MSE Colloquium: Farangis Ram, Microstructural Mechanisms: Avoiding the Red Herrings

Abstract

A load-bearing part in a car, a ship, a wind or gas turbine, or a bridge is almost never less than a few millimeters in any dimensions. Nonetheless, the fact remains that irrespective of the size, structural properties are controlled by the microstructure. Hence, examining and modelling the microstructural phenomena have become an essential part of design. Materials with superior mechanical properties have microstructures that are highly heterogeneous. They are usually polycrystalline, multi-phase, and comes with inherited heterogeneously distributed crystalline defects. There are special grain boundaries, random grain boundaries, coherent phase boundaries, large precipitates, small precipitates, special boundaries that run into small precipitates, phase boundaries that are decorated by twins, small boundaries in cube oriented grains, the same boundaries in an equiaxed cube oriented grain that is encircled by elongated Goss oriented grains and many more. Thus, to understand the properties of the bulk: we must examine the entire landscape of the microstructure; we must not change the boundary conditions when sampling; we must be statistically relevant; and we must know the errors of our analysis methods. With these principles in mind, I will present: (1) revisiting the origin of creep dislocation in Ni-base superalloys; (2) a few case studies of highly-deformed materials; and (3) the theory and realization of automated mapping of the type and density of statistically stored dislocations using electron backscatter diffraction applied to a low-cycle fatigued TRIP steel.

Bio

Farangis Ram is a postdoctoral research associate at the Department of Materials Science and Engineering at Carnegie Mellon University. The focus of her work is studying the microstructural phenomena of highly deformed materials. She Received a B.Sc. (in 2005) in metallurgical engineering and a M.Sc. (in 2008) in materials design and selection, both from Sharif University of Technology, Tehran, Iran. In the year following her graduation, she worked in the petrochemical industry. In 2009, she won the Erasmus Mundus Grant, Partnership Agreement: 2007-‎‎0076/001 FRAME MUNB123, and embarked on a journey to Europe for a master’s program titled “Materials Science Exploiting Large Scale Facilities”. She studied at the University of Turin, Italy, for six months and worked at Ludwig-Maximilian University of Munich for six months. At the end of the year 2009, she started working at the Max-Planck Institute for Iron Research GmbH (MPIE) in Düsseldorf, Germany, while working towards her Ph.D., which she received from RWTH Aachen, Germany, in 2015.