The serrated flow behavior of a binary AlLi alloy tempered to conditions with and without δ′ precipitates

The serrated flow behavior of an Al-1.65 wt.% Li alloy in compression was investigated in the present study as a function of temper condition. Same category of serrations were detected for both the δ′-hardened and the δ′-free samples of the alloy. However, it was found that the happening of the serrations is controlled predominantly by the presence and growth of shearable δ′, rather than the supersaturation of the matrix. With the presence and growth of δ′, the occurrence of serrations is greatly advanced, the serration magnitude is greatly enhanced. Based on a suggestion that the serrations are dynamic strain aging events between lithium atoms and mobile defects for both situations, the positive effect of δ′ on serrated flow is rationalized to arise from an enhanced binding energy of lithium atoms to the mobile defects generated with the shearing of ordered δ′.