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1

Workability in forging of powder metallurgy compacts  

Microsoft Academic Search

The power metallurgy (PM) technique is now applied widely to many industries and materials. To obtain more reliable PM products, many secondary processes are applied to PM preforms. The problem of deformation and fracture of PM preforms still needs a considerable amount of investigation.In this work, the effect of the relative density on the forming limit of PM compacts in

M. Abdel-Rahman; M. N. El-Sheikh

1995-01-01

2

Effect of die wall lubrication on warm compaction powder metallurgy  

Microsoft Academic Search

Die wall lubrication was applied on warm compaction powder metallurgy in the hope to reduce the concentration level of the admixed lubricant, since lubricant is harmful to the mechanical properties of the sintered material. Iron-based samples were prepared by die wall lubricated warm compaction at 135 and 175°C, using polytetrafluoroethylene (PTFE) emulsion as the die wall lubricant. Compacting pressures of

Y. Y Li; T. L Ngai; D. T Zhang; Y Long; W Xia

2002-01-01

3

Ultrasonic Fatigue Behavior of a Fe-BASED Warm-Compacted Powder Metallurgy Material  

NASA Astrophysics Data System (ADS)

Fe-2Cu-2Ni-1Mo-1C powder metallurgy material was fabricated by die-wall lubricated warm compaction and ultrasonic fatigue test was carried out for as-sintered and heat treatment samples. Material fatigue strength reaches 249 MPa under axial fatigue testing. The sintered material consists of acicular martensite, pearlite, bainite and retained austenite. Tempered martensite is the major phases after heat-treatment. Cleavage plane and dimples is mixed fracture for sample after axial fatigue test. Mechanical properties of after heat treatment materials are improved and fatigue strength reaches 382 MPa under 107 cycles in bending ultrasonic fatigue test. The fatigue strength increases significantly in high cycles range.

Lu, Yu-Heng; Ye, Xuan; Hu, Lei; Luo, Fei; Xiao, Zhi-Yu

2013-07-01

4

Active Thermography for the Detection of Defects in Powder Metallurgy Compacts  

SciTech Connect

Active thermography is an established NDE technique that has become the method of choice in many industrial applications which require non-contact access to the parts under test. Unfortunately, when conducting on-line infrared (IR) inspection of powder metallic compacts, complications can arise due the generally low emissivity of metals and the thermally noisy environment typically encountered in manufacturing plants. In this paper we present results of an investigation that explores the suitability of active IR imaging of powder metallurgy compacts for the detection of surface and sub-surface defects in the pre-sinter state and in an on-line manufacturing setting to ensure complete quality assurance. Additional off-line tests can be carried out for statistical quality analyses. In this research, the IR imaging of sub-surface defects is based on a transient instrumentation approach that relies on an electric control system which synchronizes and monitors the thermal response due to an electrically generated heat source. Preliminary testing reveals that this newly developed pulsed thermography system can be employed for the detection of subsurface defects in green-state parts. Practical measurements agree well with theoretical predictions. The inspection approach being developed can be used for the testing of green-state compacts as they exit the compaction press at speeds of up to 1,000 parts per hour.

Benzerrouk, Souheil; Ludwig, Reinhold [Powder Metallurgy Research Center, METAL PROCESSING INSTITUTE, Worcester Polytechnic Institute, Worcester, MA 01609 (United States); Department of Electrical and Computer Engineering, Worcester Polytechnic Institute, Worcester, MA 01609 (United States); Apelian, Diran [Powder Metallurgy Research Center, METAL PROCESSING INSTITUTE, Worcester Polytechnic Institute, Worcester, MA 01609 (United States)

2007-03-21

5

Densification of powder metallurgy billets by a roll consolidation technique  

NASA Technical Reports Server (NTRS)

Container design is used to convert partially densified powder metallurgy compacts into fully densified slabs in one processing step. Technique improves product yield, lowers costs and yields great flexibility in process scale-up. Technique is applicable to all types of fabricable metallic materials that are produced from powder metallurgy process.

Sellman, W. H.; Weinberger, W. R.

1973-01-01

6

Metallography of powder metallurgy materials  

SciTech Connect

The primary distinction between the microstructure of an ingot metallurgy/wrought material and one fabricated by the powder metallurgy route of pressing followed by sintering is the presence of porosity in the latter. In its various morphologies, porosity affects the mechanical, physical, chemical, electrical and thermal properties of the material. Thus, it is important to be able to characterize quantitatively the microstructure of powder metallurgy parts and components. Metallographic procedures necessary for the reliable characterization of microstructures in powder metallurgy materials are reviewed, with emphasis on the intrinsic challenges presented by the presence of porosity. To illustrate the utility of these techniques, five case studies are presented involving powder metallurgy materials. These case studies demonstrate problem solving via metallography in diverse situations: failure of a tungsten carbide-coated precipitation hardening stainless steel, failure of a steel pump gear, quantification of the degree of sinter (DOS), simulation of performance of a porous filter using automated image analysis, and analysis of failure in a sinter brazed part assembly.

Lawley, Alan; Murphy, Thomas F

2003-12-15

7

Surface Integrity of C-40 Steel Processed with WC-Cu Powder Metallurgy Green Compact Tools in EDM  

Microsoft Academic Search

Electric discharge machining (EDM) is an electrothermal process where recast layer on the machined surface and heat-affected (HAZ) zone just below the machined surface are common phenomena. Thus, the assessment of surface integrity in EDM is a very important task. In this study, an attempt was made to modify the surface integrity of C-40 steel in EDM. WC-Cu powder metallurgy

P. K. Patowari; U. K. Mishra; P. Saha; P. K. Mishra

2011-01-01

8

Advanced powder metallurgy aluminum alloys and composites  

NASA Technical Reports Server (NTRS)

The differences between powder and ingot metallurgy processing of aluminum alloys are outlined. The potential payoff in the use of advanced powder metallurgy (PM) aluminum alloys in future transport aircraft is indicated. The national program to bring this technology to commercial fruition and the NASA Langley Research Center role in this program are briefly outlined. Some initial results of research in 2000-series PM alloys and composites that highlight the property improvements possible are given.

