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Study on Mechanical Relaxations of 7075 (Al–Zn–Mg) and 2024 (Al–Cu–Mg) Alloys by Application of the Time-Temperature Superposition Principle
Rojas Gregorio, José Ignacio; Nicolas, Jorge; Crespo Artiaga, Daniel
Universitat Politècnica de Catalunya. Departament de Física; Universitat Politècnica de Catalunya. GCM - Grup de Caracterització de Materials
The viscoelastic response of commercial Al–Zn–Mg and Al–Cu–Mg alloys was measured with a dynamic-mechanical analyzer (DMA) as a function of the temperature (from 30 to 425ºC) and the loading frequency (from 0.01 to 150 Hz). The time-temperature superposition (TTS) principle has proven to be useful in studying mechanical relaxations and obtaining master curves for amorphous materials. In this work, the TTS principle is applied to the measured viscoelastic data (i.e., the storage and loss moduli) to obtain the corresponding master curves, and to analyze the mechanical relaxations responsible for the viscoelastic behavior of the studied alloys. For the storage modulus it was possible to identify a master curve for a low-temperature region (from room temperature to 150ºC) and, for the storage and loss moduli, another master curve for a high-temperature region (from 320 to 375ºC). These temperature regions are coincidental with the stable intervals where no phase transformations occur. The different temperature dependencies of the shift factors for the identified master curves, manifested by different values of the activation energy 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.
Peer Reviewed
Àrees temàtiques de la UPC::Enginyeria dels materials
Aluminum-magnesium alloys
Aluminum-magnesium-zinc alloys
Aluminum alloys--Mechanical properties.
Aluminum alloy
Time-temperature superposition
Dynamic-mechanical analysis
Mechanical relaxations
Internal friction
Alumini -- Aliatges
Attribution-NonCommercial-NoDerivs 3.0 Spain

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