By definition, malleability is the ability of a material to be hammered or rolled into thin sheets. In other words, it is the ability to deform when subjected to compression. A substance with high malleability is malleable. Many metals are malleable. Metalloids and nonmetals are not malleable. Malleability is a physical property and mechanical property of matter.
Examples of Malleable Metals
Here are examples of malleable metals:
- Gold
- Silver
- Iron
- Sodium
- Lithium
- Calcium
- Aluminum
- Copper
- Tin
- Indium
- Lead
- Electrum
- Steel
The metalloids are not malleable as pure elements, but can form malleable alloys.
What Is the Most Malleable Metal?
Gold is the most malleable metal. The second most malleable metal is silver.
Are All Metals Malleable?
Not all metals are malleable. Here are examples of metals that are not malleable:
- Osmium
- Iridium
- Tungsten
- Vanadium
- Brass
- Bronze (compared with its component metals)
How Malleability Works
Metals are malleable because of their crystal structure. Elements with close-packed crystal structures [hexagonal close packed (hcp) or face-centered cubic (fcc)] are generally more malleable than those with more open structures, such as body-centered cubic (bcc). For example, gold, silver and magnesium are more malleable than vanadium or chromium. Atoms in close-packed structures are arranged like stacked flat sheets, so the planes can slip past each other under applied force. Meanwhile, body-centered structures are more like corrugated sheets that resist slipping.
But, metals assume different structures depending on temperature, impurities, and other factors. So, how malleable a given element or alloy is depends on its conditions.
Are Any Nonmetals Malleable?
Generally speaking, the elements that are nonmetals are not malleable. However, there are a few exceptions. Certain allotropes are malleable. An example is the plastic allotrope of sulfur.
While nonmetallic elements are not malleable, some nonmetallic polymers are malleable. For example, some plastics display malleability.
Difference Between Malleable and Ductile
A malleable material deforms under compression, while a ductile material deforms under tensile stress. Malleable metals are beaten or pressed into thin sheets, while ductile metals are drawn into thin wires.
For the most part, malleability and ductility go hand in hand. However, there are some metals that are malleable, yet not ductile. For example, lead is malleable and can be pressed into thin sheets. Yet, it is not ductile and easily fractures when drawn into wires.
Malleability and Hardness
Overall, harder metals are less malleable than softer metals. For example, pure gold and silver are very soft and highly malleable. Hard metals, such as tungsten, iridium, osmium, and chromium, are not very malleable. Metals are hard and non malleable because of their crystal structures. The rows of atoms in the crystals don’t line up, so there are many grain boundaries. There isn’t an easy path for atoms to slide past one another under pressure.
Effect of Temperature on Malleability
In most metals, increasing temperature reduces the number of grain boundaries and increases malleability. So, some metals that aren’t malleable under ordinary conditions respond to heat treatment. For example, zinc is brittle until it’s heated above 300 °F (~150 °C). Above this temperature, it’s possible to roll the metal into sheets.
Effect of Alloying on Malleability
Alloying metals is another way of controlling malleability. For example, brass is less malleable than either of its component metals, copper and zinc. 14-karat gold and sterling silver are alloys that harden and reduce the malleability of gold and silver.
Measuring Malleability
There are two means of measuring malleability. The first test is measuring how much pressure or compressive stress a material withstands before breaking. The other test is measuring how thin a sheet a metal forms before fracturing.
References
- Budynas, Richard G. (2015). Shigley’s Mechanical Engineering Design (10th ed.). McGraw Hill. ISBN 978-0-07-339820-4.
- Burgin, Mark (2016). Theory Of Knowledge: Structures And Processes. World Scientific. ISBN 9789814522694.
- Dieter, G. (1986). Mechanical Metallurgy. McGraw-Hill. ISBN 978-0-07-016893-0.
- Emiliani, Cesare (1987). Dictionary of the Physical Sciences: Terms, Formulas, Data. Oxford University Press. ISBN 978-0-19-503651-0.
- Meyers, Robert A. (2001). Encyclopedia of Physical Science and Technology (3rd ed.). Academic Press.