Influence of dynamic solute-dislocation interaction on high temperature ductility of Al-Mg alloys

Abstract

High temperature ductility of Al-Mg alloys was examined as a function of stress and strain rate. The ductility was observed to depend strongly on the stress and/or the strain rate in the temperature range between 500 and 800 K. The elongation maximum experimentally observed at about 10 MPa in Al-0.94 Mg alloy at 643 K is due to the low stress exponent, which spreads the deformation out over the whole gauge length, resulting in an elongation maximum. This study also predicts the elongation minimum at about 55 MPa at 533 K. The decrease in elongation observed in the high stress region at 533 K is due to the high stress exponent, which concentrates the deformation in the necked region, resulting in a decrease in elongation. In this study, a solute strengthening map was constructed using the concept of dynamic solute-dislocation interaction. In region I of the map, the deformation is characterized by high ductility and random distribution of dislocations, while in region II, the deformation is characterized by low ductility and dislocation clusters. This map can be used to predict the deformation behavior of many alloys. The predicted strain rate range of high ductility associated with high strain rate sensitivity due to the solute-dislocation interaction coincides with the range of high temperature superplasticity of Al-Mg alloys, which suggests that the dynamic solute-dislocation interaction contributes to this superplasticity.