What is the microstructure of cementite?
Cementite (or iron carbide) is a compound of iron and carbon, more precisely an intermediate transition metal carbide with the formula Fe3C. By weight, it is 6.67% carbon and 93.3% iron. It has an orthorhombic crystal structure.
What is the microstructure of GREY cast iron?
graphite
Gray cast irons are softer with a microstructure of graphite in transformed-austenite and cementite matrix. The graphite flakes, which are rosettes in three dimensions, have a low density and hence compensate for the freezing contraction, thus giving good castings that are free from porosity.
What is the reason of law of GREY cast iron?
It has acceptable ductility, tensile strength, yield strength, and impact resistance for most applications. Grey Iron is also excellent in its ability to dampen vibrations making it ideal for machinery bases and as well as many housing applications.
Is cementite 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.
Is cementite a line compound?
Cementite has traditionally been depicted as a line compound in phase diagram calculations, but it has been shown that a thermodynamic model that permits its free energy to vary in a manner consistent with experimental data (Gohring:2016), is able to reproduce the equilibrium γ+θ/θ and α+θ/θ phase boundaries.
Is cementite a solid solution?
It is important to emphasize that, according to Baikov, cementite is a solid solution of iron and diamond, while other solid solutions in the Fe-C system are regarded as solid solutions of iron and carbon.
What is microstructure of cast iron?
Cast irons are a class of ferrous alloys with a carbon content of between 2.0 – 4.5%; they contain sufficient carbon so that the eutectic reaction occurs during solidification. Cast iron contain contrasting amount of manganese, sulphur and phosphorus. …
Why does GREY cast iron expands on cooling?
Expansion in grey iron is due to presence of free carbon(graphite). Graphite expends on cooling. Any iron which is having carbides have less expansion on cooling and maximum expansion is in case of nodular/ductile iron. Yes, gray cast iron expands upon cooling unlike most other materials which contract on cooling.
What micro scale features in gray cast iron make it brittle in tension?
Gray cast irons are comparatively weak and brittle in tension due to its microstructure; the graphite flakes have tips which serve as points of stress concentration. Strength and ductility are much higher under compression loads.
Is cementite a phase?
Cementite, a carbide phase of high hardness, has a more complicated orthorhombic crystal unit cell, with a ratio of three iron atoms to one carbon atom [4].
Is Cementite a solid solution?
What is the mixture of austenite and cementite called?
Due to the strong supercooling, a fine mixture of austenite and cementite is formed. This eutectic microstructure of finely distributed austenite and cementite is also called ledeburite-I immediately after solidification. The eutectic phase mixture of austenite and cementite immediately after solidification is called ledeburite-I!
What kind of graphite is in grey cast iron?
Gray cast iron is a broad term used for a number of cast irons whose microstructure is characterized by the presence of flake graphite in the ferrous matrix. Such castings often contain 2.5%–4% carbon, 1%–3% silicon, and some additions of manganese ranging from 0.1% to 1.2%. This is one of the most widely used alloys of iron.
How are austenite and cementite related in cast iron?
Note that on the left side of the cast iron phase diagram (at 2.06 %) the austenite phase is applied and on the right side (at 6.67 %) the cementite phase. These phases austenite and cementite are thus ultimately the components of an A/B alloy system (A ≙ “austenite”) and (B ≙ “cementite”).
What kind of microstructure is cast iron made of?
The cooled hypereutectic cast iron microstructure thus consists at room temperature of the primarily precipitated cementite strips which bed in the eutectic of ledeburit-II. The micrograph below shows a hypereutectic cast iron with 5.5 % carbon.