Ductility vs Malleability: Difference and Comparison

Metals are undoubtedly one of the most common substances used in our world. A range of metals possess a range of properties that make them useful in a wide range of fields.

They are used in small components in our smartphones to humungous rods used to create large buildings. All of this is possible because metals exhibit several chemical and physical characteristics, making them so versatile.

Among these properties, the two most exploited properties are ductility and malleability. It is important to note that both of these are physical properties, which means that they do not alter the molecular composition of the metal or any other substance involved with it.

Key Takeaways

1. Ductility is the ability of a material to stretch or deform under tensile stress without breaking.
2. Malleability is the ability of a material to be hammered, rolled, or pressed into various shapes without breaking.
3. While flexibility is essential for wire drawing, malleability is important for sheet metal forming.

Ductility vs Malleability

Malleability is the change in the shape of metal with stress, such as compressing metal into sheets without breaking. Metals change shape, but their mass and volume remain the same. In ductility, a metal becomes thin wires without losing strength, but its cross-sectional area decreases.

Ductility is the property of metal with which it can be drawn into wires. Basically, how much tensile stress can a metal sustain before getting deformed?

The malleability of metal means the capacity of a metal to be beaten into plates without breaking. This shows the ability of a metal to sustain compressive forces without deforming.

Comparison Table

Parameters of Comparison	Ductility	Malleability
Definition	The ability of a metal to be drawn into wires without breaking.	The ability of a metal to be beaten into sheets without breaking.
Forces	Tensile Stress.	Compressive Stress.
Suitable Metals	Copper, Aluminum, Platinum.	Gold, Silver, Iron.
Unsuitable Metals	Potassium, Sodium, Mercury.	Nickel, in addition to Potassium, Sodium, and Mercury.
Test	Bend Test is used to measure Ductility.	A compression Test is used to measure Malleability.

What is Ductility?

The ductility of metal means the ability of a metal to be drawn into wires without being subject to any other form of deformation.

To understand this, suppose we have a block of metal, and if they’re the metal is subject to tensile stress and is obtaining the shape of a wire, then we say that the metal is ductile.

The more stress we give, the thinner the wires will become. However, it is known that the wire will surely break after one point. Hence, that metal that can sustain the highest amount of tensile stress and keep producing thinner wires without breaking at all is known as a highly ductile metal.

Knowing the ductility of a metal is very important, as wires serve a very important role in our technological world. They are used to transport electricity over long distances; they are used in our computers, and they are used almost everywhere where transportation of electricity is required.

Hence, if we know the ductility of metal, we know whether it is suitable to cast it into a wire. Another interesting fact is that we need to consider these wires’ ductility and conductivity, as a certain wire may be very ductile but might not have good conductivity.

Conductivity is the ability of a metal to conduct electricity. Metals with good conductivity are known as conductors, and metals with low conductivity are known as insulators.

Copper, Aluminium, and Platinum are the most ductile metals, while Potassium, Sodium, and Mercury are the least ductile metals.

These metals have so low ductility because they are either liquid or soft and reactive at room temperature. This makes them unsuitable to act as wires.

What is Malleability?

Malleability is the property of metal, which can be beaten into plates or sheets without getting deformed. One can also use rollers to make the sheets. The metal is subject to some compressive stress which flattens the metal.

If the metal gives in to this stress and breaks, then the metal is regarded as non-malleable. Any metal which can keep on producing thinner and thinner sheets without breaking while the compressive stress is kept on increasing at the same time is known as a malleable metal.

The malleability of a metal greatly depends on its crystal structure. To understand how these compression forces work, we need to look into the molecular structure of the metal. The atoms of the metal are packed one on top of the other.

When any compressive force is applied to the metal, the intermolecular gap reduces, and the molecules come close to each other. This space reduction leads to the whole metal getting the shape of sheets.

When this force is huge, these molecules are permanently positioned in their new location. 

The most malleable metals are Gold, Silver, and Iron. The most non-malleable metals are Nickel, Potassium, Sodium, and Mercury. Bismuth and Antimony are two non-malleable metals too. This is because it is very difficult to reposition their atoms to new places without breaking their shape.

Main Differences Between Ductility and Malleability

1. The main difference between ductility and malleability is that ductility is the ability of a metal to be drawn into wires, while malleability is the ability of a metal to be beaten into sheets.
2. Ductility involves tensile stress, while malleability involves compressive stress.
3. The most ductile metals are copper, aluminum, and platinum, while gold, silver, and iron are the most malleable.
4. Sodium, Potassium, and Mercury are neither ductile nor malleable. However, Nickel is a nonmalleable metal too.
5. The bend test is used to test ductility, while the compression test is used to test malleability.

References

1. https://www.nature.com/articles/nmat1141
2. https://journals.sagepub.com/doi/abs/10.1207/S15327957PSPR0603_8