What is irradiation hardening's effect on stainless steels?

• A. Increases strength and hardness but reduces ductility and fracture resistance.
• B. Increases ductility and decreases hardness.
• C. Reduces both strength and hardness.
• D. Has no noticeable effect.

Answer: (A)

Irradiation introduces defects in the metal’s lattice that hinder how easily dislocations can move. That dislocation pinning makes the material stronger and harder, so strength and hardness increase. But because the lattice becomes more brittle and plastic deformation is limited, ductility and fracture resistance (toughness) decrease. In a reactor environment, this means you get higher strength with a greater risk of brittle fracture, especially at lower temperatures or with higher neutron doses. The exact amount of hardening and embrittlement depends on dose, irradiation temperature, and alloy composition, with some heating during operation allowing partial recovery.