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Abstract
The room-temperature deformation and fracture behaviour of Ti-based composites with ductile dendrites, prepared by copper mold casting and arc-melting techniques, was investigated. Under compressive loading, the Ti-based composites display high fracture strength (about 2000 MPa) and good ductility (about 4 or 10%). The yield strength of the Ti-based composites is relatively low (about 565–923 MPa). However, they have a large strain-hardening ability before failure, due to the interactions between shear bands and dendrites. For the arc-melted Ti-based composites, fracture often occurs in a shear mode with a high plasticity (about 10%). In contrast, the cast Ti-based composites break or split into several parts with a compressive plasticity of 4%, rather than failing in a shear mode. A new fracture mechanism, i.e. distensile fracture, is proposed for the first time to elucidate the failure of the as-cast Ti-based composites. Based on the difference in the fracture modes of the differently prepared composites, the relationships between shear and distensile fracture mechanisms and the corresponding fracture criteria are discussed.
Acknowledgements
The authors would like to thank M. Frey, H. Grahl, M. Gründlich, A. Güth, H.-J. Klaub, U. Kühn, S. Müller-Litvanyi, S. Roth and S. Schinnerling for technical assistance and stimulating discussions. This work was supported by the EU via the RTN-Network on bulk metallic glasses under contract HPRN-CT-2000-00033 and the ‘Hundred Talent Project’ of the Chinese Academy of Sciences and the Natural Science Funds of China (NSFC) under grant Nos. 50401019 and 50323009. The authors (Zhang, Z.F. and He, G.) wish to acknowledge the Alexander von Humboldt (AvH) Foundation.
