Date: Thursday, Feb 11th
Presenter: Dr. Mostafa Saber, Portland State University
Exceptional properties of nanocrystalline materials have been a focus of many studies in recent decades. These properties are essentially attributed to the nano-scale grain size of these materials. Severe plastic deformation (SPD) techniques such as high-energy ball milling of particulate materials are capable of providing such nano-scale microstructure. Under high-temperature conditions, large volume density of grain boundary within the microstructure provides a significant driving force for returning to a more stable state. This causes a drastic grain growth to a micron-scale known as conventional microstructure. There are two mechanisms, so called kinetic and thermodynamic mechanisms, with which thermal stabilization of nano-scale grains can be achieved. The former mechanism reduces mobility of the grain boundaries whereas the latter eliminates the driving force for grain growth. This presentation provides key-points in the high-energy mechanical alloying process as a unique approach to be industrialized for large-scale production of nanocrystalline alloys, along with strategies to design new nanocrystalline alloys stable at elevated temperatures and maintaining remarkable mechanical properties.