Lisagor, W. B.; Stein, B. A.

1982-01-01

9

Ceramic powder compaction  

SciTech Connect

With the objective of developing a predictive model for ceramic powder compaction we have investigated methods for characterizing density gradients in ceramic powder compacts, reviewed and compared existing compaction models, conducted compaction experiments on a spray dried alumina powder, and conducted mechanical tests and compaction experiments on model granular materials. Die filling and particle packing, and the behavior of individual granules play an important role in determining compaction behavior and should be incorporated into realistic compaction models. These results support the use of discrete element modeling techniques and statistical mechanics principals to develop a comprehensive model for compaction, something that should be achievable with computers with parallel processing capabilities.

Glass, S.J.; Ewsuk, K.G. [Sandia National Labs., Albuquerque, NM (United States); Mahoney, F.M. [Norton Co., Worcester, MA (United States)

1995-12-31

10

Powder-Metallurgy Process And Product  

NASA Technical Reports Server (NTRS)

Rapid-solidification processing yields alloys with improved properties. Study undertaken to extend favorable property combinations of I/M 2XXX alloys through recently developed technique of rapid-solidification processing using powder metallurgy(P/M). Rapid-solidification processing involves impingement of molten metal stream onto rapidly-spinning chill block or through gas medium using gas atomization technique.

Paris, Henry G.

1988-01-01

11

Welding of a powder metallurgy uranium alloy  

SciTech Connect

The interest at the Oak Ridge Y-12 Plant in powder metallurgy (P/M) uranium parts is due to the potential cost savings in the fabrication of the material, to achieving a more homogeneous product, and to the reduction of uranium scrap. The joining of P/M uranium-6 wt-% niobium (U-6Nb) alloys by the electron beam (EB) welding process results in weld porosity. Varying the EB welding parameters did not eliminate the porosity. Reducing the oxygen and nitrogen content in this P/M uranium material did minimize the weld porosity, but this step made the techniques of producing the material more difficult. Therefore, joining wrought and P/M U-6Nb rods with the inertia welding technique is considered. Since no gases will be evolved with the solid-state welding process and the weld area will be compacted, porosity should not be a problem in the inertia welding of uranium alloys. The welds that are evaluated are wrought-to-wrought, wrought-to-P/M, and P/M-to-P/M U-6Nb samples.

Holbert, R.K.; Doughty, M.W.; Alexander-Morrison, G.M. (Fairchild Space Co., Germantown, MD (USA))

1989-05-01

12

Fabricating sports equipment components via powder metallurgy  

Microsoft Academic Search

Powder metallurgy (P\\/M) offers a viable, cost-effective approach to fabricating sports and leisure equipment components. Both\\u000a complex, monolithic parts and parts produced from materials of quite different densities can be manufactured by this technique.\\u000a In the latter category, lightweight titanium and heavyweight tungsten can be used in combination to optimally distribute mass,\\u000a such as in golf club heads. Examples of

V. S. Moxson

2001-01-01

13

Powder metallurgy technology of NiTi shape memory alloy  

NASA Astrophysics Data System (ADS)

Powder metallurgy technology was elaborated for consolidation of shape memory NiTi powders. The shape memory alloy was compacted from the prealloyed powder delivered by Memry SA. The powder shows Ms = 10°C and As = -34°C as results from DSC measurements. The samples were hot pressed in the as delivered spherical particle's state. The hot compaction was performed in a specially constructed vacuum press, at temperature of 680°C and pressure of 400 MPa. The alloy powder was encapsulated in copper capsules prior to hot pressing to avoid oxidation or carbides formation. The alloy after hot vacuum compaction at 680°C (i.e. within the B2 NiTi stability range) has shown similar transformation range as the powder. The porosity of samples compacted in the as delivered state was only 1%. The samples tested in compression up to ? = 0.06 have shown partial superelastic effect due to martensitic reversible transform- ation which started at the stress above 300 MPa and returned back to ? = 0.015 after unloading. They have shown also a high ultimate compression strength of 1600 MPa. Measurements of the samples temperature changes during the process allowed to detect the temperature increase above 12°C for the strain rate 10-2 s-1 accompanied the exothermic martensite transformation during loading and the temperature decrease related to the reverse endothermic transformation during unloading.

Dutkiewicz, J. M.; Maziarz, W.; Czeppe, T.; Lity?ska, L.; Nowacki, W. K.; Gadaj, S. P.; Luckner, J.; Pieczyska, E. A.

2008-05-01

14

Porous Materials by Powder Metallurgy.  

National Technical Information Service (NTIS)

A porous material of desired porosity and pore size is made by mixing a particulate material and fungible beads that are thermally decomposable until the desired distribution is attained; compacting the mixed material and beads to form a green body that h...

