Regensburg 2013 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 32: Topical Session: TEM-Symposium - Structure-Property / In-Situ I

MM 32.4: Talk

Wednesday, March 13, 2013, 11:15–11:30, H25

TEM study of Co₃Ti made amorphous by high pressure torsion — •David Geist, Christoph Gammer, Hans-Peter Karnthaler, and Christian Rentenberger — University of Vienna, Physics of Nanostructured Materials, 1090 Vienna, Austria

Amorphous structures can be achieved by a solid state transformation of the crystalline structure using severe plastic deformation. This has been successfully achieved by applying high pressure torsion (HPT) deformation in the case of L1₂ ordered intermetallic Zr₃Al [1,2]. In the present work the evolution, structure and stability of the amorphous state of bulk Co₃Ti were studied on multiple length scales using a combination of scanning (SEM) and high resolution transmission electron microscopy (HRTEM) methods. L1₂ ordered Co-23at.%Ti samples were deformed by HPT to different degrees of deformation. The SEM investigations using back scattered electrons reveal that the material shows a tendency to amorphization localized in the form of bands. The TEM results of the amorphous regions show that a high density of nanosized crystals having a crystalline structure different from the initial material is embedded in the amorphous phase. Electron diffraction and HRTEM reveal the presence of nanocrystals with Co₂Ti structure showing a modified stacking sequence. Their structure is compared to that resulting from devitrification of the amorphous regions during thermal treatment. [1] D. Geist, C. Rentenberger, H. P. Karnthaler. Acta Mater. 59 (2011) 4578. [2] D. Geist, S. Ii, K. Tsuchiya, H.P. Karnthaler, G. Stefanov, C. Rentenberger. JAllComp 509 (2011) 1815.