What is bainitic transformation?
What is bainitic transformation?
The pearlite transformation involves the redistribution of carbon followed by a structure change, the martensite transformation involves the structure change alone, and, in contrast, the bainite transformation involves a structure change followed by the redistribution of carbon, which precipitates as a carbide.
What is bainitic structure?
Bainitic structure can be divided in two groups: upper bainite and lower bainite. Typically, lower bainite differs from upper bainite by the iron-based carbide precipitates within the ferrite plates with a preferred orientation. Upper bainite consists of small subunits of ferrite plates separated by carbide films.
What is bainitic ferrite?
2 Bainitic Ferrite. The growth of pearlite occurs at a common transformation front with the austenite. The growth of the ferrite and cementite phases is coupled and their compositions are complementary since the carbon which cannot be accommodated by the ferrite is incorporated into the cementite.
Can bainite transform to martensite?
In the case of high QT that close to Ms. temperature, the retained austenite was mainly ascribed to carbon enrichment of bainite. The heterogeneous carbon distribution in parent austenite deriving from ferrite formation could influence the subsequent martensite transformation and corresponding martensite structure.
Is pearlite FCC or BCC?
The alpha phase is called ferrite. Ferrite is a common constituent in steels and has a Body Centred Cubic (BCC) structure [which is less densely packed than FCC]. Fe3C is called cementite and lastly (for us), the “eutectic like” mixture of alpha+cementite is called pearlite.
What is the difference between upper and lower bainite?
Upper bainite forms at higher temperatures, permitting the excess carbon to partition before it can precipitate in the ferrite. In lower bainite, the slower diffusion associated with the reduced transformation temperature provides an opportunity for some of the carbon to precipitate in the supersaturated ferrite.
Is bainite harder than pearlite?
The hardness of the reaction product also increases continuously with decreasing temperature, lower bainite being harder than upper bainite, which is harder than most fine pearlite.
Is bainite tougher than pearlite?
When formed during continuous cooling, the cooling rate to form bainite is more rapid than that required to form pearlite, but less rapid than is required to form martensite (in steels of the same composition). The hardness of bainite can be between that of pearlite and untempered martensite in the same steel hardness.
Is pearlite stronger than ferrite?
Pearlite: Mixture of Ferrite and Cementite (alternately arranged as like pearls) Soft Phase than Austenite but posses better strength than Ferrite.