Role of twinning on texture evolution of silver during equal channel angular extrusion

Abstract

The role of deformation twinning in the texture evolution of pure polycrystalline silver subjected to equal channel angular extrusion (Route A, three passes) has been examined. Microstructural characterization using electron backscattering diffraction and transmission electron microscopy revealed high twinning activity in every pass, as well as significant grain refinement. Polycrystal modelling combined with experimental analysis shows that texture evolution is a result of slip and deformation twinning that occurs in every pass. It is shown that the primary consequence of twinning is the reorientation of the A₁ ideal component into the A₂ orientation. This process results in a weak A₁ and a strong A₂ component. This twinning mechanism is repeated in each pass aided by the strain path changes associated with Route A and an apparent regeneration of the microstructure. As a result, with each pass the A₁ and C ideal shear components weaken, whereas the components strengthen, tendencies that are distinct from those of high stacking fault fcc metals like Al, Cu and Ni.

Acknowledgements

The authors would like to thank Ben Henrie (LANL) and Dong-Ik Kim (Aachen) for their help in the analysis of the EBSD results. T. Grosdidier and J.J. Fundenberger (LETAM, University of Metz) are also gratefully acknowledged for their help in the electron microscopy investigation. Prof. W. Skrotzki (Dresden) has provided the Ag samples for testing. This work was made possible by mutual visits between University of Metz (C.N.T.) and LANL (L.S.T.). I.J.B. would like to acknowledge support by a Los Alamos Laboratory Directed Research and Development Project (No. 20030216) and C.N.T would like to acknowledge support by an Office of Basic Energy Sciences Project FWP 06SCPE401.