Which of the following describe the effects of annealing steel and aluminum alloys?

• A. Increasing hardness and strength
• B. Decreasing internal stresses and softening of the metal
• C. No change
• D. Increasing brittleness

Answer: (B)

Annealing is a heat treatment that relieves internal stresses and softens the metal by allowing the crystal structure to recrystallize and reconfigure after prior work, such as forming or machining. For steel and aluminum alloys, heating to an appropriate temperature and then cooling slowly lets dislocations rearrange and new, more ductile grains form. The practical result is a material that is easier to deform, with lower hardness and strength and reduced residual stresses. That’s why decreasing internal stresses and softening is the best description. The other outcomes—hardening and strengthening, no change, or increased brittleness—do not match what annealing accomplishes, since annealing moves the metal toward greater ductility and less resistance to deformation, not the opposite.