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Session Chairperson: Walter W. Milligan, Metallurgical and Materials Engineering, Michigan Technological University, Houghton, MI 49931
9:00 am INVITED
SYNTHESIS AND MECHANICAL PROPERTIES OF NANOCRYSTALLINE INTERMETALLICS AND MULTIPHASE MATERIALS: J.A. Eastman*, M. Choudry*,**, M.N. Rittner***, C.J. Youngdahl*,***, M. Dollar**, J.R. Weertman***, R.J. DiMelfi****, and L.J. Thompson*, *Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave., Bldg. 212, Argonne, IL 60439, **Mechanical, Materials, and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL 60616, ***Materials Science and Engineering Department, Northwestern University, Evanston, IL 60208, ****Reactor Engineering Division, Argonne National Laboratory, Argonne, IL 60439
The mechanical behavior of nanocrystalline intermetallic and multiphase materials has been investigated using disk bend, tensile, and compression techniques. Materials such as NiAl, TiAl, Al-Al3Zr, and Cu-SiOx were synthesized by the gas-condensation technique using electron beam heating. Disk bend tests of nanocrystalline NiAl and TiAl showed evidence of improve ductility at room temperature in these normally extremely brittle materials. In contrast, tensile tests of multiphase nanocrystalline Al-Al3Zr samples showed significant increases in strength, but substantial reductions in ductility with decreasing grain size. Results from compression tests of nanocrystalline Cu and Cu-SiOx will also be described. Implications for the operable deformation mechanisms in these materials will be discussed. *This work was supported by the U.S. Department of Energy, BES-Materials Science, under Contract W-31-109-Eng-38, the Alcoa Corporation, and by AFOSR Grant # FY9620-92-J.
INFLUENCE OF PROCESSING ON INTERNAL STRUCTURE OF NANOCRYSTALLINE Ni: B.R. Elliott, and J.R. Weertman, Northwestern University, Evanston, IL , Metallurgy Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-0001
Different processing routes can vary the internal structure of nanocrystalline compacts. As a result a single grain size measurement is insufficient to interpret mechanical property results. Blind comparison between samples with different processing histories may be hazardous since their internal structures (grain size distribution, grain boundary character, pore size distribution, adsorbed or chemically bonded impurities) are shown to vary. In particular, annealing samples to grow the grain size for producing Hall-Petch plots is shown to drastically change the pore size distribution and density in powder compacted samples that are not outgasssed prior to compaction. Improvements in processing, particularly compaction procedure, are illustrated by microscopy, XRD, SANS, PGAA, FNAA, archimedes density, and indentation tests. It is shown that with care and knowledge of the process inert gas condensed and compacted samples can be produced with few extrinsic defects.
MECHANICAL PROPERTIES OF NANOCRYSTALLINE Ni: B.R. Elliott, J.R. Weertman, Northwestern University, Evanston, IL
The influence of improved processing on the internal structure of n-Ni has lead to improved mechanical properties. Correlation between the internal structure (including grain size, pore size distribution, and impurities) and results of a variety of mechanical properties measurements will be presented including hardness, tensile and compression tests. Some comparison will also be made between samples produced by traditional inert gas condensation (IGC) and the newer jet blown arc IGC. (JBA-IGC). Possible deformation mechanisms will be discussed in light of the structure and property measurements.
A CRITICAL ASSESSMENT OF THE WILLIAMSON-HALL METHOD FOR THE DETERMINATION OF RESIDUAL STRESS IN NANOCRYSTALLINE STRUCTURES: F.S. Miller, D.C. Van Aken, Metallurgical Engineering, E.W. Bohannan, J.A. Switzer, Chemistry, The University of Missouri-Rolla, Rolla, MO 65409
An important aspect of the processing<>microstructure<>property relationships is the characterization of nanocrystalline structures by x-ray diffraction. The Williamson-Hall analysis is often used to deconvolute the line broadening effects of grain size and residual stress. In this study, Cu/Cu2O nanocrystalline films were produced by electro deposition. This technique produces a composite structure consisting of pure Cu and Cu2O grains each with diameters in the range of 10 to 20 nm. Electro deposited films were characterized by x-ray diffraction to determine both grain size and residual stress. The Williamson-Hall analysis was tested by direct measurement of the grain size by TEM and by using thermal treatments to vary the state of residual stress in the films.
10:30 am BREAK
MECHANICAL PROPERTIES OF Cu/Ag MULTI-LAYER COMPOSITES: Qing Zhai, Augusto Morrone, Fereshted Ebrahimi, Materials Science & Engineering, University of Florida, Gainesville, FL 32611
When materials microstructure reaches nanometer scale, their properties often appear to be unusual, which cast much consideration these days. Specifically, the extraordinarily high strength has been the subject of many recent investigations. The nanomaterials discussed in this paper is a Cu/Ag multi-layered composite, which is produced by electrodeposition in a single-bath cyanide solution. In this paper the effects of copper layer thickness and heat treatment on interfacial structure and mechanical properties of Cu/Ag multi-layered composites are presented. Tensile testing was used to investigate the mechanical properties of the samples. SEM, X-ray diffraction and TEM were used to analyze the relation between the mechanical properties and microstructure of these composites.
STABILITY OF NANOCRYSTALLINE ALLOYED AND MULTILAYER PVD NITRIDE FILMS: R. A. Andrievski, Institute for New Chemical Problems, Russian Academy of Sciences, Chernogolovka, Moscow Region, 14232 Russia
The alloyed and multilayer films of TiN, ZrN, NbN, and CrN with nanocrystalline structure prepared by arc deposition were investigated by XRD, electron microscopy and microhardness measurements. A general tendency of the microhardness to increase with decreasing layer thickness was found in TiN-NbN(ZrN) systems. The unmonotonous change has been revealed in TiN-CrN one. The influence of spinodal decomposition, recrystallization, and heterodiffusion on the films' properties is also demonstrated and discussed in detail. R.A.Andrievski, 1 A.Anisimova, V.P.Anisimov et al, Thin Solid Films 261(1995) 83.
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