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Thermal aging effects in refractory metal alloysThe alloys of niobium and tantalum are attractive from a strength and compatibility viewpoint for high operating temperatures required in materials for fuel cladding, liquid metal transfer, and heat pipe applications in space power systems that will supply from 100 kWe to multi-megawatts for advanced space systems. To meet the system requirements, operating temperatures ranging from 1100 to 1600 K have been proposed. Expected lives of these space power systems are from 7 to 10 yr. A program is conducted at NASA Lewis to determine the effects of long-term, high-temperature exposure on the microstructural stability of several commercial tantalum and niobium alloys. Variables studied in the investigation include alloy composition, pre-age annealing temperature, aging time, temperature, and environment (lithium or vacuum), welding, and hydrogen doping. Alloys are investigated by means of cryogenic bend tests and tensile tests. Results show that the combination of tungsten and hafnium or zirconium found in commercial alloys such as T-111 and Cb-752 can lead to aging embrittlement and increased susceptibility to hydrogen embrittlement of ternary and more complex alloys. Modification of alloy composition helps to eliminate the embrittlement problem.
Document ID
19880035473
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Stephens, Joseph R.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 13, 2013
Publication Date
January 1, 1987
Subject Category
Metallic Materials
Meeting Information
Meeting: Space nuclear power systems 1986
Location: Albuquerque, MN
Country: United States
Start Date: January 13, 1986
Sponsors: ANS, Los Alamos National Laboratory, USAF
Accession Number
88A22700
Distribution Limits
Public
Copyright
Other

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