<p>The effect of molybdenum on the isothermal proeutectoid ferrite reaction has been studied in low to medium (.05 - .43) carbon steels containing 1% molybdenum by weight. At 600 - 700°C molybdenum additions to steel result in the production of a dark etching ferrite constituent which has been shown to be heavily dislocated. The origin and stability of this transformation induced substrctures is considered.</p> <p>In these alloys the austenite twin boundaries are sites for nucleation of ferrite. A simple model to describe nucleation on twins has been constructed and consequences for the equilibrium shape of a ferrite crystal in austenite developed. The equilibrium shape was determined experimentally and the shape is commensurate with the model developed.</p> / Thesis / Master of Engineering (ME)