Progress towards Understanding the Synthesis and Behavior of Metals Far from Equilibrium: A SMD Symposium Honoring Enrique Lavernia on the Occasion of His 60th Birthday: Overview and Nanostructured Metals I
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Composite Materials Committee
Program Organizers: Haiming Wen, Missouri University of Science and Technology; Suveen Mathaudhu, Colorado School of Mines; Yuntian Zhu, City University of Hong Kong; Manoj Gupta, National University of Singapore; Kaka Ma, Colorado State University; Troy Topping, California State University Sacramento; Yizhang Zhou, University of California, Irvine; Joshua Yee, Sandia National Laboratories; Dalong Zhang, Pacific Northwest National Laboratory; Yaojun Lin, Wuhan University of Technology; Fei Chen, Wuhan University of Technology
Monday 8:00 AM
February 24, 2020
Room: 31B
Location: San Diego Convention Ctr
Session Chair: Haiming Wen, Missouri University of Science and Technology
8:00 AM Introductory Comments
8:10 AM Invited
Enrique J. Lavernia – A Retrospective View of his Accomplishments and Contributions: Diran Apelian1; 1Worcester Polytechnic Institute
Much will be presented and discussed at this Honorary Symposium on the special occasion of Professor Lavernia’s 60th birthyear. Many presentations will be made on powder processing, nanostructured materials, cryogenic processing of materials, spray deposition, and additive manufacturing of functional materials. A person’s contributions and accomplishments are influenced by many factors, including colleagues, and the opportunities that arise. However, none influences more a person’s work than their character and their persona. Context of Enrique Lavernia’s early years that established a work ethic and a drive for impactful work will be presented and set the stage for the presentations that follow.
8:40 AM Invited
"10": Guillermo Aguilar1; 1University of California, Riverside
While Prof. Lavernia is well known for his extensive work on thermal sprays, spray forming, and alloy spray atomization, there is a small fraction of his prolific research portfolio that encompasses studies in cryogenic spray atomization and its applications in laser dermatology. I am forever thankful for the opportunity he gave me to work with him on this new venture, and I was honored to contribute to that new research thrust for both of us during my time at UCI (1999-2003). In that four-year span, we co-authored ten publications, eight of them relative to cryogenic spray characterization and its cooling potential to prevent epidermal thermal damage in dermatologic laser therapy, and two more in another novel application of cryogenic sprays for laser reshaping of nasal cartilage. My talk will entail highlights of those studies, along with a recount of the impact they had and continue to have until this day.
9:10 AM
Microstructurally Stable Nanocrystalline Mg Alloys: Suveen Mathaudhu1; 1University of California, Riverside
Compared to fcc and bcc alloys, nanocrystalline hcp Mg has not been fully investigated due to preconceived notions of thermal stability against grain growth, the possibility of improvement of concurrent mechanical properties, and competing deformation mechanisms. This lecture will highlight collaborative efforts with Prof. Lavernia to process nanocrystalline Mg and Mg alloys with enhanced mechanical response. In addition, new insights into processing effects and emerging understandings of deformation in these systems will be explored. Lastly, anecdotes of EJ Lavernia as a colleague, friend and mentor will highlight his tremendous impact beyond scientific and technological contributions.
9:30 AM
Hetero-deformation Induced (HDI) Hardening in Heterostructured Materials: Yuntian Zhu1; Xiaolei Wu2; 1North Carolina State University; 2Institute of Mechanics
Heterostructured materials have been reported as a new class of materials with superior mechanical properties, which is attributed to the mechanical incompatibility. During their tensile testing, the soft domains will start plastic deformation with geometrically necessary dislocations piled up against the boundary with the hard domains. This produces back stress in the soft domains to make them appear stronger, while the stress concentration at the domain boundary exerts forward stress to the hard domain, making hard domain appear weaker. The combination of the back stress and forward stress represents hetero-deformation induced (HDI) stress to enhances the yield stress of the heterostructured material. The HDI stress also produces extra strain hardening to improve ductility. The “back stress” reported in the literature should be more accurately redefined ac the HDI stress. In this presentation, I’ll analyze the evolution of back stress and forward stress and raises issues for future study.
9:50 AM Break
10:10 AM Invited
Processing Pathways to Stabilized Nanocrystalline Structures: Christopher Schuh1; 1Massachusetts Institute of Technology
There are now many examples—both in the scientific literature and deployed in engineering products—in which grain boundary segregation has been used to stabilize a nanocrystalline structure. Such stabilization is necessary for the long-term use of nanocrystalline metals, and it opens interesting questions in processing science as well. Most notably, grain boundary segregation competes energetically with bulk second phase formation, so processing pathways that are sufficiently far from equilibrium to avoid bulk phases are often desirable. However, processes that are very far from equilibrium often also suppress grain boundary segregation, which is counter to the goal of stabilizing the nanostructure. In some cases subsequent thermal treatments can evoke the grain boundary segregated state in a nanocrystalline material. In every case the balance between “driven” or “ballistic” driving forces (those that drive away from equilibrium) with diffusional processes (that favor equilibrium) is a pivotal issue. This talk will review the interplay of alloying effects, grain boundary segregation, and non-equilibrium processing in the fabrication of nanocrystalline materials.
10:40 AM Invited
Using High-pressure Torsion for the Processing of Ultra-strong Bulk Solids: Megumi Kawasaki1; Terence Langdon2; 1Oregon State University; 2University of Southampton
High-pressure torsion (HPT) is a conventional processing procedure that may be used to achieve exceptional grain refinement in pure metals and metallic alloys. Recently, this procedure was extended to simultaneously process two different metals placed together in an HPT facility. The results from these experiments demonstrate the potential for producing nano-composites having remarkably high strength with outstanding strength-to-weight ratios. This presentation describes this new approach to HPT processing and gives examples of the types of results that may be achieved.
11:10 AM Invited
Recent Findings on Paradoxes of Severe Plastic Deformation: Ruslan Valiev1; 1UFA State Aviation Technical University
Recent studies in processing of metallic materials by severe plastic deformation (SPD) techniques clearly showed that target nanostructuring can result in their paradoxial properties that usually are not typical for the materials subjected to conventional thermomechanical treatment. Such paradoxes constitute the combinations of high strength and ductility, demonstration of high strength and electrical conductivity, increased thermal stability and other. Herein, unusual combinations of mechanical and functional properties are reported following recent results and findings on a number of metallic materials processed by SPD as well as the physical mechanisms that are key to their origin associated with various nanostructured features from grain refinement to nanoscale and phase transformation. High innovation potential for application of these multifunctional materials in engineering and medicine is considered and discussed.