written 8.1 years ago by | modified 2.6 years ago by |
Mumbai University > Mechanical Engineering > Sem 4 > Material Technology
Marks: 10M, 8M
Year: May 2014, Dec 2014
written 8.1 years ago by | modified 2.6 years ago by |
Mumbai University > Mechanical Engineering > Sem 4 > Material Technology
Marks: 10M, 8M
Year: May 2014, Dec 2014
written 8.1 years ago by |
Ferriteis known as α solid solution.
Austeniteis an interstitial solid solution of Carbon dissolved in (FCC) iron.
Martensite a super-saturated solid solution of carbon in ferrite.
Ledeburite is the eutectic mixture of austenite and cementite.
Cementiteor iron carbide is very hard, brittle intermetallic compound of iron & carbon, as Fe3C, contains 6.67 % C.
Pearliteis the eutectoid mixture containing 0.80 % C and is formed at 723°C on very slow cooling.
Transformations
Peritectic reaction
Liquid+Solid1↔Solid2
L(0.53wt%C)+δ(0.09wt%C)↔γ(0.17wt%C) at 1495°C
Liquid-18.18wt% +δ-ferrite 81.82 wt%→100wt% γ
Eutectic reaction
Liquid↔Solid1+Solid2
Liquid (4.3wt%C) ↔ γ(2.11wt%C) + Fe3C (6.67wt%C) at 1147˚C
Liquid-100 wt% →51.97wt% γ +Fe3C (48.11wt%)
The phase mixture of austenite and cementite formed at eutectic temperature is called ledeburite.
Eutectoid reaction
Solid1↔Solid2+Solid3
γ(0.77wt%C) ↔ α(0.0218wt%C) + Fe3C(6.67wt%C) at 727°C
γ (100 wt%) →α(89 wt% ) +Fe3C(11wt%)
Typical density
α ferrite=7.87 gcm-3
Fe3C=7.7 gcm-3
Volume ratio of α- ferrite: Fe3C=7.9:1