Inverse deformation-fracture responses between dendrite and matrix in Ti-based nanostructure–dendrite composite

Abstract

The room-temperature deformation and fracture mechanisms of Ti-based nanostructured alloys are investigated. The monolithic nanostructured alloy goes through a shear banding ↔ kinetic softening vicious cycle and exhibits very limited plasticity. The nanostructure–dendrite composite exhibits large plasticity while retaining a very high strength. Three fracture modes, namely shear fracture of the nanostructured matrix phase, normal ductile fracture of the dendritic phase and the peeling off of the dendrites from the matrix, are clearly observed. With increasing deformation, the nanostructured matrix is kinetically softened while the dendrite phase is work hardened. The inverse deformation responses and the interaction between the nanostructured matrix and the dendrites can effectively retard the inhomogeneous shear deformation of the nanostructured phase and lead to a large plasticity.

Acknowledgements

The authors are grateful to Q.L. Dai, M. Frey, H. Grahl, M. Gründlich, A. Güth, H.-J. Klauβ, S. Kuszinski, E. Ma, S. Müller-Livanyi and M.L. Sui for technical assistance and stimulating discussions. Funding by the EU within the framework of the Research Training Networks on bulk metallic glasses (HPRN-CT-2000-00033) is gratefully acknowledged.