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STUDY OF THE BALL SIZE EFFECT ON NANOSTRUCTURED
Fe50Al50 ALLOYS PRODUCED BY MECHANICAL ALLOYING
H. BUSTOS RODRIGUEZ1, D. OYOLA LOZANO1, Y. A.
ROJAS MARTÍNEZ1 AND G. A. PÉREZ ALCÁZAR2
1DEPARTAMENTO DE FÍSICA, UNIVERSIDAD DEL TOLIMA,
A. A. 546, IBAGUÉ, COLOMBIA 2DEPARTAMENTO DE
FÍSICA, UNIVERSIDAD DEL VALLE, A. A. 25360, CALI,
COLOMBIA
Abstract In this work we report the study of the
effect of the ball size in the structural and
magnetic properties of Fe50Al50 alloys produced
by mechanical alloying using the planetary ball
mill Fritsch pulverisette 7. The XRD pattern
obtained for the Fe50Al50 sample milled during 48
hours using balls of 15 mm shown a pattern
corresponding to a bcc phase with mean grain size
of 51 nm. The Fe50Al50 sample milled during 48
hours using balls of 11 mm, presents a Mössbauer
spectrum with a majority of paramagnetic sites,
whereas that sample milled during the same time
using balls of 15 mm, presents a paramagnetic
site (doublet) and a majority of ferromagnetic
sites which include pure Fe. However for 72 hours
milling this sample presents a paramagnetic
phase, very similar to the sample prepared with
balls of 11 mm of diameter. These results show
that the conditions used with balls of 11 mm make
more efficient the milling process, due that the
corresponding melted alloy is paramagnetic.
Introduction The Fe Al system is of interest
due to its potential commercial application as
structural or magnetic materials when they are
produced by melting. The Fe50Al50 alloy presents
a paramagnetic behaviour when it is prepared by
melting 1. In the recent years a number of
studies were carried out on mechanically alloyed
FeAl alloys 2,3,4 milled during 36 h or more,
the majority devoted to the magnetic behavior
around x 0.5, composition in which the system
changes from ferromagnetic to paramagnetic phase.
 In this work we study samples of the Fe50Al50
system prepared mechanical alloying with
different ball size and we report a comparative
study of the magnetic and structural properties
of the alloys.
Experimental The Fe50Al50 alloy was prepared by
mechanical alloying with two different ball sizes
using high purity iron and aluminum powders. A
high energy planetary ball mill Fritsch
pulverisette 7, with hardened stainless steel
vials of 50 ml of volume and balls of the same
material with 15 and 11 mm of diameter was used.
A speed of 280 rpm and a ball to powder mass
ratio of 161 were used. Milling times of 48 and
72 hours were employed. Mössbauer spectra were
obtained at room temperature in transmission
geometry using a conventional constant
acceleration spectrometer with a 57Co-Rh source.
The spectra were fitted with hyperfine field
distribution (HFD) and doublets using the MOSFIT
program 5. The a-Fe patter was used as
calibration sample. The X-ray analysis to
establish the structure of the lattice were
performed at room temperature for all samples
using a RINT2000l diffractometer with the Cu Ka
radiation and the patterns were refined by using
Maud program 6.
Results and discussion
Conclusion Mechanical alloying has been used to
produce Fe50Al50 alloys. The obtained alloy for
48 and 72 hours using balls of 15 mm are in the
consolidation process of the BCC phase, while
those obtained for 48 hours using balls of 11 mm
is practically consolidated in the BCC phase and
behaves as a ferromagnetic disordered system with
a tendency to the typical paramagnetic behavior
of melted alloys. With these results it can be
also conclude that balls with 11 mm of diameter
are more efficient to alloy due that they can
give more mean kinetic energy to the powder in
each impact and with bigger frequency.
Fig. 1. XRD patterns of the Fe50Al50 sample using
ball size of 15 and 11 mm of diameter.
Fig. 2. Mössbauer spectra and hyperfine field
distributions of Fe50Al50 alloys using balls of
15 mm of diameter.
Acknowledgements The authors would like to thank
to the Central Committee of Research of the
University of Tolima, to COLCIENCIAS and to the
Excellence Center for Novel Materials (ECNM), for
financial support given. G.A.P.A. thanks the
Spanish Science and Culture Ministery for a
Sabbatical Year grant.
References 1 J. Vincze, Phys. Status Solidi A
7, K43 (1971). 2 M. Pekala and D.Oleszak, J.
Magn. Magn. Mater 157, 231 (1996). 3 D.
A.Eelman, J. R. Dahn, G. R. Mackayu and R. A.
Dunlap, J. Alloys and Compounds 266, 234
(1998). 4 P. Pochet, E. Tominez, L. Chaffron
and G. Martin, Phys. Rev. B 52, 4006 (1995). 5
J. Teillet, F. Varret, Université du Maine,
unpublished Mosfit program. 6 L. Lutterotti
and P. J. Scardi, Appl. Crystallogr. 23, 246
(1990).
Table 1. Results of the XRD parameters of the
samples of the Fe50Al50 system using ball size of
15 and 11 mm.
Table 2. Mössbauer Parameters of the samples of
the Fe50Al50 system. Hyperfine field (HF) values
are in Tesla, the isomer shift (DI ), line width
(GA) and the quadrupolar splitting (SQ) are in
mm/s