Chapter 7: Annealing

Question 1

Stress relief anneal

Answer 1

Reduces the internal residual stresses caused due to cold work (strain hardening), welding, or in large castings, but does not result in drastic property changes.

Question 2

Recovery stage

Answer 2

Lowest activation energy and no large drop in strength or increase in ductility. Strength is retained but internal stresses are removed. Used to prevent corrosion cracking. Grain size or shape does not change.

Question 3

Recrystallization stage

Answer 3

New smaller grains replace heavily deformed, elongated ones, low dislocation density is restored. Hardness and strength drop, ductility is restored. Obeys the Arrhenius equation and is used to process metals.

Question 4

Grain growth stage

Answer 4

Reduction in grain boundary area (reduction in high energy grain boundaries) with a drop in strength with increase in grain size.

Question 5

Hot working

Answer 5

Plastic deformation with dynamic recrystallization occurring at the same time as the generation and multiplication of dislocations. Dislocations are anneal out as the sample is worked at temperatures greater than the recrystallization temperature.

Question 6

Hot working advantages

Answer 6

Less energy required in plastic deformation

Question 7

Hot working disadvantages

Answer 7

Oxidization of the surface which leads to not as good dimension control