Displacive solid-state phase transformations from the face centered cubic (fcc) austenite phase to body centered cubic (bcc) ferrite phase play a pivotal role in the physical properties of steels and ferrous alloys. In this context, a new phase-field-crystal (PFC) type model , called Quasi-particles Approach (QA) was developed in this work, to study the atomic structure, propagation mode, and propagation kinetics of the fcc/bcc interface, during the fcc→ bcc structural phase transformation in Iron.  With this, the QA qualitatively reproduces the underlying mechanism of this class of transformations, thereby proving its potential to model displacive phase transformations. One step further, the solute-fcc/bcc interface interaction was prospected in the Fe-C binary system, offering a unique opportunity to screen the mechanism by which carbon and other solute atoms or impunities alter the propagation of the fcc/bcc interface in steel.