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Rabelani Masindi

This project investigates the influence of steckel mill deformation process parameters on the dynamic and static annealing response of AISI430 ferritic stainless steel. The final microstructure is influenced by phase transformations and annealing processes that occur during each deformation stage and inter-pass time of the multi-step hot rolling process.

During steckel mill deformation process, AISI430 ferritic stainless steel consists of two phases, austenite and ferrite. Consequently, the evolution of the microstructure is influenced by both the phase balance, as well as the imposed deformation on each phase during processing. The transformation of austenite to ferrite depends on a number of factors. These factors include: the volume fraction of austenite and ferrite at deformation temperature, the deformation conditions and the alloy composition.

The objective of this project is to determine the volume fractions of austenite and ferrite as a function of deformation temperature and strain, where the parameters are determined by those experienced in a steckel mill. The volume fraction of austenite controls strain distribution during hot deformation. The volume fraction of austenite controls the strain distribution during hot deformation, which in turn will affect the occurrence of the dynamic and static restoration mechanisms during inter-pass time. The restoration mechanisms of interest are recrystallization, recovery, phase transformation and grain growth.

Testing will be performed on the Gleeble 3800, using high temperature tensile deformation and concurrent dilatometry. The microstructure evolution will be evaluated using light microscopy, scanning electron microscopy (SEM), and the electron backscattered diffraction EBSD technique.