Metallic composities can be fabricated in one-step process in which mixture is directionally solidified. Phase-reinforced eutectic alloys have superior high-temperature mechanical properties

George, F. D.

English

NASA Technical Reports Server

March 1973	 .	 B73-10081 
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Metallic Composites as High-Temperature Fasteners 
0
Composites, as the name implies, are combinations 
of two or more materials, usually with combined 
properties superior to, either material by itself. The 
technique of incorporating one of the composite com-
ponents with directional ordering to provide added 
strength has been extensively used with fiber-polymer 
composites. A similar technique can be used with 
metallic alloys. 
Metallic composites can be fabricated in a one-step 
casting process in which a eutectic mixture of the metals 
is directionally solidified. These phase-reinforced eutectic 
alloys have superior high-temperature mechanical prop-
erties. Because of their superior characteristics, such as 
microstructural stability, shear strength, creep-rupture 
strength, and fatigue resistance, they are excellent 
materials for high-temperature fasteners. 
Prototype bolts and rivets have been made from 
directionally solidified, eutectic alloys of Ni3A1-Ni3Cb 
and (Co,Cr,Al)-(Cr,Co) 7 C 3 . The former is lamellar 
ordered or reinforced and the latter a fibrous re-
inforced eutectic composite. 
The Ni3 Al-Ni 3 Cb alloy consists of sheet-like dis-
persions of Ni 3 Cb 'within an Ni 3 A1 matrix. The re-
inforcing Ni 3 Cb phase makes up about 44% of the 
volume of the alloy. The alloy melts at 1279° C and 
has a density of 8.5 g/cm 3 . It is a high-modulus 
material with a tensile strength and creep-rupture 
strength markedly superior to conventional superalloys. 
Fasteners of the nickel-aluminum-columbium eutectic 
have been fabricated by casting, grinding, and creep 
forming. The bolts have high-temperature (538° C) 
transverse shear strengths as high as 609 x 106 N/rn2 
(88.3 x 103 psi) and longitudinal shear strengths as 
high as 262 x 106 N/rn 2
 (38.0 x 103 psi). 
The reinforced composite (Co,Cr,Al)4Cr,Co)7C3has 
a fibrous microstructure in which the reinforcing phase 
(Cr,Co)7 C 3 is 26% of the volume. The matrix is a solid 
solution of cobalt and chromium with aluminum
added to improve the oxidation resistance. The eutectic 
melts at 1297° C and has a density of 8 g/cm3. 
This alloy is not as strong as the Ni3Al-Ni3Cb 
eutectic, but is more easily grown, 50cm/hr as compared 
to 2 cm/hr, and is more oxidation-resistant. The cobalt-
chromium-carbon alloy is stronger than conventional 
nickel-base superalloys and has a high elastic modulus. 
Bolts of this material have exhibited transverse shear 
strengths of 559 x 106 N/rn 2
 (81 x 103 psi) and 
longitudinal shear strengths of 297 x 106 N/rn 2 (43 x 
103 psi) at 538° C. 
Both Ni3 A1-Ni 3 Cb and (Co,Cr,Al)-(Cr,Co) 7 C 3
 show 
promise as high-temperature fastener materials. The 
transverse shear strengths are higher than those reported 
for dispersion-strengthened metals (e.g., TD NiCr). 
Furthermore, both materials may be used in the manu-
facture of fasteners by all three methods tested: 
grinding, creep-forming, and casting. 
Note: 
Further information is available on the fabrication, 
properties, and testing of these fasteners. Requests for 
further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&PS-TU 
Marshall Space Flight Center, Alabama 35812 
Reference: B73-10081 
Patent status: 
NASA has decided not to apply for a patent. 
Source: F. D. George of

United Aircraft Corp.

under contract to

Marshall Space Flight Center

(MFS-22438) 
Category 04 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned riohts,
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Metallic composites as high-temperature fasteners

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