Light metals · Workhorse

Beryllium

Bevalues describe: S-200F

Vacuum electronics & X-ray sourcesBig science (accelerators, light sources, public fusion)

Why it wins

Lowest-Z structural metal: near transparent to X-rays while holding one bar. X-ray tube exit windows and detector beam pipes.

Why not the alternative

Aluminum absorbs too much at low energy; polymer windows creep and permeate; diamond costs more per square centimeter.

Watch out

Toxic dust, licensed machining. Exiting fusion first walls since 2023.

Properties

The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: ITER and JET ITER-like wall programme; ASM Handbook: properties, corrosion, heat treatment.

Wet cleaning

Recipe	wet machining and wet cleaning only, in a controlled enclosure with captured effluent
Forbidden	ANY dry operation: the dust is the hazard, not the metal
Limit	the occupational exposure limit, not vacuum performance

Vacuum and outgassing

Outgassing, unbaked (10 h)	2e-9 mbar·L/s/cm²
Outgassing, baked	1e-11 mbar·L/s/cm²
Vapour pressure	negligible below 1000 °C

Temperature

Bake, assembled	250 °C
Vacuum degas	750 °C
Braze / H2 firing	900 °C
Metallurgical limit	oxidises above 700 °C in air

Thermal

CTE	11.5 ppm/K
Thermal conductivity	200 W/m·K
Specific heat	1825 J/kg·K
Emissivity	0.1 polished
Melting / softening	1287 °C

Mechanical

Strength	240 ys MPa
Tensile	320 MPa
Elongation	2–3 %
Young's modulus	303 GPa
Hardness	~150 HV
Density	1.85 g/cm3

Electrical and magnetic

Relative permeability	diamagnetic
Resistivity	4 µΩ·cm

Engineering

Corrosion	oxide-passivated; attacked by chlorides
Joining	brazed with Al-Si; welding is specialist
Process notes	chronic beryllium disease risk governs every step
Availability and cost	restricted, licensed handling

Brazing

Sourced pairings

With	Filler	Atmosphere	Expansion gap at set
Beryllium one built object beryllium vacuum chamber of the Mark II detector at PEP, longitudinal seam of the sheet rolled into a tube	named only in prose: aluminium alloy 1100 strip, with 1100 wire laid on both sides to enlarge the fillets. No catalog filler of this corpus covers it.	not stated by the source	no filler identified, nothing to derive
CuCrZr (copper-chromium-zirconium) one built object beryllium saddle-block tiles brazed onto CuCrZr cooling tubes, neutron converter of the SPES BNCT source	named only in prose: the source does not name the filler. It states only that the joint was made under electron-beam heating at the Tsefey test facility of the Efremov Institute.	not stated by the source	no filler identified, nothing to derive

Preparation

beryllium sheet hot-rolled to 1.5 mm then chemically etched to 1.4 mm to remove the damaged surface crystals that start cracks

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 BAg
The 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.
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. 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 table groups Be, Zr, V and alloys as reactive metals and does not separate them. The corpus carries beryllium alone, so the entry names one member of a group the document treats together.
[A]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 generalizationAl and Al Alloys
The AWS combination table states that no generalization can be made about brazing this base metal to Al and Al 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 Al and Al Alloys, and the corpus carries 6061.
[A]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 generalizationBe, Zr, V, and Alloys Reactive Metals
The AWS combination table states that no generalization can be made about brazing this base metal to Be, Zr, V, and Alloys Reactive Metals.
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.
[A]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 Alloys
The 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 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.
[A]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 TZM
The AWS combination table states that no generalization can be made about brazing this base metal to Be, Zr, V, and Alloys Reactive Metals.
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 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.
[A]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 300
The AWS combination table states that no generalization can be made about brazing this base metal to Be, Zr, V, and Alloys Reactive Metals.
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 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.
[A]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 generalizationTantalum
The AWS combination table states that no generalization can be made about brazing this base metal to Be, Zr, V, and Alloys Reactive Metals.
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 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.
[A]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 generalizationTi and Ti Alloys
The 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.
[A]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 Steels
The 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 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.
[A]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 generalizationTungsten
The AWS combination table states that no generalization can be made about brazing this base metal to Be, Zr, V, and Alloys Reactive Metals.
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 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.
[A]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: Be, the material is the element.

brittle intermetallic21 fillersCu against Be1 source+1 statement

The two elements combine into a compound that is harder and less tolerant of strain than either of them. It sits in the filler, in the base next to the interface, or in both.

Copper beryllides form at the faying surfaces of a beryllium joint. They are an intermetallic and the document reports them as USEFUL: they inhibit rapid penetration of the silver into the beryllium and keep the liquid phase more stable at the brazing temperature.Cu against Be

21 fillers: 10Sn-30Cu-60Ag, 13In-27Cu-60Ag, 35Au-62Cu-2Ti-1Ni, 35Au/65Cu, 49Ti-49Cu-2Be, 50Cu-40Pd-10Ni, 97Ag-1Cu-2Zr, Ag-31.5Cu-10Pd, BAu-1, BCu-1, Cusil, Cusil-ABA, Cusin-1 ABA, Incusil 10, Incusil 15, Incusil-ABA, Nicoro-80, Nicusil 3, Palcusil 10, Palcusil 15, Ticusil

Conditions and verbatim

Book page 78, section on brazing beryllium with silver-base filler metals. The chapter states that copper beryllides, which generally form at the faying surfaces, inhibit rapid penetration of silver into the beryllium components, and hence a more stable liquid phase is present at the brazing temperature. The same page states two things this entry does NOT carry as values. First, that silver interacts favourably with beryllium in that hard or brittle intermetallics do not remain on cooling, which is a statement about silver and not about copper. Second, in a sentence that runs onto page 79, that beryllium forms brittle intermetallic compounds with MOST OTHER METALS, which names no pair and cannot be keyed. This is the second entry of the corpus, with Ti2Cu, whose mechanism is an intermetallic and whose document reports no harm, and both exist so that the mechanism code is never read as a verdict.

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.

low-melting eutectic21 fillersCu against Be1 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.

Beryllium and copper form a eutectic. A copper-bearing filler on a beryllium member has a temperature above which the couple melts.Cu against Be

Conditions and verbatim

Book page 79, in the passage on joining beryllium to CuCrZr. The chapter states that beryllium and copper form a eutectic at approximately 850 C, and in the same sentence that beryllium recrystallizes above 730 C, which is a lower ceiling and belongs to beryllium alone rather than to the couple. The fillers the same passage reports as successful, BAg-18 at 650 to 680 C and an Incusil ABA at 720 C, both work below the eutectic.

Characteristic temperature850 °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

Open in the brazing abacus →

Outgassing

1 sourced measurement 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: no unbaked reading unbaked to 1e-14 baked.

Sourced outgassing measurements for this card
Material as published	Species	State	Pumping time	Rate
Beryllium	H2	baked	not applicable, the source states the rate independent of pumping time	less than1.00e-14mbar·L/s/cm²

Sources: S-CHIGGIATO-CAS-2017. Full citations and conditions at the base and in /data/outgassing.json.

Grades

PF-60, IF-1 foil	X-ray window grades, thin foil transparency
S-65	structural and first wall heritage grade (JET, ITER original baseline)
S-200F	general structural beryllium