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Lehigh UniversityLehigh PreserveTheses and Dissertations1-1-1981An electron microscope investigation of eightataxite and one mesosiderite meteorites.Paul M. NovotnyFollow this and additional works at: http://preserve.lehigh.edu/etdPart of the Materials Science and Engineering CommonsRecommended CitationNovotny, Paul M., "An electron microscope investigation of eight ataxite and one mesosiderite meteorites." (1981). Theses andDissertations. Paper 1944.This Thesis is brought to you for free and open access by Lehigh Preserve. It has been accepted for inclusion in Theses and Dissertations by anauthorized administrator of Lehigh Preserve. For more information, please contact preserve@lehigh.edu.

AN ELECTRON MICROSCOPE INVESTIGATION OFEIGHT ATAXITE AND ONE MESOSIDERITE METEORITESbyPaul M. NovotnyA ThesisPresented to the Graduate Committeeof Lehigh Universityin Candidacy for the Degree ofMaster of ScienceinMetallurgy and Materials EngineeringLehigh University1981

ProQuest Number: EP76217All rights reservedINFORMATION TO ALL USERSThe quality of this reproduction is dependent upon the quality of the copy submitted.In the unlikely event that the author did not send a complete manuscriptand there are missing pages, these will be noted. Also, if material had to be removed,a note will indicate the deletion.uestProQuest EP76217Published by ProQuest LLC (2015). Copyright of the Dissertation is held by the Author.All rights reserved.This work is protected against unauthorized copying under Title 17, United States CodeMicroform Edition ProQuest LLC.ProQuest LLC.789 East Eisenhower ParkwayP.O. Box 1346Ann Arbor, Ml 48106-1346

CERTIFICATE OF APPROVALThis thesis is accepted in partial fulfillment ofthe requirements for the degree of Master of Science.(date)(Drofessor in Charge)(Department Chairman)ii

TABLE OF CONTENTSPageCERTIFICATE OF APPROVALiiTABLE OF CONTENTSiiiLIST OF TABLESvLIST OF ation of Meteorites5Metallic Phases in Meteorites7Estherville14Ataxites16Analytical Electron Microscopy17Cooling Rates24Fe-Ni Phase Diagram27EXPERIMENTAL PROCEDURESLight and Scanning Electron Optical Sample Preparation29TEM/STEM Sample Preparation30STEM Procedure31K-Factor Determination34RESULTSEstherville37Microstructure - Light and SEMiii37

Microchemistry38Microprobe Analysis38STEM Analysis38TEM ght and SEM Microstructure Examination41TEM Results44Microchemistry47K . ResultsTe-Ni49DISCUSSIONSInterfall Measurements52X-ray Analysis56Estherville58Ataxites67a TA169iv

LIST OF TABLESPageTable 1Comparison of Structural and Chemical80ClassesTable 2Ataxites Investigated in This Study81

FIGURE TITLESPa PPFigure 1Log-log plot of gallium vs. nickel.The82chemical groupings of the iron meteoritesare shown.Figure 2Log-log plot of germanium vs. nickel.the similar groupings"Note82as in Figure 1.Figure 3Fe-Ni and Fe-Ni(P) Phase Diagrams.83Figure kAustcnite start and martensite start83temperatures for the Fe-Ni binary system.Figure 5M-shaped composition profile across a kamacite- 84taenite-plessite-taenite-kamacite region.Figure 6Schematic composition profiles of plessiteformation.Figure 7a) y a yb) Y "* *2 "*85a YLight photomicrograph of the cloudy zone in86a taenite lamellae in Estherville.Figure 8TEM bright field photomicrograph of the cloudy 86zone in Carlton.Figure 9Schematic ray diagram of a TEM/STEM.87Figure 10Rapid method for determining the cooling rates 88of iron meteorites.Figure 11Light photomicrograph of taenite (T) fingerin kamacite (K) matrix.vi2% Nital etch.88

