Light metals · Workhorse
Titanium Gr 2 / Ti-6Al-4V
Tivalues describe: Gr 2
Why it wins
Hydrogen outgassing 10 to 100x below stainless: at 1e-11 Torr wall hydrogen is the residual gas, and collision-driven qubit loss follows it. Non-magnetic, half the density of steel. Monolithic Ti multi-port chambers now ship as catalog XHV products.
Why not the alternative
Stainless is cheaper and easier to machine and weld; Ti wins when hydrogen, magnetics, or mass is the spec.
Watch out
Galls, poor thermal conductor, embrittles if welded dirty.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: ASM Handbook: properties, corrosion, heat treatment; SAES Getters datasheets and NEG literature.
Wet cleaning
| Recipe | alkaline degrease, DI rinse, nitric-HF pickle to strip the alpha case, ultrapure rinse |
|---|---|
| Forbidden | chlorinated solvents: stress corrosion cracking; unbuffered HF over-etches |
| Limit | alpha case depth from any prior hot work |
Vacuum and outgassing
| Outgassing, unbaked (10 h) | 1e-9 mbar·L/s/cm² |
|---|---|
| Outgassing, baked | 1e-12 mbar·L/s/cm² |
| Vapour pressure | negligible below 1000 °C |
Temperature
| Bake, assembled | 500 °C |
|---|---|
| Vacuum degas | 750 °C |
| Braze / H2 firing | 900 °C |
| Metallurgical limit | β transus 882 °C (Gr 2) |
Thermal
| CTE | 8.6 ppm/K |
|---|---|
| Thermal conductivity | 17 W/m·K |
| Specific heat | 523 J/kg·K |
| Emissivity | 0.2 |
| Melting / softening | 1668 °C |
Mechanical
| Strength | 275 ys (Gr2) / 830 (Gr5) MPa |
|---|---|
| Tensile | 345 / 950 MPa |
| Elongation | 20 % |
| Young's modulus | 105 GPa |
| Hardness | 145–160 HV |
| Density | 4.51 g/cm3 |
Electrical and magnetic
| Relative permeability | 1.00005 |
|---|---|
| Resistivity | 52 µΩ·cm |
Engineering
| Corrosion | outstanding |
|---|---|
| Joining | TIG under full argon shielding; Ti-based braze fillers |
| Process notes | galls badly; getters O and N above 400 °C |
| Availability and cost | stock, moderate premium |
Brazing
Sourced pairings
| With | Filler | Atmosphere | Expansion gap at set |
|---|---|---|---|
| Alumina 94 to 99.8 percent | Cusil | vacuum | expansion of side B absent: 780 °C is outside the range of titanium-grade-2 (20 to 700 °C), never extrapolated |
| Graphite, pyrolytic graphite, glassy carbon / CVD diamond windows / Silicon carbide (CVD) / Aluminum nitride and Shapal | Ticusil | vacuum 1e-5 mm Hg or inert gas | expansion of side B absent: 780 °C is outside the range of titanium-grade-2 (20 to 700 °C), never extrapolated |
| Sapphire
one built object
weld-in window cell for the nonmagnetic UHV chambers of atomic fountain clocks: an optical blank brazed into a thin weld collar which is then welded into the chamber. The cells are fabricated commercially and mounted, one titanium chamber carrying several windows, three welded directly into the chamber and one into a titanium ConFlat flange. | named only in prose: the source names a family and not an alloy: sapphire and titanium can be brazed with copper-silver-titanium (or closely related) brazes, and this type of braze uses a small addition of titanium to a copper-silver eutectic to enhance wetting to ceramics and metals other than copper and silver. No trade name and no composition are printed. | not stated by the source | no filler identified, nothing to derive |
Preparation
- Mo-Mn then Ni plating
- none
Compatibility
What documents state about this material faced with a filler metal, without the other member of the joint. A statement that names the exact filler comes first. A statement about a whole AWS class comes after it: a class covers dozens of alloys, so it is the weaker of the two, and the corpus never turns one into the other. Last come statements about a pair of base metals that name no filler at all. They are the weakest of the three, and they do not contradict the two above: a table that cannot generalize about a pair can still list a filler class for each metal of that pair separately. The three levels answer three different questions.
- listedAWS class BAgThe AWS combination table lists the BAg class for brazing this base metal to Cu and Cu alloys, carbon and low-alloy steels, cast iron, stainless steel, Ni and Ni alloys, Ti and Ti alloys.
