Abstract

The performance of nickel aluminum bronze (NAB) propellers can be limited by the resistance of the alloy to fatigue. Friction stir processing (FSP) is a potential method for improving the fatigue life and fracture toughness of this material through grain structure refinement. As friction stir processing is a surface treatment, as-cast, thermo-mechanically affected zone (TMAZ), and FSP zone microstructures can all occur in components with thick cross sections and when FSP is performed on only selected areas of the component surface. The boundary between modified and unmodified microstructures produced by traditional processing techniques (i.e., heat affected zones produced by welding) are often the source of in-service failures as they can contain defects, residual stresses, deleterious microstructures or any combination thereof. In this paper, the mechanical behavior of FSP nickel aluminum bronze specimens containing as-cast, TMAZ, and FSP microstructures are evaluated using monotonic tensile tests and rotating bending fatigue tests. Analysis of the fatigue specimen fracture surfaces indicate that fatigue cracks initiated and propagated through the as-cast microstructure before penetrating the TMAZ and the FSP microstructures. The tensile specimens failed in the as-cast structure away from the FSP zone and the TMAZ. These results indicate that the as-cast material is weaker than both the FSP and the TMAZ, implying that localized friction stir processing is not detrimental to the mechanical behavior of a NAB component, even in the boundary region.

References

1.
Palko
,
W. A.
,
Fielder
,
R. S.
, and
Young
,
P. F.
, “
Investigation of the Use of Friction Stir Processing to Repair and Locally Enhance the Properties of Large Ni Al Bronze Propellers
,”
Mater. Sci. Forum
 0255-5476, Vol.
426–432
,
2003
, pp.
2909
2914
.
2.
Fuller
,
M. D.
,
Swaminathan
,
S.
,
Zhilyaev
,
A. P.
, and
McNelley
,
T. R.
, “
Microstructural Transformations and Mechanical Properties of Cast Ni Al Bronze: Effects of Fusion Welding and Friction Stir Processing
,”
Mater. Sci. Eng., A
 0921-5093, Vol.
463
,
2007
, pp.
128
137
.
3.
Fuller
,
C. B.
,
Mahoney
,
M. W.
,
Bingel
,
W. H.
,
Calabrese
,
M.
, and
London
,
B.
Tensile and Fatigue Properties of Friction Stir Processed Ni Al Bronze
,”
Mater. Sci. Forum
 0255-5476, Vol.
539–543
,
2007
, pp.
3751
3756
.
4.
Culpan
,
E. A.
and
Rose
,
G.
, “
Microstructural Characterization of Cast Nickel Aluminium Bronze
,”
J. Mater. Sci.
 0022-2461, Vol.
13
,
1978
, pp.
1647
1657
.
5.
Oh-Ishi
,
K.
and
McNelley
,
T. R.
, “
Microstructural Modification of As-Cast Ni Al Bronze by Friction Stir Processing
,”
Metall. Mater. Trans. A
 1073-5623, Vol.
35A
,
2004
, pp.
2951
2961
.
6.
McNelley
,
T. R.
,
Oh-Ishi
,
K.
, and
Zhilyaev
,
A. P.
, “
Microstructures and Properties of Copper Alloys After Friction Stir Welding/Processing
,” in
Friction Stir Welding and Processing
,
R. S.
Mishra
, and
M. W.
Mahoney
, Eds.,
ASM International
,
Materials Park, OH
,
2007
, Chap. 8, pp.
155
174
.
7.
Oh-Ishi
,
K.
,
Zhilyaev
,
A. P.
, and
McNelley
,
T. R.
, “
A Microtexture Investigation of Recrystallization During Friction Stir Processing of As-Cast NiAl Bronze
,”
Metall. Mater. Trans. A
 1073-5623 https://doi.org/10.1007/BF02586143, Vol.
37A
,
07
2006
, pp.
2239
2251
.
8.
ASTM Standard E466-96, “
Standard Practices for Conducting Force Controlled Constant Amplitude Axial Fatigue Tests of Metallic Materials
,”
ASTM International
,
West Conshohocken, PA
,
2000
.
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