Difference Between Ductile and Brittle

Main Difference – Ductile vs Brittle

The two terms ductile and brittle are used to describe two physical changes in substances. Ductile substances can be easily hammered or stretched into thin wires without breakage. This physical property is explained as ductility. Brittle substances are liable to break easily. These substances are hard, and cannot be hammered or stretch like ductile substances; instead, they break. The main difference between ductile and brittle is that ductile substances are can be drawn out into thin wires whereas brittle substances are hard but liable to break easily.

Key Areas Covered

1. What is Ductile
     – Definition, Examples, Effect of Temperature
2. What is Brittle
    – Definition, Examples, Effect of Stress
3. What is the Difference Between Ductile and Brittle
     – Comparison of Key Differences

Key Terms: Brittle, Deformation, Ductile, Ductility, Metal, Metallic Bond

What is Ductile

Ductility is a physical property of a material that is associated with the ability to be hammered thin or stretched into wire without breaking. The materials having this property are known as ductile materials. A ductile material can easily be drawn into wires.

Figure 1: Copper is a Ductile Material

Metals are the best examples of ductile materials. For example, gold, silver, copper are ductile. Although aluminum is a metal, it is not ductile. The ductility of metals can be high or low. Copper is highly ductile and can be drawn into thin wires without breakage.

Moreover, the temperature also has a great influence on the ductility of metals. Generally, when metals are heated, they become less brittle. Some nonmetals also become ductile when heated, so they can be stretched. But lead (Pb) is an exception. It becomes more brittle when heated.

Ductility in metals is due to the high degree of metallic bonds present in metals. Metals have a lattice structure where valence electrons are delocalized from the metal atoms, and the electrons are shared between atoms forming metallic bonds. Due to this electron delocalization, metal atoms can slide past each other, allowing it to be drawn into thin wires.

What is Brittle

The term brittle describes materials that are easily broken, cracked, or snapped. Materials break when a stress is applied to them. Brittle materials break without any deformation. Therefore, they cannot be stretched like ductile substances.

The breaking of brittle substances objects with a snapping sound. When these objects are broken, the edges fit each other because there is no deformation before breakage. Many materials such as ceramic and glass are brittle. Even steel become brittle at low temperatures.

Figure 2: Breaking of Brittle Substances

When a stress is applied to a material, there is a limit to which the stress can be tolerated by that material. When that limit is reached, the material may either deform or break down. Ductile materials deform at this point while brittle materials break apart.

Difference Between Ductile and Brittle

Definition

Ductile: Ductile materials can be drawn into wires by stretching.

Brittle: Brittle materials break, crack or snap easily.

Deformation

Ductile: Ductile materials show deformation.

Brittle: Brittle materials do not show deformation.

Factors Affecting the Process

Ductile: Ductility is affected by temperature.

Brittle: Brittleness is affected by pressure (or stress).

Examples

Ductile: Major examples for ductile materials are metals.

Brittle: Examples of brittle materials include ceramic and glass.

Conclusion

Materials can be named as ductile materials or brittle materials based on their response to an applied stress on them. The main difference between ductile and brittle materials is that ductile materials are able to be drawn out into thin wires whereas brittle materials are hard but liable to break easily.

Reference:

1. Helmenstine, Anne Marie. “Ductile Definition and Examples.” ThoughtCo, Mar. 21, 2016, Available here.
2. “Brittleness.” Wikipedia, Wikimedia Foundation, 21 Dec. 2017,  Available here.

Image Courtesy:

1. “Stranded lamp wire” By Scott Ehardt – Own work (Public Domain) via Commons Wikimedia
2. “Cast iron tensile test” By Sigmund – Own work (CC BY-SA 3.0) via Commons Wikimedia