Structural Uses for Ductile Ordered Alloys (1984) / Chapter Skim
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'AVAILABLE DATA ON DUCTILE ORDERED ALLOYS'
'AVAILABLE DATA ON DUCTILE ORDERED ALLOYS'
Pages 69-86
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From page 69... ...
Time Independent Mechanical Properties a. Yield and tensile strength b.
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From page 70... ...
In higher temperature applications, on the other hand, time- and cycle-dependent mechanical properties such as creep and rupture strength, creep-fatigue, and slow crack growth may be most important. Environmental compatibility requirements will vary greatly with application.
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From page 71... ...
The density-compensated yield strength and ultimate tensile strength of the ductilized Ni3Al alloys, for example, increase with temperature and can achieve levels comparable to those of some of the highest strength alloys currently available (Figure 24 and 25) (Engineering Alloys Digest Inc.
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From page 72... ...
72 260 i -- 240 MAR•M•246 and Adv LRO Alloys 200 400 600 TEMPERATURE (°C) 800 1000 FIGURE 24 Comparison of the density-compensated yield strength of advanced LRO alloy and nickel aluminides with commercial structural alloys.
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From page 73... ...
73 280 r -- 260 AF115 200 400 600 800 1000 TEMPERATURE (°C) FIGURE 25 Comparison of the density-compensated ultimate tensile strength of advanced LRO alloys and advanced nickel aluminides with commercial structural alloys.
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From page 74... ...
74 70 i -- 60 50 40 30 LU 0 20 10 1000 Hours 800 900 TEMPERATURE (°C) 1000 1100 FIGURE 26 Comparative density compensated stress-rupture behavior of several alloys.
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From page 75... ...
The emphasis should be on more extensive characterization of properties studied in Phase I as well as studies of effects of multiaxial stress states, product anisotropy, feasibility of joining, and compatibility with a wide range of relevant corrosion environments. Phase III -- Extensive testing of multiple production heats representing all relevant product forms and processing routes.
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From page 76... ...
Mechanical and physical properties should be determined from three or more production heats of material. This involves not only extensive mechanical property data generation but also the evaluation of a full range of applicable product forms, the development of detailed materials and process specifications, and so on.
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From page 77... ...
Phase Diagrams Although an understanding of phase equilibria underlies all work with ordered alloys and will be discussed later in other contexts, it is important to emphasize that there is considerable need for classical phase diagram determinations for portions of many binary ordering systems as well as for the more complex, but highly practical, cases of ternary and higher order alloys on which little systematic work has been done. It also should be noted that, in many instances, earlier work should be examined in light of the current understanding of phase transformations, particularly the occurrence of precursor transformations and metastable transformation products.
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From page 78... ...
W.-jh o Fl 10 20 30 40 50 60 70 60 9O Al Weight Percentage Aluminum FIGURE 27 Fe-Al phase diagram (American Society for Metals 1973)
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From page 79... ...
The solubility limit for alloy additions to binary-ordered phases is usually unknown, and, in many cases, the site occupancies associated with
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From page 80... ...
, there are several types of sublattice sites available and that the addition of certain elements favoring particular sublattice sites may enhance properties while other choices may result in much smaller, or even deleterious, effects on properties. Of course, the solubility limits may vary considerably with the particular sublattice as well as with the competition for sites between solutes for the case of multiple alloy additions.
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From page 81... ...
It is particularly important that the evaluation of properties include specification of the chemistry, degree of order, and detailed thermal-mechanical processing history. Dislocations, Antiphase Boundaries, and Stacking Faults Because ordering changes the translation vectors of the lattice, the motion of normal dislocations creates disorder.
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From page 82... ...
Grain Boundary Characteristics Probably the most important factor limiting the engineering use of many ordered alloys, particularly those of interest for elevated-temperature applications, has been poor ductility. In many cases it appears that these ductility problems stem from segregation to grain boundaries and/or the intrinsic properties of grain boundaries.
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From page 83... ...
. The results of the quantum mechanical calculations will generally yield the energies, lattice parameters, and elastic constants, at absolute zero, for perfectly ordered arrangements of two or more atom types.
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From page 84... ...
1980. High Temperature Low Cycle Fatigue Data for Three High Strength Nickel Base Superalloys.
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From page 85... ...
1979. Cohesive properties of metallic compounds augmented spherical wave calculations.
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