Friction stir processing of 7075 Al alloy and subsequent aging treatment

The effect of temperatures and time of post-process aging on the microstructure, mechanical properties and wear behavior of friction stir processed 7075 Al alloy was investigated, using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Vickers microhardness tester. The results indicate that homogeneous, equiaxed and fine recrystallized microstructure is obtained with the grain size of 4-5 μm. The hardness value increases up to 30% and 80% in the stir zone and the base material, respectively. Based on the TEM observations, it is concluded that the improved properties following the duplex friction stir-aging process can be attributed to the very fine precipitates. Comparing the single and double aging conditions, the hardness of single aging sample is higher than that of double aging one which can be attributed to the high fraction of very fine spheroidal precipitate in single aging sample. The wear rate is reduced by the aging of Al alloy and a more decrease is achieved after the aging of FSPed sample.