Influence of carbide formation in tempering on steel martensite decomposition and plasticity

Relationship is studied between the carbide transformations and the properties (electric resistance, coercive force, hardness, strength and plasticity in twisting) of 45, U10, 6Kh2, 10N6 steels after tempering at temperatures between 200 and 600 deg C. It is shown that there are sharp drops in electric resistivity and dips (or plateaus) of plasticity in the temperature ranges of intensive decomposition of intermediate carbides (epsilon-Fe2C and chi-Fe5C2). The carbon content of martensite in metastable martensite-epsilon-carbide and martensite-chi-carbide equilibria is 0.23 and 0.08-0.09 %, respectively. The correlation between the carbide transformations, physical and mechanical properties is common for all the steels investigated. A mechanism is suggested for describing the above phenomena