TVET
S. Ahmadi; A. Shokouh Far; M.R. Abutalebi; A. Rezaee
Abstract
Aluminum-lithium alloys are among the ultra-lightweight and workable alloys that have replaced some air alloys (such as 2000 and 7000 groups) due to their higher elastic modulus and lower specific gravity. Increasing the mechanical properties of these alloys using various thermal-mechanical methods (Thermo ...
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Aluminum-lithium alloys are among the ultra-lightweight and workable alloys that have replaced some air alloys (such as 2000 and 7000 groups) due to their higher elastic modulus and lower specific gravity. Increasing the mechanical properties of these alloys using various thermal-mechanical methods (Thermo Mechanical) has always been considered by researchers. Creating GP regions through low temperature aging processes has a great impact on the physical and mechanical properties of aluminum-lithium alloys. In this research, in the first part of the experiments, by performing natural aging and artificial aging at a temperature of 100 اد C, the formation and impact of these areas on the properties of the alloy were investigated. In the second part of the experiments, the precipitation of phase T1 during the aging process and the effective effect on the optimal time of the aging process at temperatures C150 and C190 for a sample of aluminum-copper-copper-lithium alloy sheet have been investigated. The results show that the formation of GP areas in the structure increases the hardness, strength and special strength of the alloy and by performing the aging process at higher temperatures and forming stable sediments, the process of increasing the hardness and strength continues while the special strength of the alloy decreases. It was found that the change in energy level in the range C250 to C300 is related to the deposition of phase T1 and the change in energy level in the temperature range C450 to C305 due to its dissolution in the alloy structure. The energy of the formation and dissolution activations of phase T1 in this study was calculated to be (kj / mol) 1/122 and (/ mol (kj3 / 130), respectively, which is equal to the activation energy of the penetration of the constituent elements of this phase (copper and lithium) in the network structure. It is aluminum.
