Vad innebär plasticitet? (?)
(?)
Först yield stress, sen plastic strain, och sist elongation
How do you measure hardness?
Measered with indentation (intryckning), several different methods of it. Linked to yield strength
Give 4 examples of imperfections in crystals
- vacancies = missing atoms
- solute atoms = atoms of different kinds
- dislocation = extra atomic planes (alltså sammanghängande atomer inuti kristallen typ)
- Grain boundaries
When and how does dislocations move?
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
What is hardening mechanisms?
Change in microstructure to make dislocation movement more difficult, defects are obstacles for dislocations movement
Examples of hardening mechanisms (4)
- solution hardening - solute atoms “löses in” in the crystal, alloys
- precipitation hardening - particles of another phase is formed in the material
- strain hardening - dislocations prevent other dilocations to move
- grain boundary hardening - small grains provide harder materials
Alloys, and where it is used for hardening: Pure Al
strain hardening = Work hardening
Alloys, and where it is used for hardening: Pure Cu
strain hardening =Work hardening
Alloys, and where it is used for hardening: Cast Al, Mg
Solution hardening (sometimes precipitation hardening)
Alloys, and where it is used for hardening: Bronze (Cu_Sn)
Solution hardening (sometimes strain and precipitation hardening)
Alloys, and where it is used for hardening: Low-carbon steels
solution and strain hardening
Alloys, and where it is used for hardening: Low alloy steels
Precipitation hardening (sometimes solution and strain) hardening
Alloys, and where it is used for hardening: Stainless steels
solution, strain (sometimes precipitation) hardening
Alloys, and where it is used for hardening: cast Ni alloys
solution, precipitation hardening
