بررسي اثر اكستروژن در كانال زاويه دار همسان بر رفتار پير كرنشي ديناميكي يك آلياژ AL-MG-SI-CU

Effect of Equal Channel Angular Extrusion on Dynamic Strain Aging of an AI-Mg-Si-Cu Alloy

An AI-Mg-Si-Cu attoy was subjected to tensile testing, both under sotuttontzed and ECAE-ed conditions, using strain rates of uris:ʹ to toʹ .o;-J at temperatures of 25 0(ʹ to 325 T 10 investigate the dynamic strain aging (DSA) phenomenon in lite uttoy Negative strain rate sensitivity (m) and increasing ultimate tensile stress were observed in tile DSA region with increasing temperature. Regarding tile activation energy of the phenomenon, it was sugge:;ledthat the process is controlled by the interaction of1~lg atoms with mobile dislocations at lower temperatures of DSA occurrence while at higher temperatures, tile aggregation oj.lʹdg atoms and precipitates ofa second pllwie decreases the amount (JIMg atoms ill tire solid solution, resulting in the inverse DSA effect. Moreover, it was shown that at temperatures greater ttum 250 "C, the ratio of post-uniform to uniform elongation increases with increasing temperature or with decreasing strain rate due to the solute drag of Mg atoms in the AI matrix. Processing the alloy hy ECAE transferred tire negative m values to lower temperatures and decreased the tendency to DSA at higher temperatures. Calculating the mentioned ratio for the ECAE·ed specimens revealed that ʹIre post-uniform elongation dominates the uniform elongutton at all examined temperatures anti strain rates. A15o, it wasfound thai for ECAE-ed specimens, the ratio is not so sensitive to variations of temperature and strain rate.