Mechanical Behavior of Nanostructured Materials: Mechanical Behavior of Bulk Nanostructured Materials I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Xinghang Zhang, Purdue University; Yuntian Zhu, North Carolina State University; Joseph Poon, University of Virginia; Suryanarayana Challapalli, University of Central Florida; Enrique Lavernia, University of California, Irvine; Haiyan Wang, Texas A&M University

Monday 8:30 AM
February 27, 2017
Room: 30D
Location: San Diego Convention Ctr

Funding support provided by: AJA International; Hysitron Inc.

Session Chair: Xinghang Zhang, Purdue University; Ron Scattergood, North Carolina State University; Kris Darling, Army Research Laboratory

8:30 AM Introductory Comments

8:40 AM  Invited
High Temperature Mechanical Properties of Ultrafine-grained and Nanocrystalline Materials : Megumi Kawasaki1; Roberto Figueiredo2; Terence Langdon3; 1Hanyang University; 2Universidade Federal de Minas Gerais; 3University of Southern California
    The processing of metals with exceptionally small grain sizes, within the submicrometer or nanometer regions, has led to the development of significant interest in the mechanical properties of these materials. When the grain size is very small there is a potential for achieving excellent superplastic properties, even in materials such as magnesium alloys where the h.c.p. crystal structure limits the number of available slip systems. This paper examines these recent developments with an emphasis on the occurrence of superplasticity at elevated temperatures.

9:05 AM  Invited
15 Years SPD-Processed Bulk Nanostructured Materials: From Mechanical to Functional Highlights: Michael Zehetbauer1; 1University of Vienna
     15 years have passed since the pioneering works of R.Z.Valiev et al. [1] introducing the top–down approach of nanostructures in bulk materials. While the first years brought highlights in mechanical properties [2], recent researches prove outstanding functional properties, like those of shape memory [3], magnetic [3], and biomedical nanomaterials [4]. Last results in hydrogen storage and thermoelectric nanomaterials prove that for functional properties low-dimensional SPD-induced lattice defects like vacancy clusters and dislocations can be more beneficial than high-dimensional ones like grain- or phase boundaries [4]. [1] R.Z. Valiev, I. Alexandrov, R. Islamgaliev, Progr.Mater.Sci. 45, 103-189 (2000) [2] M. Zehetbauer, Y.T. Zhu, Bulk nanostructured materials, Wiley (2009) [3] M. Zehetbauer, R. Groessinger, H. Krenn, M. Krystian, R. Pippan, P. Rogl, T. Waitz, R. Wuerschum, Adv.Eng.Mater. 12, 692-700 (2010) [4] R. Z. Valiev, Y. Estrin, Z. Horita, T. G. Langdon, M. J. Zehetbauer, Y. T. Zhu, Mater.Res.Lett. 4, 1-21 (2016)

9:30 AM  Cancelled
Bulk Nanocrystalline Materials: Mechanical Behavior and Deformation Mechanisms : Farghalli Mohamed1; 1University of California, Irvine
    Nanocrystalline (nc) materials are characterized by a unique substructural feature: grain sizes are less than 100 nm. With grain sizes less than 100 nm, the intragrain Frank-Read dislocation sources become inoperable since the grain size is too small to accommodate the size of the source. As a result, conventional dislocation mechanisms that produce plastic deformation in coarse-grained materials cease to be operational in nc-materials. However, recent research activities have demonstrated that a proposed deformation mechanism involving dislocation activity can account for the mechanical behavior of nc-materials. Details of this deformation mechanism will be discussed and its correlations with experimental results will be examined.

9:55 AM  Invited
Hardening by Annealing and Abnormal Hall-Petch Relationship in Nanocrystalline Elements and Alloys: T. D. Shen1; B. R. Sun1; S. W. Xin1; 1Yanshan University
    We have found a hardening effect in annealed iron- and nickel-based nanocrystalline (NC) alloys and a softening effect in annealed pure NC iron. As a result, abnormal Hall-Petch relations were observed in annealed NC alloys. These abnormal phenomena could be explained by the segregation of solutes and/or impurities in the grain boundary because of three evidence: i) hardening by annealing has been observed in many annealed NC alloys and low-purity (< 99%) NC metals, but not in annealed high-purity (> 99.9%) NC metals; ii) annealing embrittlement; and iii) cooling rate dependent microhardness. In addition, our experiment results suggest that i) the dislocations stored in the grain interiors of NC alloys do not change the microhardness, and ii) it is the grain size and the grain boundary structure, rather than the dislocations stored in the grain interiors, that determine the strength of deformed and annealed NC elements and alloys.

10:20 AM Break