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any metal powder, including Ti2 AlNb, can be used given
that the particle size falls in the specified range and segre-
gation is expected to be minimal. Two major concerns re-
garding AM parts are columnar grains in the build
direction and residual stress due to high solidification
rates. For aerospace, complex AM processes must be de-
veloped to meet stringent property requirements estab-
lished by traditional manufacturing methods such as
casting and forging. One major challenge is to devise a
means of rapidly qualifying AM parts in order to take full
advantage of the compression of production cycle time.
Another challenge is to develop a comprehensive cost
model for this manufacturing process[24]. These factors are
just as important to the acceptance of new production
methods as the AM technology itself.
Summary
Introducing any new material is an enormous under-
taking. It is important to realize that it took more than 50
years of research for γ-TiAl to mature before GE Aircraft
Engines introduced it into the low-pressure turbine (LPT)
of GEnx engines, specified in the Boeing 787 in 2005. De-
spite the immaturity of current Ti2 AlNb alloys compared
to γ-TiAl, they offer a well-balanced property profile as well
as good formability. Over time, further improvements can
be expected with the development of more complex com-
positions and processing.
Acknowledgment
The authors are grateful to Prof. Jim Williams for reviewing
this article.
For more information: Wei Chen is a senior research scientist
at the Science and Technology on Power Beam Processes
Laboratory, Beijing Aeronautical Manufacturing Technology Re-
search Institute, Beijing 100024, China, .
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ADVANCED MATERIALS & PROCESSES • MAY 2014 27
Fig. 6 — g-TiAl LPT blades made by EBM additive
manufacturing. Courtesy of Avio S.p.A.