Sponsored by: MDMD Powder Metallurgy Committee and FEMS (Federation of European Materials Societies)
Program Organizers: Dr. David L. Bourell, The University of Texas at Austin, Materials Science & Engineering, MC C2201, Austin TX 78712. Dr. Liisa Kuhn-Spearing, Laboratory for the Study of Skeletal Disorders and Rehabilitation, Harvard Medical School, Children's Hospital, 300 Longwood Avenue, Boston MA 02115. Professor Dr. Herbert Gleiter, Karlsruhe Research Center, P.O. Box 3640, D-76021 Karlsruhe, Federal Republic of Germany
Tuesday, PM Room: Grand G
February 6, 1996 Location: Anaheim Marriott Hotel
Session Chairperson: Robert D. Shull, Magnetic Materials Group, Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg MD 20899
SYNTHESIS, COMPACTION AND PROPERTIES OF NANOCRYSTALLINE ATTRITED POWDER: C. Schmidt, C. Moelle, K. Müller, H.J. Fecht, Technical University Berlin, 10623 Berlin Germany
Mechanical attrition has been developed as a versatile alternative to other processing routes in preparing nanocrystalline structures. In this process, the internal refining process with a reduction of the average grain size by a factor of about 104 results from the creation and self-organization of dislocation to high-angle grain boundaries within the powder particles during the high energy milling process. These powder particles have been compacted to solid wire shaped samples with a density of about 93% by a hydrostatic extrusion process. Recent results for aluminum alloys are discussed with a special emphasis on the achieved mechanical properties.
SYNTHESIS OF NANOSTRUCTURED TITANIUM BASED MATERIALS BY PLASMA PROCESSING OR MECHANICAL ALLOYING AND HOT ISOSTATIC PRESSING: F.H. Froes, Institute for Materials and Advanced Processes. P.R. Taylor, Metallurgical and Mining; C. Suryanarayana, Institute for Materials and Advanced Processes, University of Idaho, Moscow, ID 83844-3026; J. Hebeisen, Industrial Materials Technology, 155 River St., Andover MA 01810
Both plasma processing (PP) and Mechanical Alloying (MA) allow the product of "large" amounts of equiaxed nanostructured materials; in contrast to many of the "laboratory curiosity" processes being evaluated. This paper will discuss both the PP and MA techniques as applied to the titanium system. It will also discuss the critical step of compaction to a usable article using hot isostatic pressing.
SYNTHESIS AND CHARACTERIZATION OF BULK NANOCRYSTALLINE M50 STEEL: Maggy L. Lau, Benlih Huang, Robert J. Perez, Enrique J. Lavernia, Department of Chemical Engineering and Materials Science, University of California, Irvine CA 92717-2575
M50 steel (4.0 wt% Cr, 4.5 wt% Mo, 1.0 wt% V, 0.8 wt% C, balance of Fe) is a technologically important alloy due to its good resistance to tempering, wear, and rolling contact fatigue, and has been used extensively in the bearings in gas- turbine engines. The present study has been conducted using both mechanical alloying of elemental powders as well as spray atomization of pre- alloyed M50 with subsequent ball milling to synthesize M50 steel powders. In order to improve the thermal stability of the nanocrystalline M50, incorporation of Al and subsequent cryomilling in liquid nitrogen resulted in thermally stable bulk nanocrystalline M50 steel. Characterization of the bulk nanocrystalline M50 is being conducted to study the mechanical and damping properties. The authors would like to acknowledge the financial support provided by the Office of Naval Research under grants N00014- 93- 1072 and N00014- 94- 0017.
PRODUCTION OF TITANIUM NITRIDE AND CARBONITRIDE POWDERS BY REACTIVE MILLING IN DIFFERENT ATMOSPHERES: S. Quintana-Molina, J.G. Cabañas-Moreno, H. Balmori-Ramírez, R. Martinez-Sánchez, Instituto Politechnico Nacional, ESIQIE, Apdo, Postal 75-373, 07300 México, D.F., México
Titanium powders, with or without graphite additions, have been milled under atmospheres of NH3, N2 or laboratory air. In all cases, the titanium powders have become reactive during milling, with the main products of the reaction being TiN, Ti(N,0) and Ti(N,C). These products have been characterized by XRD, SEM, TEM and chemical analysis. Milling of mixtures of Ti and graphite powders have yielded Ti(N,C) compounds with lattice parameters between those of pure TiN and TiC. In some occasions, the as- milled powders have ignited simultaneously after removal from the mill. Milling in air has mainly produced a Ti(N,O) phase, while the pure N2 atmosphere has yielded a product which is closer to pure TiN. The crystallite size of all the products is within the nanometer range, with some exceptions in those mixtures which ignited. The results of additional sintering experiments will also be described. This work was supported by DEPI- PIFI and COFAA- IPN and CONACYT.
