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Malleability and ductility are related. A malleable material is one in which a thin sheet can be easily formed by hammering or rolling. In other words, the material has the ability to deform under compressive stress.
![Malleability: Metal hammered into thin sheets, shows hammer hitting gold to make thin circle](/matse81/sites/www.e-education.psu.edu.matse81/files/images/lesson04/malleability.jpeg)
In contrast, ductility is the ability of a solid material to deform under tensile stress. Practically, a ductile material is a material that can easily be stretched into a wire when pulled as shown in the figure below. Recall pulling is applying tensile stress.
If we pull on a rod of material, some of the possible profiles of the rods at fracture are shown in the figure below.
![Breaking profiles: A) Snap w/ jagged edges. B) some contour and pulling then snap, C)pull all the way into smooth contours and points](/matse81/sites/www.e-education.psu.edu.matse81/files/images/lesson04/500px-Ductility.png)
Profile (a) is an example of the material that fractures with no plastic deformation, i.e., it is a brittle material. Profile (b) is an example of a material that fractures after very little plastic deformation. These two profiles would be classified as having low ductility. Profile (c) in contrast is a material that plastically deforms before fracture. This material has high ductility. The stress-strain curves for the brittle, profile (a), and the ductile material, profile (c), are shown in the figure below.
![brittle materials have short and tall curves. Ductile materials rise quickly but level out for a long time](/matse81/sites/www.e-education.psu.edu.matse81/files/images/lesson04/Brittle_v_ductile_stress-strain_behaviour.png)
To Read
Now that you have learned a bit about the mechanical behavior of metals, please go to your e-textbook and read pages 75 to 84 in Chapter 4 of Materials for Today's World, Custom Edition for Penn State University to learn more about this subject. When finished with the reading proceed to the next web page.