Metals are undoubtedly one of the most common substances used in our world. There is a range of metals, possessing a range of properties, which make it useful in a wide range of fields. They are used in small components in our smartphones, to humungous rods which are used to create large buildings.
All of this is possible because metals exhibit a number of characteristics, both chemical and physical, which make them so versatile. Among these properties, the two of the most exploited properties are its ductility and malleability. It is important to note that both of these are physical properties, which means that both of these properties do not alter the molecular composition of the metal or any other substance involved with it.
Ductility vs Malleability
The main difference between ductility and malleability is that ductility is the property by which a metal can be drawn into wires, while malleability is the property by which a metal can be drawn into plates.
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 between Ductility and Malleability
| 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. | Compression Test is used to measure Malleability. |
What is Ductility?
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 there 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 after one point the wire is sure to break. Hence, that metal which can sustain the highest amount of tensile stress, and keep on 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 computer, 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 or not.
Another interesting fact is that we need to take into account the ductility and the conductivity of these wires, as a certain wire may be very ductile, but might not have good conductivity. Conductivity is basically the ability of a metal to conduct electricity. Metals having good conductivity are known as conductors, and metals having 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. The main reason for these metals to have so low ductility is because they are either liquid or really soft and reactive at room temperature. This makes them unsuitable to act as wires.
What is Malleability?
Malleability is the property of metal by which it can be beaten into plates or sheets without getting deformed. One can also use rollers to make the sheets. Basically, the metal is subject to some kind of 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 kind of compressive force is applied to the metal, the intermolecular gap reduces and the molecules come close to each other. This reduction of space leads to the whole metal getting the shape of sheets in general. When this force is huge, then 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 its shape.
Main Differences Between Ductility and Malleability
- 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.
- Ductility involves tensile stress, while malleability involves compressive stress.
- The most ductile metals are copper, aluminum, and platinum, while the most malleable metals are gold, silver, and iron
- Sodium, Potassium, and Mercury are neither ductile nor malleable, however, Nickel is a nonmalleable metal too.
- Bend test is used to test ductility, while compression test is used to test malleability.
Conclusion
Metals have a lot of properties, both physical and chemical. There are plenty of exceptions in the field of chemical properties, however, the physical properties of metals are defined and pretty simple. Hence, it is really easy to understand, and once anyone knows the subtle differences between terms like these, they can apply this knowledge to a vast array of fields.
References
- https://www.nature.com/articles/nmat1141
- https://journals.sagepub.com/doi/abs/10.1207/S15327957PSPR0603_8