Conditions and source
Book page 75, chapter 3, table 3.2, Base Metal-Brazing Filler Metal Combinations. The cells that carry this class for this base metal name these partners: Cu and Cu alloys, carbon and low-alloy steels, cast iron, stainless steel, Ni and Ni alloys, Ti and Ti alloys. A partner is what the cell pairs the base metal with, it does not index this entry. The table lists classes, it does not qualify them, and an empty cell is never a prohibition. The class is written as the document writes it, BAl-Si becoming BAlSi here, and it is never mapped to any grade of the corpus. The dagger printed by the document on this cell reads: special brazing filler metals are available and used successfully for specific metal combinations. The asterisk printed by the document on this cell reads: refer to the text for information and appropriate individual chapters on the specific compositions within each classification. The table names the family Ti and Ti alloys. The corpus carries CP grade 2 under titanium-grade-2, so the entry is narrower than the cell it records.
AWS Brazing Handbook, American Welding Society, chapter 3 Brazing Filler Metals and chapter 33 Electron Tubes and Vacuum Equipment
Handbook of the American Welding Society. Three tables are read by the corpus. Table 3.2 page 75, Base Metal-Brazing Filler Metal Combinations, a two-entry matrix of base metal families whose cells carry AWS filler classes. Table 3.3 page 76, Maximum Service Temperatures Recommended for Various Brazing Filler Metal Compositions, one continuous and one short-term temperature per class. Table 33.1 page 585, Composition of Brazing Filler Metals Specially Produced for the Brazing of Vacuum Devices and Equipment, with liquidus and solidus in Fahrenheit and Celsius. The chapter, the table and the page of each statement are carried by the entry that uses it, never by this registry line.
- listedAWS class BAlSiThe AWS combination table lists the BAlSi class for brazing this base metal to Al and Al alloys, Ti and Ti alloys.
Conditions and source
Book page 75, chapter 3, table 3.2, Base Metal-Brazing Filler Metal Combinations. The cells that carry this class for this base metal name these partners: Al and Al alloys, Ti and Ti alloys. A partner is what the cell pairs the base metal with, it does not index this entry. The table lists classes, it does not qualify them, and an empty cell is never a prohibition. The class is written as the document writes it, BAl-Si becoming BAlSi here, and it is never mapped to any grade of the corpus. The asterisk printed by the document on this cell reads: refer to the text for information and appropriate individual chapters on the specific compositions within each classification. The table names the family Ti and Ti alloys. The corpus carries CP grade 2 under titanium-grade-2, so the entry is narrower than the cell it records.
AWS Brazing Handbook, American Welding Society, chapter 3 Brazing Filler Metals and chapter 33 Electron Tubes and Vacuum Equipment
Handbook of the American Welding Society. Three tables are read by the corpus. Table 3.2 page 75, Base Metal-Brazing Filler Metal Combinations, a two-entry matrix of base metal families whose cells carry AWS filler classes. Table 3.3 page 76, Maximum Service Temperatures Recommended for Various Brazing Filler Metal Compositions, one continuous and one short-term temperature per class. Table 33.1 page 585, Composition of Brazing Filler Metals Specially Produced for the Brazing of Vacuum Devices and Equipment, with liquidus and solidus in Fahrenheit and Celsius. The chapter, the table and the page of each statement are carried by the entry that uses it, never by this registry line.
Against another base metal, no filler named:
- no generalizationBerylliumThe AWS combination table states that no generalization can be made about brazing this base metal to Ti and Ti Alloys.
Conditions and source
Book page 75, chapter 3, table 3.2, Base Metal-Brazing Filler Metal Combinations. The cell names no filler metal of any kind, neither a grade nor an AWS class. It states something about the combination of two base metals and nothing else. The document prints this reserve under the table and it is carried here in full: Y means generalizations on these combinations cannot be made, refer to appropriate individual chapters for usable filler metals. The document names this family Be, Zr, V, and alloys reactive metals and enumerates three metals of which the corpus carries only beryllium, so the entry names one member of a group the document treats together. The row label of the same family is printed without the comma after Zr. The table names the family Ti and Ti Alloys, and the corpus carries CP grade 2.
