Table of Contents
- 1 Why β phase is not appeared in the Fe Fe3C phase diagram?
- 2 Which is the hardest structure that appears on iron-carbon equilibrium diagram?
- 3 What is a martensite microstructure?
- 4 What microstructure does martensite have?
- 5 Why Fe-Fe3C system is not called as a perfectly equilibrium system?
- 6 Why is the FE-Fe3C phase diagram a metastable PD instead of a true equilibrium PD?
- 7 How martensite is formed in steels?
- 8 Where is martensite found in tools?
Why β phase is not appeared in the Fe Fe3C phase diagram?
The alpha iron which exist between 768 to 910 o C is paramagnetic in nature is called beta iron, just it is non magnetic in nature while iron- iron carbide is drawn for temp v/s wt \% carbon so no need to show magnetic nature of aplha iron.
Which is the hardest structure that appears on iron-carbon equilibrium diagram?
Detailed Solution Cementite or Iron Carbide has the chemical formula Fe3C and contains 6.67\% carbon by weight. It is the hardest structure that appears in the iron-carbon equilibrium diagram. Cementite has an orthorhombic crystal structure and is extremely hard and brittle as compared to austenite and ferrite.
Why iron iron carbide equilibrium diagram is not a true equilibrium diagram?
It may be noted that though it is called as equilibrium diagram, it is not a true equilibrium diagram, since equilibrium implies no change of phase with time. In fact, the compound iron carbide decomposes into iron and carbon (graphite).
What is a martensite microstructure?
Martensite was originally named for a very hard, very brittle phase of steel that has needle-shaped microstructural features, with a microstructure being the arrangement of the phases on the microscopic scale. In steel, martensite forms due to the very fast cooling of a high-temperature phase called austenite.
What microstructure does martensite have?
Why iron carbon diagram is called equilibrium diagram?
The iron carbide is called meta stable phase. Therefore, iron-iron carbide diagram even though technically represents meta stable conditions, can be considered as representing equilibrium changes, under conditions of relatively slow heating and cooling.
Why Fe-Fe3C system is not called as a perfectly equilibrium system?
All Answers (3) Fe-Fe3C is not considered an equilibrium phase diagram, because Fe3C is behaving metastable in iron. On the other hand, cementite or iron carbide (Fe3C) has 6.67\% carbon and is metastable, but its decomposition into graphite is so slow that in practice it can be considered a stable phase.
Why is the FE-Fe3C phase diagram a metastable PD instead of a true equilibrium PD?
Fe-Fe3C phase diagram is not a true equilibrium phase diagram because of un- stability of iron carbide (Fe3C) compound. Under certain conditions Fe3C will decompose into more stable phases of iron and graphite.
Why is martensite not shown in the equilibrium phase diagram?
Martensite is not shown in the equilibrium phase diagram of the iron-carbon system because it is not an equilibrium phase. Equilibrium phases form by slow cooling rates allowing sufficient time for diffusion, whereas martensite is usually formed by fast cooling rates.
How martensite is formed in steels?
Martensite is formed in steels when the cooling rate from austenite is sufficiently fast. It is a very hard constituent, due to the carbon which is trapped in solid solution.
Where is martensite found in tools?
Martensite commonly is found in tools such as hammers and chisels and in swords. The martensite is formed by rapid cooling (quenching) of austenite which traps carbon atoms that do not have time to diffuse out of the crystal structure.
What are the different phases of iron carbon equilibrium diagram?
Various phases that appear on the Iron- Carbon equilibrium phase diagram are as under: •Austenite •Ferrite •Pearlite •Cementite •Martensite •Ledeburite Definition of structures: Austeniteis an interstitial solid solution of Carbon dissolved in(F.C.C.) iron.