Plasticity in hexagonal metals

David Rodney (MMCI and Soprano groups) with colleagues from the CEMES in Toulouse and the CEA Saclay have published a paper entitled«Dislocation locking versus easy glide in titanium and zirconium »  in the journal Nature Materials.

Plasticity in hexagonal metals is still poorly understood. D. Rodney and collaborators have studied Zirconium and Titanium, used in nuclear and aerospace applications. These two hexagonal metals were supposed up-to-now to have similar plastic behaviors. However, in-situ electronic microscopy observations done at CEMES in Toulouse have shown that the dislocations responsible for plastic deformation glide continuously in Zr, while they move with serrations in Ti. The authors performed ab initio electronic structure calculations and showed that the dislocations may adopt similar structures in both metals but with reversed stability: the stable configuration in Zr is mobile and can glide continuously while in Ti, the stable configuration is immobile and must transit through the mobile configuration to glide, resulting in a “stick-slip” motion. These first results obtained in pure metals open the way to the study of alloying elements, in particular Oxygen, which strongly affect the plastic properties.

24/07/2015