DEVELOPMENT OF COMPOSITE POWDERS OF THE Ti – Al – N SYSTEM
PRODUCED FROM Ti – Al INTERMETALLIC COMPOUNDS
T. V. Mosina
Translated from Novye Ogneupory, No. 8, pp. 52 – 54, August, 2006.
Original article submitted April 10, 2006.
The kinetics of nitrating intermetallic compounds Ti
Al, TiAl, and TiAl
in the range of 1200 – 1400°C is
studied; the compositions of the reaction products and the process mechanisms are identified. It is established
that nitration of Ti
Al and TiAl is intense at 1200°C and complete nitration is achieved at 1400°C with 3 h ex
posure. Nitration of TiAl
differs significantly from nitration of Ti
Al and TiAl; the process has several stages,
is slow, and complete nitration is achieved only after 6 h exposure at 1400°C.
High-melting Ti and Al nitrides and intermetallic com-
pounds are widely used as modifying additives to high-tem-
perature titanium alloys. Furthermore, they can be used as
initial components for developing various composites and
coatings. The high-melting nitrides of the specified metals
are of great interest due to their low density, high strength,
plasticity above 800°C, and corrosion resistance. The use of
titanium and aluminum as initial components involves con-
siderable difficulties in milling and preparing homogeneous
powder mixtures. The high level of undesirable impurities
contained in initial powders, as well as impurities introduced
in milling, impair the service properties of the developed ma
terials. Intermetallic compounds used as initial components
for nitration make it possible to avoid contamination and
produce high-purity finely dispersed materials.
The specifics of nitration of Al, Ti, and TiAl
low-temperature range are described in [1, 2]. However, no
published data have been found on nitrating intermetallic
compounds of the Ti – Al system (including TiAl
) at high
We have investigated nitration kinetics of intermetallic
Al, TiAl, and TiAl
in the range of 1200 –
1400°C and identified the compositions of reaction products
and process mechanisms.
PRODUCTION OF INTERMETALLIC MATERIALS
AND INVESTIGATION METHODS
Initial intermetallic materials were obtained in an arc fur
nace by melting aluminum of grade A (99.995% Al) and tita
nium iodide in a protective nitrogen medium. The alloys
were milled in liquid nitrogen and then nitrated in a purified
nitrogen flux at 1200 – 1400°C. The isothermal exposure
lasted from 1 to 6 h and the flow rate varied from 0.1 to
The phase composition of the reaction products was in-
vestigated by x-ray phase analysis in CuK
radiation using a
DRON-2.0 diffractometer and the Fazan software program.
The morphology of the nitride powders was studied by local
x-ray-spectral analysis with a Camebax device produced by
the Jeol Company.
EXPERIMENTAL RESULTS AND DISCUSSION
Analysis of the nitration of TiAl
rather intense interaction occurs at 1200°C. Nitrogen satura
tion after 3 h of isothermal exposure grows from 6.3 to
13.5 wt.% as the flow rate grows from 0.1 to 0.5 liters/min.
Local x-ray spectral analysis data on the distribution of ele
ments indicate that nitrating Ti
Al produces only titanium
and aluminum nitride. Their presence in the reaction prod
ucts is also corroborated by x-ray phase analysis (Fig. 1a,
The weight ratio of the quantities of titanium and alumi
num nitrides formed at 1200°C is TiN : AlN = 94 : 6. This
ratio changes to TiN : AlN = 88 : 12 at 1300°C and to
TiN : AlN = 84 : 16 at 1400°C. We can see that the quantity
of AlN formed at these temperatures is not too high. The esti
mated absolute error in measuring the lattice parameters of
titanium and aluminum nitrides formed in nitration is not
more than ± 0.0002 nm. Titanium nitride is formed first at all
Refractories and Industrial Ceramics Vol. 47, No. 4, 2006
1083-4877/06/4704-0256 © 2006 Springer Science+Business Media, Inc.
I. N. Frantsevich Institute of Problems of Material Science, Na
tional Academy of Sciences of Ukraine, Kiev, Ukraine.