Host Atom Diffusion in Ternary Fe-Cr-Al Alloys

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.

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Observation of faint contrast at planar faults in alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100108842 ◽

1978 ◽

Vol 36 (1) ◽

pp. 340-341

Author(s):

K. Kuroda ◽

Y. Tomokiyo ◽

T. Kumano ◽

T. Eguchi

Keyword(s):

Reciprocal Lattice ◽

Beam Theory ◽

Al Alloys ◽

Small Displacement ◽

Electron Microscopic ◽

Lattice Vector ◽

Fringe Contrast ◽

Planar Fault ◽

Lattice Displacement ◽

The Many

The contrast in electron microscopic images of planar faults in a crystal is characterized by a phase factor , where is the reciprocal lattice vector of the operating reflection, and the lattice displacement due to the fault under consideration. Within the two-beam theory a planar fault with an integer value of is invisible, but a detectable contrast is expected when the many-beam dynamical effect is not negligibly small. A weak fringe contrast is also expected when differs slightly from an integer owing to an additional small displacement of the lattice across the fault. These faint contrasts are termed as many-beam contrasts in the former case, and as ε fringe contrasts in the latter. In the present work stacking faults in Cu-Al alloys and antiphase boundaries (APB) in CuZn, FeCo and Fe-Al alloys were observed under such conditions as mentioned above, and the results were compared with the image profiles of the faults calculated in the systematic ten-beam approximation.

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Microstructure of an extruded rapidly solidified Al-8Fe-2Mo alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144218 ◽

1986 ◽

Vol 44 ◽

pp. 548-549

Author(s):

W. T. Donlon ◽

J. E. Allison ◽

S. Shinozaki

Keyword(s):

Electron Microscopy ◽

Automotive Industry ◽

Fuel Economy ◽

High Strength ◽

Al Alloys ◽

Light Weight ◽

Thin Sections ◽

Strength And Durability ◽

Rapidly Solidified ◽

Whitney Aircraft

Light weight materials which possess high strength and durability are being utilized by the automotive industry to increase fuel economy. Rapidly solidified (RS) Al alloys are currently being extensively studied for this purpose. In this investigation the microstructure of an extruded Al-8Fe-2Mo alloy, produced by Pratt & Whitney Aircraft, Goverment Products Div. was examined in a JE0L 2000FX AEM. Both electropolished thin sections, and extraction replicas were examined to characterize this material. The consolidation procedure for producing this material included a 9:1 extrusion at 340°C followed by a 16:1 extrusion at 400°C, utilizing RS powders which have also been characterized utilizing electron microscopy.

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