Crystal defects and effects on properties (Excluding diameter reduction procedure)

Question 1

What are the stages of solidification in steelmaking?

Answer 1

1. Preparation of load
2. Reduction
3. Steel refining
4. Teeming (or casting)
5. Lamination
6. Products

Question 2

What are the packing characteristics of single crystal, polycrystalline and an amorphous solid?

Answer 2

Single crystal - periodic across the whole volume.
Polycrystalline - periodic across each grain.
Amorphous - not periodic

Question 3

What are the four classifications of defects and give examples of each?

Answer 3

1. Point defects (0D) (vacancy atoms, interstitial atoms, substitutional atoms)
2. Line defects (1D) (dislocations)
3. Planar defects (2D) (grain boundaries, stacking faults)
4. Bulk defects (3D) (pores, inclusions, cracks)

Question 4

What is the equation for number of vacancies in a volume?

Answer 4

Nv=ne(-Qv/KbT)

Question 5

What are the two types of dislocations?

Answer 5

1. Edge dislocation

2. Screw dislocation

Question 6

Give four strengthening mechanisms for metals

Answer 6

1. Decreasing grain size
2. Solid solution strengthening
3. Precipitation hardening
4. Strain hardening

Question 7

Impact of cold work on Yield strength, Tensile strength, Ductility and Modulus

Answer 7

Yield Strength - Increases
Tensile Strength - Increases
Ductility - Decreases
Modulus - Remains unchanged

Question 8

What is the equation for cold work?

Answer 8

%CW = (Ao - Ad/Ao)x100

Question 9

TRUE OR FALSE - If dislocations move with ease the material will get stronger

Answer 9

FALSE

Question 10

TRUE OR FALSE - If dislocations move with ease the material will be more difficult to deform

Answer 10

FALSE

Question 11

TRUE OR FALSE - If dislocations move with ease the material will get harder

Answer 11

FALSE

Question 12

What should be done to recover a material’s original properties after a deformation process?

Answer 12

The material should be annealed