Optimal Parameters in Precipitation Hardening of 6061 Aluminium Alloy Using Box-Behnken Design

Precipitation hardening process is important to increase the hardness of 6061 aluminium alloy. In order to achieve the desired hardness, this process has several controlled parameters including solution soaking temperature, solution soaking time, aging temperature and aging time. The identification of each appropriate parameter is important in the precipitation hardening process of aluminium alloy. Because there has been no method or exact pattern, therefore this research work applies the response surface methodology with Box-Behnken design to determine these appropriate parameters. The experimental result is found that there are three factors significantly affecting on the hardness obtained from the precipitation hardening process. The experimental data is well fit a quadratic model due to high coefficient of determination (R2=0.92). When this regression model is taken to construct the three-dimensional surface response plot and the contour plot, it is found that the optimum condition is the solution treatment time of 5 hours and 18 minutes, aging temperature of 181C and the aging time of 10 hours which yield the maximum predicted Vicker hardness of 132.5 HV.