Modeling and optimization of precipitation hardening heat treatment factors of Al2024 alloy using a two-level full factorial design

Abstract

In the current study, the sources of variation in the mean hardness value of heat treated aluminum 2024 samples were identified by using metallurgical study and design of experiment methodology (full factorial method). Hardness measurements and microstructural investigations of the samples were carried out using Brinell hardness test and optical microscopy, respectively. The effects of several control factors including solution treatment temperature, aging temperature and also aging time on the hardness were evaluated. The main and interactions effects of the factors were studied by means of analysis of variance (ANOVA) technique. Moreover, the best model which can estimate the hardness of heat treated Al2024specimens was found whereas the aging temperature and interaction of aging time and aging temperature have significant effects on the hardness value. Finally, the optimum conditions of the factors were found for obtaining conditions of heat treatment to maximize hardness of the sample according to results of designing and regarding statistical factors. The Al2024 alloy with the hardness 133 Brinell was assessed as the optimum hardness during heat treatment conditions including solution treatment temperature of 530 °C, aging temperature of 180 °C and aging time of 12 hr value that it has good agreement with the estimated value by the model i.e. about131 Brinell.