γ → ε martensite transformation and twinning deformation in fcc cobalt during surface mechanical attrition treatment

The deformation microstructure of face-centered cubic cobalt subjected to surface mechanical attrition treatment was studied as a function of strain levels. Strain-induced gamma --> epsilon transformation and twinning deformation were evidenced by transmission electron microscopy and were found to progress continuously in ultrafine and nanocrystalline grains as the strain increased. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.