Material
Tantalum Ta
Almost completely inert to acids, ductile at room temperature unlike the other refractory metals, and the basis of the capacitors inside nearly every piece of military electronics. Also the material of choice for explosively formed penetrator liners.
Overview
Tantalum is unusual among refractory metals in being genuinely ductile at room temperature, which means it can be deep drawn, spun and cold formed like a conventional metal despite a melting point above 3000 degrees Celsius. It is essentially immune to attack by most acids, which is why chemical processing equipment uses it where even nickel alloys corrode. Its two defense-critical roles are quite different from each other: tantalum capacitors, which dominate high reliability electronics because of their volumetric efficiency and stability, and explosively formed penetrator liners, where tantalum's density and ductility let a charge form a coherent slug rather than fragmenting. Supply is a persistent concern because tantalum ore has a well documented conflict minerals history.
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Defense applications
Explosively formed penetrators
Tantalum liners form coherent high velocity slugs under explosive loading rather than breaking up, because the metal stays ductile through extreme strain rates. This is the application where no practical substitute performs comparably.
EFP warhead liners, Shaped charge liners, Anti-armor submunitions
High reliability electronics
Tantalum capacitors deliver more capacitance per unit volume than alternatives and are stable across temperature and time, which is why they persist in avionics, missiles and space hardware despite cost and supply concerns.
Avionics capacitors, Missile guidance electronics, Space-qualified power supplies, Radar and EW systems
Corrosion resistant process equipment
Tantalum-lined vessels, heat exchangers and thermowells handle hot concentrated acids that destroy nickel alloys, in chemical and energetics production.
Acid service heat exchangers, Thermowells and sensors, Vessel linings, Energetic material production equipment
High temperature structure
Rocket nozzle inserts and hot gas hardware, often as tantalum-tungsten alloys, where extreme temperature and erosion resistance are both required.
Nozzle throat inserts, Hot gas valve components, Furnace hardware
Alloys and grades
| Designation | Grade | Class | Notes | Typical forms |
|---|---|---|---|---|
| Unalloyed Tantalum | Unalloyed refractory metal | Commercially pure tantalum, supplied as electron beam or powder metallurgy grade. The standard for chemical process equipment and formed components. | Sheet, Plate, Bar and Rod, Wire, Tube and Pipe, Powder | |
| Ta-2.5W | Tantalum-tungsten alloy | A small tungsten addition raises strength appreciably while keeping most of tantalum's formability and corrosion resistance. | Sheet, Plate, Bar and Rod, Tube and Pipe | |
| Ta-10W | Tantalum-tungsten alloy | Substantially higher strength and better high temperature performance at the cost of formability. Used for hot structure and nozzle hardware. | Sheet, Plate, Bar and Rod, Forgings | |
| Capacitor Grade Tantalum Powder | High surface area powder | Not a structural product. Very high surface area powder pressed and sintered into capacitor anodes, characterized by charge per gram rather than by mechanical properties. | Powder, Wire |
Properties
| Property | Value | Unit | Note |
|---|---|---|---|
| Density | 16.65 | g/cm3 | 0.601 lb/in3; between molybdenum and tungsten |
| Melting point | 3017 | degrees C | 5463 degrees F; fourth highest of all elements |
| Elastic modulus | 186 | GPa | Comparable to steel, notably lower than tungsten or molybdenum |
| Tensile strength, annealed | 205 to 350 | MPa | Soft and ductile in the annealed condition |
| Elongation, annealed | 30 to 40 | percent | Genuinely ductile at room temperature, unlike tungsten and molybdenum |
| Coefficient of thermal expansion | 6.3 | micrometre/m-K | |
| Thermal conductivity | 57 | W/m-K | |
| Corrosion behavior | Inert to most acids below 150 C | Resists nitric, sulfuric and hydrochloric acid; attacked by hydrofluoric acid and strong alkalis | |
| Biocompatibility | Excellent | Inert in the body, supporting a surgical implant market alongside the industrial one |
Advantages
- Ductile and cold formable at room temperature, unlike tungsten and molybdenum
- Essentially inert to most acids, outperforming nickel alloys in aggressive chemical service
- Melting point above 3000 degrees Celsius
- Highest volumetric capacitance efficiency of practical capacitor materials
- Retains ductility at extreme strain rates, which is what makes EFP liners work
- Biocompatible and non-toxic
Limitations
- Expensive, and among the most supply-constrained materials in defense use
- Conflict mineral status requires supply chain due diligence and smelter traceability
- No meaningful US mine production; the domestic industry depends entirely on imported concentrate and recycled material
- Oxidizes rapidly above roughly 300 degrees Celsius in air, requiring vacuum or inert atmosphere at temperature
- Attacked by hydrofluoric acid and strong alkalis despite general acid immunity
- Very high density for its strength, so it is never a structural weight choice
- Absorbs hydrogen readily, which causes embrittlement
Governing specifications
| Designation | Body | Scope |
|---|---|---|
| ASTM B708 | ASTM International | Tantalum and tantalum alloy plate, sheet and strip |
| ASTM B365 | ASTM International | Tantalum and tantalum alloy rod and wire |
| ASTM B521 | ASTM International | Tantalum and tantalum alloy seamless and welded tube |
| Dodd-Frank Section 1502 | United States Congress | Conflict minerals due diligence and disclosure, covering tantalum, tin, tungsten and gold |