Figure 12Light photomicrograph of cloudy zone (C.Z.)with its rim of cleartaenite (C.T.).8922Nital etch.Figure 13Microprobe trace (black dots) across areato be made into TEM/STEM disc.89Polarizedlight reveals ordered taenite as regions oflight and dark contrast within the cleartaenite.Figure 14Unetched.Polarized light.SEK photomicrograph of taenite finger.Note90veinlikc network within the cloudy zone.27. Nital etch.Figure 15SEM photomicrograph of cloudy zone inEstherville.90A vein of taenite is seen aswell as the expected honeycomb structure.The kamacite appears as the etched out phase.2% Nital etch.Figure 16SEM photomicrograph of Estherville cloudyzone near clear taenite.Figure 172% Nital etch.SEM photomicrograph of Estherville cloudyzone.9191Taenite crystallites can be seenstarting to coalesce at several locations.2% Nital etch.Figure 18SEM photomicrograph of taenite finger incloudy zone.Note how some taenitevii92

crystallites appear to have coalescedor grown together.Figure 1922 Nital etch.SEM photomicrograph showing region of92Estherville sample that was spark machinedinto 3 mm rod,Figure 202% Nital.Composition profile obtained from the micro-93probe trace across the taenite shownin Figure 13.Figure 21Composition profile obtained from SEM94trace across the Widmanstatten a/cleartaenite interface in Estherville.Figure 22Composition profile obtained from STEM95trace across the clear taenite/cloudy zoneinterface.Figure 23Composition profile obtained from STEM96trace across a single y crystallite borderedby martensite within the cloudy zone.Figure 24TEM bright field image of cloudy zone in97Estherville (T taenite).Figure 25TEM bright field image of cloudy zone.Note97the fine structure within the bec phase.Figure 2CTEM bright field image of cloudy zone showingthe fine structure within the bec phase.viii98

Figure 27TEM bright field of the cloudy zone.The98lath-like fine structure of the bec phaseis clearly evident.Figure 28[100] zone axis diffraction pattern fromclear taenite.99Note the superlatticespots indicating ordering.Figure 29[100] zone axis diffraction pattern fromclear taenite.99Note Che superlatticespots.Figure 30[100 ] zone axis diffraction pattern fromclear taenite.100Note the superlatticespots.Figure 31a)[l00] zone axis microdiffraction patternfrom clear taenite.spots.101Note the superlatticeb) Indexed 1100] pattern withall superlattice spots.Figure 32f122 ] clear taenite zone axis diffraction102pattern with superlattice spots.Figure 33Bright field (a) and centered dark field (b)from ordered spot in diffraction pattern shownin Figure 33c.taenite in 33b.Note small particles of ordered33d shows the indexed diff-raction pattern.ix103

Figure 34Microdiffraction pattern from a singleY crystallite in the cloudy zone.105Thepattern is a [100] zone axis with [001]superlattice spots.Figure 35Microdiffraction pattern from a single105Y crystallite in the cloudy zone. [l00]zone axis with [001] superlattice spots.Figure 36Bright field (a) centered dark field106from Y spot (b) and centered dark fieldfrom superlattice spot (c) from diffractionpattern (d) of cloudy zone.Note particulatenature of both Y and ordered Y in the cloudyzone.Figure 37Bright field (a) centered dark field from108Y spot (b) and centered dark field fromsuperlattice spot (c) from diffractionpattern (d) of the cloudy zone.AFigure 38Note par-ticulate nature of both Y and ordered Y.VMicrodiffraction patterns from two adjacentY crystallites in the cloudy zone.zone axis patterns.Figure 39110[100]Note the superlattice spots.a) Microdiffraction pattern from clearadjacent to the cloudy zone,b) Microdiffraction111

pattern from y crystallite withinthe cloudy zone.Figure 40a) Selected area diffraction pattern ofthe cloudy zone.112b) Indexed pattern showingNishyama-Wassterman orientation.Figure 41Light photomicrograph of Arltunga.2%113Note113Nital etch.Figure 42SEM photomicrograph of Arltunga.Widmanstatten a grains with taenite rims.2% Nital etch.Figure A3SEM photomicrograph of Arltunga.Note114internal structure of the taenite rims.2Z Nital etch.Figure 44SEM photomicrograph of Arltunga.Internal114structure within the taenite is very evident.22 Nital etch.Figure 45Light photomicrograph of Nordheiin.Large115Widmanstatten a platelets can be seen in centerof picture.Figure 4627, Nital etch.SEM photomicrograph of Nordheim.Ribbon-like115taenite rims are clearly seen surrounding thekamacite.Figure 472% Nital etch.SEM photomicrograph of Nordheim.Multigranularkamacite is seen to be surrounded by taenite.xi116