R. Everett

1998-01-01

15

FINITE ELEMENT ANALYSIS OF CAPPING MECHANISMS DURING PHARMACEUTICAL POWDER COMPACTION  

E-print Network

Institute for Pharmaceutical Materials Science, Department of Materials Science and Metallurgy, UniversityFINITE ELEMENT ANALYSIS OF CAPPING MECHANISMS DURING PHARMACEUTICAL POWDER COMPACTION Chuan-Yu. Wu1 In this paper, the compaction of lactose powder, a typical pharmaceutical excipient, is modelled using finite

de Gispert, Adrià

16

Numerical Simulation on Pharmaceutical Powder Compaction Lianghao Han1,a  

E-print Network

Numerical Simulation on Pharmaceutical Powder Compaction Lianghao Han1,a , James Elliott1,b Department of Materials Science and Metallurgy, University of Cambridge, CB2 3QZ,UK 2 Pfizer Global R elasticity law developed to describe the compaction behavior of pharmaceutical powders. The model

Elliott, James

17

Low-Cobalt Powder-Metallurgy Superalloy  

NASA Technical Reports Server (NTRS)

Highly-stressed jet-engine parts made with less cobalt. Udimet 700* (or equivalent) is common nickel-based superalloy used in hot sections of jet engines for many years. This alloy, while normally used in wrought condition, also gas-atomized into prealloyed powder-metallurgy (PM) product. Product can be consolidated by hot isostatically pressing (HIPPM condition) and formed into parts such as turbine disk. Such jet-engine disks "see" both high stresses and temperatures to 1,400 degrees F (760 degrees C).

Harf, F. H.

1986-01-01

18

Ti Multicomponent Alloy Bulks by Powder Metallurgy  

NASA Astrophysics Data System (ADS)

In this study, CrCuFeMnMo0.5Ti multicomponent alloy bulks were prepared by powder metallurgy of mechanical alloying and sintering. A simple body-centered cubic (bcc) solid solution was prepared after 40 h ball milling of the raw CrCuFeMnMo0.5Ti metallic powder. Particles of the alloyed powder are in microsized structures, which are actually a soft agglomeration of lamellar grains with thicknesses less than 1 ?m. Meanwhile, the lamellar granules are consisted of nanosized grains under rigid cold welding. The 80-h ball-milled powder was consolidated by cold pressing and subsequent sintering at 800°C. The observed main phase in the consolidated sample after milling for 80 h is still a bcc solid solution. The solidified sample of 80-h ball-milled powder exhibits a Vickers hardness of 468 HV, which is much higher than 171 HV of the counterpart prepared from the raw metallic powder.

Zhang, Kuibao; Wen, Guanjun; Dai, Hongchuan; Teng, Yuancheng; Li, Yuxiang

2014-10-01

19

Superplastic deformation mechanism in powder metallurgy magnesium alloys and composites  

Microsoft Academic Search

The parametric dependencies for superplastic flow in powder metallurgy (PM) magnesium alloys and composites were characterized so as to elucidate the deformation mechanism. The mechanism was proposed to be slip accommodated grain boundary sliding. However, the PM alloys and composites were strengthened at low temperatures below ?550K. This was different from the case in ingot metallurgy (IM) magnesium alloys, that

H. Watanabe; T. Mukai; M. Mabuchi; K. Higashi

2001-01-01

20

Sintering of powder mixtures and the growth of ferrous powder metallurgy  

Microsoft Academic Search

Advances in the understanding of sintering of powder mixtures contributed significantly to the growth of ferrous powder metallurgy industry. Solid-state sintering and liquid-phase activated sintering play an important role in the sintering of powder mixtures. In this paper, sintering of iron powder with graphite; iron powder with copper and graphite; iron powder with nickel and graphite; iron powder with phosphorus;

K. S Narasimhan

2001-01-01

21

Numerical investigation of Powder Metallurgy manufactured gear wheels subjected to fatigue loading  

Microsoft Academic Search

A 2D numerical study of the damage accumulation at the root of a Powder Metallurgy (PM) manufactured gear wheel subjected to frequent overloads, i.e. low cycle fatigue loading, has been performed. The initial porosity distribution of the gear was obtained from a 3D simulation of double action compaction of the gear. The porosity distributions over the centre plane and at

J. Cedergren; S. Melin; P. Lidström

2005-01-01

22

Powder metallurgy process for manufacturing core projectile  

NASA Astrophysics Data System (ADS)

Bullets are part of the defense equipment which the development is very rapid. There are a variety of forms but the bullet Lead is a metal that has always been used for applications projectiles. Lead core constituent materials are combined with antimony. In this research will be conducted by making the material for the core projectile with Tin Lead. The addition of Tin will increase the stiffness of Lead which is soft in nature. The Lead Tin composition variation was given in 10% weight of Sn. The manufacturing process using powder metallurgy using temperature and holding time variations of sintering at 100, 150, and 200°C for 1,2, and 3 hours. XRD samples will be tested to determine the form and phase morphology was observed using SEM-EDX. These results revealed that Pb-10%wtSn Composite which is sintered in temperature 200°C for 3 hours has the greatest density, 10.695 g/cm3 as well as the smallest porosity, 2.2%. In agreement with theoretical analysis that increasing higher temperature and longer holding time give decrease in porosity level due to activation energy which further promotes grain growth. Moreover, there is no intermetallic phase formation as well as no oxide found on composites.

Akbar, Taufik; Setyowati, Vuri Ayu; Widyastuti

2013-09-01

23

Aluminium powder metallurgy technology for high-strength applications  

Microsoft Academic Search

A literature survey of aluminium powder metallurgy (PM) for high-strength applications was undertaken. Improvements in aluminium—base alloys made via ingot metallurgy (IM) are reaching the point of diminishing returns. PM offers an alternative technology, capable of producing alloys having improved fatigue, corrosion, and stress-corrosion resistance, as well as improved strength and toughness at room or elevated temperatures. The steps involved

J. R. Pickens

1981-01-01

24

Modelling the mechanical behaviour of pharmaceutical powders during compaction  

E-print Network

Modelling the mechanical behaviour of pharmaceutical powders during compaction C.-Y. Wua,T, O.M. Ruddyb , A.C. Benthamb , B.C. Hancockc , S.M. Besta , J.A. Elliotta a Pfizer Institute for Pharmaceutical Materials Science, Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street

Elliott, James

25

Metallurgical examination of powder metallurgy uranium alloy welds  

SciTech Connect

Inertia welding provided a successful technique for joining full density, powder metallurgy uranium-6 wt pct niobium alloy. Initial joining attempts concentrated on the electron beam method, but this method failed to produce a sound weld. The electron beam welds and the inertia welds were evaluated by radiography and metallography. Electron beam welds were attempted on powder metallurgy plates which contained various levels of oxygen and nitrogen. All welds were porous. Sixteen inertia welds were made and all welds were radiographically sound. The tensile properties of the joints were found to be equivalent to the p/m base metal properties.

