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Effect of grain size on reactive diffusion between Ti-Al

Piotr Wieciński 1Halina Garbacz 1Hideyuki Murakami 2Krzysztof J. Kurzydlowski 1

1. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland
2. NIMS National Institute for Material Science (NIMS), Ibaraki 305-0047, Japan, Tukuba 3050047, Japan


Nanocrystalline alloys represent a unique materials group exhibiting better or new properties in comparison with traditional polycrystalline alloys. One of this kind of materials is nanocrystalline titanium obtained by hydrostatic extrusion. Hydrostatic extrusion is a method which allows to achieve very large imposed strains in bulk samples without fracture, to realize grain refining and significant hardening. The performance properties of nanomaterials can be improved using surface treatment. Ti-Al layers increase the wear and corrosion resistance of titanium alloys. The aim of this paper was to examine the effect of titanium substrate structure refinement (to the nanometric scale) on the chemical and phase composition of Ti-Al intermetallic layers. An accent was placed on evaluation of surface hardness and microstructural aspects. The material examined in the study was commercially available pure titanium with average grain size of 90 um in as-received state. The titanium samples in the form of 30 mm rods were extruded to a diameter of 5 mm, which corresponds to the true strain of 3.8. HE resulted in a strong refinement of the microstructure. After HE the nano-titanium with grain size about 60 nm was obtained. In the next step, the aluminium coatings have been deposited on the titanium in initial state and after hydrostatic extrusion using magnetron sputtering technique. The samples with aluminium coatings have been annealed at 600°C in argon atmosphere. The microstructures of the titanium with aluminium coatings, before and after annealing, have been investigated using scanning transmission electron microscope (Hitachi STEM 5500) and transmission electron microscope (JEOL 1200EX). The samples for  the observations have been prepared using Focus Ion Beam microscope (Hitachi FB 2100). The performed investigations allow to determined the role of the nanostructure on the diffusion and intermettalic phase occurrence rates, and on the layers mechanical properties.


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Presentation: Poster at E-MRS Fall Meeting 2009, Symposium H, by Piotr Wieciński
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-06-19 15:05
Revised:   2009-06-19 15:06