Effects of natural aging and post-processed heat treatment on the microstructure and mechanical properties of friction stir processed Al-7B04

Abstract

2 mm thick Al-7B04 alloy sheets under T4 and O tempers were subjected to friction stir processing (FSP). The microstructure, Vickers hardness and tensile properties of the stir zone were characterized. The results show that FSP led to the formation of full recrystallized microstructure, the average grain size in the stir zone (SZ) was about 2 μm. Besides, the stir zone produced using the base metal under T4 temper was softened, while a significant strengthening was observed when the base metal temper was O. Furthermore, both the natural aging (NA) and post-processed heat treatment (PPHT) were also conducted on FSP samples. And it indicates that NA was beneficial to strengthening the SZ regardless of the initial base metal temper. On the contrary, PPHT only contributed to the strengthening of SZ using the base metal under T4-temper.