Muhammad Umair Bukhari   Engr.umair.bukhari@gmail.com      www.bzuiam.webs.com         03136050151
 T-T-T diagram is plotted for different  length of times and temperature These curves gives us the information of  trans...
 The  left side of C-  shape curve is  Austenitic region The right side of C-  shape curve contain  three regions   • Pe...
 The left line of C-shape  curve shows the start of  phase transformation The right line shows the  end of transformatio...
The region below Ms is martensitic regionMs shows start and Mf shows end of Martensite transformation
 Martensitic   crystal structure is Body  centered tetragonal (BCT) It is the intermediate structure of Fcc and  Bcc It...
 Atoms   arrange themselves to move  towards stability from higher  temperature to lower temperature Only realignment is...
 Due  to the realignment of atoms the lattice smmetry is different from the parent phase
 At 300oc the bainite and  martensite are formed  along curve 3 As temperature  decreases the bainite  formation rate is...
 Mf line which shows  the end of martensite  transformation But 100% martensite  can’t be formed even  theoretically at ...
 The  reason is the retained  autenite As the little amount of  austanite is remain it is  difficult to transform That’...
•Regular  arrangements of atoms in acrystal is called order.•Order of atoms in crystals are mostlyat room temperature
 Irregular  arrangements of atoms in a  crystal is called disorder . Disorder mostly occurs at elevated  temperature.
 In  most substitutional solid solutions two kinds  of atoms A and B are arranged more or less  random on the atomic site...
 The  gold and copper atoms of AuCu3 above a  critical temperature of about 390’C are  arranged more or less random on th...
 When  the periodic arrangement of A and B atoms persists over longer range distance in a crystal than it is called a lon...
Ttt diagram of eutectoid steel and martensitic transformation
Ttt diagram of eutectoid steel and martensitic transformation
Ttt diagram of eutectoid steel and martensitic transformation
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Ttt diagram of eutectoid steel and martensitic transformation

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Ttt diagram of eutectoid steel and martensitic transformation

  1. 1. Muhammad Umair Bukhari Engr.umair.bukhari@gmail.com www.bzuiam.webs.com 03136050151
  2. 2.  T-T-T diagram is plotted for different length of times and temperature These curves gives us the information of transformation for different phases With the help of T-T-T diagram we can control the phase transformation by changing the conditions
  3. 3.  The left side of C- shape curve is Austenitic region The right side of C- shape curve contain three regions • Pearlite • Pearlite+Bainite • Bainite
  4. 4.  The left line of C-shape curve shows the start of phase transformation The right line shows the end of transformation The dotted line is theoretically determined line shows 50% transformation
  5. 5. The region below Ms is martensitic regionMs shows start and Mf shows end of Martensite transformation
  6. 6.  Martensitic crystal structure is Body centered tetragonal (BCT) It is the intermediate structure of Fcc and Bcc It forms due to the realignment of atoms from austenitic structure to martensitic structure
  7. 7.  Atoms arrange themselves to move towards stability from higher temperature to lower temperature Only realignment is occur but there is no diffusion There is no concentration change in parent and product phase
  8. 8.  Due to the realignment of atoms the lattice smmetry is different from the parent phase
  9. 9.  At 300oc the bainite and martensite are formed along curve 3 As temperature decreases the bainite formation rate is lowers At 160oC for 20min the 50% martensite and austenite are formed
  10. 10.  Mf line which shows the end of martensite transformation But 100% martensite can’t be formed even theoretically at absolute zero At room temperature there is 3% retaine austenite
  11. 11.  The reason is the retained autenite As the little amount of austanite is remain it is difficult to transform That’s why Mf lline is showed dotted
  12. 12. •Regular arrangements of atoms in acrystal is called order.•Order of atoms in crystals are mostlyat room temperature
  13. 13.  Irregular arrangements of atoms in a crystal is called disorder . Disorder mostly occurs at elevated temperature.
  14. 14.  In most substitutional solid solutions two kinds of atoms A and B are arranged more or less random on the atomic sites of the lattice. In solution of this type of a change in temperature is to Increase or decrease of a thermal vibrations. If the ordered solution is heated above Tc the atomic arrangement becomes more or less random again and the solution is said to be disordered.
  15. 15.  The gold and copper atoms of AuCu3 above a critical temperature of about 390’C are arranged more or less random on the atomistic sites of FCC lattice as shown in following figure. Below the critical temperature the gold atoms in a perfectly ordered alloy occupy only the corner position of the unit cube and the copper atoms on the face centered cubic as shown in following figure.
  16. 16.  When the periodic arrangement of A and B atoms persists over longer range distance in a crystal than it is called a long range order.
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