3:40 pm BREAK
OXIDE-METAL NANOCOMPOSITES BY BALL MILLING: Laszlo Takacs, The University of Maryland Baltimore County, Department of Physics, Baltimore MD 21228
High energy ball milling is a promising low- tech method to produce large quantities of oxide- metal nanocomposites. However, the price for the apparent simplicity of the process is difficulty of control. The possibilities to monitor the process are limited, prior information on the expected kinetics is crucial. Some nanocomposites can be prepared by milling the final components until the desired particle size and grain structure is reached. Excessively long milling times may result in contamination and deteriorating properties. Additional control may be possible via in situ chemical reactions between an oxide and a more reactive metal. The process usually occurs in three overlapping steps: An activation period of attrition, mixing, and defect formation; a relatively fast reaction when an intermediate sub- oxide is produced; and the decomposition of this oxide into a fine dispersion of the final oxide and metal phases. Several examples including the preparation of iron particles on Al203, MgO, and ZnO will be discussed.
PROCESSING OF NANOCRYSTALLINE MATERIALS BY SEVERE PLASTIC DEFORMATION CONSOLIDATION: Ruslan Z. Valiev, Institute of Physics of Materials, Ufa State Aviation Technical University, Ufa 450000 Russia
Recent investigations show that severe plastic deformation, i.e. intense plastic straining under high hydrostatic pressure, is not only a method to refine microstructures effectively, but also is an innovative method for consolidation of powders into bulk samples. The present paper focuses on three types of severe plastic deformation consolidation (SPDC) methods. First is a compaction of ordinary sized powders, characterized by a formation of supersaturated nanocrystals, because second phases get dissolved during SPDC. Second is a consolidation of metal and ceramic powders in order to produce nanocomposites with high strength and thermostability. Third is the consolidation of ball-milled powders. This latter SPDC process is capable of producing quasi-amorphous nanosolids, formed due to a presence of a very high density of dislocations (up to 1017 m-2) situated at grain boundaries. Atomic structure and some attractive properties of these unusual materials are considered.
STRUCTURE AND PROPERTIES OF MECHANICALLY ALLOYED Ni -Al AND Ag-Al POWDERS BEFORE AND AFTER LEACHING OF ALUMINUM: B. Zeifert, R. Esquivel, D. Jaramillo-Vigueras, J.G. Cabañas-Moreno, Instituto Politechnico Nacional, ESIQIE, Apdo, Postal 75-373, 07300 México, D.F., México
Elemental powder mixtures of Al+Ni and Al+Ag, in a variety of nominal compositions, have been milled in an attritor mill and a horizontal ball mill. The mechanically alloyed powders have been characterized by XRD, SEM, TEM, DSC and chemical analysis. Ni-Al mixtures with nominal aluminum contents in the range from 55 to 70 atomic % mainly containing the NiAl-type intermetallic phase after sufficiently long milling times. On the other hand, the composition Ag65Al35 was identified as the [[gamma]]-Ag2Al phase. Leaching of aluminum from the mechanically alloyed powders has been successfully accomplished and the leached materials are currently being tested as potential catalytic solids. This work was funded by IPN (DEPI, COFAA, PIFI) and CONACYT.
COMPACTION OF MECHANICALLY ALLOYED IRON POWDERS: J.C. Rawers, D. Alman, U.S. Bureau of Mines, Albany Research Center, Albany OR 97321-2198; J. Groza, Materials Science, University of California Davis, Davis CA, G. Korth, Idaho National Engineering Laboratory, Idaho Falls ID
Although much has been written about high-
Milling of powders and the properties of the resulting powder, there has been
limited information about consolidation of these materials. This study
describes and compares the results of several techniques recently attempted to
consolidate mechanically alloyed, micron size, nanograin iron alloys. Powers
were all prepared using a high energy attrition ball-
and analyzed for phase, grain size, and internal strain. Consolidation
included: (i) explosive compaction, (ii) high pressure (>3GPa) cold
compaction, and (iii) low pressures (~50MPa) compaction at temperatures from
600 to 1000deg.C with hold times from a few minutes to an hour. Consolidated
samples were examined for phase, grain size, and hardness.
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