What Is Malleability?
Malleability is a physical property of metals that defines their ability to be hammered, pressed, or rolled into thin sheets without breaking. In other words, it is the property of a metal to deform under compression and take on a new shape.
A metal’s malleability can be measured by how much pressure (compressive stress) it can withstand without breaking. Differences in malleability among different metals are due to variances in their crystal structures.
Malleable materials can be flattened into metal leaf. One well-known type of metal leaf is gold leaf. Many metals with high malleability also have high ductility. Some do not; for example lead has low ductility but high malleability.
Malleability is a physical property of matter, usually metals. The property usually applies to the family groups 1 to 12 on the modern periodic table of elements.
Malleability in metals are very important in the appliance and automotive industries. This property helps to construct refrigerators, microwaves and stoves, and also helps to construct flat and curved metal objects.
Introduction Of Malleability
Malleability is commonly characterized by a material’s ability to create a skinny sheet by blow or rolling. This property isn’t seen in non-metals. Malleable metals will bend and twist into numerous shapes when affected by a hammer, whereas non-malleable metals might break apart into pieces.
Examples of malleable metals are gold, iron, aluminum, copper, silver and lead.
Ductility and malleability don’t invariably correlate with one another — as an example, gold is ductile and malleable, however, lead is merely malleable. A metal’s physical property is often measured by what proportion of pressure (compressive stress) it will face up to but not breaking. Variations in the physical properties of metals are due to variances in their crystalline structures.
Metals tend to fracture at grain boundary areas wherever atoms aren’t as powerfully connected. Therefore, the metal will be harder when it possesses many grain boundaries. On the other hand, it will be brittle and less malleable when it has fewer grain boundaries. Most metals become more malleable once heated due to the effects of the increased temperature on the crystal grains.
Gold and silver are highly malleable. When a piece of hot iron is hammered it takes the shape of a sheet. The property is not seen in non-metals. Non-malleable metals may break apart when struck by a hammer. Malleable metals usually bend and twist in various shapes.
Zinc is malleable at temperatures between 100 and 200 °C but is brittle at other temperatures.
On a molecular level, compression stress forces atoms of malleable metals to roll over each other into new positions without breaking their metallic bond. When a large amount of stress is put on a malleable metal, the atoms roll over each other and permanently stay in their new position.
Examples of malleable metals are:
Products made from these metals can demonstrate malleability as well, including gold leaf, lithium foil, and indium shot.
How does Malleability Work?
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 depend 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
While malleability is the property of a metal that allows it to deform under compression, ductility is the property of a metal that allows it to stretch without damage.
Copper is an example of a metal that has both good ductility (it can be stretched into wires) and good malleability (it can also be rolled into sheets).
While most malleable metals are also ductile, the two properties can be exclusive. Lead and tin, for example, are malleable and ductile when they are cold but become increasingly brittle when temperatures start rising towards their melting points.
Most metals, however, become more malleable when heated. This is due to the effect that temperature has on the crystal grains within metals.
Malleability and Hardness
The crystal structure of harder metals, such as antimony and bismuth, makes it more difficult to press atoms into new positions without breaking. This is because the rows of atoms in the metal don’t line up.
In other words, more grain boundaries exist, which are areas where atoms are not as strongly connected. Metals tend to fracture at these grain boundaries. Therefore, the more grain boundaries a metal has, the harder, more brittle, and less malleable it will be.
Effect of Temperature on Malleability
In most metals, the 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 or zinc. 14-karat gold and sterling silver are alloys that harden and reduce the malleability of gold and silver.
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 of metal forms before fracturing.