We have developed mechanistic and predictive models for dynamic strain aging, and in particular negative rate sensitivity that drives Portevin-LeChatelier instabilities. The main application is in Al-5XXX alloys widely used in the automotive industry, and where the major solute element is Mg. The new mechanisms – “cross-core diffusion” and its effects on mobile dislocations and forest junctions – are significant departures from earlier concepts, and capture the dependence of rate-sensitivity on Mg concentration, temperature, strain rate, and total plastic strain. The fundamental mechanisms use quantum and atomistic level input, and are the basis of new macroscopic constitutive laws for plastic deformation. This constitutive model has recently been applied to explain the observed reduction in tensile ductility around room temperature in Al-Mg alloys, which is a major problem for forming of this class of alloys.
Key publications
- D. Olmsted, W. A. Curtin, and L. G. Hector, “A predictive mechanism for dynamic strain aging in Al-Mg”, Nature Materials 5, 875-880 (2006).
- M. Soare and W. A. Curtin, “A rate theory for dynamic strain aging in metals: II. Mobile and Forest dislocation strengthening”, Acta Mater. 56, 4046-4061 (2008).
- S. Keralavarma et al., Ductility Predictions in Al-Mg alloys, Nature Communications (2014).
Additional work:
- M. Soare and W. A. Curtin. “A rate theory for dynamic strain aging in metals: I. Single strengthening mechanism”, Acta Mater. 56, 4091-4101 (2008).
- F. Zhang and W. A. Curtin, “Atomistically-informed solute drag in Al/Mg”, Mod. Sim. Mat. Sci. Eng. 16, Art. # 055006 (2008).
- F. Zhang, A. Bower, and W. A. Curtin, “The influence of serrated flow on the necking in tensile specimens”, Acta Mater. 60, 43-50 (2012).
- P. E. Krajewski, L. G. Hector Jr. , Y. Qi, et al., “Atoms to Autos: a Multiscale Approach to Modeling Aluminum Deformation”, Multiscale Modeling of Metals”, feature article, Journal of Metals 63, 24-32 (2011).
- F. Zhang, A. F. Bower, and W. A. Curtin, “Finite element implementation of a kinetic model of dynamic strain aging in aluminum-magnesium alloys”, Int. J. Numerical Methods in Eng. 86, 70-92 (2011).