thorium, its alloys and intermetallic compounds...feb 08, 2020 · 2) • two primary phases ......
TRANSCRIPT
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
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
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.
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).
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).
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
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† Spedding, F. H., unpublished information (November, 1944).§ Foote, Frank, Metallurgy Division Progress Report, CT‐2794 (April, 1945)
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.
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
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
Mag‐Thor (ThMg2)
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).
Mg‐Th
• Demonstrably skewed toward Mg‐rich side
• Low mp (790°C)
• Peritecticdecomposition
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
Th‐Cr
• Tensile data for Th‐rich (~98% %wt) Th‐Cr surprising• Weldable, machinable, double T‐strength of 316‐SS,• Non‐magnetic
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