Abstract

The fatigue properties of a Ti-48Al-2Cr-2Nb alloy obtained by electron-beam melting (EBM) with a patented process has been examined by conducting high cycle fatigue tests performed at different R ratios at room temperature. Fatigue-crack propagation tests have been performed for the purpose of characterizing the fatigue-crack growth rate and threshold of the material. Additionally, specimens with artificially introduced defects have been fatigue tested with the objective of studying the growth behavior of small cracks. Artificial defects with different sizes have been generated in the gauge section of the specimens by electron-discharge machining (EDM). After EDM defects are produced, the specimens are pre-cracked in cyclic compression, so that small cracks can be generated at the root of the EDM starter defects. Fatigue tests are conducted by applying the staircase technique with the number of cycles of censored test (runout) fixed at 107 cycles. By employing the Murakami model for the calculation of the range of stress intensity factor, the threshold stress intensity factor range dependence on the loading ratio R and on the defect size is evaluated, highlighting the relevant parameters that govern the specific mechanisms of failure of the novel γ–TiAl alloy studied in the present work.

References

1.
Winstone
,
M. R.
,
Partridge
,
A.
, and
Brooks
,
J. W.
, “
The Contribution of Advanced High-Temperature Materials to Future Aero-Engines
,”
Proc. Inst. Mech. Eng/ L-J Mater.
, Vol.
215
,
2001
, pp.
63
73
. https://doi.org/10.1177/146442070121500201
2.
Dimiduk
,
D. M.
, “
Gamma Titanium Aluminide Alloys—An Assessment within the Competition of Aerospace Structural Materials
,”
Mater. Sci. Eng. A-Struct.
, Vol.
263
, No.
2
,
1999
, pp.
281
288
. https://doi.org/10.1016/S0921-5093(98)01158-7
3.
Bartolotta
,
P.
,
Barrett
,
J.
,
Kelly
,
T.
, and
Smashey
,
R.
, “
The Use of Cast Ti-48Al-2Cr-2Nb in Jet Engines
,”
JOM, J. Min. Met. Mater. Soc.
, Vol.
49
, No.
5
,
1997
, pp.
48
50
, 76. https://doi.org/10.1007/BF02914685
4.
Henaff
,
G.
and
Gloanec
,
A.-L.
, “
Fatigue Properties of TiAl Alloys
,”
Intermetallics
, Vol.
13
, No.
5
,
2005
, pp.
543
558
. https://doi.org/10.1016/j.intermet.2004.09.007
5.
Murr
,
L. E.
,
Gaytan
,
S. M.
,
Ceylan
,
A.
,
Martinez
,
E.
,
Martinez
,
J. L.
,
Hernandez
,
D. H.
,
Machado
,
B. I.
,
Ramirez
,
D. A.
,
Medina
,
F.
,
Collins
,
S.
, and
Wicker
,
R. B.
, “
Characterization of Titanium Aluminide Alloy Components Fabricated by Additive Manufacturing Using Electron Beam Melting
,”
Acta Mater.
, Vol.
58
, No.
5
,
2010
, pp.
1887
1894
. https://doi.org/10.1016/j.actamat.2009.11.032
6.
Andersson
,
L.-E.
and
Larsson
,
M.
, “
Device and Arrangement for Producing a Three-Dimensional Object
,” Patent No. WO 01/81031 A1, International Application Number PCT/SE01/00932, World Intellectual Property Organisation,
2001
.
7.
Biamino
,
S.
,
Penna
,
A.
,
Ackelid
,
U.
,
Sabbadini
,
S.
,
Tassa
,
O.
,
Fino
,
P.
,
Pavese
,
M.
,
Gennaro
,
P.
, and
Badini
,
C.
, “
Electron Beam Melting of Ti-48Al-2Cr-2Nb Alloy: Microstructure and Mechanical Properties Investigation
,”
Intermetallics
, Vol.
19
, No.
6
,
2011
, pp.
776
781
. https://doi.org/10.1016/j.intermet.2010.11.017
8.
Wu
,
X.
,
Huang
,
A.
,
Hu
,
D.
, and
Loretto
,
M. H.
, “
Oxidation-Induced Embrittlement of TiAl Alloys
,”
Intermetallics
, Vol.
17
, No.
7
,
2009
, pp.
540
552
. https://doi.org/10.1016/j.intermet.2009.01.010
9.
ASTM E647-08,
2008
, “
Standard Test Method for Measurement of Fatigue Crack Growth Rates
,”
Annual Book of ASTM Standards
, Vol.
03.01
,
ASTM International
,
West Conshohocken, PA
. https://doi.org/10.1520/E0647-08
10.
ISO12107,
2003
, “
Metallic Materials-Fatigue Testing-Statistical Planning and Analysis of Data
,”
International Organisation for Standardisation
,
Geneva, Switzerland
.
11.
Forth
,
S.
,
Newman
,
J. C.
, and
Forman
,
R.
, “
On Generating Fatigue Crack Growth Thresholds
,”
Int. J. Fatigue
, Vol.
25
, No.
1
,
2003
, pp.
9
15
. https://doi.org/10.1016/S0142-1123(02)00066-X
12.
Newman
,
J. C.
and
Yamada
,
Y.
, “
Compression Precracking Methods to Generate Near-Threshold Fatigue-Crack-Growth-Rate Data
,”
Int. J. Fatigue
, Vol.
32
, No.
6
,
2010
, pp.
879
885
. https://doi.org/10.1016/j.ijfatigue.2009.02.030
13.
Pippan
,
R.
,
Hageneder
,
P.
,
Knabl
,
W.
,
Clemens
,
H.
,
Hebesberger
,
T.
, and
Tabernig
,
B.
, “
Fatigue Threshold and Crack Propagation in Gamma-TiAl Sheets
,”
Intermetallics
, Vol.
9
,
2001
, pp.
89
96
. https://doi.org/10.1016/S0966-9795(00)00111-4
14.
Campbell
,
J.
,
Rao
,
K.
, and
Ritchie
,
R.
, “
The Effect of Microstructure on Fracture Toughness and Fatigue Crack Growth Behavior in Gamma-Titanium Aluminide Based Intermetallics
,”
Metall. Mater. Trans. B
, Vol.
30
, No.
3
,
1999
, pp.
563
577
. https://doi.org/10.1007/s11661-999-0048-2
15.
Gloanec
,
A.-L.
,
Henaff
,
G.
,
Bertheau
,
D.
,
Belaygue
,
P.
, and
Grange
,
M.
, “
Fatigue Crack Growth Behaviour of a Gamma-Titanium-Aluminide Alloy Prepared by Casting and Powder Metallurgy
,”
Scripta Mater.
,
2003
, Vol.
49
, pp.
825
830
. https://doi.org/10.1016/S1359-6462(03)00482-
16.
Murakami
,
Y.
, and
Metal Fatigue: Effect of Small Defects and Nonmetallic Inclusions
,
Elsevier
,
Oxford
,
2002
.
17.
Tanaka
,
K.
,
Nakai
,
Y.
, and
Yamashita
,
M.
, “
Fatigue Growth Threshold of Small Cracks
,”
Int. J. Fract.
, Vol.
17
, No.
5
,
1981
, pp.
519
533
. https://doi.org/10.1007/BF00033345
18.
Voice
,
W. E.
,
Henderson
,
M. B
,
Shelton
,
E. F. J.
, and
Wu
,
X. H.
, “
Gamma Titanium Aluminide, TNB
,”
Intermetallics
, Vol.
13
, No.
9
,
2005
, pp.
959
964
. https://doi.org/10.1016/j.intermet.2004.12.021
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