Effects of thermomechanical processing on strength and toughness of Fe-12Ni reactive metal alloys at 77K
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Stephens, J. R.↗
Engineering topics
Stephens, J. R.
Publications and source records attributed to Stephens, J. R..
Application of advanced technology to space automation
Automated operations in space provide the key to optimized mission design and data acquisition at minimum cost for the future. The results of this study strongly accentuate this statement and should provide further incentive for immediate development of specific automtion technology as defined herein. Essential automation technology requirements were identified for future programs. The study was undertaken to address the future role of automation in the space program, the potential benefits to be derived, and the technology efforts that should be directed toward obtaining these benefits.
Schappell, R. T.↗
Laboratory analogues to cosmic dust
Results are reported for a study of the condensation of a number of solids that are likely candidates for dust formed in astronomical environments. The condensate materials were produced by vaporizing a portion of a solid target of chosen composition by a laser pulse in an atmosphere of H2, O2, or Ar at 1 atm pressure. The systems studied include olivine, pyroxene, Fe-Ni alloy, Al2O3, carbon, CaCO3, SiC, Au-olivine powders, and Au-Al2O3 powders. Possible relations among the sizes, chainlike structures, and chemistries of the condensates and of grains formed in astronomical systems are investigated. The results indicate that the laser evaporation technique is useful for providing a wide variety of grain systems that are analogous to astronomical grain systems and that the grain materials produced are useful for spectral studies of materials believed to exist in astronomical environments, both as single materials and as multicomponent grain systems
Stephens, J. R.↗
Effects of thermomechanical processing on strength and toughness of iron - 12-percent-nickel - reactive metal alloys at -196 C
Thermomechanical processing (TMP) was evaluated as a method of strengthening normally tough iron-12-nickel-reactive metal alloys at cryogenic temperatures. Five iron-12 nickel alloys with reactive metal additions of aluminum, niobium, titanium, vanadium, and aluminum plus niobium were investigated. Primary evaluation was based on the yield strength and fracture toughness of the thermomechanically processed alloys at -196 C.
Stephens, J. R.↗
Low-chromium stainless steels
Two modified stainless-steel formulations, with only two-thirds chromium content found in conventional type 304, have mechanical and chemical properties comparable to type 304. Low-chromium stainless steels have potential uses in heat exchangers, transfer lines for chemicals, automobile trim, and other applications.
Barrett, C. A.↗
New alloys to conserve critical elements
Previous studies and surveys on availability of domestic reserves have shown that chromium is a most critical element within the U.S. metal industry. More precisely, the bulk of chromium is consumed in the production of stainless steels, specifically Type 304 stainless steel (304SS) which contains 18% Cr. The present paper deals with means of reducing chromium in commercial stainless steels by substituting more abundant or less expensive elements with the intent of maintaining the properties of 304SS. The discussion focuses on some of the oxidation and corrosion properties of new substitute stainless steels with only 12% Cr, which represents a potential saving of 33% of the chromium consumed in the production of 304SS. The alloying elements substituted for Cr in 304SS are selected according to their potential for protective oxide formation during high-temperature oxidation; these are Al, Si, Ti, Y, and misch metal which is 99.7% rare-earth metals containing 50 to 55% cerium. Other alloying elements to impart corrosion resistance are Mn, Mo, and V.
Stephens, J. R.↗
Materials technology assessment for Stirling engines
The objectives are to assess the current state-of-the-art of metals and ceramics that are potential candidate materials for hot components in the improved or advanced Stirling engines; identify materials research, development, and testing required to support the development of automotive Stirling engines; and recommend materials technology program plans to assure material readiness in time with the engine system development programs.
Stephens, J. R.↗
New alloys to conserve critical elements
Based on availability of domestic reserves, chromium is one of the most critical elements within the U.S. metal industry. New alloys having reduced chromium contents which offer potential as substitutes for higher chromium containing alloys currently in use are being investigated. This paper focuses primarily on modified Type 304 stainless steels having one-third less chromium, but maintaining comparable oxidation and corrosion properties to that of type 304 stainless steel, the largest single use of chromium. Substitutes for chromium in these modified Type 304 stainless steel alloys include silicon and aluminum plus molybdenum.
Stephens, J. R.↗
Comparison of equivalent energy and energy per unit area /W bar/A/ data with valid fracture toughness data for iron, aluminum, and titanium alloys
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Witzke, W. R.↗
Substitution for chromium in 304 stainless steel
An investigation was conducted to determine the effects of substituting less strategic elements for Cr on oxidation and corrosion resistance of AISI 304 stainless steel. Cyclic oxidation resistance was evaluated at 870 C. Corrosion resistance was determined by exposure of specimens to a boiling copper-rich solution of copper sulfate and sulfuric acid. Alloy substitutes for Cr included Al, Mn, Mo, Si, Ti, V, Y, and misch metal. A level of about 12% Cr was the minimum amount of Cr required for adequate oxidation and corrosion resistance in the modified composition 304 stainless steels. This represents a Cr saving of 33 percent. Two alloys containing 12% Cr plus 2% Al plus 2% Mo and 12% Cr plus 2.65% Si were identified which exhibited oxidation and corrosion resistance comparable to AISI 304 stainless steel.