Morrison, A.G.M.; Dobbins, A.G.; Holbert, R.K.; Doughty, M.W.

1986-06-01

26

Generalised yield criteria of porous sintered powder metallurgy metals  

Microsoft Academic Search

A new form of yield criterion considering an anisotropic parameter for porous sintered powder metallurgy metals has been proposed in this technical paper. In addition to the above, the flow rule with anisotropic parameter for porous metal is introduced. The mathematical expression for the calculation of flow stress in the case of simple compression or tension test is deduced from

R. Narayanasamy; R. Ponalagusamy; K. R. Subramanian

2001-01-01

27

One step HIP canning of powder metallurgy composites  

NASA Technical Reports Server (NTRS)

A single step is relied on in the canning process for hot isostatic pressing (HIP) powder metallurgy composites. The binders are totally removed while the HIP can of compatible refractory metal is sealed at high vacuum and temperature. This eliminates outgassing during hot isostatic pressing.

Juhas, John J. (inventor)

1990-01-01

28

Powder-metallurgy superalloy strengthened by a secondary gamma phase.  

NASA Technical Reports Server (NTRS)

Description of experiments in which prealloyed powders of superalloy compositions were consolidated by extrusion after the strengthening by precipitation of a body-centered tetragonal gamma secondary Ni3 Ta phase. Thin foil electron microscopy showed that the mechanical properties of the resultant powder-metallurgy product were correlated with its microstructure. The product exhibited high strength at 1200 F without loss of ductility, after thermomechanical treatment and aging.

Kotval, P. S.

1971-01-01

29

Near-Net Shape Powder Metallurgy Rhenium Thruster  

NASA Technical Reports Server (NTRS)

This paper describes the development of a method to produce a near-net shape (NNS) powder metallurgy (PM) rhenium combustion chamber of the size 445 N (100 lbf) used in a high performance liquid apogee engine. These engines are used in low earth Orbit and geostationary orbit for satellite positioning systems. The developments in near-net shape powder metallurgy rhenium combustion chambers reported in this paper will reduce manufacturing cost of the rhenium chambers by 25 percent, and reduce the manufacturing time by 30 to 40 percent. The quantity of rhenium metal powder used to produce a rhenium chamber is reduced by approximately 70 percent and the subsequent reduction in machining schedule and costs is nearly 50 percent.

Leonhardt, Todd; Hamister, Mark; Carlen, Jan C.; Biaglow, James; Reed, Brian

2001-01-01

30

A powder metallurgy approach for production of innovative radioactive waste forms  

SciTech Connect

The feasibility of producing a single metal-matrix composite form rather than two separate forms consisting of a cast metal alloy ingot (such as Type 316SS + Zr) and a ceramic glass-bonded zeolite Na{sub 12}(AlO{sub 2}){sub 12}(SiO{sub 2}){sub 12} has been demonstrated. This powder metallurgy approach consists of mixing the powder of the two separate waste forms together followed by compaction by hot isostatic pressing. Such a radioactive waste form would have the potential advantages of reducing the total waste volume, good thermal conductivity, stability, and surfaces with limited oxide layer formation. 5 refs., 8 figs., 2 tabs.

Keiser, D.D. Jr.; Crawford, D.C. [Argonne National Lab., Idaho Falls, ID (United States); Bhaduri, S. [Univ. of Idaho, Moscow, ID (United States)] [and others

1997-07-01

31

Milling and Drilling Evaluation of Stainless Steel Powder Metallurgy Alloys  

SciTech Connect

Near-net-shape components can be made with powder metallurgy (PM) processes. Only secondary operations such as milling and drilling are required to complete these components. In the past and currently production components are made from powder metallurgy (PM) stainless steel alloys. process engineers are unfamiliar with the difference in machining properties of wrought versus PM alloys and have had to make parts to develop the machining parameters. Design engineers are not generally aware that some PM alloy variations can be furnished with machining additives that greatly increase tool life. Specimens from a MANTEC PM alloy property study were made available. This study was undertaken to determine the machining properties of a number of stainless steel wrought and PM alloys under the same conditions so that comparisons of their machining properties could be made and relative tool life determined.

Lazarus, L.J.

2001-12-10

32

Laboratory Powder Metallurgy Makes Tough Aluminum Sheet  

NASA Technical Reports Server (NTRS)

Aluminum alloy sheet exhibits high tensile and Kahn tear strengths. Rapid solidification of aluminum alloys in powder form and subsequent consolidation and fabrication processes used to tailor parts made of these alloys to satisfy such specific aerospace design requirements as high strength and toughness.

Royster, D. M.; Thomas, J. R.; Singleton, O. R.

1993-01-01

33

Shock compaction of molybdenum powder  

NASA Technical Reports Server (NTRS)

Shock recovery experiments which were carried out in the 9 to 12 GPa range on 1.4 distension Mo and appear adequate to compact to full density ( 45 (SIGMA)m) powders were examined. The stress levels, however, are below those calculated to be from 100 to approx. 22 GPa which a frictional heating model predicts are required to consolidate approx. 10 to 50 (SIGMA)m particles. The model predicts that powders that have a distension of m=1.6 shock pressures of 14 to 72 GPa are required to consolidate Mo powders in the 50 to 10 (SIGMA)m range.

Ahrens, T. J.; Kostka, D.; Vreeland, T., Jr.; Schwarz, R. B.; Kasiraj, P.

