Shock wave determination of the strengthening of commercial aluminum alloy 6061 by point defects

The strengthening of aluminum alloy 6061 (AA6061) by different point defects was determined experimentally using a shock wave technique. Decay of the amplitude of elastic precursor wave τ_el with propagation distance h was studied in four groups of AA6061 samples, namely, that in the super-saturated solid solution state (SSSS), and those strengthened by atomic clusters (short-range order), by Guinier-Preston zones I and by Guinier-Preston zones II after, respectively 7.5, 240 and 960 min aging of the SSSS samples at 145 °C. The dependences τ_el(h) were found to be kinked at stress τ^*, corresponding to the transition of the control of dislocation motion from phonon viscous drag at τ_el>τ^* to thermally activated obstacle passage at τ_el<τ^*. The values of strengthening by atomic clusters, GP-I, and GP-II zones were found equal to τ_sro=67, τ_GP-I=67, and τ_GP-II=124MPa, respectively. Activation volumes corresponding to the interaction of dislocations with the studied defects, estimated based on τ_el<τ^* segments of the measured dependences τ_el(h), were found to be in reasonable agreement with existing concepts of dislocation/defect interactions.