Stephens, J. R.↗
Development of strong and tough cryogenic Fe-12Ni alloys containing reactive metal additions
The fracture toughness and tensile behaviour of arc-melted and hot-rolled Fe-12Ni alloys containing up to 4 atomic percent reactive metal additions of Al, Nb, Ti, or V were determined at 77 K. Cryogenic toughness was improved up to 7.5 times that of binary Fe-12Ni, depending on the reactive metal, its concentration, and annealing temperature.
Witzke, W. R.↗
Tough strong iron alloys for cryogenic service
Series of alloys with minor additions of reactive metals possesses outstanding strength and toughness at cryogenic temperatures. Effective metal additons include aluminum, niobium, titanium, and vanadium. Strengthening of series is achieved by thermomechanical processing and by precipitate strengthening while maintaining high level of toughness. Possible applications include liquefied natural-gas storage and transmission, structural members in superconducting machinery, and welding rod for other alloys such as nine nickel steels.
Stephens, J. R.↗
Materials technology assessment for stirling engines
A materials technology assessment of high temperature components in the improved (metal) and advanced (ceramic) Stirling engines was undertaken to evaluate the current state-of-the-art of metals and ceramics, identify materials research and development required to support the development of automotive Stirling engines, and to recommend materials technology programs to assure material readiness concurrent with engine system development programs. The most critical component for each engine is identified and some of the material problem areas are discussed.
Stephens, J. R.↗
Cryogenic Properties of a New Tough-Strong Iron Alloy
A program was undertaken to develop an iron-base alloy having a fracture toughness of 220 MPa. m superscript 1/2 with a corresponding yield stress of 1.4 GPa (200 ksi) at-196 C. An Fe-12Ni alloy was selected as the base alloy. Factors considered included reactive metal additions, effects of interstitial impurities, strengthening mechanisms, and weldability. The goals were met in an Fe-12Ni-0.5Al alloy strengthened by thermomechanical processing or by precipitate strengthening with 2 percent Cu. The alloy is weldable with the weld metal and heat affected zone in the postweld annealed condition having toughness equivalent to the base alloy.
Stephens, J. R.↗
Cryogenic properties of a new tough-strong iron alloy
A program was undertaken to develop an iron-base alloy having a fracture toughness of 220 MPa-sq root meters with a corresponding yield stress of 1.4 GPa (200 ksi) at -196 C. An Fe-12Ni alloy was selected as the base alloy. Factors considered include reactive metal additions, effects of interstitial impurities, strengthening mechanisms, and weldability. The goals of this program were met in an Fe-12Ni-0.5Al alloy strengthened by thermomechanical processing or by precipitate strengthening with 2 percent Cu. The alloy is weldable with the weld metal and heat affected zone in the post-weld annealed condition having toughness equivalent to the base alloy.
Stephens, J. R.↗
Oxidation and corrosion behavior of modified-composition, low-chromium 304 stainless steel alloys
The effects of substituting less strategic elements than Cr on the oxidation and corrosion resistance of AISI 304 stainless steel were investigated. Cyclic oxidation resistance was evaluated at 870 C. Corrosion resistance was determined by exposure of specimens to a boiling copper-rich solution of copper sulfate and sulfuric acid. Alloy substitutes for Cr included Al, Mn, Mo, Si, Ti, V, Y, and misch metal. A level of about 12% Cr was the minimum amount of Cr required for adequate oxidation and corrosion resistance in the modified composition 304 stainless steels. This represents a Cr saving of at least 33%. Two alloys containing 12% Cr and 2% Al plus 2% Mo and 12% Cr plus 2.65% Si were identified as most promising for more detailed evaluation.
Stephens, J. R.↗
Weldability of high toughness Fe-12% Ni alloys containing Ti, Al or Nb
Three exceptionally high-toughness Fe-12%Ni alloys designed for cryogenic service were welded using the GTA welding process. Evaluation of weldability included equivalent energy (KIed) fracture toughness tests, transverse-weld tensile tests at -196 and 25 C and weld crack sensitivity tests. The Fe-12%Ni-0.25%Ti alloy proved extremely weldable for cryogenic applications, having weld and HAZ properties comparable with those of the wrought base alloy. The Fe-12%Ni-0.5%Al had good weld properties only after the weld joint was heat treated. The Fe-12%Ni-0.25%Nb alloy was not considered weldable for cryogenic use because of its poor weld joint properties at -196 C and its susceptibility to hot cracking.
Devletian, J. H.↗
Weldability of high-toughness iron - 12 percent-nickel alloys with reactive metal additions of titanium, aluminum, or niobium
Three exceptionally high toughness Fe-12Ni alloys designed for cryogenic service were welded by using the gas tungsten arc welding process. Evaluation of their weldability included equivalent energy fracture toughness tests, transverse weld tensile tests at -196 and 25 C, and weld crack sensitivity tests. The Fe-12Ni-0.25Ti alloy proved extremely weldable for cryogenic applications, having weld and heat affected zone properties comparable to those of the wrought base alloy. The Fe-12Ni-0.5Al alloy had good weld properties only after the weld joint was heat treated. The Fe-12Ni-0.25Nb alloy was not considered weldable for cryogenic use because of its poor weld joint properties at -196 C and its susceptibility to hot cracking.
Delvetian, J. H.↗