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  • 1
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    Deformation and fatigue behavior of SSME turbopump blade materials (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Directionally solidified and single crystal superalloys which are intended for use as turbopump blade materials are anisotropic both elastically and plastically. Therefore, isotropic constitutive models must be modified. Several models which are now being developed are based on metallurgical theories of deformation in these types of alloys. However, these theories have not been fully justified, and the temperature and strain regimes over which they may be valid are poorly defined. The objective of this work is to study the deformation behavior of the alloys, in order to determine the validity of these models and to thereby support the ongoing research efforts in solid mechanics.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Structural Integrity and Durability of Reusable Space Propulsion Systems; p 65-81
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  • 2
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    Constitutive Cyclic Deformation Behavior in Single-crystal and Directionally Solidified SSME High-pressure Fuel Turbopump Airfoil Materials (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-04
    Description: The major goal of the project is to correlate mechanical properties with microstructural deformation behavior and to develop models for constitutive response under a variety of monotonic and cyclic loading cycles, temperatures, strain levels, strain rates, and environments. Two alloys are being studied as candidate SSME turbine blade materials. The first is PWA 1480, which is a single-crystal alloy whose nominal composition is reported. The second alloy being studied is D.S. Mar-M 246 + Hf. This is a directionally solidified material, and its nominal composition is also reported. The major areas of interest for the two materials will be slightly different. The single-crystal alloy lends itself well to fundamental deformation studies, since resolved shear stresses on slip planes are all known and only one grain is present. The D.S. material presents an excellent opportunity to study the effects of slightly misaligned grains on deformation behavior. The two materials will be studied by using approximately the same test matrix, so a good degree of direct comparison will also be possible.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Struct. Integrity and Durability of Reusable Space Propulsion Systems; p 163-169
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  • 3
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    The effects of temperature and strain rate on the yielding behavior of the single crystal superalloy PWA 1480 (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Interrupted tensile tests were conducted on (001) oriented single crystals at temperatures from 20 to 1093 C. Two strain rates were used, 0.5 and 50 percent/min. After the tests, the deformation substructures were characterized by transmission electron microscopy. Results of these tests are given.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center, Nonlinear Constitutive Relations for High Temperature Applications, 1986; p 291-294
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  • 4
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    Yielding and deformation behavior of the single crystal nickel-base superalloy PWA 1480 (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Interrupted tensile tests were conducted to fixed plastic strain levels in 100 ordered single crystals of the nickel based superalloy PWA 1480. Testing was done in the range of 20 to 1093 C, at strain rate of 0.5 and 50%/min. The yield strength was constant from 20 to 760 C, above which the strength dropped rapidly and became a stong function of strain rate. The high temperature data were represented very well by an Arrhenius type equation, which resulted in three distinct temperature regimes. The deformation substructures were grouped in the same three regimes, indicating that there was a fundamental relationship between the deformation mechanisms and activation energies. Models of the yielding process were considered, and it was found that no currently available model was fully applicable to this alloy. It was also demonstrated that the initial deformation mechanism (during yielding) was frequently different from that which would be inferred by examining specimens which were tested to failure.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-175100 , NAS 1.26:175100 , USAAVSCOM-TR-86-C-18 , AD-A171035
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  • 5
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    Low cycle fatigue behavior of conventionally cast MAR-M 200 AT 1000 deg C (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The low cycle fatigue behavior of the nickel-based superalloy MAR-M 200 in conventionally cast form was studied at 1000 C. Continuous cycling tests, without hold times, were conducted with inelastic strain ranges of from 0.04 to 0.33 percent. Tests were also conducted which included a hold time at peak strain in either tension or compression. For the conditions studied, it was determined that imposition of hold times did not significantly affect the fatigue life. Also, for continuous cycling tests, increasing or decreasing the cycle frequency did not affect life. Metallographic analysis revealed that the most significant damage mechanism involved environmentally assisted intergranular crack initiation and propagation, regardless of the cycle type. Changes in the gamma morphology (rafting and rod formation) were observed, but did not significantly affect the failure.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83769 , E-2260 , NAS 1.15:83769 , USAAVSCOM-TR-84-C-16 , AD-A149178
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  • 6
