Magnetic Analysis of Precipitation and Coarsening of Carbides in Steels
Dispersion microstructures in C-, Cr- and Mn-alloyed steels result from the precipitation and coarsening of carbide particles from the martensitic initial condition. The changes in the microstructure were observed at aging temperatures <i>T</i>=500, 600, 650 and 700°C and for the time <i>t</i>=1 to 4290 min by measuring the coercive field strength <i>H</i><sub>C</sub>. The particle size analysis on scanning electron micrographs of M<sub>3</sub>C in the steels and of M<sub>6</sub>C (+MC) carbide particles in the case of the high-alloyed steel X80WMo6.5 yielded to a certain connection with <i>H</i><sub>C</sub>. Thus <i>H</i><sub>C</sub> can be taken as an indirect microstructural characteristic quantity insteed of directly observed microstructure data.<br>It was found that nucleation, growth and the dominating coarsening of the particles take place permanently in so-called generations. With increasing time the particle sizes in the one after another following generations become smaller because of the matrix depletion of the participated elements by precipitation. The Ostwald-ripening law is to apply separately to each generation. All the processes and relationships, which are connected with <i>H</i><sub>C</sub>, can be written mathematically.
- ISIJ international
ISIJ international 37(1), 65-73, 1997-01-15
The Iron and Steel Institute of Japan