Plastic deformation defects Flashcards
What are the ideal conditions for hot plastic deformation?
Homogenous alloy subjected to unifor temperature and is homogenously deformed by the same amount of strain throughouts its volume at the same time.
What are failure mechanisms maps?
Maps showing different mechanisms active under specific conditions of strain rate and temperature.
Why are cast metals first subjected to hot working, before they can be subjected to cold working?
The structure needs to improved by hot working first.
What type of fracture will always happen in steels that has a loss of ductility at untermediate temperature (region 2)?
Intergranular fracture
What is the grain size in a hot worked metal ruled by?
- time spent at higt temperature
- strain and strain rate
- temperature and strain gradients in the part volume
What can secondary elements in a metal do, and what happens?
They govern the grain size evolution by generating small precipitates that can stimulate recrystallisation during deformation and control grain boundary (limit grain growth)
what can plastic deformation often stimulate the development of?
- texture
- fibrous structure
- banding phenomena
- different thermal response
What generates the fibrous structure in hot forged and hot rolled parts?
Alignment of different phases and secondary particles along plastic flow lines
What lead to texture in plasticly deformed metals?
Preferred crystallographic grain orientation
What is the effect of fibrous structure?
It emphasizes the strength properties along the fibres but also depletes toughness along the transverseto-fibre direction
What are dead zones ?
Material regions where virtually no deformation is felt
What needs to be specially paid attention to during cold deformation?
Residual stresses
What are the defect edge crack, and when can it happen?
They are very common in cold rolling, when the material progressively becomes brittle due to accumulated train-hardening and tension stresses accumulate at the edges of sheets.
