Pistons are made of which material?

• A. Steel
• B. Titanium
• C. Cast iron
• D. Aluminium alloy

Answer: (D)

Piston material is chosen for a combination of light weight, strength, and heat dissipation, because the piston must withstand high pressure and rapid heating while moving with the engine. Aluminium alloy provides the best balance: it is much lighter than other metals, giving lower reciprocating inertia and reducing stresses on the crankshaft and connecting rods. It also has excellent thermal conductivity, so heat from combustion is carried away quickly to the cooling system, helping to keep the piston and cylinder walls from overheating. Alloying aluminum with elements like silicon or copper improves hardness and wear resistance without adding significant weight, and the material can be manufactured to tight tolerances needed for piston rings and clearances. Other options are less suitable: cast iron is heavy and not as good at removing heat; steel adds too much weight; titanium, while strong and heat-tolerant, is costly and harder to machine, making it impractical for standard pistons.