The composition effect of W to the structure and self
diffusivity of the liquid Ni1-xWx (x=0.1 and 0.2)
W.Y.
a
Wang, *
H.Z.
a
Fang,
S.L.
a
Shang,
Y.
a
Wang,
S.N.
b
Mathaudhu,
X.
c
Hui
and Z.K.
a
Liu
a. Department of Materials Science and Engineering, The Pennsylvania State University, PA 16802, USA
b. Materials and Manufacturing Sciences Division, US Army Research Laboratory, Aberdeen Proving Ground, MD 21005, USA
c. The State Key Laboratory of Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
Introduction
Diffusivity
Short Range Orders
Improving the performance of jet engine turbine blades requires
new nickel based superalloys that are thermodynamically stable
and durable at high temperatures. And it is a potential way to
predict the phases stability in the solid state by studying their
liquid properties, using the ab initial molecular dynamic method.
Mean-squared displacements
(MSDs) of different atoms in
the liquid Ni1-xWx alloys at
different temperatures, (a) (b)
Ni atoms and (c)(d) W atoms.
Calculation method (MSD)
1 
D (T )  lim
u 2 (t )
t  6 t
l
2
u (t )
l

Bond Pair Analysis
Ni90W10
Ni90W20
Fig. 1 Pair correlation functions at various
temperatures of liquid Ni1-xWx.
Fig. 3 Average coordination Number (CN)
distribution around all atoms at various
temperatures. The increasing bonds are
1431, 1541, 1551, 1441 and 1661, while the
decreasing bonds are 1321 and 1311.
n
nl
Voronoi Polyhedral Analysis
Fig. 2 (a)low CN; (b) high CN.
1. From the structure analysis, we can see that the
Ni80W20 is more close packed than the Ni90W10. For
instance, at 1500K, the average CN of Ni90W10 is 10.0,
while Ni80W20 is 10.6. And there are more Voronoi
cells with high CN in the Ni80W20 than that in the
Ni90W10.
2. The self diffusivity of Ni and W are very close to
each other. The DNi will be decreased with the
addition of W comparing to the pure Ni, while the DW
be increased comparing to the pure W.
Appendix- Method Evaluation
11
Table 1 the average
value of CN
T Ni90W10 Ni80W20
5000
4500
8.5
4000
9.4
9.3
2500
9.5
9.6
2000
9.7
1500 10.0
10.6
Short range orders are made up of CN=12 Voronoi
cells at 1500K, (a) Ni90W10; (b) Ni80W20. The Ni atoms
in the center, the normal and the shared positions
are separately in the green, the golden and the blue
colors, while W atoms are in the pink, the red and
the black colors.
Conclusion
2
R（t+t0）-R（t0）
n
Pair Correlation Function (PCF)
Coordinate Number (CN)
l
Arrhenius plot of the
self
diffusion coefficient of liquid
W, Ni and Ni1-xWx (x=10, 20).
The DNi will be decreased with
the addition of W comparing to
the pure Ni, while the DW be
increased comparing to the
pure W.
Fig. 5 The frequency variation of observed
Fig. 4 The relation patterns between bonds
Voronoi cell types with same coordination
and structures.
number as a function of temperature. The
number of polyhedral with high CN will
FCC & HCP : 1421 1422 BCC : 1441 1661
increase
when
the
temperature
is
Icosahedra : 1541 1551 Random : Others
decreasing.
Ni80W20 uses the solid symbols and Ni90W10 open symbols.
The structure and self diffusivity of liquid Al80Cu20
J. Brillo, et.al., J. Non-Cryst. Solids 352, (2006) 4008
J. R. Morris, et.al., J. Non-Cryst. Solids 353, (2007) 3444.
A. Meyer, et.al., Phys. Rev. Lett. 104, 035902 (2010).
Acknowledgements
This work was financially
supported by National Science
Foundation (Grant No. DMR0510180) and the Army Project
(Project No. W911NF-08-2-0064)