Which element is described as adding strength and toughness to steel and producing an elastic alloy that returns to its original shape after experiencing vibration?

• A. Chromium
• B. Copper
• C. Molybdenum
• D. Nickel

Answer: (D)

Nickel enhances strength and toughness in steel and enables elastic behavior in certain alloys. Adding nickel to steel improves toughness and impact resistance by stabilizing the austenitic structure and providing solid-solution strengthening, which helps the material resist brittle failure and maintain ductility. In alloys like nickel-titanium, nickel is essential for shape-memory and superelastic properties, allowing the material to return toward its original shape after deformation such as vibration. That combination of higher strength, better toughness, and the ability to recover shape makes nickel the best match among the elements listed. The other elements mainly contribute hardness, high-temperature strength, or machinability, but they do not provide the same level of toughness improvement or shape-memory/superelastic behavior as nickel.