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    High temperature low-cycle fatigue mechanisms in single crystals of nickel-based superalloy Mar-M 200 (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Twenty three high temperature low-cycle fatigue tests were conducted on single crystals of the nickel-based superalloy Mar-M 200. Tests were conducted at 760 and 870 C. SEM fractography and transmission electron microscopy were used to determine mechanisms responsible for the observed orientation dependent fatigue behavior. It has been concluded that the plastic characteristics of the alloy lead to orientation-dependent strain hardening and fatigue lives at 760 C. At 870 C, the elastic characteristics of the alloy dominated the behavior, even though the plastic strain ranges were about the same as they were at 760 C. This led to orientation-dependent fatigue lives, but the trends were not the same as they were at 760 C.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-174739 , NAS 1.26:174739
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  • 7
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    Low cycle fatigue of MAR-M 200 single crystals at 760 and 870 deg C (1984)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Fully reversed low cycle fatigue tests were conducted on single crystals of the nickel-base superalloys Mar-M 200 at 760 C and 870 C. At 760 C, planar slip (octahedral) lead to orientation-dependent strain hardening and cyclic lives. Multiple slip crystals strain hardened the most, resulting in relatively high stress ranges and low lives. Single slip crystals strain hardened the least, resulting in relatively low stress ranges and higher lives. A preferential crack initiation site which was related to slip plane geometry was observed in single slip orientated crystals. At 870 C, the trends were quite different, and the slip character was much more homogeneous. As the tensile axis orientation deviated from 001 , the stress ranges increased and the cyclic lives decreased. Two possible mechanisms were proposed to explain the behavior: one is based on Takeuchi and Kuramoto's cube cross-slip model, and the other is based on orientation-dependent creep rates.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-86933 , E-2444 , NAS 1.15:86933 , USAAVSCOM-TR-85-C-1 , TMS-AIME Fall Meeting; Sep 17, 1984 - Sep 19, 1984; Detroit, MI; United States
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  • 8
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    The correlation between the temperature dependence of the CRSS and the formation of superlattice-intrinsic stacking faults in the nickel-base superalloy PWA 1480 (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The PWA 1480 nickel-base superalloy is known to exhibit a unique minimum in the critical resolved shear stress (CRSS) at about 400 C. This paper reports an observation of a deformation mechanism whose temperature dependence correlates exactly with the reduction in the CRSS. It was found that, after monotonic or cyclic deformation of PWA 1480 at 20 C, the deformation substructures typically contain high density of superlattice-intrinsic stacking faults (S-ISFs) within the gamma-prime precipitates. As the temperature of deformation is increased, the density of S-ISFs is reduced, until finally no faults are observed after deformation in the range from 400 to 705 C. The reduction in the fault density corresponds exactly to the reduction in the CRSS, and the temperature at which the fault density is zero corresponds with the minimum in the CRRS. Two possible mechanisms related to the presence of the S-ISFs in the alloy are considered.
    Keywords: METALLIC MATERIALS
    Type: Metallurgical Transactions A - Physical Metallurgy and Materials Science (ISSN 0360-2133); 20A; 1888
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  • 9
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    The mechanisms and temperature dependence of superlattice stacking fault formation in the single-crystal superalloy PWA 1480 (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The mechanism of the formation of superlattice staking faults in the single-crystal nickel-base superalloy PWA 1480 was investigated by observing deformation microstructures in the superalloy single crystals in the temperature range 20-1100 C. Results showed that, in addition to superlattice stacking faults observed after slow strain rate deformation at temperatures from 700 to 950 C, a high-density of superlattice staking faults formed after deformation at 200 C and below. The mechanisms of fault formation, which are different in the high- and the low-temperature regimes, are discussed.
    Keywords: METALLIC MATERIALS
    Type: Metallurgical Transactions A - Physical Metallurgy and Materials Science (ISSN 0360-2133); 22A; 2309-231
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  • 10
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    Yielding and deformation behavior of the single crystal superalloy PWA 1480 (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Interrupted tensile tests were conducted to fixed plastic strain levels in 100 ordered single crystals of the nickel based superalloy PWA 1480. Testing was done in the range of 20 to 1093 C, at strain rate of 0.5 and 50 percent/min. The yield strength was constant from 20 to 760 C, above which the strength dropped rapidly and became a strong function of strain rate. The high temperature data were represented very well by an Arrhenius type equation, which resulted in three distinct temperature regimes. The deformation substructures were grouped in the same three regimes, indicating that there was a fundamental relationship between the deformation mechanisms and activation energies. Models of the yielding process were considered, and it was found that no currently available model was fully applicable to this alloy. It was also demonstrated that the initial deformation mechanism (during yielding) was frequently different from that which would be inferred by examining specimens which were tested to failure.
    Keywords: METALLIC MATERIALS
    Type: Metallurgical Transactions A - Physical Metallurgy and Materials Science (ISSN 0360-2133); 18A; 85-95
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