Analysis of the mechanical relaxations of 6061 and 6082 (Al–Mg–Si) alloys by using the time-temperature superposition principle
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The viscoelastic response of commercial 6061 and 6082 (Al–Mg–Si) alloys was measured with a dynamic-mechanical analyzer (DMA) as a function of both the temperature (in the range 30 to 425ºC) and the loading frequency (in the range 0.01 to 150 Hz). The time-temperature superposition (TTS) principle has proven useful in studying the mechanical relaxations and in obtaining master curves for the viscoelastic behavior of amorphous materials. In this work, a similar approach is used for the studied Al–Mg–Si alloys. In particular, the TTS principle is applied to experimental viscoelastic data obtained with the DMA (i.e., the storage and loss moduli) for the studied alloys, both in the as-received condition (the T6 temper) and after application of solution treatment. The analysis allows first to obtain the corresponding master curves, and second to study the mechanical relaxations responsible for the viscoelastic behavior of the alloys. For the storage modulus it was possible to identify a master curve for a low temperature region (below 150ºC) and, for both the storage and loss moduli, it was possible to identify another mater curve for a high temperature region (above 320ºC). The different temperature dependencies of the shift factors for the identified master curves, manifested by different activation energies in the Arrhenius expressions for the shift factor, are due to the occurrence of microstructural changes and variations in the relaxation mechanisms between the mentioned temperature regions.
CitationRojas, J.I., Crespo, D. Analysis of the mechanical relaxations of 6061 and 6082 (Al–Mg–Si) alloys by using the time-temperature superposition principle. A: European Congress and Exhibition on Advanced Materials and Processes. "EUROMAT 2017. Symposium B.11 ORAL Presentations". Thessaloniki: 2017, p. 17.