Define ductility and explain its importance in welded joints.

• A. Ductility is the ability to deform elastically before fracture; high ductility reduces brittleness.
• B. Ductility is the ability to deform plastically before fracture; high ductility reduces risk of sudden brittle failure in welded structures.
• C. Ductility is the hardness of the metal.
• D. Ductility refers to corrosion resistance.

Answer: (B)

Ductility is the ability to deform plastically before fracture, allowing the material to stretch and neck rather than snap. In welded joints, this quality is crucial because the weld metal and surrounding heat-affected zone often carry residual stresses and may form brittle microstructures if not. A ductile weld can yield and redistribute stresses under load, absorbing energy and delaying or preventing sudden brittle failure, which is especially important in real-world service where impacts or temperature changes can occur. The description that highlights plastic deformation and reduced risk of sudden brittle failure best captures why ductility matters for welded joints. Ductility is not about elastic deformation, hardness, or corrosion resistance, which are different material properties.