Abstract: Phase transformations in metals have a major influence on the material behavior in several common engineering applications. Steels exhibiting enhanced response to transformation-induced plasticity (e. g. high strength TRIP-steels for automotive production) are examples of the important role martensite formation can play. An externally stressed specimen in the process of a phase transformation may show a significant nonlinear behavior, which is known as transformation plasticity. Even under an externally applied load stress with the corresponding equivalent stress being small in relation to the “normal” yield stress of the material, plastic deformation occurs. The aim of the work was to determine the influence of external compression and tension stress on the transformation plasticity and evolution of microstructure of alloyed steel during quenching. Tool steel grades were tested. All steel grades differ in carbon content and amount of alloying elements and behave differently when transformation plasticity occurs. This phenomenon was observed during bending test when bending stress was 100 MPa and was less than 10 % of yield strength of the steel. The steel specimens were heated to 860-1100 °C temperature and then bent during air or oil quenching at a special bending device. Plastic deflections were observed over all cooling process that involved martensitic transformation as well. It was determined that chemical composition of steel had influence on transformation plasticity of steel. The steel with solid solution saturated with the biggest content of dissolved carbon and alloying elements presented the highest transformation plasticity.
Authors: Rasa Kandrotaite Janutiene, Arunas Baltusnikas, and Darius Mazeika
Keywords: Steel, Heat treatment, Transformation plasticity, Stress, Deformation