1983-01-01

34

Application of superalloy powder metallurgy for aircraft engines  

NASA Technical Reports Server (NTRS)

In the last decade, Government/Industry programs have advanced powder metallurgy-near-net-shape technology to permit the use of hot isostatic pressed (HIP) turbine disks in the commercial aircraft fleet. These disks offer a 30% savings of input weight and an 8% savings in cost compared in cast-and-wrought disks. Similar savings were demonstrated for other rotating engine components. A compressor rotor fabricated from hot-die-forged-HIP superalloy billets revealed input weight savings of 54% and cost savings of 35% compared to cast-and-wrought parts. Engine components can be produced from compositions such as Rene 95 and Astroloy by conventional casting and forging, by forging of HIP powder billets, or by direct consolidation of powder by HIP. However, each process produces differences in microstructure or introduces different defects in the parts. As a result, their mechanical properties are not necessarily identical. Acceptance methods should be developed which recognize and account for the differences.

Dreshfield, R. L.; Miner, R. V., Jr.

1980-01-01

35

Device for preparing combinatorial libraries in powder metallurgy.  

PubMed

This paper describes a powder-metering, -mixing, and -dispensing mechanism that can be used as a method for producing large numbers of samples for metallurgical evaluation or electrical or mechanical testing from multicomponent metal and cermet powder systems. It is designed to make use of the same commercial powders that are used in powder metallurgy and, therefore, to produce samples that are faithful to the microstructure of finished products. The particle assemblies produced by the device could be consolidated by die pressing, isostatic pressing, laser sintering, or direct melting. The powder metering valve provides both on/off and flow rate control of dry powders in open capillaries using acoustic vibration. The valve is simple and involves no relative movement, avoiding seizure with fine powders. An orchestra of such valves can be arranged on a building platform to prepare multicomponent combinatorial libraries. As with many combinatorial devices, identification and evaluation of sources of mixing error as a function of sample size is mandatory. Such an analysis is presented. PMID:15244416

Yang, Shoufeng; Evans, Julian R G

2004-01-01

36

A modified Drucker-Prager Cap model for die compaction simulation of pharmaceutical powders  

E-print Network

Institute for Pharmaceutical Materials Science, Department of Materials Science and Metallurgy, UniversityA modified Drucker-Prager Cap model for die compaction simulation of pharmaceutical powders L of pharmaceutical powders. In particular, a nonlinear elasticity law is proposed to describe the observed nonlinear

Elliott, James

37

In vitro bioactivity of a biocomposite fabricated from HA and Ti powders by powder metallurgy method  

Microsoft Academic Search

Traditionally, hydroxyapatite was used as a coating material on titanium substrate by various techniques. In the present work, a biocomposite was successfully fabricated from hydroxyapatite and titanium powders by powder metallurgy method. Bioactivity of the composite in a simulated body fluid (SBF) was investigated. Main crystal phases of the as-fabricated composite are found to be Ti2O, CaTiO3, CaO, ?-Ti and

C. Q. Ning; Y. Zhou

2002-01-01

38

Ceramic Inclusions in Powder Metallurgy Disk Alloys: Characterization and Modeling  

NASA Technical Reports Server (NTRS)

Powder metallurgy alloys are increasingly used in gas turbine engines, especially in turbine disk applications. Although powder metallurgy materials have many advantages over conventionally cast and wrought alloys (higher strength, higher temperature capability, etc.), they suffer from the rare occurrence of ceramic defects (inclusions) that are inherent to the powder atomization process. These inclusions can have a potentially large detrimental effect on the durability of individual components. An inclusion in a high stress location can act as a site for premature crack initiation and thereby considerably reduce the fatigue life. Because these inclusions are exceedingly rare, they typically do not reveal themselves in the process of characterizing the material for a particular application (the cumulative volume of the test bars in a fatigue life characterization is typically on the order of a single actual component). Ceramic inclusions have, however, been found to be the root cause of a number of catastrophic engine failures. To investigate the effect of these inclusions in detail, we have undertaken a study where known populations of ceramic particles, whose composition and morphology are designed to mimic the "natural" inclusions, are added to the precursor powder. Surface-connected inclusions have been found to have a particularly large detrimental effect on fatigue life; therefore, the quantity of ceramic "seeds" added is calculated to ensure that a minimum number will intersect the surface of the fatigue test bars. Because the ceramic inclusions are irregularly shaped and have a tendency to break up in the process of extrusion and forging, a method of calculating the probability of occurrence and expected intercepted surface area was needed. We have developed a Monte Carlo simulation to determine the distributions of these parameters and have verified the simulated results with observations of ceramic inclusions found in macroscopic slices from extrusions and forgings. Fatigue specimens have been machined from Udimet 720 (a powder metallurgy superalloy) forgings, to determine the effects of the inclusions on fatigue life. The ultimate goal of this study will be to use probabilistic methods to determine the reliability detriment that can be attributed to these ceramic inclusions. This work has been supported by the Ultra Safe and Ultra- Efficient Engine Technologies programs.

Bonacuse, Peter J.

