Which statement correctly contrasts ductile and brittle materials?

Which statement correctly contrasts ductile and brittle materials?

• A. Brittle materials deform plastically.
• B. Ductile materials fracture with little plastic deformation.
• C. Ductile materials deform plastically before fracture (steel, aluminum); brittle materials fracture with little plastic deformation (cast iron, ceramics).
• D. Both types behave identically under stress.

Answer: (C)

Understanding how materials behave under stress involves comparing ductile and brittle responses. Ductile materials, such as steel and aluminum, can undergo substantial plastic deformation before they fail; they yield and often neck, absorbing a lot of energy as they stretch. Brittle materials, like cast iron and ceramics, tend to fracture with little or no plastic deformation, breaking abruptly after a small amount of elastic strain. This difference shows up in their stress–strain behavior: ductile metals have a yield point and a long plastic region, while brittle materials fail soon after the elastic limit with minimal strain. So, the statement that correctly contrasts them is that ductile materials deform plastically before fracture, whereas brittle materials fracture with little plastic deformation. The contrast is rooted in their microstructure and bonding: in ductile materials, dislocations move easily allowing plastic flow; in brittle materials, limited dislocation motion leads to almost no plastic deformation before cracking. Examples reinforce the idea: steel and aluminum are ductile; cast iron and ceramics are brittle.

Understanding how materials behave under stress involves comparing ductile and brittle responses. Ductile materials, such as steel and aluminum, can undergo substantial plastic deformation before they fail; they yield and often neck, absorbing a lot of energy as they stretch. Brittle materials, like cast iron and ceramics, tend to fracture with little or no plastic deformation, breaking abruptly after a small amount of elastic strain. This difference shows up in their stress–strain behavior: ductile metals have a yield point and a long plastic region, while brittle materials fail soon after the elastic limit with minimal strain.

So, the statement that correctly contrasts them is that ductile materials deform plastically before fracture, whereas brittle materials fracture with little plastic deformation. The contrast is rooted in their microstructure and bonding: in ductile materials, dislocations move easily allowing plastic flow; in brittle materials, limited dislocation motion leads to almost no plastic deformation before cracking. Examples reinforce the idea: steel and aluminum are ductile; cast iron and ceramics are brittle.