| A variety of thermo mechanical processes are commonly used to produce alloys and control their microstructures, and the length scale. In the present thesis, two approaches were chosen to develop new microstructures or engineer steels.; The first approach consisted in utilizing rapid heat treatment methods such as immersion in a salt bath, capacitance discharge, and pulsed lasers, to develop new microstructures in several systems, or control the length scale of the microstructure and/or its spatial distribution. Examples are given in the case of dual phase steels, duplex grain size alloys, and in grain boundary engineering.; Rapid heat treatment methods were also used to investigate the "nucleation" event for recrystallization in Fe and Cu. In this case, it was shown that "nucleation" occurred mainly near multiple junction at the early stages of the annealing process. A model for recrystallization was implemented to take into account the heterogeneous nature of the "nucleation" event.; A second approach relied on conventional carburization and decarburization processes, in order to develop Compositionally Graded steels. This work was based on the Fe-C and Fe-Mn-C systems, and it was shown that a significant improvement of the mechanical properties of the steels was achieved. |
