Lüders strain of the fine-grained material under the electric current

Abstract

The Hall-Petch-like relationship between the Lüders strain and the average grain size of an Al-5.16Zn-2.2Mg-1.46Cu alloy under the pulsed electric current is investigated. It is found that the Lüders strain increases as the average grain size decreases. In addition, when the average grain size is the same, the current parameter has a significant effect on the absolute value of the slope in the Hall-Petch-like relationship. Based on the characteristics of interaction between the solute atoms and dislocations during the Lüders strain, the competition between pinning behavior of solute atoms and depinning behavior of dislocations under the electric current is explored, and a relevant mathematical model is established. According to the new mathematical model, the difference of the above competitive behavior under two different current densities is analyzed. When the current density is 5 A/mm2, the pinning behavior of solute atoms is dominant in the competition, and the length of the yield plateau of each grain size becomes shorter; however, when the current density is 55 A/mm2, the dislocation depinning behavior dominants the competition and the Lüders strain of each grain size increases. It is found that the current density can affect the competition between the pinning of solute atoms and the depinning of dislocations, thus affecting the Lüders strain.