The lower temperature boundary of the onset of the formation of α-martensite upon cooling in iron-based alloys

Abstract

The concept of the leading role of the subsystem of 3d electrons in changing the stabilities of the γ (fcc) and α (bcc) phases is used to conclude that the stability of the α phase having a smaller thermal expansion coefficient β increases as the temperature decreases. It is suggested to find the smallest possible temperature Ms(min) of the onset of spontaneous γ-α martensite transformation in iron-based alloys from the condition of the equality between the volume of the γ-phase unit cell and the quantity specified by the effective atomic radii of alloy components given in the generalized Periodic Table. The calculated Ms(min) values are shown to agree with the experimental data for pure iron and Fe-Ni and Fe-C alloys.