Tuesday, October 10, 2017 | 8:00 – 10:30 a.m.
AIST Adolf Martens Memorial Steel Lecture
Mechanical Twinning in Formable Advanced Ultra-high Strength Steel
Iron alloys and steels have impressive plasticity-enhancing potential that is often not exploited in engineering applications, as it requires a thorough understanding of the underlying mechanisms and their activation during straining. This requires a steel design approach incorporating a selection of composition, microstructure, and processing parameters based on sound theoretical principles. Most formable ferritic steels exhibit a uniform engineering elongation less than 25% and a relatively low ultimate tensile strength (<1GPa). The formability of these steels is based on the control of their crystallographic texture, rather than the strain hardening. As a consequence, a higher strength is usually achieved at the cost of ductility. There is a way to outsmart this dichotomous conflict of properties, though: by designing fully austenitic steels or austenite-containing multi-phase steels with an enhanced strain hardening rate, both high strength and good formability can be achieved. Transformation-induced plasticity (TRIP) steel, twinning-induced plasticity (TWIP) steel and medium Mn steel belong to this category of ferrous alloys. They are characterized by a high strain hardening, a large uniform elongation and high ultimate tensile strength levels. These properties make them candidate lightweighting materials for large-scale use in the automotive industry, LNG-shipbuilding, oil-and-gas exploration and structural applications. The lecture will focus on the progress made in the understanding of deformation twinning in TWIP steel and medium Mn steel. The experimental analysis of the properties of these steels has profited from the use of advanced techniques for microstructural characterization of materials, such as synchrotron X-ray diffraction, electron backscattering diffraction, 3D atom probe tomography, and micro-mechancial testing methods (nano-hardness, micro-pillar testing). A more sophisticated analysis of the results of standard macroscopic mechanical tests involving the strain rate and temperature dependence of the mechanical properties has also contributed to a better understanding of the mechanisms underlying the strength and plasticity of these steels.
Alexander H. King, Director of the Critical Materials Institute, a U.S. Department of Energy (DOE) Energy Innovation Hub at Ames Laboratory
What Do We Need and How Will We Get It?
The global economy will be transformed over the next decade or so. The ranks of the world’s wealthy and middle classes will swell from today’s 1.9 billion to about 5.2 billion by 2030, and all of those extra consumers will demand goods and energy, among other resources, that will impact the supplies of many materials. We examine some natural, technological, social and political trends that will affect the demand and supply of materials. We discuss the options for meeting the materials needs in a rapidly changing world, and identify some emerging challenges and research opportunities. Finally, drawing on some specific success stories, we will describe approaches to doing research that may increase the likelihood of having an impact.
Steven J. Zinkle, UTK/ORNL Governor’s Chair
Department of Nuclear Engineering and Department of Materials Science and Engineering; University of Tennessee, Knoxville
What’s New in Nuclear Reactors?
In the nearly 75 years since the first human-controlled sustained nuclear reaction was achieved on Dec. 2, 1942, at Stagg field in Chicago, nuclear power has grown to produce approximately 20% of the annual electricity consumed in the United States and about 13% of worldwide electricity. The vast majority of current nuclear power reactors are based on light water reactor technology originally developed in the 1950s. Numerous new nuclear reactor concepts with significant improvements in performance, safety, and economics have been proposed and/or deployed over the past 15 years. These concepts include so-called Generation III light water reactors with improved passive safety, small modular reactors with inherent passive safety that have the potential to be largely factory built and transported via rail or heavy duty trucks to the reactor site for final assembly; accident tolerant fuels that have the potential to increase coping time and reduce the consequences of a loss of coolant accident in existing light water reactors; and Generation IV reactors with improved thermodynamic efficiency, safety, and reduced waste. In nearly all of these emerging new concepts, utilization of high-performance materials are key for achieving their full potential. The potential role of SiC/SiC composites and other high-performance materials in new and retooled nuclear power reactors will be discussed.