Interplay of dynamic strain aging and dynamic precipitation in the Portevin-Le Chtelier effect in an Al-Mg-Zn-based crossover aluminum alloy

Zhang, X.*; Li, Y.*; Wei, S.*; Guo, H.*; He, Z.*; Yang, C.*; Gong, W.   ; Harjo, S.   ; Zhou, D.*; Li, Z.*; Zhang, D.*; Raabe, D.*; Qin, G.*

Zhang, X.*; Li, Y.*; Wei, S.*; Guo, H.*; He, Z.*; Yang, C.*; Gong, W.; Harjo, S.; Zhou, D.*; Li, Z.*; Zhang, D.*; Raabe, D.*; Qin, G.*

Dynamic strain aging (DSA) causes serrated flow, known as the Portevin-Le Chtelier (PLC) effect, through interactions between solute atoms and dislocations. In this study, tensile tests on an Al-Mg-Zn crossover solid-solution alloy revealed that DSA and strain-induced dynamic precipitation jointly control serration behavior. At low strain rates, DSA-assisted precipitation produced Type C serrations, whereas high strain rates suppressed precipitation and promoted Type A serrations. High-energy X-ray diffraction and TEM analyses showed that screw dislocations dominated early deformation and governed plastic flow localization through cross-slip. Frequent cross-slip at high strain rates generated dislocation microbands responsible for Type A serrations, highlighting the primary role of screw dislocations rather than edge dislocations. A constitutive model incorporating DSA-assisted strengthening successfully predicted flow behavior over a wide strain-rate range.