case for new meteorite metallurgy

The Case for aNew Metallurgy for Meteorites

Phyllis Z. BudkaTechnical Communications Unlimited

e-mail: [email protected]

Phyllis Z. Budka September 1, 2005 2

For nearly 200 years,the meteoritic Widmanstätten Structure

has been used to:

• Understand the fundamentals of irons and steels1800s to 1930s

– Invar effect 1900s to Present– Martensite 1920s to 1930s

• Develop metallurgical tools and techniques– Metallograph - 1850s– X-ray 1920s to 1930s– Microprobe - 1950s

• Develop the Fe-Ni phase diagram - 1904 to Present

• Calculate “Metallographic Cooling Rates” - Serve as the“thermometer” (geo-speedometer) for the study of small planetarybodies and asteroids - 1960s - Present

1813

Assumptions made long ago about nickel-iron meteorite formation conditions must be re-evaluated in the light of modern metallurgical understanding.


The 1904 Fe-Ni Phase Diagram

Osmond and Cartaud1904

Assumptions - 1904• The meteoritic Widmanstätten structure is an equilibrium structure formed on

slow cooling.• The meteoritic Widmanstätten structure is formed by a solid state phase

transformation below 800C.• Meteoritic irons are similar to terrestrial irons except that meteoritic irons are

in equilibrium, whereas terrestrial irons are metastable.

KamaciteBody-centered cubic iron

Alpha ferrite

TaeniteFace-centered cubic iron

Gamma (Austenite)

Meteoritic Widmanstätten StructureTombouctou 25 diameters


1948 Metals Handbook Fe-Ni Phase Diagram includes region above 1300 oC

Body Centered CubicDelta Ferrite

Body-centered cubic Delta Ferrite:• A primary crystallization structure formed above ~1500 oC.• Can be retained at room temperature.• Cannot be distinguished metallographically from body-centered cubic alpha iron.

Kamacite can also be interpreted as Delta Ferrite, formed by solidification from a melt.


Today - Fe-Ni Phase Diagrams:Metallurgy vs Earth & Planetary Sciences

1987 McSween

1992 ASM Handbook 1992

Meteoritics

Metallurgy

Body Centered CubicDelta Ferrite

Face-centered cubic Austenite

Body Centered Cubic Alpha Ferrite


Metallurgical EquilibriumBinary Phase Diagram Determination Today

Today, equilibrium metallurgical binary phase diagrams aredetermined in carefully controlled laboratory experiments.

Nickel-iron meteorites are “metallurgical garbage cans,” containingelements such as carbon, sulfur, phosphorus, etc. that impact phaseformation.

Nickel-iron meteorites are completely inappropriate for metallurgical phase diagram determination.


Assumptions about meteoritic Widmanstätten Structure made in 1904 remain unchanged today in the Earth & Planetary Sciences.

Kamacite

Taenite

1987 McSweenAssumptions• The meteoritic Widmanstätten structure is

an equilibrium structure formed on slowcooling.

• The meteoritic Widmanstätten structure isformed by a solid state phasetransformation below 800C.

• Meteoritic irons are similar to terrestrialirons except that meteoritic irons are inequilibrium, whereas terrestrial irons aremetastable.

Assumptions• The meteoritic Widmanstätten structure is

an equilibrium structure formed on slowcooling.

• The meteoritic Widmanstätten structure isformed by a solid state phasetransformation below 800C.800C. 910C

• Meteoritic irons are similar to terrestrialirons except that meteoritic irons are inequilibrium, whereas terrestrial irons aremetastable.

Osm

ond

& C

arta

ud19

04After Owen & Liu1949 ++++

Kamacite is not necessarily an equilibrium structure.


Definition of Widmanstätten Structure:Change in meaning from Morphology to Mechanism over Time

1985 ASM Metals Handbook

Widmanstätten structure. A structure characterized by a geometrical patternresulting from the formation of a new phase along certain crystallographicplanes of the parent solid solution. The orientation of the lattice in the newphase is related crystallographically to the orientation of the lattice in theparent phase. This structure was originally observed in meteorites, but isreadily produced in many other alloys, such as titanium by appropriate heattreatment.

1948 ASM Metals Handbook

Between 6 and 25% Ni, the alloys are martensitic after fast cooling; afterslow cooling or reheating, they decompose into alpha + gamma. Thestructure varies from the martensitic to the Widmanstätten typeobserved in meteorites.


Widmanstätten Structure: 1813 - TodayA change in meaning over time: From Morphology to Mechanism

Cast single crystal nickel superalloy

Morphology does not imply mechanism.

Specimen courtesy of Dr. V. Buchwald

Agpalilik Nickel-Iron

Vacuum deposited nickel superalloy


Meteoritic Widmanstätten StructuresCourtesy Dr. C.B. Moore

Equilibrium Assumption Microstructures are considered to be unchanged from theirstructure inside the meteorite parent body, except for a 10 mm heat-affected zone.

Implication: In the transition from inside the meteorite parent body to Earth arrival, these materials never reached their melting point.

The melting point of pure iron is 1538 oC.


Metallographic Cooling Rate Theory and the“Widmanstätten Mechanism”

After Wood 1967Co

FCC

FCC

BCC

FCC

BCC


FCC

BCC

340

Assumed equilibrium compositionof FCC taenite inside the

meteorite parent body.

After Wood 1967


Metallographic Cooling Rates are derived from theslope of this line

BCC BCC

BCC BCC

through a mathematicalmodel based on theassumption that this point isthe equilibrium compositionof taenite/”austenite” insidethe meteorite parent body.