2001-01-01

39

The Powder Metallurgy of Platinum AN HISTORICAL ACCOUNT OF ITS ORIGINS AND GROWTH  

Microsoft Academic Search

The history of the powder metallurgy of platinum may well be claimed to hr. the history o,f powder metallurgy itself. For very many years all the malleable platinum used in industry was made by this process, drvdoped independently in Spain, in England and in Russia. The author outlines the struggles of the early workers in this field and discussm the

J. C. Chaston

40

Novel synthesis of high phase-purity Mg2SnO4 from metallic precursors via powder metallurgy route  

E-print Network

Novel synthesis of high phase-purity Mg2SnO4 from metallic precursors via powder metallurgy route of composition Mg2Sn was prepared by the conventional powder metallurgy route. This up on heating in air under

Azad, Abdul-Majeed

41

Ceramic Inclusions In Powder Metallurgy Disk Alloys: Characterization and Modeling  

NASA Technical Reports Server (NTRS)

Powder metallurgy alloys are increasingly used in gas turbine engines, especially as the material chosen for turbine disks. Although powder metallurgy materials have many advantages over conventionally cast and wrought alloys (higher strength, higher temperature capability, etc.), they suffer from the rare occurrence of ceramic defects (inclusions) that arise from the powder atomization process. These inclusions can have potentially large detrimental effect on the durability of individual components. An inclusion in a high stress location can act as a site for premature crack initiation and thereby considerably reduce the fatigue life. Because these inclusions are exceedingly rare, they usually don't reveal themselves in the process of characterizing the material for a particular application (the cumulative volume of the test bars in a fatigue life characterization is typically on the order of a single actual component). Ceramic inclusions have, however, been found to be the root cause of a number of catastrophic engine failures. To investigate the effect of these inclusions in detail, we have undertaken a study where a known population of ceramic particles, whose composition and morphology are designed to mimic the 'natural' inclusions, are added to the precursor powder. Surface connected inclusions have been found to have a particularly large detrimental effect on fatigue life, therefore the volume of ceramic 'seeds' added is calculated to ensure that a minimum number will occur on the surface of the fatigue test bars. Because the ceramic inclusions are irregularly shaped and have a tendency to break up in the process of extrusion and forging, a method of calculating the probability of occurrence and expected intercepted surface and embedded cross-sectional areas were needed. We have developed a Monte Carlo simulation to determine the distributions of these parameters and have verified the simulated results with observations of ceramic inclusions found in macro slices from extrusions and forgings. The ultimate goal of this study will be to use probabilistic methods to determine the reliability detriment that can be attributed to these ceramic inclusions.

Bonacuse, Pete; Kantzos, Pete; Telesman, Jack

2002-01-01

42

Thixoforming of Stellite Powder Compacts  

NASA Astrophysics Data System (ADS)

Thixoforming involves processing metallic alloys in the semi-solid state. The process requires the microstructure to be spheroidal when part-solid and part-liquid i.e. to consist of solid spheroids surrounded by liquid. The aim of this work was to investigate whether powder compacts can be used as feedstock for thixoforming and whether the consolidating pressure in the thixoformer can be used to remove porosity from the compact. The powder compacts were made from stellite 6 and stellite 21 alloys, cobalt-based alloys widely used for e.g. manufacturing prostheses. Isothermal heat treatments of small samples in the consolidated state showed the optimum thixoforming temperature to be in the range 1340°C-1350°C for both materials. The alloys were thixoformed into graphite dies and flowed easily to fill the die. Porosity in the thixoformed components was lower than in the starting material. Hardness values at various positions along the radius of the thixoformed demonstrator component were above the specification for both alloys.

Hogg, S. C.; Atkinson, H. V.; Kapranos, P.

2007-04-01

43

Powder metallurgy: Solid and liquid phase sintering of copper  

NASA Technical Reports Server (NTRS)

Basic powder metallurgy (P/M) principles and techniques are presented in this laboratory experiment. A copper based system is used since it is relatively easy to work with and is commercially important. In addition to standard solid state sintering, small quantities of low melting metals such as tin, zinc, lead, and aluminum can be added to demonstrate liquid phase sintering and alloy formation. The Taguchi Method of experimental design was used to study the effect of particle size, pressing force, sintering temperature, and sintering time. These parameters can be easily changed to incorporate liquid phase sintering effects and some guidelines for such substitutions are presented. The experiment is typically carried out over a period of three weeks.

Sheldon, Rex; Weiser, Martin W.

1993-01-01

44

Phase Stability of a Powder Metallurgy Disk Superalloy  

NASA Technical Reports Server (NTRS)

Advanced powder metallurgy superalloy disks in aerospace turbine engines now entering service can be exposed to temperatures approaching 700 C, higher than those previously encountered. They also have higher levels of refractory elements, which can increase mechanical properties at these temperatures but can also encourage phase instabilities during service. Microstructural changes including precipitation of topological close pack phase precipitation and coarsening of existing gamma' precipitates can be slow at these temperatures, yet potentially significant for anticipated disk service times exceeding 1,000 h. The ability to quantify and predict such potential phase instabilities and degradation of capabilities is needed to insure structural integrity and air worthiness of propulsion systems over the full life cycle. A prototypical advanced disk superalloy was subjected to high temperature exposures, and then evaluated. Microstructural changes and corresponding changes in mechanical properties were quantified. The results will be compared to predictions of microstructure modeling software.

Gabb, Timothy P.; Gayda, John; Kantzos, P.; Telesman, Jack; Gang, Anita

2006-01-01

45

N18, powder metallurgy superalloy for disks: Development and applications  

SciTech Connect

The preliminary industrial development of a powder metallurgy (PM) superalloy, designated N18, for disk applications has been completed. This alloy exhibits good overall mechanical properties after appropriate processing of the material. These properties have been measured on both isothermally forged and extruded billets, as well as on specimens cut from actual parts. The temperature capability of the alloy is about 700 C for long-term applications and approximately 750 C for short-term use because of microstructural instability. Further improvements in creep and crack propagation properties, without significant reduction in tensile strength, are possible through appropriate thermomechanical processing, which results in a large controlled grain size. Spin pit tests on subscale disks have confirmed that the N18 alloy has a higher resistance than PM Astrology and is therefore an excellent alloy for modern turbine disk applications.

Guedou, J.Y.; Lautridou, J.C.; Honnorat, Y. (SNECMA, Evry (France). Materials and Processes Dept.)

