Effect of Heat Treatment on Friction-Stir-Processed Nanodispersed AA7075 and 2024 Al Alloys

Abstract

Friction stir processing (FSP) is gaining wide recognition in producing surfaces with high hardness and enhanced properties for light weight transportation application and armored vehicles. This work compares the effect of T6 peak-aging heat treatment on the toughness properties and the aging precipitation behavior of friction stir processed and nanodispersed AA2024 and AA7075 alloys. Plates of aluminum alloy AA7075-O with and without the addition of alumina nano-particles (Al2O3) of average size ~40 nm were FSP. The AA2024 nanodispersed alloys were prepared by casting, then were FSP. Combining nanodispersion and friction stir processing with peak-aged condition has shown to be an effective route in enhancing the elongation% of AA2024 alloy to double that of the T6 peak aged condition, and improving the impact toughness of AA7075 by 35% compared to the peak aged condition. The presence of nanodispersions affects the precipitation behavior of both AA2024 and AA7075 in peak aged condition, where the precipitates attach themselves to the nanoparticles and spinel type precipitates form resulting de-acceleration of the aging process.