Q1: On being hit with a hammer, __________ will readily fracture.

ANS:C - cast iron

Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. It is one of the oldest ferrous (iron-based) materials known to humans and has been used for centuries in various applications due to its excellent casting properties, strength, and wear resistance. Here are some key points about cast iron:

1. Composition: Cast iron primarily consists of iron (Fe) and carbon (C), typically with a carbon content ranging from 2% to 4%. Other alloying elements such as silicon (Si), manganese (Mn), sulfur (S), and phosphorus (P) are also present in varying amounts, depending on the specific type of cast iron and its intended application.
2. Types of Cast Iron:
   • Gray Cast Iron: Gray cast iron is the most common type of cast iron. It has graphite flakes dispersed throughout its microstructure, which give it its characteristic gray color and excellent machinability.
   • White Cast Iron: White cast iron contains carbon in the form of cementite (iron carbide). It is hard and brittle, making it suitable for applications requiring wear resistance.
   • Ductile Cast Iron (Nodular Cast Iron): Ductile cast iron contains nodules or spheroidal graphite, which provide greater ductility and toughness compared to gray cast iron. It offers improved strength, impact resistance, and machinability.
   • Malleable Cast Iron: Malleable cast iron is produced by heat treating white cast iron, which converts the cementite into graphite nodules. It has good ductility and shock absorption properties, making it suitable for applications requiring deformation without fracture.
3. Properties:
   • Strength: Cast iron has high compressive strength, making it suitable for applications where high strength and rigidity are required.
   • Wear Resistance: Cast iron exhibits excellent wear resistance due to the presence of graphite flakes or nodules, which act as solid lubricants and reduce friction between surfaces.
   • Machinability: Gray cast iron is known for its excellent machinability, allowing for easy cutting, drilling, and shaping using conventional machining processes.
   • Corrosion Resistance: Some types of cast iron, particularly those containing alloying elements like chromium (Cr) and nickel (Ni), exhibit good corrosion resistance, making them suitable for use in corrosive environments.
4. Applications: Cast iron is used in a wide range of applications, including:
   • Automotive components (engine blocks, cylinder heads, brake rotors)
   • Machinery and equipment (gears, pulleys, housings)
   • Pipe and fittings (water and sewage systems)
   • Cookware (pots, pans, griddles)
   • Architectural and decorative elements (railings, columns, ornamental structures)

Overall, cast iron is valued for its versatility, durability, and cost-effectiveness in various industrial, commercial, and residential applications. Its properties can be tailored through alloying and heat treatment to meet specific performance requirements for different applications.