High-pressure flank cooling and chip morphology in turning Alloy 718

A nickel-base superalloy is essentially a Ni/Cr solid solution hardened by additions of Al (Ti, Nb, etc.) to precipitate a coherent, ordered phase. In most commercial alloy systems, e.g. B-1900, IN-100 and Mar-M200, the stable precipitate is Ni3 (Al,Ti) γ′, with an LI2structure. In A lloy 901 the normal precipitate is metastable Nis Ti3 γ′ ; the stable phase is a hexagonal Do2 4 structure. In Alloy 718 the strengthening precipitate is metastable γ″, which has a body-centered tetragonal D022 structure.Precipitate MorphologyIn most systems the ordered γ′ phase forms by a continuous precipitation re-action, which gives rise to a uniform intragranular dispersion of precipitate particles. For zero γ/γ′ misfit, the γ′ precipitates assume a spheroidal.

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High-pressure freezing of cells in suspension for low-voltage scanning electron microscopy (LVSEM)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100084624 ◽

1991 ◽

Vol 49 ◽

pp. 64-65

Author(s):

Marek Malecki ◽

James Pawley ◽

Hans Ris

Keyword(s):

Electron Microscopy ◽

High Pressure ◽

Low Voltage ◽

Culture Media ◽

Cell Structure ◽

Freeze Substitution ◽

Ice Crystal ◽

High Pressure Freezing ◽

Cell Culture Media ◽

Voltage Scanning

The ultrastructure of cells suspended in physiological fluids or cell culture media can only be studied if the living processes are stopped while the cells remain in suspension. Attachment of living cells to carrier surfaces to facilitate further processing for electron microscopy produces a rapid reorganization of cell structure eradicating most traces of the structures present when the cells were in suspension. The structure of cells in suspension can be immobilized by either chemical fixation or, much faster, by rapid freezing (cryo-immobilization). The fixation speed is particularly important in studies of cell surface reorganization over time. High pressure freezing provides conditions where specimens up to 500μm thick can be frozen in milliseconds without ice crystal damage. This volume is sufficient for cells to remain in suspension until frozen. However, special procedures are needed to assure that the unattached cells are not lost during subsequent processing for LVSEM or HVEM using freeze-substitution or freeze drying. We recently developed such a procedure.

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Prolonged Fixation Studies For Spaceflight

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100072101 ◽

1973 ◽

Vol 31 ◽

pp. 332-333

Author(s):

Robert Corbett ◽

Delbert E. Philpott ◽

Sam Black

Keyword(s):

High Pressure ◽

Living Systems ◽

Prolonged Storage ◽

Time Intervals ◽

Early Signs ◽

Large Numbers

Observation of subtle or early signs of change in spaceflight induced alterations on living systems require precise methods of sampling. In-flight analysis would be preferable but constraints of time, equipment, personnel and cost dictate the necessity for prolonged storage before retrieval. Because of this, various tissues have been stored in fixatives and combinations of fixatives and observed at various time intervals. High pressure and the effect of buffer alone have also been tried.Of the various tissues embedded, muscle, cartilage and liver, liver has been the most extensively studied because it contains large numbers of organelles common to all tissues (Fig. 1).

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