Key difference - ductility vs. formability
Ductility and formability are properties related to the deformation of metals. Ductility is the ability of a metal to be subjected to tensile stresses . Malleability is the ability to withstand compressive stress . This is the main difference between ductility and formability. These two remarkable properties are due to the unique metallic bond found only in metals.
This article examines
1. What is ductility - definition, features, examples 2. What is malleability - definition, features, examples 3. What is the difference between ductility and malleability?
What is ductility?
When a force is applied to the two ends of a material to pull each other away, tension is applied to the material. This is known as tensile stress. The plastic deformation occurs due to tensile stress. Tension is applied along a single axis and the material can be rolled into a wire. Most metals show a great ability to withstand this tension. Copper, for example, shows high ductility, while bismuth has a comparatively low ductility and tends to burst easily due to tensile stresses.
The ductility depends on the grain size of the material. Smaller grain size, harder movement of the dislocations due to the greater resistance; therefore the ductility decreases. The opposite occurs with larger grain sizes.
Ductility is based on the ability of metal atoms to slide over one another and deform under load. This is also proportional to the temperature. When metals are heated, their ductility increases. However, lead is an exception in that it becomes more brittle when heated.
The process of stretching metal is known as twisting . Chains and necklaces are made by twisting valuable metals such as gold and silver.
Ductility is the tensile stress of a material. Higher tensile stress, higher ductility and easier to stretch material.
The ductility is measured by a bending test. This is done by bending the specimen at a given angle or until it breaks. Ductile materials are used to make pipes, wires, and various other vehicle parts.
Alloys are highly ductile because the compositions are not pure. Materials like carbon are less ductile. By increasing the carbon composition, steel can be made more ductile.
What is malleability?
Formability correlates with the ability of a material to plastically deform under a compression test. Compressive stress leads to a shortening of the dimensions of a material, as a result of which its volume becomes smaller. Metals are very malleable because the sea of electrons surrounding the positive metal ions can adapt to their small volume.
A malleable material can be rolled, pressed, or hammered into thin sheets without breaking. Different materials have different malleability due to their arrangement of the crystal structure. NaCl has an ion lattice structure that requires positive and negative ions to be in specific locations. Therefore, when pressure is applied, the ions cannot displace and the structure is broken. Therefore, NaCl is not a malleable material. On the other hand, Cu can adapt its crystal structure under pressure. Hence it is very malleable.
Some examples of highly malleable materials include gold, silver, iron, copper, aluminum, tin, and lithium. Antimony and bismuth are much harder because their atoms do not line up under pressure. Therefore the material is harder and more brittle.
The increase in temperature also increases the moldability. Impurities also impair moldability. They make the dislocations difficult to move. Malleability is useful for making various objects by changing the shape of metals.
Difference between ductility and malleability
Ductility: Ductility refers to the ability of a material to stretch under tension.
Malleability: Malleability refers to the ability to deform and change shape under pressure.
Ductility: Ductile materials can be rolled into wires.
Malleability: Malleable materials can be rolled into sheets.
Ductility: The ductility is measured by a bending test.
Malleability: Malleability is measured by the ability to withstand pressure.
Factors that affect formability and ductility
Ductility: The ductility is influenced by the grain size.
Malleability: The malleability is influenced by the crystal structure.
Ductility refers to the ability of a material to stretch under tension, and malleability is the ability to deform and change shape under compressive stress. This is the main difference between ductility and formability.
Both properties increase with increasing temperature, but lead and tin show decreasing ductility and malleability when heat is applied. Most ductile materials are malleable. Gold is both highly ductile and malleable. Therefore very popular in jewelry making.
Alloys show pressure resistance when the grain size becomes more machinable due to the metal mixture. The ductility depends on the grain size of the material, while the formability depends on the crystal structure.
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