Explanation:

Introduction to Cast Iron:
Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. It is widely used in engineering applications due to its excellent castability, good machinability, and low cost. Cast iron is known for its high resistance to wear and its ability to retain its shape even under high loads and temperatures.

Ductility:
Ductility is a material property that describes its ability to undergo plastic deformation before fracturing. Ductile materials can be elongated or stretched without breaking. They can be drawn into wires or formed into various shapes without losing their structural integrity.

Cast Iron and Ductility:
Cast iron is classified as a brittle material rather than a ductile material. Brittle materials, unlike ductile materials, exhibit little or no plastic deformation before failure. When subjected to stress, brittle materials tend to fracture immediately without significant deformation.

Microstructure of Cast Iron:
The microstructure of cast iron is characterized by the presence of graphite flakes dispersed in a matrix of ferrite and/or pearlite. This unique microstructure gives cast iron its distinctive properties. However, it also makes cast iron brittle and prone to fracture.

Effect of Carbon Content:
The carbon content in cast iron is relatively high, typically ranging from 2% to 4%. This high carbon content contributes to the formation of graphite flakes, which act as crack initiators and reduce the ductility of the material.

Conclusion:
In conclusion, cast iron is not a ductile material. It is classified as a brittle material due to its low ductility and tendency to fracture without significant plastic deformation. The high carbon content and unique microstructure of cast iron contribute to its brittleness.