Microstructure and creep properties of cast near-eutectic Al–Ce–Ni alloys

The carbon and nitrogen free new alloys which were composed of the supersaturated martensitic microstructure with high dislocation density before the creep test have been investigated systematically. These alloys were produced from the new approach which raised creep strength by the utilization of the reverse transformed austenite phase as a matrix and intermetallic compounds such as Laves and μ-phases as precipitates during creep test. It is important that these alloys are independent of any carbides and carbo-nitrides as strengthening factors. Creep behavior of the alloys is found to be different from that of the conventional high-Cr ferritic heat resistant steels. The minimum creep rates of the Fe-Ni alloys at 700°C are found to be much lower than that of the conventional steel, which is due to fine dispersion strengthening useful even at 700°C in these alloys. As a result carbon and nitrogen free alloys exhibited superior creep properties at temperatures more over 700°C, and steam oxidation resistance.

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Microstructures of Ti-1.5 w/o Ni Alloys with Mo and A1 Additions

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113895 ◽

1975 ◽

Vol 33 ◽

pp. 54-55

Author(s):

Anna C. Fraker

Keyword(s):

Corrosion Resistance ◽

Beneficial Effect ◽

Crevice Corrosion ◽

Local Corrosion ◽

Precipitate Size ◽

Ni Alloys

Small amounts of nickel are added to titanium to improve the crevice corrosion resistance but this results in an alloy which has sheet fabrication difficulties and is subject to the formation of large Ti2Ni precipitates. These large precipitates can serve as local corrosion sites; but in a smaller more widely dispersed form, they can have a beneficial effect on crevice corrosion resistance. The purpose of the present work is to show that the addition of a small amount of Mo to the Ti-1.5Ni alloy reduces the Ti2Ni precipitate size and produces a more elongated grained microstructure. It has recently been reported that small additions of Mo to Ti-0.8 to lw/o Ni alloys produce good crevice corrosion resistance and improved fabrication properties.

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Spherulite Structures in a Melt Spun Fe-Ni Austenitic Steel

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117339 ◽

1985 ◽

Vol 43 ◽

pp. 52-53

Author(s):

G. M. Michal ◽

T. K. Glasgow ◽

T. J. Moore

Keyword(s):

Austenitic Steel ◽

Room Temperature ◽

Elevated Temperatures ◽

Large Range ◽

Amorphous Structure ◽

Nucleation And Growth ◽

Ni Alloys ◽

Melt Spun ◽

Crystal Fibers ◽

Rapidly Solidified

Large additions of B to Fe-Ni alloys can lead to the formation of an amorphous structure, if the alloy is rapidly cooled from the liquid state to room temperature. Isothermal aging of such structures at elevated temperatures causes crystallization to occur. Commonly such crystallization pro ceeds by the nucleation and growth of spherulites which are spherical crystalline bodies of radiating crystal fibers. Spherulite features were found in the present study in a rapidly solidified alloy that was fully crysstalline as-cast. This alloy was part of a program to develop an austenitic steel for elevated temperature applications by strengthening it with TiB2. The alloy contained a relatively large percentage of B, not to induce an amorphous structure, but only as a consequence of trying to obtain a large volume fracture of TiB2 in the completely processed alloy. The observation of spherulitic features in this alloy is described herein. Utilization of the large range of useful magnifications obtainable in a modern TEM, when a suitably thinned foil is available, was a key element in this analysis.

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AEM analysis of solidification catalysts in atomized Fe-Ni

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144395 ◽

1986 ◽

Vol 44 ◽

pp. 584-585

Author(s):

Matthew R. Libera

Keyword(s):

Powder Particle ◽

Alloy Composition ◽

Particle Diameter ◽

Metastable Phases ◽

Liquid Droplets ◽

Nucleation Kinetics ◽

Ni Alloys ◽

Nonequilibrium Solidification

The liquid droplets produced by atomization processes are believed to undergo substantial supercooling during solidification, because the catalytic heterogeneities, for statistical reasons, tend to be isolated in the larger droplets. This supercooling can lead to the nucleation of metastable phases. As part of a study on the effect of liquid supercooling on nonequilibrium solidification, three binary Fe-Ni alloys have been produced by conventional argon atomization (Fe-20Ni, Fe-30Ni, and Fe-40Ni). The primary variables in these experiments are: i) the alloy composition; and ii) the powder particle diameter (inversely proportional to supercooling). Of particular interest in this system is the competitive nucleation kinetics between the stable fee and metastable bec phases. Bcc is expected to nucleate preferentially with decreasing %Ni and decreasing particle diameter.

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