Influence of Strain Hardening 1% by Torsion on the Behavior of a Single Crystal Alloy (Cu–at.9% Al) in Internal Friction at High Temperature

Abstract:

The purpose of this study is to highlight the influence of the strain hardening on internal friction behaviour of a copper single crystal alloy Cu-Al (9% at.) using Isothermal Mechanical Spectroscopy (IMS) technique. To do this, the sample was cold worked about 1% by torsion and tested at different stabilized levels of temperatures. Thus the specimen have been progressively heated to 1179 K and then cooled down to room temperature. The advantage of IMS experiments is to allow to compare the isothermal internal friction spectra obtained during heating (in this case, the annealing temperature (T_A) is equal to the temperature of measurement (T_M) with the measurements performed at various temperatures during cooling after annealing at 1179 K (T_M < T_A in this case). The results obtained in increasing temperature step by step (T_A = T_M) show the existence of two (02) independent relaxation peaks from 914 K to 1179 K. The first one, called here P₁ (at about 0.7 T_Melt at 1Hz), decreased with increasing the annealing temperature, while a new relaxation peak P₂ (at about 0.9 T_Melt at 1Hz) progressively developed. However for high temperature annealing, IMS tests (T_A > T_M) does reveal only one peak P₂. It appears, therefore, clearly that the strain hardening is responsible for the P₁ existence. To monitor the evolution of P₁ and P₂ with the temperature, a method of peaks decomposition already published was applied. The relaxation parameters, deduced from the Arrhenius plots, were thus accurately determined. The mechanism responsible of the P₁ and P₂ peaks appearance has been attributed to the movement of dislocation segments inside the sample microstructure.

• Periodical: Solid State Phenomena (Volume 184)
• Pages: 143-148
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.184.143
• Online since: January 2012
• Authors: C. Belamri, S. Belhas, S. Derdour, Andre Rivière
• Keywords: Cu-Al Alloy, Dislocation, Microstructure, Single Crystal, Sothermal Mechanical Spectroscopy, Strain Hardening

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