Steel has been present in the human history for nearly 4000 years and it has been industrially produced for nearly 170 years. Still there are many challenges in understanding the steel behavior in a lot of aspects. For instance the plastic deformation of steels is still not entirely understood, although it has been actively researched since 1934. The industry uses the phenomenon of plastic deformation when they are producing thin sheets by rolling, cutting them by shearing, forming them by pressing, forging them with hammer etc. However, the underlying mechanisms are still not thoroughly understood.

 


Slip lines caused on the surface of an austenitic stainless steel sample by a Vickers indenter. One can observe a beautiful annealing twin (marked with arrow) decorated with slip lines.

The deformation of austenitic stainless steels can be quite interesting and diverse. There are a plenty of phenomena such as dislocations, deformation-, and annealing twins and stacking faults that can influence the deformation behavior of these materials. Despite the fact that these pehnomena are well known, their global effect on each other and thus on the deformation mechanisms are not completely understood. In order to grasp the essence of the mechanisms within the material it is important to do different kind of experiments and set up good models. For example, by fine-tuning the microstructure and composition, these mechanisms can be controlled and defined very well. An important parameter, the stacking fault energy plays a crucial role by influencing the deformation behavior by restricting the possibility of the deformation twinning and cross-slip.  So, attaining the stacking fault energy by experimental work and theoretical ab initio calculation can help us to give a more clear explanation on the deformation processes within the austenitic stainless steel and construct a reasonable model that can predict the behavior of these materials. The aim of my work is to join together the experimental and theoretical work in order to give a better picture of the underlying deformation mechanisms.