Correct Answer: C) Cast iron that has been alloyed with silicon and other elements to improve its ductility and tensile strength, allowing it to deform without breaking.
- Explanation: Ductile cast iron (also known as ductile iron or nodular cast iron) is a type of cast iron that has been alloyed with elements like silicon and nickel to improve its ductility and tensile strength. The addition of these elements changes the structure of the graphite within the iron, forming nodules instead of flakes, which enhances the material’s ability to deform under stress without fracturing. This makes ductile cast iron suitable for applications where toughness and impact resistance are required.
Incorrect Options:
A) Cast iron that has high hardness but low tensile strength, used primarily for applications requiring resistance to wear.
- Explanation: This option describes white cast iron, not ductile cast iron. White cast iron is known for its high hardness and wear resistance but has low tensile strength and is brittle, making it unsuitable for applications where ductility and impact resistance are needed.
B) Cast iron that contains graphite flakes, making it brittle and unsuitable for applications requiring high impact resistance.
- Explanation: This describes gray cast iron, not ductile cast iron. Gray cast iron contains graphite flakes, which contribute to its machinability but also make it relatively brittle. This material is not suited for applications requiring high impact resistance or ductility.
D) Cast iron that has a high carbon content and is heat-treated to increase its brittleness, used for applications requiring high hardness.
- Explanation: This option is incorrect because it describes white cast iron or a type of cast iron that has been heat-treated to increase hardness and brittleness. Ductile cast iron is specifically designed to be more flexible and less brittle, which is contrary to this description.
Correct Answer: C) Cast iron that has been alloyed with silicon and other elements to improve its ductility and tensile strength, allowing it to deform without breaking.
- Explanation: Ductile cast iron (also known as ductile iron or nodular cast iron) is a type of cast iron that has been alloyed with elements like silicon and nickel to improve its ductility and tensile strength. The addition of these elements changes the structure of the graphite within the iron, forming nodules instead of flakes, which enhances the material’s ability to deform under stress without fracturing. This makes ductile cast iron suitable for applications where toughness and impact resistance are required.
Incorrect Options:
A) Cast iron that has high hardness but low tensile strength, used primarily for applications requiring resistance to wear.
- Explanation: This option describes white cast iron, not ductile cast iron. White cast iron is known for its high hardness and wear resistance but has low tensile strength and is brittle, making it unsuitable for applications where ductility and impact resistance are needed.
B) Cast iron that contains graphite flakes, making it brittle and unsuitable for applications requiring high impact resistance.
- Explanation: This describes gray cast iron, not ductile cast iron. Gray cast iron contains graphite flakes, which contribute to its machinability but also make it relatively brittle. This material is not suited for applications requiring high impact resistance or ductility.
D) Cast iron that has a high carbon content and is heat-treated to increase its brittleness, used for applications requiring high hardness.
- Explanation: This option is incorrect because it describes white cast iron or a type of cast iron that has been heat-treated to increase hardness and brittleness. Ductile cast iron is specifically designed to be more flexible and less brittle, which is contrary to this description.