Processing-controlled suppression of Lüders elongation in AlMgMn alloys

Abstract

The Lüders elongation, εL, its dependence on grain size, and its processing-controlled suppression are examined on several AlMgMn alloys. We found that grain size variations result in a Hall-Petch-type εL relation. We interpret the increase in macroscopic flow stress upon εL as a transitional increase in the activation stress of dislocation sources, expressed by an additional term of the Hall-Petch coefficient. The decisive measure for suppressing εL is based on the formation of non-aged dislocations. We demonstrate that these can be created intrinsically by utilization of the difference in the thermal expansion of matrix and primary constituents upon quenching.