1993-08-01

46

POWDER METALLURGY TiAl ALLOYS: MICROSTRUCTURES AND PROPERTIES  

SciTech Connect

The microstructures and properties of powder metallurgy TiAl alloys fabricated by hot extrusion of gas-atomized powder at different elevated temperatures were investigated. Microstructure of the alloy fabricated at 1150 C consisted of a mixture of fine ({gamma} + {alpha}{sub 2}) equiaxed grains and coarse ordered B2 grains. Particles of ordered hexagonal {omega} phase were also observed in some B2 grains. The alloy containing B2 grains displayed a low-temperature superplastic behavior: a tensile elongation of 310% was measured when the alloy was tested at 800 C under a strain rate of 2 x 10{sup -5} s{sup -1}. Microstructure of the alloy fabricated at 1250 C consisted of a mixture of fine ({gamma} + {alpha}{sub 2}) equiaxed grains, coarse {alpha}{sub 2} grains, and lamellar ({gamma} + {alpha}{sub 2}) colonies. An observation of stacking faults associated with fine {gamma} lamellae in {alpha}{sub 2} grains reveals that the stacking fault of {alpha}{sub 2} phase plays an important role in the formation of lamellar ({gamma} + {alpha}{sub 2}) colonies. Unlike the alloy fabricated at 1150{sup o}, the alloy fabricated at 1250{sup o} displayed no low-temperature superplasticity, but a tensile elongation of 260% at 1000 C was measured. Microstructure of the alloy fabricated at 1400 C consisted of fully lamellar ({gamma} + {alpha}{sub 2}) colonies with the colony size ranging between 50 {micro}m and 100 {micro}m, in which the width of {gamma} lamella is in a range between 100 nm and 350 nm, and the width of {alpha}{sub 2} lamella is in a range between 10 nm and 50 nm. Creep behavior of the ultrafine lamellar alloy and the effects of alloying addition on the creep resistance of the fully lamellar alloy are also investigated.

Hsiung, L

2006-12-11

47

Electrosintering of iron powder compacts  

NASA Astrophysics Data System (ADS)

The influence of a nominal external electric fieldE=3 to 10 kV/cm on the sintering of iron powder compacts for 30 minutes at 1140°C in a vacuum of ˜10-6 torr was investigated. It was found that the field reduced the porosity by as much as 29 to 73 pct compared to sintering without a field, the magnitude depending on the procedure employed to measure the density of the specimen. Optical microscopy revealed that the specimen electrosintered withE=10 kV/cm had a skin of ˜0.2 mm in thickness, where the porosity was significantly less than in the interior. This was also the depth of carburization that was obtained upon carburizing the electrosintered specimens. It is proposed that the decrease in porosity produced by the field results from a decrease in the chemical potential of vacancies at or just below the charged external surface. Vacancy flux equations employed to calculate the porosity as a function of distance below the external surface showed that the porosity becomes approximately zero at a distance ofx c=0.4 to 0.5 mm below the surface, which is in reasonable accord with the microscopy measurements. Similar values ofx c were obtained by assuming that the entire porosity decrease given by the density measurements occurred in a ring of thickness ofx c below the external surface. The difference in the density measured by two Archimedes-principle procedures and microscopy observations suggests that the cavities open to the external surface of the electrosintered specimens are smaller or narrower than those for specimens sintered without a field.

Fahmy, Yusef; Conrad, Hans

2001-03-01

48

Superplasticity in powder metallurgy aluminum alloys and composites  

SciTech Connect

Superplasticity in powder metallurgy Al alloys and composites has been reviewed through a detailed analysis. The stress-strain curves can be put into 4 categories: classical well-behaved type, continuous strain hardening type, continuous strain softening type and complex type. The origin of these different types of is discussed. The microstructural features of the processed material and the role of strain have been reviewed. The role of increasing misorientation of low angle boundaries to high angle boundaries by lattice dislocation absorption is examined. Threshold stresses have been determined and analyzed. The parametric dependencies for superplastic flow in modified conventional aluminum alloys, mechanically alloyed alloys and Al alloy matrix composites is determined to elucidate the superplastic mechanism at high strain rates. The role of incipient melting has been analyzed. A stress exponent of 2, an activation energy equal to that for grain boundary diffusion and a grain size dependence of 2 generally describes superplastic flow in modified conventional Al alloys and mechanically alloyed alloys. The present results agree well with the predictions of grain boundary sliding models. This suggests that the mechanism of high strain rate superplasticity in the above-mentioned alloys is similar to conventional superplasticity. The shift of optimum superplastic strain rates to higher values is a consequence of microstructural refinement. The parametric dependencies for superplasticity in aluminum alloy matrix composites, however, is different. A true activation energy of superplasticity in aluminum alloy matrix composites, however, is different. A true activation energy of 313 kJ/mol best describes the composites having SiC reinforcements. The role of shape of the reinforcement (particle or whisker) and processing history is addressed. The analysis suggests that the mechanism for superplasticity in composites is interface diffusion controlled grain boundary sliding.

