Authors: A M AlObaisi E A ElDanaf A E Ragab M S Soliman
Publish Date: 2016/04/25
Volume: 25, Issue: 6, Pages: 2432-2444
Abstract
The addition of Ag to AlCuMg systems has been proposed to replace the existing highstrength 2xxx and 7xxx Al alloys The aged AlCuMgAg alloys exhibited promising properties due to special type of precipitates named Ω which cooperate with other precipitates to enhance the mechanical properties significantly In the present investigation the effect of changing percentages of alloying elements aging time and aging temperature on the hardness values was studied based on a factorial design According to this design of experiments DOE—23 factorial design eight alloys were cast and hot rolled where Cu Mg and Ag were added to aluminum with two different levels for each alloying element These alloys were aged at different temperatures 160 190 and 220 °C over a wide range of time intervals from 10 min to 64 h The resulting hardness data were used as an input for Minitab software to model and relate the process variables with hardness through a regression analysis Modifying the alloying elements’ weight percentages to the high level enhanced the hardness of the alloy with about 40 as compared to the alloy containing the low level of all alloying elements Through analysis of variance ANOVA it was figured out that altering the fraction of Cu had the greatest effect on the hardness values with a contribution of about 49 Also secondlevel interaction terms had about 21 of impact on the hardness values Aging time quadratic terms and thirdlevel interaction terms had almost the same level of influence on hardness values about 10 contribution Furthermore the results have shown that small addition of Mg and Ag was enough to improve the mechanical properties of the alloy significantly The statistical model formulated interpreted about 80 of the variation in hardness values
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