Which material is most susceptible to brittle fracture?

Which material is most susceptible to brittle fracture?

• A. Austenitic stainless steel
• B. Aluminum alloys
• C. Ferritic carbon steel and low alloy stainless steel
• D. Ductile iron

Answer: (C)

Brittle fracture tendency comes from having low toughness and a higher brittle-ductile transition temperature. Ferritic carbon steel and low alloy stainless steels have a ferritic (body-centered cubic) structure that tends to be less tough, especially at lower temperatures, so cracks can grow rapidly with little plastic deformation. This makes them more prone to brittle fracture under impact or at temperatures near the transition point. By contrast, austenitic stainless steels have an FCC structure that stays ductile and tough across a wide temperature range, aluminum alloys typically combine good toughness and ductility, and ductile iron’s graphite features help blunt cracks and improve toughness. So the materials most susceptible to brittle fracture are ferritic carbon steel and low alloy stainless steel.

Brittle fracture tendency comes from having low toughness and a higher brittle-ductile transition temperature. Ferritic carbon steel and low alloy stainless steels have a ferritic (body-centered cubic) structure that tends to be less tough, especially at lower temperatures, so cracks can grow rapidly with little plastic deformation. This makes them more prone to brittle fracture under impact or at temperatures near the transition point. By contrast, austenitic stainless steels have an FCC structure that stays ductile and tough across a wide temperature range, aluminum alloys typically combine good toughness and ductility, and ductile iron’s graphite features help blunt cracks and improve toughness. So the materials most susceptible to brittle fracture are ferritic carbon steel and low alloy stainless steel.