Pronounced yield drop phenomenon at high temperatures in Al-Mg alloys with high contents of Mg (5–13 wt%)

Abstract

The high-temperature yield drop phenomenon in Al-Mg alloys with high contents of Mg (5–13 wt%) was examined in a wide range of strain rates under compression. Yield drop was highly pronounced when the added amount of Mg was beyond 10 wt%. For example, at 1 s−1 at 698 K, the yield drop ratio between the upper yield stress and the lower yield stress was as high as 1.43 in the Al-13Mg alloy, while the yield drop ratios for the Al-5Mg, Al-7Mg and Al-10Mg alloys were 1, 1.1 and 1.1, respectively. Analysis of the deformation mechanism associated with the yield drop phenomenon suggests that dynamic deformation model based on a sudden increase in the dislocation density during initial straining is more suitable in explaining the observed yield drop behavior than the static theory based on the critical stress for the breakaway of dislocations from the solute atmosphere.