Typical Meteoritic Widmanstätten Structure

Typical microprobe trace

FCC

After Mc Sween 1987


FCC

BCC

340

Metallographic Cooling Rates

• 1985 Narayan and Goldstein: Major revision of iron meteorite coolingrates:150 to 6000C per million years.

• 1987 McSween: “Cooling rate data foriron meteorites favor the last 3 models,unless parent bodies with central coreswere very small.”

McSween 1987

Meteorite Parent Body Models


Metallographic Cooling Rate Theory

This is circular reasoning!

The Metallographic Cooling Rate theory is founded on the 1904 assumptionthat kamacite (alpha ferrite) is formed from taenite (austenite) in a solid statephase transformation.


Potential Factors Influencing the Macro/MicrostructuralDevelopment of the Meteoritic Widmanstätten Structure

• Solidification• Microgravity / Low Gravity / Free Fall• Undercooling

• Thermal and Compositional Gradients• Local Equilibrium

• Solid State Phase Transformations• Other??

It is time for a New Metallurgy for Meteorites!


Year Author

1982 P.Z. Budka

1984 P.Z. Budka

1984 P.Z. Budka, F.F. Milillo

1984 P.Z. Budka




1988 P.Z. Budka1993 P.Z. Budka & J.R.M. Viertl

1993 P.Z. Budka, J.R.M. Viertl, S.V. Thamboo



1996 P.Z. Budka1996 P.Z. Budka

1997 P.Z. Budka, J.R.M. Viertl, S.V. Thamboo, R.E. LaRose

1998 P.Z. Budka and J.R.M. Viertl

1998 P.Z. Budka, J.R.M. Viertl T. B Schumaker

2001 P.Z. Budka and J.R.M. Viertl

2002 P.Z. Budka

2003 P.Z. Budka

2003 P.Z. Budka

2004 P.Z. Budka

TitleThe Formation of Pallasitic Chondrules: Evidence for Rapid Solidification Under Microgravity ConditionsThe Influence of Gravitational Body Force in Meteoritic Chondrule and Lunar Glass FormationSpeculations on the Formation of Metallic Meteorite PhasesThe Formation of Chondrule-Containing Extraterrestrial Materials: Evidence for Rapid Solidification Under Microgravity CondditionsThe Inverse Peritectic Phase Transformation in the Fe-S System: Evidence for the Remelting of Troilite During CoolingSome Common Microstructural Features of Nickel-Iron Meteorites and Cast Ferrous AlloysImportance of Meteoritic Materials in Assessing the Influence of Microgravity on SolidificationMeteorites as Specimens for Microgravity ResearchMundrabilla: A Microgravity Casting

Meteorites and Microgravity Research

Gravity Independent Macro/Micro-structural Features: Lessons from Nickel-Iron Meteorites

Microgravity Solidification Microstructures as Illustrated by Nickel-Iron and Stony-Iron MeteoritesMeteorites and the Iron-Nickel Phase DiagramThe Evolution of Meteoritics and MetallurgyMundrabilla's Anomalous Macrostructural Features Revealed as Microgravity Cast Structures Based on Classical Solidification PrinciplesMetallography, Meteorites and the Fe-Ni Phase Diagram

Metallography, Meteorites and the Fe-Ni Phase Diagram

Industrial X-Ray Technique Applied to Mundrabilla

Stony-Iron Meteorites (Pallasites) - A Study of Nature's Microgravity Specimens

Reconstructing Meteorite Microstructures

Stepping Back in Time: Digital Reconstruction of the Imilac Pallasite Formation, Stepping Back in Time #2, Digital Reconstruction of the Gibeon Widmanstätten Structure,

Journal Vol., Pages

Meteoritics: The Journal of the Meteoritical Society Vol. 17, No. 4

Meteoritics: The Journal of the Meteoritical Society Vol. 19, No. 4, p. 201

Meteoritics: The Journal of the Meteoritical Society Vol. 19, No. 4, pp. 201 - 202

Journal of Non-Crystalline Solids pp. 413 - 419

Meteoritics: The Journal of the Meteoritical Society Vol. 24, No. 4, p.342

Meteoritics: The Journal of the Meteoritical Society Vol. 24, No. 4, pp. 342 - 343

Metallurgical Transactions A Vol. 19A, August 1988 pp. 1919 - 1923Meteoritics Vol. 28, No. 3, p. 333

Advanced Materials & Processes Vol. 144, No. 5, Nov. 1993, p. 4

7th International Symposium on Experimental Methods for Microgravity Materials Science, The Mineral, Metals & Materials Society

pp. 27 - 36

8th International Symposium on Experimental Methods for Microgravity Materials Science, The Mineral, Metals & Materials Society

pp. 49 - 57

Advanced Materials & Processes Vol. 150 No. 1, July 1996, pp. 27 - 30Meteorite! Vol. 2 No. 3, pp. 22 - 23

28th Lunar and Planetary Science Conference

28th Lunar and Planetary Science Conference Feb. 1998, pp. 22 - 23

61st Meteoritical Society Meeting

64th Meteoritical Society Meeting

14th International Symposium on Experimental Methods for Microgravity Materials Science

Advanced Materials & ProcessesVol. 161 No. 5, May 2003, www.asminternational.org/AMP, "Web Exclusives"

Meteorite Nov. 2003 Vol. 9, No. 4, pp. 21 - 22

Meteorite Nov. 2004 Vol. 10, No. 4, pp. 21 - 22

Budka Publications on Meteorite Metallurgy

case for new meteorite metallurgy

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