1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University (2. College of Mechanical and Vehicle Engineering, Hunan University
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DOI:
10.7502/j.issn.1674-3962.2016.04.04
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Abstract:
The dynamic mechanical properties of extruded 6061 aluminum alloy under different heat treatment conditions were investigated by split Hopkinson pressure bar (SHPB). The compression strain rates were 2000 s-1 and 5500 s-1. Vickers hardness, optical microscopy (OM) and transmission electron microscopy (TEM) have been used to study the microstructure evolution. The results show that the dynamic stress of extruded 6061 aluminum alloy increases with increasing solution temperature until the temperature reaches 535 ℃. Most of the phases have dissolved in the matrix, and the grain size has no obvious change. During dynamic deformation, the motion of the dislocations was impeded due to the lattice distortion, and the dislocation walls were found. The solution treated 6061 aluminum alloy was aging treated at 180℃. The dynamic stress increases with aging time. The peak stress of the alloy was obtained when the aging time was 8 h. At the beginning of artificial aging, a number of GP zones are formed. As the aging time increasing, the GP zones transform to β″. The density of strengthening precipitation reaches the peak when the aging time was 8 h. The pinning effect of the precipitation on the dislocation during dynamic deformation, results in the pile-up of dislocation, and forms a large number of dislocation walls and dislocation cells.