Intercrystalline Martensite Embrittlement of a Model Fe-Ni-C Alloy Caused by Segregation and Precipitation Processes in Austenite.

It has been founc that martensite embrittlement of a model Fe-Ni-C alloy after annealing of austenite at 600 degree C for 1 hour is caused by segregation and precipitation processes which take place during heat treatment of the alloy. The presence of complex Fe-based intermetallic phases with Ni, Si, and Mn has been demonstrated. The precipitation of these particles at the boundaries of austenite grains causes a lower cohesion strength of the boundaries which is a dominant factor determining the character of failure in the range from minus 196 degree C to plus 100 degree C. The aging processes in martensite in the range from 20-100 degree C result in lowering the relaxation capacity of the martensitic matrix which contributes to an even more pronounced martensite embrittlement.