# Article

**Keywords:**

phase transformation; interface migration; bulk diffusion; Onsager extremal thermodynamic principle

**Summary:**

Physical analysis of phase transformation of materials consisting from several (both substitutional and interstitial) components, coming from the Onsager extremal thermodynamic principle, leads, from the mathematical point of view, to a system of partial differential equations of evolution type, including certain integral term, with substantial differences in particular phases ($\alpha$, $\gamma$) and in moving interface of finite thickness ($\beta$),
in whose center the ideal liquid material behaviour can be detected. The numerical simulation of this process in MATLAB
is able to explain some phenomena (e.g. the interface velocity as a function of temperature) better than known simplified models assuming the sharp interface
and additional boundary and transfer conditions.