Effect of morphology of carbide and nitride precipitates on the elongationof Fe-30 mass%Cr alloys

Effect of morphology of carbide and nitride precipitates on the elongation of Fe-30 mass%Cr alloys containing 0.026%C and 0.033%N was investigated. Th ree kinds of heat treatment process were adopted to obtain different types of the morphology of carbide and nitride precipitates, namely grain boundar y carbide and nitride precipitates, coarse globular carbide particles (5 mu m) within the grains, and fine spheroidal carbide and nitride particles (l ess than or equal to 0.5 mu m) within the grains. Tensile tests were carrie d out at temperatures ranging from 4.2 K to room temperature. The grain bou ndary carbide and nitride precipitates cause more remarkable decreases in t he elongation than the carbide and nitride particles within the grains. Fin e spheroidal carbide and nitride particles within the gains keep ductile-br ittle transition temperature of the elongation lower than the coarse globul ar carbide particles within the grains. The flat plate-like continuous grai n boundary nitride enhances intergranular fracture more than the discontinu ous grain boundary carbide. Initiation of microcracks for brittle fracture is promoted by intergranular fracture of decohesion at the interfaces betwe en the matrix and grain boundary precipitates.