Calculation of the energy and migration characteristics of carbon in martensite

Abstract

A model previously used for the calculation of the energy and migration characteristics of carbon in α-iron has been extended to simulate martensite. Iron atoms near a carbon interstitial are treated as individual particles interacting with a nearest and next-nearest neighbor two-body central force, and the remainder of the lattice is treated as an elastic continuum. A two-body central force is also used for the carbon-iron interaction. Computer experiments are performed by inserting a carbon atom into a perfect body-centered tetragonal lattice of iron atoms with the lattice parameters adjusted for a given carbon concentration. The carbon migration energy was found to increase with carbon concentration, e.g. from 0.86 eV in α-iron to 1.00 eV for motion in the plane perpendicular to c axis and 1.09 eV for motion parallel to the c axis for 1 wt. % carbon in martensite. The di-carbon binding energy shows a little change and the carbon-vacancy binding energy decreases with increasing carbon concentration, and no carbon reorientation internal friction peak is predicted by this model for martensite.