LAUSR

A framework for more ductile magnesium Development of ductile magnesium alloys is key to their use in reducing the weight of vehicles and other applications. Wu et al. tackle this issue by determining the underlying mechanisms in unprocessed magnesium alloys. Dilute amounts of solutes enhanced certain ductility-improving mechanisms over ones that cause brittle fracture. From this, the authors developed a theory that may be helpful for screening the large number of potential magnesium alloy compositions. Science, this issue p. 447 Specific solutes promote ductility-improving slip mechanisms in magnesium alloys. Pure magnesium exhibits poor ductility owing to pyramidal 〈 c+a 〉 dislocation transformations to immobile structures, making this lowest-density structural metal unusable for many applications where it could enhance energy efficiency. We show why magnesium can be made ductile by specific dilute solute additions, which increase the 〈 c+a 〉 cross-slip and multiplication rates to levels much faster than the deleterious 〈 c+a 〉 transformation, enabling both favorable texture during processing and continued plastic straining during deformation. A quantitative theory establishes the conditions for ductility as a function of alloy composition in very good agreement with experiments on many existing magnesium alloys, and the solute-enhanced cross-slip mechanism is confirmed by transmission electron microscopy observations in magnesium-yttrium. The mechanistic theory can quickly screen for alloy compositions favoring conditions for high ductility and may help in the development of high-formability magnesium alloys.