Tungsten (W) is a refractory metal renowned for its extreme properties, including the highest melting point of all pure metals and a density comparable to gold. There is no simple, single answer to how much force it takes to break it. The required force depends on several factors, including the material’s form (wire, rod, or composite), the temperature, and the specific way the force is applied, such as stretching, crushing, or shearing. Understanding the force to break tungsten requires examining the material science metrics that define its resistance to mechanical stress.
Defining the Force Required
The force required to break tungsten is quantified using measurements of stress, which is force distributed over a cross-sectional area, typically expressed in Megapascals (MPa). One Megapascal represents one million Newtons of force applied over a square meter.
The Ultimate Tensile Strength (UTS) measures a material’s resistance to being pulled apart. For pure, commercially prepared tungsten, the UTS is high, typically around 980 MPa. This figure represents the maximum stress the material can endure before it fractures when stretched.
Yield Strength defines the stress at which the tungsten begins to permanently deform. Pure tungsten exhibits a high yield strength, generally in the range of 750 MPa, meaning it resists permanent shape change until a very high load is applied.
Tungsten is also exceptionally hard, demonstrating high resistance to localized surface deformation like scratching or indentation. Its Vickers hardness, a measurement of resistance to penetration, typically ranges from 3,430 to 4,600 MPa. This extreme hardness is why tungsten carbide, an alloy, is widely used in cutting tools and armor-piercing ammunition.
Material Properties that Confer Strength
Tungsten’s immense strength originates deep within its atomic structure. The metal crystallizes in a Body-Centered Cubic (BCC) lattice, where atoms are positioned at the corners of a cube with one atom in the center. This arrangement results in a rigid structure that resists the movement of dislocations—defects that allow metals to bend and deform.
The atoms are held together by some of the strongest metallic bonds known, exhibiting characteristics similar to covalent bonds. Separating these tightly bound atoms requires immense energy to cause fracture, contributing to its high melting point of 3,422°C.
This strong atomic bonding and dense structure are also responsible for tungsten’s high density, nearly 19.3 grams per cubic centimeter. This density, combined with the rigidity conferred by the BCC structure, means the material maintains mechanical strength under extreme temperature and stress. The stiffness of the bonds is reflected in a high Young’s Modulus, a measure of stiffness, of approximately 410 GigaPascals (GPa).
How Tungsten Fails
Despite its high tensile strength, the practical reality of breaking tungsten is often dictated by its inherent brittleness. The BCC crystal structure, while rigid, possesses fewer available slip systems compared to other crystal structures, making it difficult for the material to deform plastically. This limited ability to “flow” under stress causes it to fail suddenly and catastrophically.
This tendency toward sudden failure is quantified by the material’s low Fracture Toughness (\(K_{IC}\)), which is its resistance to crack propagation. Because tungsten is brittle, a microscopic flaw or crack on its surface can quickly lead to complete failure, even if the applied force is well below the ultimate tensile strength. The energy that would be absorbed by a ductile material through bending is instead used to drive the crack forward in tungsten.
The material’s brittle nature is strongly influenced by temperature, a phenomenon known as the Ductile-Brittle Transition Temperature (DBTT). At room temperature, most polycrystalline tungsten is below its DBTT, which can be as high as 400°C for some forms, making it highly brittle. If the tungsten is heated significantly, it crosses this transition point and becomes more ductile, allowing it to deform slightly before breaking.