AWS Brazing Handbook, American Welding Society, chapter 3 Brazing Filler Metals and chapter 33 Electron Tubes and Vacuum Equipment
Handbook of the American Welding Society. Three tables are read by the corpus. Table 3.2 page 75, Base Metal-Brazing Filler Metal Combinations, a two-entry matrix of base metal families whose cells carry AWS filler classes. Table 3.3 page 76, Maximum Service Temperatures Recommended for Various Brazing Filler Metal Compositions, one continuous and one short-term temperature per class. Table 33.1 page 585, Composition of Brazing Filler Metals Specially Produced for the Brazing of Vacuum Devices and Equipment, with liquidus and solidus in Fahrenheit and Celsius. The chapter, the table and the page of each statement are carried by the entry that uses it, never by this registry line.
- not recommendedMg and Mg AlloysThe AWS combination table does not recommend brazing this base metal to Mg and Mg Alloys.
Conditions and source
Book page 75, chapter 3, table 3.2, Base Metal-Brazing Filler Metal Combinations. The cell names no filler metal of any kind, neither a grade nor an AWS class. It states something about the combination of two base metals and nothing else. The document prints this reserve under the table and it is carried here in full: X means not recommended, however special techniques may be viable for certain dissimilar metal combinations. The table names the family Ti and Ti Alloys, and the corpus carries CP grade 2.
AWS Brazing Handbook, American Welding Society, chapter 3 Brazing Filler Metals and chapter 33 Electron Tubes and Vacuum Equipment
Handbook of the American Welding Society. Three tables are read by the corpus. Table 3.2 page 75, Base Metal-Brazing Filler Metal Combinations, a two-entry matrix of base metal families whose cells carry AWS filler classes. Table 3.3 page 76, Maximum Service Temperatures Recommended for Various Brazing Filler Metal Compositions, one continuous and one short-term temperature per class. Table 33.1 page 585, Composition of Brazing Filler Metals Specially Produced for the Brazing of Vacuum Devices and Equipment, with liquidus and solidus in Fahrenheit and Celsius. The chapter, the table and the page of each statement are carried by the entry that uses it, never by this registry line.
- no generalizationMolybdenum and TZMThe AWS combination table states that no generalization can be made about brazing this base metal to Ti and Ti Alloys.
Conditions and source
Book page 75, chapter 3, table 3.2, Base Metal-Brazing Filler Metal Combinations. The cell names no filler metal of any kind, neither a grade nor an AWS class. It states something about the combination of two base metals and nothing else. The document prints this reserve under the table and it is carried here in full: Y means generalizations on these combinations cannot be made, refer to appropriate individual chapters for usable filler metals. The document names this family W, Mo, Ta, Nb, and alloys refractory metals and enumerates its four metals itself, so the corpus writes the cell under each of the four it carries. The table names the family Ti and Ti Alloys, and the corpus carries CP grade 2.
AWS Brazing Handbook, American Welding Society, chapter 3 Brazing Filler Metals and chapter 33 Electron Tubes and Vacuum Equipment
Handbook of the American Welding Society. Three tables are read by the corpus. Table 3.2 page 75, Base Metal-Brazing Filler Metal Combinations, a two-entry matrix of base metal families whose cells carry AWS filler classes. Table 3.3 page 76, Maximum Service Temperatures Recommended for Various Brazing Filler Metal Compositions, one continuous and one short-term temperature per class. Table 33.1 page 585, Composition of Brazing Filler Metals Specially Produced for the Brazing of Vacuum Devices and Equipment, with liquidus and solidus in Fahrenheit and Celsius. The chapter, the table and the page of each statement are carried by the entry that uses it, never by this registry line.
- no generalizationNiobium RRR 300The AWS combination table states that no generalization can be made about brazing this base metal to Ti and Ti Alloys.
Conditions and source
Book page 75, chapter 3, table 3.2, Base Metal-Brazing Filler Metal Combinations. The cell names no filler metal of any kind, neither a grade nor an AWS class. It states something about the combination of two base metals and nothing else. The document prints this reserve under the table and it is carried here in full: Y means generalizations on these combinations cannot be made, refer to appropriate individual chapters for usable filler metals. The document names this family W, Mo, Ta, Nb, and alloys refractory metals and enumerates its four metals itself, so the corpus writes the cell under each of the four it carries. The table names the family Ti and Ti Alloys, and the corpus carries CP grade 2.
