Abstracts Book - IMRC 2018

• SD3-O018
EVOLUTION OF ROLLING AND RECRYSTALLIZATION TEXTURES IN
Ti-35Nb-7Zr-5Ta ALLOY AND ITS EFFECTS ON THE GROWTH OF
TiO2 NANOTUBES
Leonardo Fanton 1 , Alberto Fatichi 1 , Márcia de Oliveira Taipina 1 , Mariana Gerardi de Mello 1 ,
Rubens Caram 1
1 Universidade Estadual de Campinas, School of Mechanical Engineering, Brazil.
Titanium and its alloys possess high specific strength, excellent biocompatibility,
and great corrosion resistance in aqueous media. The Ti-35Nb-7Zr-5Ta (TNZT) is
a β-type Ti alloy designed for medical applications. As biocompatibility is closely
related to surface properties, several surface modifications have been proposed
for Ti alloys. One example is the growth of TiO 2 nanotubes, carried out by a
simple electrochemical anodization process. The TiO 2 nanotubes present a very
large surface area, which is good for cellular attachment, have excellent
biocompatibility and can be used for drug delivery. It is known that the crystal
planes exposed on the surface may affect properties like wettability and
corrosion resistance. For this reason, it may also affect the morphology of TiO 2
nanotubes. The aims of this study were to evaluate, firstly, the texture evolution
of a TNZT alloy after cold rolling and recrystallization heat treatment, and
second, the effect of grain crystallographic orientation on the TiO 2 nanotube
morphology. Four samples were used: unidirectional rolled (UR), cross rolled
(CR), UR followed by recrystallization (UR-REC) and CR followed by
recrystallization (CR-REC). Texture was measured by means of X-ray diffraction
pole figures and EBSD orientation mapping. For the TiO 2 nanotubes growth, the
samples were anodized by using an electrolyte with 0.3 vol% hydrofluoric acid
at 20V for 1 hour. The UR and CR samples both presented the (001)[110] and
(001)[100] texture components, however the texture was significantly stronger
for the UR sample. The UR-REC and CR-REC samples presented the (-2-23)[8-52]
and (118)[441] components, with similar volume fractions for both samples. The
nanotubes grew with a length of 1300 nm, being divided in two groups with
different diameters. The wider nanotubes (Ø96 nm) were surrounded by smaller
ones (Ø50 nm). Despite the literature shows that the morphology of TiO 2
nanotubes may vary according to the grain orientation in α-type (hexagonal) Ti
alloys, such a behavior was not observed for the β-type (cubic) TNZT alloy. A
possible explanation could be the fact that cubic crystals have lower anisotropy
than hexagonal ones. Other factors, as surface preparation and anodization
parameters, are being currently tested.