1. Complete Calculation of Steel Microstructure for Strong Alloys J. Chen, H. K. D. H. Bhadeshia, University of Cambridge S. Hasler, H. Roelofs, U. Ulrau, Swiss Steel AG

2. Outline of presentation Introduction Mechanism of the program Predictions Conclusions

3. Introduction Metallographic microstructures Metallurgical analysis Chemical composition Heat treatment Initial designModelling Alloy Design Cycle Modelling

4. Mechanism of the program

5. C, Si, Mn, Ni, Mo, Cr, V Austenite grain size Heat treatment method Calculate various driving forces Calculate nucleation rates and growth rates of individual phases Call subroutine that calculates transformation kinetics Print out microstructures INPUTS OUTPUTS PROGRAM INPUT 

6. Avrami Method Time = t Time = t +  t

7. parallel plane grain boundary

8. I+1 I Time I+2 Growth Mechanism: Allotrimorphic ferrite, Widmanstätten ferrite, Pearlite

9. sub-unit sheaf t1t1 t2t2 t3t3 t4t4 time The physical metallurgy of bainite kinetics (Bhadeshia, Proc. R. Soc. Lond. A, 2004, 460, 1707-1722) Bainite Growth Mechanism

10. time Nucleation interval  t i+n i Incubation time  = f(T,  G m ) function of temperature and maximum Gibbs energy of forming nucleus

11. I+1 Grain boundary Nucleation time I time I I+1 1 1 Grain boundary Nucleation time

12. Predictions

13. Bhadeshia, H. K. D. H. 1982 Bainite: overall transformation kinetics. J. Phys. Paris C 43 (Colloq. C4), 443-448. CSiMnNiMoCrVGS 0.441.740.671.850.830.390.0986 µm

15. Carbon Steel 1566 - C 0.64, Mn 1.13 Atlas of isothermal transformation and cooling transformation diagrams. American society for metals. 1977

16. 620 o C

17. 600 o C

18. 570 o C

19. 390 o C

20. 380 o C

21. Conclusions Complete information of microstructure Diverse calculations (cc,iso,TTT,CCT..) Reasonable accuracy Transferable to other applications

22. Gracias !