THE CONTRIBUTION OF DISLOCATION - IMPURITIES INTERACTION TO KINETICS OF MARTENSITIC-TRANSFORMATION OF QUENCHED FCC FE-NI-MO ALLOYS

The kinetics of martensitic transformation in austenitic Fe-Ni-Mo allo ys depends on the carbon content. Analysis of carbon redistribution be tween f.c.c. solid solution and dislocation has been carried out with the help of internal friction (amplitude and temperature effects) stud y and stress relaxation tests. The martensitic transformation was prov ed by magnetic induction and thermal differential analyses. The increa se of carbon content in quenched austenitic alloys leads to the satura tion of dislocation atmospheres and to the supersaturation of f.c.c. s olid solution. The type of martensitic transformation (athermal or iso thermal) kinetics depends on different relaxation resistance of austen ite which is controlled by different dislocation pinning degree. The s trong correlation between the degree of dislocation pinning, the type of martensitic transformation and the: stress relaxation effect allows to make the conclusion that the dislocation mobility plays an importa nt role in the nucleation and formation of the low temperature structu re of Fe-Ni-Mo alloys.