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 e l 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 e l ( 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 e l > τ * to thermally activated obstacle passage at τ e l 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 = 124 MPa , respectively. Activation volumes corresponding to the interaction of dislocations with the studied defects, estimated based on τ e l τ * segments of the measured dependences τ e l ( h ) , were found to be in reasonable agreement with existing concepts of dislocation/defect interactions.