Deformation behavior of a modified 5083 aluminum alloy

The deformation behavior of a 0.2% Zr and 1.6% Mn modified 5083 aluminum alloy was studied in the temperature range of 250–570 °C over seven orders of magnitude of strain rates. It was shown that the modified 5083 alloy exhibits threshold behavior in the temperature interval of 250–500 °C. There exists a temperature dependence of threshold stress with the energy term Qo = 18 kJ/mol. It was shown by transmission election microscopy that detachment of dislocations from dispersoids under extra force takes place. Threshold stress tends to disappear with increasing temperature at T > 500 °C despite the fact that evidence for interactions between mobile dislocations and dispersoids was found at these temperatures. Analysis of creep data in terms of threshold stress revealed three different types of deformation behavior. At high values of normalized strain rate, ε ˙ k T / ( D 1 G b ) > 4 × 10 − 8 , the exponential law creep takes place. At normalized strain rates, ε ˙ k T / ( D 1 G b ) , ranging from 4 × 10−8 to 4 × 10−14, the n value is ∼4 and the true activation energy, Qc, is equal to 139 ± 12 kJ/mol, suggesting high temperature dislocation climb. At low normalized strain rate, a transition to Newtonian viscous flow occurs.