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FIZIKA A 9 (2000) 3 , 137-146
EFFECT OF MECHANICAL EXCITATION ON THE OVER-RECOVERY OF INTERNAL FRICTION OF Al-16 Wt% Ag AND Al-16 Wt% Ag-0.28 Wt% Fe ALLOYSG. GRAISS and M. A. MAHMOUD Physics Department, Faculty of Education, Aim-Shams University, Cairo, Egypt Received 3 July 2000; Accepted 6 November 2000The phenomenon of internal friction (IF) of Al-16 wt% Ag and Al-16 wt% Ag-0.28 wt% Fe alloys aged at 428 and 523 K was studied at different testing temperatures using the free-decay method. The wire specimens were investigated for IF recovery under two different conditions of excitation. In the first, the specimens were continuously excited and in the other, they were subjected to normal condition of restrictive excitation. Under certain conditions of heat treatment and mode of excitation, an anomalous behaviour of IF recovery has been observed. TEM investigations confirmed that addition of Fe to Al-Ag alloy accelerates the precipitation of metastable phases. The mean values of the excitation energy of both alloys were found to be equal to that quoted for precipitate-dislocation interactions. PACS numbers: 62.40.+1, 61.72.Ff
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