Seminar, June 19 th, 10:00 am
Using high-pressure torsion for metal processing: fundamentals and applications
A. P. Zhilyaev
Centro Nacional de Investigaciones Metalúrgicas, CSIC, 28040 Madrid, Spain and Institute for Metals Superplasticity Problems, RAS, 450001 Ufa, Russia
High-pressure torsion (HPT) refers to the processing of metals whereby samples are subjected to a compressive force and concurrent torsional straining. Although the fundamental principles of this procedure were first proposed more than sixty years ago, processing by HPT became of major importance only within the last twenty years when it was recognized that this metal forming process provides an opportunity for achieving exceptional grain refinement, often to the nanometer level, and exceptionally high strength. This presentation summarizes the background and basic principles of processing by HPT and then outlines the most significant recent developments reported for materials processed by HPT. It is demonstrated that HPT processing leads to an excellent value for the strength of the material, reasonable microstructural homogeneity if the processing is continued through a sufficient number of torsional revolutions and there is a potential for achieving a capability for various attractive features including superplastic forming and hydrogen storage. The review also describes very recent developments including the application of HPT processing to bulk and ring samples and the use of HPT for the consolidation of powders.
Seminar, June 23 rd, 10:00 am
Atomic-level computer modelling of FeCr alloys for nuclear applications
L. Malerba
Studiecentrum voor kernenergie • Centre d’études de l’énergie nucléaire. Boeretang 200 – B-2400 Mol (Belgium)
In this seminar I provide an overview of the work performed to model at the atomic-level the behaviour under irradiation of FeCr alloys, model materials for high-Cr ferritic/martensitic steels of use in almost all future nuclear energy options, from fusion to GenIV reactors and accelerator-driven systems. The problems to be addressed according to experimental data and the currently existing knowledge about the FeCr system from ab initio calculations are presented, showing how the latter provide keys for the interpretation of the former. The effort made in recent years to produce cohesive models for large scale simulations in these alloys is reviewed, showing achievements and limitations of the followed approaches and discussing ways of improvement. Examples of the application of these cohesive models for atomic-level simulations, in view of further understanding the fundamental mechanisms of radiation damage production and evolution and of developing coarse-grained models of microstructure evolution under irradiation and radiation-induced hardening models, are provided. The difficulties to be faced in order to succeed along this research path are discussed.
Seminar, June 24 th, 10:00 am
Some Issues on Toughening, Scratch Damage, and Fire Retardancy/Thermal Stability in Polymer Nanocomposites
A. Dasari
Center for Advanced Materials Technology (CAMT) School of Aerospace, Mechanical & Mechatronic Engineering The University of Sydney, Sydney, NSW 2006, Australia
It is well-known that materials can show significantly improved properties if they possess multi-component phase separated morphology at the nanoscale. Polymer nanocomposites are a good example of this class of nanostructured materials that provide unique combinations of mechanical, physical, optical and thermal properties at relatively low filler loading compared to traditional micro-composites. This is due to (a) the exceptionally large surface area-to-volume ratio of the nano-additives available for interaction with the polymer matrix; (b) nanoscale arrangement and presence of large number of reinforcements; and (c) the confinement of polymer matrix chains at the nano-level. These fundamental characteristics of the nano-reinforcements, if fully exploited, will affect the microstructure, crystallinity, glass transition and degradation temperatures, and other inherent properties of the resulting nanocomposites, which in turn enable enhanced multi-functional properties to be achieved. However, there are still many unanswered and critical issues to be addressed, particularly in polymer/clay nanocomposites, which have wide applications. Some of these include embrittlement, thermal stability/flame retardancy, tribological response of the resultant nanocomposites, which will require in-depth understanding and rigorous theoretical/numerical analyses. I will address these issues in more detail and outline some of our recent developments and achievements in these issues at the CAMT, University of Sydney.