AWS Brazing Handbook, American Welding Society, chapter 3 Brazing Filler Metals and chapter 33 Electron Tubes and Vacuum Equipment
Handbook of the American Welding Society. Three tables are read by the corpus. Table 3.2 page 75, Base Metal-Brazing Filler Metal Combinations, a two-entry matrix of base metal families whose cells carry AWS filler classes. Table 3.3 page 76, Maximum Service Temperatures Recommended for Various Brazing Filler Metal Compositions, one continuous and one short-term temperature per class. Table 33.1 page 585, Composition of Brazing Filler Metals Specially Produced for the Brazing of Vacuum Devices and Equipment, with liquidus and solidus in Fahrenheit and Celsius. The chapter, the table and the page of each statement are carried by the entry that uses it, never by this registry line.
- no generalizationTantalumThe AWS combination table states that no generalization can be made about brazing this base metal to Ti and Ti Alloys.
Conditions and source
Book page 75, chapter 3, table 3.2, Base Metal-Brazing Filler Metal Combinations. The cell names no filler metal of any kind, neither a grade nor an AWS class. It states something about the combination of two base metals and nothing else. The document prints this reserve under the table and it is carried here in full: Y means generalizations on these combinations cannot be made, refer to appropriate individual chapters for usable filler metals. The document names this family W, Mo, Ta, Nb, and alloys refractory metals and enumerates its four metals itself, so the corpus writes the cell under each of the four it carries. The table names the family Ti and Ti Alloys, and the corpus carries CP grade 2.
AWS Brazing Handbook, American Welding Society, chapter 3 Brazing Filler Metals and chapter 33 Electron Tubes and Vacuum Equipment
Handbook of the American Welding Society. Three tables are read by the corpus. Table 3.2 page 75, Base Metal-Brazing Filler Metal Combinations, a two-entry matrix of base metal families whose cells carry AWS filler classes. Table 3.3 page 76, Maximum Service Temperatures Recommended for Various Brazing Filler Metal Compositions, one continuous and one short-term temperature per class. Table 33.1 page 585, Composition of Brazing Filler Metals Specially Produced for the Brazing of Vacuum Devices and Equipment, with liquidus and solidus in Fahrenheit and Celsius. The chapter, the table and the page of each statement are carried by the entry that uses it, never by this registry line.
- not recommendedTool SteelsThe AWS combination table does not recommend brazing this base metal to Tool Steels.
Conditions and source
Book page 75, chapter 3, table 3.2, Base Metal-Brazing Filler Metal Combinations. The cell names no filler metal of any kind, neither a grade nor an AWS class. It states something about the combination of two base metals and nothing else. The document prints this reserve under the table and it is carried here in full: X means not recommended, however special techniques may be viable for certain dissimilar metal combinations. The table names the family Ti and Ti Alloys, and the corpus carries CP grade 2.
AWS Brazing Handbook, American Welding Society, chapter 3 Brazing Filler Metals and chapter 33 Electron Tubes and Vacuum Equipment
Handbook of the American Welding Society. Three tables are read by the corpus. Table 3.2 page 75, Base Metal-Brazing Filler Metal Combinations, a two-entry matrix of base metal families whose cells carry AWS filler classes. Table 3.3 page 76, Maximum Service Temperatures Recommended for Various Brazing Filler Metal Compositions, one continuous and one short-term temperature per class. Table 33.1 page 585, Composition of Brazing Filler Metals Specially Produced for the Brazing of Vacuum Devices and Equipment, with liquidus and solidus in Fahrenheit and Celsius. The chapter, the table and the page of each statement are carried by the entry that uses it, never by this registry line.
- no generalizationTungstenThe AWS combination table states that no generalization can be made about brazing this base metal to Ti and Ti Alloys.
Conditions and source
Book page 75, chapter 3, table 3.2, Base Metal-Brazing Filler Metal Combinations. The cell names no filler metal of any kind, neither a grade nor an AWS class. It states something about the combination of two base metals and nothing else. The document prints this reserve under the table and it is carried here in full: Y means generalizations on these combinations cannot be made, refer to appropriate individual chapters for usable filler metals. The document names this family W, Mo, Ta, Nb, and alloys refractory metals and enumerates its four metals itself, so the corpus writes the cell under each of the four it carries. The table names the family Ti and Ti Alloys, and the corpus carries CP grade 2.
