Julie Schoenung
Professor and Vice Chair
Dept. of Chemical Engineering & Materials Science
University of California, Davis

Tri-modal Composites: Highlighting the Role of Particle Reinforcement Length Scale on Microstructure and Mechanical Deformation Mechanisms

Location: EB1 Room 1011

Friday, April 17th 2015 - 11:00 am

The concept of a tri-modal composite brings together the two materials design strategies of metal matrix composites and bi-modal microstructures. As such these materials consist of three primary microconstituents: ultrafine grain matrix, coarse grain matrix and hard ceramic particle reinforcement. Because these materials are fabricated through the application of cryomilling and thermo-mechanical consolidation techniques, they also contain finely dispersed oxides and nitrides, as well as a substantial volume fraction of interfaces and grain boundaries. As we have continued to develop these materials, we have often had the goal of enhancing performance through controlled microstructural design. In parallel, these materials provide extensive opportunity to study fundamental phenomena within the realm of materials science and engineering.

In this presentation, I will begin with a review of the key performance characteristics that stimulated initial interest in these materials, namely extremely high strength for an aluminum-based material ( > 1000 MPa) and extreme thermal stability (at temperatures up to ninety-seven percent of the absolute melting point). I will then discuss two recent studies focused on the fundamental investigation into the effects of one degree of freedom available in these multi-attribute materials: particle reinforcement size. The first of these studies describes the application of nanoscratch characterization to explore the influence of particle reinforcement size on deformation mechanisms. The second describes an in-depth investigation into the influence of particle reinforcement size on interfacial characteristics, including particle location within the microstructure, interface chemistry and interface crystallographic orientation. Mechanisms associated with the development of these features will also be discussed.

North Carolina State University