Thorium, its Alloys and Intermetallic Compounds...Feb 08, 2020 · 2) • Two primary phases ......
Transcript of Thorium, its Alloys and Intermetallic Compounds...Feb 08, 2020 · 2) • Two primary phases ......
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Thorium, its Alloys and Intermetallic Compounds
A chemicophysical and mechanical retrospective
Stephen A. Boyd, Ph.D.Havelide Systems, Inc.118 Division AvenueBlue Point, NY 11715
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Thorium – the element: synthesis
– Three sources for “modern” synthesis:
• Ames Protocol
–(Th(NO3)4•4H2O + (COOH)2 → Th(oxo) 2–Th(oxo) 2 +∆H → ThO2
– ThO2 + HF ‐> ThF4– ThF4 + 2Ca0 + ZnCl2 +∆H →Th0
• Battelle: 2I2 + Th +∆H ‐> ThI4; ∆H → Th0
• Westinghouse: ThO2 + Ca0 + ∆H → Th0
1829 – Jakob Berzelius Original reaction: KThF5 + K0 → Th0
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Thorium – the element: performance
• Vicker’s Hardness: 36‐100 (depending on purity); remarkably soft – very similar to Al– Easily cold‐rolled to 0.1mm
– cold‐workable,
– Extrudable
– machinable
– Weldable – arc, MIG, TIG
– Intermetalic welding, braising
INTERIM REPORT ON METALLURGY OF THORIUM AND THORIUM ALLOYS. ORNL 1090 METALLURGY AND CERAMICS. 1949 ‐ 1951 Contract No. W‐740S, eng‐26.
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Thorium – the element – α phase
• Face‐centered Cubic†
_– Fm3m
• a = 5.08Å
• ⟩ ≈ 11.6 g/cm3
†Wilson, W. B., Austin, A. E., and Schwartz, C. M., "The Solid Solubility of Uraniumin Thorium and the Allotropic Transformation of Thorium‐Uranium Alloys", BMI‐ 11 11(July 12, 1956).
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Thorium – the element – β phase
• Body‐centered Cubic at
High temperature:
transition temp:
1360°C†
_– Space group: Im3m
• a = 4.12Å
• ⟩ ≈ 9 g/cm3
†Chiotti, P., "High‐Temperature Crystal Structure of Thorium", J. Electrochem. Soc,,‐101, 567‐70 (1954).
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Binary Alloys: ASTM Nomenclature• Letters = major alloying elements
• first letter = the highest amount (wt%)
• second letter = the second highest amount (wt%)
• Numbers = wt% of each, in same order
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Binary Th alloys
• Containment vessels a challenge– Refractory materials few and far between
– ZrO2 vessels (<1800°C) discovered…<1% reactivity with Th0
– BeO excellent, but highly toxic and Th‐Bex(2<x<13; solid solution) microlayer readily formed above 1200°C; high shear plane number†§
† Spedding, F. H., unpublished information (November, 1944).§ Foote, Frank, Metallurgy Division Progress Report, CT‐2794 (April, 1945)
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Silica Tube Alloying Furnace
INTERIM REPORT ON METALLURGY OF THORIUM AND THORIUM ALLOYS. ORNL 1090 METALLURGY AND CERAMICS. 1949 ‐ 1951 Contract No. W‐740S, eng‐26.
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Mag‐Thor (ThMg2)
• Much vaulted, due to its chemical and physical properties:– High tensile strength at elevated (350°C) temperatures
– High corrosion resistance
– Little creep, despite prolonged elevated temperature exposure
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Mag‐Thor (ThMg2)
• Two primary phases– Temperature dependent
– Low‐temperature (<700°C) phase: hexagonal (P63/mmm)
– a = 6.086Å– c = 19.64Å
Peterson, D. R., Diljak, P. F., and Vold, C. L., "The Structure of Thorium‐MagnesiumIntermetallic Compounds", Acta Cryst., 1‐90, 1036 (1956
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Mag‐Thor (ThMg2)
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Mag‐Thor – high‐temp cubic phase
Cubic: Fd3m
a = 8.57 Å
Small stability rangeBefore peritecticdecomposition
Yamamoto, A. S., Levinson, D. W., and Rostoker, W., "Research on Phase Relationshipsin Magnesium Alloys", WADC TN‐649 (November 1, 1955).
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Mg‐Th
• Demonstrably skewed toward Mg‐rich side
• Low mp (790°C)
• Peritecticdecomposition
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Th‐CrClassic eutectic phase curve, But NO intermetallic at eutecticpoint
Alloy (non‐intermetallic) withOnly 2% Cr has incredibly high Tensile strength
α‐phase (<1360°C)face‐centered cubic (Fm3m)
β‐phase (1360‐1755°C)body‐centered cubic (Im3m)
Venkatraman, M., Neumann, J.P., Peterson, D.E. Bull Alloy Phase Diag. 6, 5 1985
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Th‐Cr
• Tensile data for Th‐rich (~98% %wt) Th‐Cr surprising• Weldable, machinable, double T‐strength of 316‐SS,• Non‐magnetic
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Conclusions
• Hundreds of Binary, Ternary alloys
• Poorly studied, nearly zero present‐day research
• Remarkable properties– Simple machining for both elemental Th and binary alloys
– Non‐magnetic behavior
– High‐temperature performance