Refractories · Workhorse

Tungsten heavy alloys

WHAvalues describe: W-Ni-Fe 95 %

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

Why it wins

Machinable density: collimator inserts, shielding close to beamlines, anode balance weights.

Why not the alternative

Pure W is unmachinable for complex shielding shapes; lead is soft, toxic, and outgasses at bake.

Watch out

Ni-Fe binder is ferromagnetic: use Ni-Cu binder grades near beams and qubits.

Properties

The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: Plansee refractory metal and alloy data; CERN Accelerator School, vacuum and materials proceedings.

Wet cleaning

Recipe	degrease and DI rinse; the binder phase is porous, so bake before UHV service
Forbidden	acidic cleaners leach the binder
Limit	binder porosity holds water

Vacuum and outgassing

Outgassing, unbaked (10 h)	3e-9 mbar·L/s/cm²
Outgassing, baked	2e-11 mbar·L/s/cm²
Vapour pressure	the Ni-Fe binder limits vacuum service, not the tungsten

Temperature

Bake, assembled	450 °C
Vacuum degas	900 °C
Metallurgical limit	liquid-phase sintered; binder softens above 900 °C

Thermal

CTE	5.4 ppm/K
Thermal conductivity	70–90 W/m·K
Specific heat	150 J/kg·K
Emissivity	0.2
Melting / softening	binder melts ~1450 °C

Mechanical

Strength	600–900 ys MPa
Tensile	700–1000 MPa
Elongation	5–15 %
Young's modulus	340–390 GPa
Hardness	280–350 HV
Density	17.0–18.5 g/cm3

Electrical and magnetic

Relative permeability	W-Ni-Fe ferromagnetic; specify W-Ni-Cu for non-magnetic
Resistivity	~10

Engineering

Corrosion	moderate; the binder corrodes first
Joining	machinable, unlike pure W
Process notes	the machinable dense shielding material
Availability and cost	to drawing

Grades

W-Ni-Fe (Densimet, Inermet 180)	standard machinable shielding, magnetic binder
W-Ni-Cu	the low-permeability binder for field-sensitive zones

Sources · 2

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