ACTIVATION OF PHASE TRANSFORMATIONS ACTIVATION POWER AT STEEL MARTENSITE DECAY Russian patent published in 2016 - IPC G01N25/02 C21D1/78 

FIELD: metallurgy.

SUBSTANCE: claimed process exploits the determination of activation energy of the formation of nuclei of new ferrite and cementite phases and that of activation of their growth to determine the phase transformation activation energy. Steel specimens are quenched and tempered at different temperatures. The number N of microstructural structures formed at martensite decay and mean grain area S_mean defining the temperature coefficient α_r of the grain mean diameter increase are defined by the formula: $${\alpha }_r=\frac{{\Delta }_{mean}}{Т},$$ where $${\Delta }_{mean}=\sqrt{S_{mean}},$$ T is the tempering temperature, °C. Then, the graph of natural logarithm of the number N of microstructural structures is plotted as the function of inverse product of Boltzmann constant and RT temperature in the form of the straight line and to define activation energy of the ferrite and martensite phases formation by the tangent of the straight line inclination. Then, the graph of natural logarithm of said temperature factor α_r of the grain mean diameter as the function of inverse product of Boltzmann constant and RT temperature in the form of the straight line is plotted to define activation energy of the ferrite and martensite phases formation by the tangent of the straight line inclination. The activation energy of phase transformations at the martensite decay in steel is defined as the sum of activation energies of the ferrite and cementite phase nuclei formation and the activation energy of growth of said nuclei.

EFFECT: higher accuracy of determination, possibility of determination of activation energy fraction.

7 dwg, 1 tbl