the second group was rapidly quenched in iced water. Both groups were tested in the temperature range from 493K to 553K in steps of 10K. The sheets were aged for 2 hours at different temperatures then quenched in iced water. Q-1 and the dynamic Young’s modulus, Y measurements by applying resonance technique were obtained at room temperature. The wires used for stress-strain measurements were tested in the working temperature range, and the yield stress y at different temperatures was obtained. The Vickers hardness, Hv, was obtained from its relation to y. Increasing temperature Q-1 increased showing abrupt increase at 523K, while Y and Hv decreased showing minima at 523K. Above 533K, Q-1 increased, while Y and Hv decreased. This behavior indicated a thermal softening in the tested range; structure measurements disclosed phase transformation from (+ ) phases into the single -phase at 523K. The quenched samples showed higher hardness levels than the slowly cooled samples due to the presence of excess point defects and their interaction with dislocations. The activation energy values were 17.33 and 59.184 kJ/mol before and after transition, respectively. The microstructure of the aged slowly cooled samples examined by X-ray diffraction measurements supported the phase transformation at 523K. | ||||
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