27. Nital etch.Figure 48SEM photomicrograph of Nordheim.No internal116structure is seen within the taenite.2% Nital etch.Figure 49Light photomicrograph of Guffey showingWidmanstatten a - a y type plessite.11727.Nital.Figure 50SEM photomicrograph of Guffey.Note117multigranular kamacite structure withtaenite rims.Figure 512% Nital etch.SEM photomicrograph of Guffey.Fine118structure within taenite can be seen.2% Nital.Figure 52SEM photomicrograph of Guffey.Fine118structure within taenite is clearly seen.2% Nital.Figure 53Light photomicrograph of Tawallah Valley.H9Widmanstatten a platelets are shown ina matrix of fine plessite.Figure 542% Nital etch.SEM photomicrograph of Tawallah Valley.119Fine plessite from decomposed martensite ispresent between a platelets.Figure 5527. Nital etch.SEM photomicrograph of Tawallah Valley.Fine120 0plessite structure is evident.xii27, Nital etch,

Figure 56SEM photomicrograph of Tawallah Valley.120Left side of picture shows the part of theY rim surrounding an a platelet.Notethe various size y rods in the plessite.21 Nital.Figure 57Light photomicrograph of Hoba.A kamacite121platelet surrounded by its taenite rimis shown in the matrix of plessite.2%Nital etch.Figure 58SEM photomicrograph of fine plessite structurein Hoba.Figure 592% Nital etch.SEM photomicrograph of fine plessite inHoba.121122Martensite decomposition is evidentwith Y rims around duplex structure.27.Nital etch.Figure 60SEM photomicrograph of fine plessite neara platelet in Hoba.Note the different sizes ofY rods which are present.Figure 611222% Nital etch.SEM photomicrograph of Weaver Mts. showing123Widmanstatten platelets in the fine decomposedmartensite matrix.Figure 622% Nital.SEM photomicrograph of plessite region nearkamacite platelet in Weaver Mts.Y rods in a matrix.xiii2% Nital.Note fine123

Figure 63SEM photomicrograph showing plessitenear a platelets in Weaver Mts.124Notevariety of sizes of y rods in a matrix.27; Nital.Figure 64SEM photomicrograph of Chinga.Plessite124had formed from martensite decomposingto a y.Figure 6522 Nital etch.Higher magnification SEM photomicrographof Chinga.Decomposed martensite structureis easily seen.Figure 6612527. Nital etch.SEM micrograph of one of the few a plateletsin Chinga and the adjacent plessite.1252%Nital etch.Figure 67Higher magnification SEM micrograph ofplessite near a platelet.Y rod sizes is easily seen.Figure 68Figure 69Variety of27. Nital etch.SEM micrograph of plessite in Cape of GoodHope.1261262% Nital etch.SEM photomicrograph of plessite in Cape ofGood Hope.127Note fine Y rods in a matrix.2% Nital etch.Figure 70SEM photomicrograph of one of the few aplatelets in Cape of Good Hope.etch.xiv2% Nital127

Figure 71Higher magnification SEM photomicrographof plessite near a platelet.128Note thefiney rods near the taenite rim.Figure 72TEM bright field image of Tawallah Valley.129The montage shows V.'idmanstatten kamacite(K) with its rim of clear taenite (C.T.).Martensite (M) and plessite which formedfrom martensite decomposition are also shown.Figure 73TEM bright field image of plessite structurein Tawallah Valley.130Note rim of cleartaenite outlining prior martensite plate.Figure 74Detail of Figure 73.TEM bright field image130clearly shows various size taenite rods ina matrix.Figure 75TEM bright field of another plessite region inTawallah.Figure 76131Note various size y rods.TEM bright field image of another plessite131region in Tawallah Valley.Figure 77TEM bright field image of plessite adjacentto martensite in Tawallah Valley.132Note the.very fineY rods.Figure 78a) Selected area diffraction pattern (S.A.D.P.)from a/y interface.133b) Indexed patternshowing Nishyama-Wasserman orientation relationship.xv