The thermodynamical effect of third alloying elements on cementite precipitation in tempered martensite

摘要

Third alloying elements are frequently used to retard cementite (theta) growth during tempering of martensite. However, the effect of those elements on the growth kinetics of theta is not well understood. In the present study, focusing on the third elements that are partitioned between ferrite and 8 without forming alloy carbide, we aim to (1) estimate the thermodynamical stability of the alloy cementite (M_3C) by first principle calculation, (2) examine the phase diagram considering para equilibrium, partition and negligible partition local equilibrium (PARA, PLE and NPLE respectively) and (3) reveal the partitioning behavior of the third alloying elements and their effects on the precipitation of 8 during tempering of the martensite in Fe-0.6 mass percent C-M alloys.