Berlin 2012 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 9: Topical Session Bulk Nanostrucured Materials II - Processing

MM 9.3: Vortrag

Montag, 26. März 2012, 12:30–12:45, H 0107

Solid state amorphization of bulk Co₃Ti using high pressure torsion — Christoph Gammer, David Geist, Christian Rentenberger, and •Hans-Peter Karnthaler — University of Vienna, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Wien, Austria

Amorphous structures can be achieved by a solid state transformation of the crystalline structure using severe plastic deformation. This has been proven to be successful by applying high pressure torsion (HPT) deformation in the case of L1₂ ordered Zr₃Al [1]. In addition, a cyclic transformation from crystalline to amorphous and back to a crystalline phase was reported to occur in Co₃Ti upon high-energy ball milling of a mixture of elemental powders [2]. In the present study bulk material of intermetallic Co₃Ti is transformed locally to an amorphous phase by HPT deformation. The deformation structures are analysed on different length scales using both scanning and transmission electron microscopy (TEM) methods. To avoid crystallization during preparation, the TEM samples were prepared electrochemically. They show amorphous bands that contain a debris structure of small grains (∼ 5 nm) as in Zr₃Al. In addition, the presence of some large (∼ 50 nm) defect free grains occurring in the amorphous bands indicate the reverse transition from an amorphous phase back to a crystalline one.

[1] D. Geist, C. Rentenberger, H. P. Karnthaler. Acta Mater. 59, 4578 (2011) [2] M. Sherif El-Eskandarany, K. Aoki, K. Sumiyama, K. Suzuki. Acta Mater. 50, 1113 (2002). This work was supported by the Austrian Science Fund (FWF): [P22440].