Why ceramics are brittle and metal are ductile

One method is to put the surface of the glass under compressive stress we will discuss this further in the next section. When you do this, you are building in a stress to help you with a property of the glass. This is different from annealing glass. In the case of annealed glass, the glass is heated, but not melted, and residual stress is allowed to release. Skip to main content. So Why are Ceramics Brittle? Print Why can metals be scratched and develop cracks and yet not catastrophically fail?

To Watch. Crack in Metal and Ceramics Click for the transcript of Crack in metal and ceramic. That is why, generally speaking, metals are ductile and ceramics are brittle. Due to ceramic materials wide range of properties, they are used for a multitude of applications. In general, most ceramics are: hard, wear-resistant, brittle, refractory, thermal insulators, electrical insulators, nonmagnetic, oxidation resistant, prone to thermal shock, and chemically stable. Ceramic Processing.

Ceramic History. The bonding of atoms together is much stronger in covalent and ionic bonding than in metallic. That is why, generally speaking, metals are ductile and ceramics are brittle. Why metals are ductile instead of brittle? Because the delocalised electrons are free to move. These delocalised electrons are free to move throughout the giant metallic lattice, so as one layer of metal ions slides over another, the electrons can move too keeping the whole structure bonded together.

See Figure 8. Dislocations move easily in metals, due to the delocalized bonding, but do not move easily in ceramics. This largely explains why metals are ductile, while ceramics are brittle. If placed under too large of a stress, metals will mechanically fail, or fracture.

The least brittle structural ceramics are silicon carbide mainly by virtue of its high strength and transformation-toughened zirconia. Some ceramics, like bricks, have large pores. Zinc is a lustrous bluish-white metal. It is found in group IIb of the periodic table. Metals are malleable — they can be bent and shaped without breaking.

This is because they consist of layers of atoms that can slide over one another when the metal is bent, hammered or pressed.

Tempering martensitic steel—i. Are metals usually brittle?