L4 Plasticity

Question 1

Vad innebär plasticitet? (?)

Answer 1

(?)
Först yield stress, sen plastic strain, och sist elongation

Question 2

How do you measure hardness?

Answer 2

Measered with indentation (intryckning), several different methods of it. Linked to yield strength

Question 3

Give 4 examples of imperfections in crystals

Answer 3

1. vacancies = missing atoms
2. solute atoms = atoms of different kinds
3. dislocation = extra atomic planes (alltså sammanghängande atomer inuti kristallen typ)
4. Grain boundaries

Question 4

When and how does dislocations move?

Answer 4

When load is higher than the yield stress, driven by shear strains. It moves in small steps and leads to permanent deformation of the crystal

Question 5

What is hardening mechanisms?

Answer 5

Change in microstructure to make dislocation movement more difficult, defects are obstacles for dislocations movement

Question 6

Examples of hardening mechanisms (4)

Answer 6

1. solution hardening - solute atoms “löses in” in the crystal, alloys
2. precipitation hardening - particles of another phase is formed in the material
3. strain hardening - dislocations prevent other dilocations to move
4. grain boundary hardening - small grains provide harder materials

Question 7

Alloys, and where it is used for hardening: Pure Al

Answer 7

strain hardening = Work hardening

Question 8

Alloys, and where it is used for hardening: Pure Cu

Answer 8

strain hardening =Work hardening

Question 9

Alloys, and where it is used for hardening: Cast Al, Mg

Answer 9

Solution hardening (sometimes precipitation hardening)

Question 10

Alloys, and where it is used for hardening: Bronze (Cu_Sn)

Answer 10

Solution hardening (sometimes strain and precipitation hardening)

Question 11

Alloys, and where it is used for hardening: Low-carbon steels

Answer 11

solution and strain hardening

Question 12

Alloys, and where it is used for hardening: Low alloy steels

Answer 12

Precipitation hardening (sometimes solution and strain) hardening

Question 13

Alloys, and where it is used for hardening: Stainless steels

Answer 13

solution, strain (sometimes precipitation) hardening

Question 14

Alloys, and where it is used for hardening: cast Ni alloys

Answer 14

solution, precipitation hardening