Question

Which mechanical property of a metal represents its ability to resist permanent deformation?

• A. Elasticity
• B. Plasticity
• C. Hardness
• D. Toughness

Hint:

Logic Tip: Think of diamonds! A diamond is incredibly hard because you cannot scratch or permanently dent it. However, it is not very tough, because if you hit it with a heavy hammer, it shatters instead of bending.

Answer 1

The Correct Option is C

Concept:
Mechanical properties dictate how a solid material behaves when subjected to various types of applied forces. Differentiating between temporary deformation, permanent deformation, and fracture is crucial for material selection.

Step 1:
Elasticity is the physical ability of a material to deform under stress and then perfectly return to its original shape and size once the stress is removed. It resists deformation, but it does not specifically define the permanent (plastic) threshold.

Step 2:
Plasticity is the exact opposite of the target property. It is the ability of a material to intentionally undergo permanent, non-reversible deformation without rupturing or breaking (vital for forging and bending).

Step 3:
Toughness is the ability of a material to absorb energy and deform plastically before it finally fractures. It is a combination of strength and ductility, not merely a resistance to permanent deformation.

Step 4:
Hardness is strictly defined in material science as the measure of a material's resistance to localized plastic (permanent) deformation. This is typically measured by its resistance to scratching, abrasion, or indentation by a harder body.

Step 5:
Since the question specifically asks for the ability to *resist* permanent (plastic) deformation, Hardness perfectly fulfills this exact definition.