TABLE OF CONTENTS Modelling can be simply defined as the representation of a physical entity or a process by another physical or conceptual entity or a process with a view to obtain greater insights into the behaviour of the subject. Models developed for complex processes cannot be expected to be absolutely precise. Rather, they are intended to identify important parameters, define the functional dependence of the process output on process variables and predict results with an acceptable level of precision. One useful result of such process modelling is a considerable reduction in the empirical studies needed to refine a process into a useful engineering tool.
Some aspects regarding what is occurring during the MA process have been known qualitatively for some time, but the description of the MA process is complex and manifested as it involves concepts of mechanics, mechanical behaviour, heat flow, thermodynamics and kinetics. In spite of this, modelling of MA has been an avenue of recent interest for further understanding.
Though the models for MA are in the early stage of development, various physical/theoretical models developed can be subdivided into mechanistic, atomistic, thermodynamic and kinetic. Mechanistic models deal with powder deformation, coalescence and fracturing, and ball dynamics in a milling device. Atomistic models permit a deeper insight into the physics of non-equilibrium phase formation using the CALPHAD method of thermodynamics data fitting and phase diagram calculations. Kinetic models consider the competitive diffusion-controlled growth kinetics of crystalline phase [1]. In the following section, these are discussed in brief.