AWS Brazing Handbook, American Welding Society, chapter 3 Brazing Filler Metals and chapter 33 Electron Tubes and Vacuum Equipment
Handbook of the American Welding Society. Three tables are read by the corpus. Table 3.2 page 75, Base Metal-Brazing Filler Metal Combinations, a two-entry matrix of base metal families whose cells carry AWS filler classes. Table 3.3 page 76, Maximum Service Temperatures Recommended for Various Brazing Filler Metal Compositions, one continuous and one short-term temperature per class. Table 33.1 page 585, Composition of Brazing Filler Metals Specially Produced for the Brazing of Vacuum Devices and Equipment, with liquidus and solidus in Fahrenheit and Celsius. The chapter, the table and the page of each statement are carried by the entry that uses it, never by this registry line.
Chemical affinity
What documents state about a BINARY SYSTEM, one element of a filler metal faced with one element of this material. An affinity is not a verdict on a joint: a joint brings many binaries together at once, some helpful and some harmful, and what follows is the list of those the corpus can name. The count below is not written anywhere. It falls out of the crossing of this material's elements with the composition of every filler the corpus holds, so it grows on its own the day a binary enters the corpus.
Elements of this material: Ti, the material is the element.
low-melting eutectic7 fillersNi against Ti1 source+1 statement
The two elements form a liquid at a temperature below the melting point of either of them. The joint or the fixture can fuse where nothing was meant to melt.
7 fillers: 35Au-62Cu-2Ti-1Ni, 50Cu-40Pd-10Ni, 71.5Ti-28.5Ni, BNi-2, Nicoro-80, Nicusil 3, Nioro
Conditions and verbatim
Book page 115, prose, in the paragraph on the choice of fixture materials for brazing titanium. The chapter states that nickel and titanium form a low-melting eutectic of 28.4 percent nickel at approximately 940 C. The SAME sentence is the source of rule R16, and the two do not say the same thing: R16 is about a FIXTURE or a retort made of a nickel-base alloy, this entry is about the binary system wherever its two elements meet, including inside the joint when a nickel-bearing filler faces a titanium member. Written separately for that reason, and both cite the one sentence.
Characteristic temperature940 °C, M. M. Schwartz, Brazing, 2nd edition, ASM International, 2003, chapter 4, Base Metals and Base-Metal Family Groups, DOI 10.1361/brse2003p063
Source[A] M. M. Schwartz, Brazing, 2nd edition, ASM International, 2003, chapter 4, Base Metals and Base-Metal Family Groups, DOI 10.1361/brse2003p063
Source conditionsChapter 4 of the second edition, book pages 63 to 162 in the copy read, which treats base metals family by family and states metallurgical reactions, atmosphere limits and filler selection guides. It is a handbook chapter, not a qualification record. The page of each statement is carried by the entry that uses it, never by this registry line.
Outgassing
4 sourced measurements for this card. A rate means nothing without the pumping time it was read at, so each one states it or declares it missing. The whole base, filters included, is at /tools/outgassing/.
Signature: 1e-8 unbaked to 1e-14 baked, a drop of 5.8 decades.
| Material as published | Species | State | Pumping time | Rate |
|---|---|---|---|---|
| titanium, ASTM grade 2 (unalloyed), no heat treatment | H2 | baked | not applicable, the source states the rate independent of pumping time | 2.50e-14mbar·L/s/cm² |
| titanium, ASTM grade 2 (unalloyed), no heat treatment | H2O | unbaked | the abscissa of the curve below | 6.40e-9 at 0.556 h to 1.30e-10 at 27.778 h |
| Titanium | total | unbaked | the abscissa of the curve below | 1.51e-8 at 1 h to 2.45e-9 at 10 h |
| Titanium | total | unbaked | the abscissa of the curve below | 5.33e-9 at 1 h to 4.91e-10 at 10 h |
Sources: S-FEDCHAK-2021, S-ELSEY-1975-II. Full citations and conditions at the base and in /data/outgassing.json.
Grades
| Gr 1 | softest CP grade: deep drawn and formed parts |
|---|---|
| Gr 2 | CP workhorse: chambers, low hydrogen stock |
| Gr 5 (Ti-6Al-4V) | strength: flanges, printed chambers, structural |
| Gr 23 (Ti-6Al-4V ELI) | extra-low interstitial for cryogenic toughness and AM powder |
| Ti-Mo 85/15 wire | titanium sublimation pump filaments |
Sources · 3
Used by
Tools
- Brazing Abacustitanium grade 2
- Brazing Route Enginetitanium grade 2
- Outgassing base