Mishra, R.S. [Defence Metallurgical Research Lab., Hyderabad (India)] [Defence Metallurgical Research Lab., Hyderabad (India); Bieler, T.R. [Michigan State Univ., East Lansing, MI (United States). Dept. of Materials Science and Mechanics] [Michigan State Univ., East Lansing, MI (United States). Dept. of Materials Science and Mechanics; Mukherjee, A.K. [Univ. of California, Davis, CA (United States). Dept. of Mechanical, Aeronautical and Materials Engineering] [Univ. of California, Davis, CA (United States). Dept. of Mechanical, Aeronautical and Materials Engineering

1995-03-01

49

A neural network approach for selection of powder metallurgy materials and process parameters  

Microsoft Academic Search

The artificial neural network (NN) methodology presented in this paper has been developed for selection of powder and process parameters for Powder Metallurgy (PM) part manufacture. This methodology differs from the statistical modelling of mechanical properties in that it is not necessary to make assumptions regarding the form of the functions relating input and output variables. Employment of a NN

R. P. Cherian; L. N. Smith; P. S. Midha

2000-01-01

50

Testing of electroformed deposited iridium/powder metallurgy rhenium rockets  

NASA Technical Reports Server (NTRS)

High-temperature, oxidation-resistant chamber materials offer the thermal margin for high performance and extended lifetimes for radiation-cooled rockets. Rhenium (Re) coated with iridium (Ir) allow hours of operation at 2200 C on Earth-storable propellants. One process for manufacturing Ir/Re rocket chambers is the fabrication of Re substrates by powder metallurgy (PM) and the application of Ir coatings by using electroformed deposition (ED). ED Ir coatings, however, have been found to be porous and poorly adherent. The integrity of ED Ir coatings could be improved by densification after the electroforming process. This report summarizes the testing of two 22-N, ED Ir/PM Re rocket chambers that were subjected to post-deposition treatments in an effort to densify the Ir coating. One chamber was vacuum annealed, while the other chamber was subjected to hot isostatic pressure (HIP). The chambers were tested on gaseous oxygen/gaseous hydrogen propellants, at mixture ratios that simulated the oxidizing environments of Earth-storable propellants. ne annealed ED Ir/PM Re chamber was tested for a total of 24 firings and 4.58 hr at a mixture ratio of 4.2. After only 9 firings, the annealed ED Ir coating began to blister and spall upstream of the throat. The blistering and spalling were similar to what had been experienced with unannealed, as-deposited ED Ir coatings. The HIP ED Ir/PM Re chamber was tested for a total of 91 firings and 11.45 hr at mixture ratios of 3.2 and 4.2. The HIP ED Ir coating remained adherent to the Re substrate throughout testing; there were no visible signs of coating degradation. Metallography revealed, however, thinning of the HIP Ir coating and occasional pores in the Re layer upstream of the throat. Pinholes in the Ir coating may have provided a path for oxidation of the Re substrate at these locations. The HIP ED Ir coating proved to be more effective than vacuum annealed and as-deposited ED Ir. Further densification is still required to match the integrity of chemically vapor deposited Ir coatings. Despite this, the successful long duration testing of the HIP ED Ir chamber, in an oxidizing environment comparable to Earth-storable propellants, demonstrated the viability of this Ir/Re rocket fabrication process.

Reed, Brian D.; Dickerson, Robert

1996-01-01

51

Elevated temperature crack growth in advanced powder metallurgy aluminum alloys  

NASA Technical Reports Server (NTRS)

Rapidly solidified Al-Fe-V-Si powder metallurgy alloy FVS0812 is among the most promising of the elevated temperature aluminum alloys developed in recent years. The ultra fine grain size and high volume fraction of thermally stable dispersoids enable the alloy to maintain tensile properties at elevated temperatures. In contrast, this alloy displays complex and potentially deleterious damage tolerant and time dependent fracture behavior that varies with temperature. J-Integral fracture mechanics were used to determine fracture toughness (K sub IC) and crack growth resistance (tearing modulus, T) of extruded FVS0812 as a function of temperature. The alloy exhibits high fracture properties at room temperature when tested in the LT orientation, due to extensive delamination of prior ribbon particle boundaries perpendicular to the crack front. Delamination results in a loss of through thickness constraint along the crack front, raising the critical stress intensity necessary for precrack initiation. The fracture toughness and tensile ductility of this alloy decrease with increasing temperature, with minima observed at 200 C. This behavior results from minima in the intrinsic toughness of the material, due to dynamic strain aging, and in the extent of prior particle boundary delaminations. At 200 C FVS0812 fails at K levels that are insufficient to cause through thickness delamination. As temperature increases beyond the minimum, strain aging is reduced and delamination returns. For the TL orientation, K (sub IC) decreased and T increased slightly with increasing temperature from 25 to 316 C. Fracture in the TL orientation is governed by prior particle boundary toughness; increased strain localization at these boundaries may result in lower toughness with increasing temperature. Preliminary results demonstrate a complex effect of loading rate on K (sub IC) and T at 175 C, and indicate that the combined effects of time dependent deformation, environment, and strain aging may play a role. Fractography showed that microvoid coalescence was the microscopic mode of fracture in FVS0812 under all testing conditions. However, the nature of the microvoids varied with test temperature and loading rate, and is complex for the fine grain and dipersoid sizes of FVS0812.

Porr, William C., Jr.; Gangloff, Richard P.

1990-01-01

52

Investigation of the Environmental Durability of a Powder Metallurgy Material  

NASA Technical Reports Server (NTRS)

PM304 is a NASA-developed composite powder metallurgy material that is being developed for high temperature applications such as bushings in high temperature industrial furnace conveyor systems. My goal this summer was to analyze and evaluate the effects that heat exposure had on the PM304 material at 500 C and 650 C. The material is composed of Ni-Cr, Ag, Cr2O3, and eutectic BaF2-CaF2. PM304 is designed to eliminate the need for oil based lubricants in high temperature applications, while reducing friction and wear. However, further investigation was needed to thoroughly examine the properties of PM304. The effects of heat exposure on PM304 bushings were investigated. This investigation was necessary due to the high temperatures that the material would be exposed to in a typical application. Each bushing was cut into eight sections. The specimens were heated to 500 C or 650 C for time intervals from 1 hr to 5,000 hrs. Control specimens were kept at room temperature. Weight and thickness measurements were taken before and after the bushing sections were exposed to heat. Then the heat treated specimens were mounted and polished side by side with the control specimens. This enabled optical examination of the material's microstructure using a metallograph. The specimens were also examined with a scanning electron microscope (SEM). The microstructures were compared to observe the effects of the heat exposure. