Alireza Rahnama

Room temperature texturing of austenite/ferrite steel by electropulsing

The work reports an experimental observation on crystal rotation in a duplex (austenite + ferrite) steel induced by the electropulsing treatment at ambient temperature, while the temperature rising due to ohmic heating in the treatment was negligible. The results demonstrate that electric current pulses are able to dissolve the initial material’s texture that has been formed in prior thermomechanical processing and to produce an alternative texture. The results were explained in terms of the instability of an interface under perturbation during pulsed electromigation.

Modelling the Microstructure of Polycrystalline Austenite‐Martensite Steels

A method based on the kinetics of crystal growth has been developed and applied to the computation of 3D microstrucuture in polycrystaline austenite-matensite steels. The detailed crystallography of the transformation and the effect of austenite grain size on the martensite-start temperature are employed to simulate a realistic martensitic microstrucuture. The interaction energy based on the plastic work model of Patel and Cohen is taken into account to model the variant selection under external system of applied stresses. The method has been integrated to the homogeneous deformation theory for computation of microstructure evolution in thermomechanical processing.

Quantifying the pathway and predicting spontaneous emulsification during material exchange in a two phase liquid system

Kinetic restriction of a thermodynamically favourable equilibrium is a common theme in materials processing. The interfacial instability in systems where rate of material exchange is far greater than the mass transfer through respective bulk phases is of specific interest when tracking the transient interfacial area, a parameter integral to short processing times for productivity streamlining in all manufacturing where interfacial reaction occurs. This is even more pertinent in high-temperature systems for energy and cost savings. Here the quantified physical pathway of interfacial area change due to material exchange in liquid metal-molten oxide systems is presented. In addition the predicted growth regime and emulsification behaviour in relation to interfacial tension as modelled using phase-field methodology is shown. The observed in-situ emulsification behaviour links quantitatively the geometry of perturbations as a validation method for the development of simulating the phenomena. Thus a method is presented to both predict and engineer the formation of micro emulsions to a desired specification.