The Most Ductile Metals

What is Metal Ductility?

Metal ductility measures the way that metals are able to withstand tensile, or stretching, stress without failing. A metal is ductile when it can be drawn out without losing its strength or breaking. At high temperatures most metals are ductile, however at cooler temperatures many metals are brittle and can only handle a small tensile deformation before fracturing.

Ductility is measured by determining the percentage increase in length that a metal deforms after it is pulled to failure, or by measuring the narrowest cross section of the metal following a tensile test failure.

The Most Ductile Metals

Gold, Platinum and Silver are the most ductile natural metals, and each of these metals can be stretched into thin wires and used for jewelry. Copper is another highly ductile metal and that property is commonly exploited in electrical wiring.

What Makes Metals Ductile?

The atoms within metals form what is known as metallic bonds which, in simple terms, means that the electrons from each of the atoms are free to move between each other. This property also allows the individual atoms within the metal to slide past each other which allows the metal to be stretched.

The way the electrons are structured within the atom coupled with the number of electrons determines how ductile a metal is. Electrons are arranged in rings around the nucleus of the atom and each of these rings are called electron shells. The electrons in the most outer shell for any metal are called valence electrons, and it is these electrons that move within the metal. In general, metals that have a higher number of outer shell electrons and have the most electron shells are the most ductile.

By increasing the temperature of a metal the valence electrons become more mobile and the ductility of the metal increases.

What Are Ductile Metals Used For?

Aluminum alloys are a ductile structural metal that are also a low weight option, while steel with low carbon content is a high strength metal with enough ductility to deform before fracturing. Common applications of ductility include jewelry (gold and silver), electrical wires (copper and aluminum), and cable wires (steel).

Ductility is an important factor in the shaping or forming of metals, while arguably the most important consideration is in the safety of larger structures like bridges and buildings. Structures are generally not designed to deform, however it is an important safety feature if a structure is overloaded or damaged in some way the structure will not simply snap and fall. If structures are built using materials that have some ductility, any overload or accident will result in a structure that will bend or deform before a catastrophic collapse.