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A microstructural study of the Tishomingo meteoriteMetallography, electron microscopy, and X-ray diffraction techniques were employed to study a fragment of the Tishomingo iron meteorite. The results suggest the following thermal-mechanical history: The fragment was originally a large crystal of taenite (gamma). Cooling through the alpha + gamma phase boundary did not result in accompanying precipitation of kamacite (alpha). Transformation to a martensitic structure initiated between -25 and -65 C. Transformation continued as the temperature fell to -75 to -115 C, resulting in approx 80% martensite (alpha-prime). Subsequent shock deformation and thermal aging processes substantially modified the taenite and martensite microstructures. Twins in the retained taenite phase are attributed to shock deformation at a pressure estimated for a single event at about 170 kbar. The existing complex altered martensite structure containing both taenite and kamacite (3-15% Ni) particles was apparently the product of both shock deformation and thermal aging processes. The maximum temperature reached during thermal aging is estimated to be less than 400 C and perhaps below 310 C.
Document ID
19780060590
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Ives, L. K.
(National Bureau of Standards Washington, DC, United States)
Kasen, M. B.
(National Bureau of Standards Washington, DC, United States)
Schramm, R. E.
(National Bureau of Standards Washington, DC, United States)
Ruff, A. W.
(National Bureau of Standards Washington, DC, United States)
Reed, R. P.
(National Bureau of Standards, Washington, D.C. and Boulder Colo., United States)
Date Acquired
August 9, 2013
Publication Date
July 1, 1978
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 42
Subject Category
Lunar And Planetary Exploration
Accession Number
78A44499
Distribution Limits
Public
Copyright
Other

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