25 / 74
ADVANCED MATERIALS & PROCESSES •
SEPTEMBER 2014
25
impart oxidation resistance
[21]
. Another approach to
achieving effective oxidation resistance involves applying a
pack cementation coating based on incorporating compat-
ible Mo-Si-B phases.
Progress in processing
The importance of processing as a principal means of
achieving certain microstructure designs is highlighted
for a variety of intermetallic phases for structural applica-
tions. The synthesis of Co-W and Ni-Mo
alloys provides an example of the appli-
cation of high energy ball milling to form
intermetallic phases such as Co
3
W and
Ni
3
Mo with high hardness. In another
example of the use of high energy ball
milling, a systematic study of alloying re-
actions between equiatomic mixtures of
Al and elements from Groups IV and V
documents the intermetallic phase prod-
ucts and associated microstructures.
Analysis of the reaction products from
ball milling can often be understood by
evaluating the relative free energies of
formation of the competing phases as il-
lustrated for intermetallic phase forma-
tion in Ni-Al alloys.
The pioneering research into struc-
tural intermetallics has now matured and
is beginning to yield an economic benefit
with increased commercialization. These
advances are spurring a new wave of re-
search that will be reported later this
month at MS&T14. Structural inter-
metallics provide attractive materials op-
portunities that will help meet the energy
challenges of the 21st century.
For more information:
John Perepezko
is Professor, Materials Science and Engi-
neering, University of Wisconsin-Madi-
son, 1509 University Ave., Madison, WI
53706, 608.263.1678,
perepezk@engr. wisc.edu.
Acknowledgments
Financial support for Bruce Pint from the
U.S. DOE, and for John Perepezko from
ONR (N00014-10-1-0913) and AFOSR
(FA9550-11-1-1201), is gratefully ac-
knowledged. Mike Brady at ORNL pro-
vided helpful insights on background
information.
References
1. E. A. Loria, Gamma Titanium Alu-
minides as Prospective Structural Mate-
rials,
Intermetallics,
Vol 8, p 1339-1345,
2000.
2. E. Schwaighofer, et al., Microstructural Design and Me-
chanical Properties of a Cast and Heat Treated
Intermetallic Multi-Phase γ-TiAl Based Alloy,
Inter-
metallics
, Vol 44, p 128-140, 2014.
3. J. Doychak, Oxidation Behavior of High Temperature In-
termetallics,
Intermetallic Compounds, Vol 1: Principles,
J.H. Westbrook and R.L. Fleischer eds., JohnWiley & Sons,
New York, p 977-1016, 1994.
4. M.P. Brady, et al., High-Temperature Oxidation and Cor-
rosion of Intermetallics,
Mat. Sci. and Tech.: A Compre-