Influence of prolonged natural aging followed by artificial aging on tensile properties and compressive behavior of a thin-walled 6005 aluminum alloy tube

The effects of aging treatments on the tensile properties and compressive behavior of a thin-walled 6005 aluminum alloy tube were studied. Samples after three natural aging (NA) conditions were subsequently aged at 180 degrees C for 0.5-12.0 h artificial aging (AA). Tensile and compressive tests were performed after AA. The results show that for samples with the same NA, the longer the AA time is, the higher the strengths alloy owns, and at the same time the material shows a much lower elongation and faster process from plastic deformation to fracture. However, with NA prolonging, the alloy exhibits much better plastic deformation ability after AA, though its strength is decreased. The major cause of strength and plasticity variation induced by changing NA time is that the size of the main strengthening beta '' precipitates is larger and the density is lower. This character is evaluated by the strain hardening exponent n. Compressive results show that the optimum energy absorption characteristics can be acquired at a moderate n (14<n<17). Large n (n > 18) results in the fracture of tube during axial compression while low n (n <= 13) causes lower energy absorption.