Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
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Magnetic field controlled single crystal growth and surface modification of titanium alloys exposed for biocompatibility
Hermann, R.; Calin, M.; Uhlemann, M.; Wendrock, H.; Gerbeth, G.; Büchner, B.; Eckert, J.
The aim of the work is the growth and characterisation of Ti55Nb45 (wt %) single crystals with the floating-zone single crystal growth of intermetallic compounds using two-phase radio-frequency (RF) electromagnetic heating. Thereby, the process and, in particular, the flow field in the molten zone is influenced via additional magnetic fields. The growth of massive intermetallic single crystals is very often unsuccessful due to an unfavourable solid-liquid interface geometry enclosing concave fringes. It is generally known that the crystallization process stability is enhanced if the crystallization interface is convex. As a result, a tailored magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards to outwards flows. Due to their attractive properties such as light, strong and totally biocompatible, titanium is one of few materials that naturally match the requirements for implantation in the human body. Therefore, the magnetic system was applied to crystal growth of Ti alloys. The grown crystals were oriented and cut to cubes with the desired crystallographic orientations (-1,0,0) and (1,0,1) normally on a plane. The electron backscatter diffraction (EBSD) technique was applied to clearly define crystal orientation and orientation changes in the crystallographic textures. The elastic modulus, the shear modulus and the bulk modulus were determined in dependence on the crystal orientation using ultrasonic measurements. Moreover, the oxide formation behavior on Ti surfaces in dependence on the grain orientation was investigated, performed anodically from fluoride containing electrolyte.
The 16th International Conference on Crystal Growth (ICCG-16), 08.-13.08.2010, Beijing, China
Journal of Crystal Growth 318(2011)1, 1048-1052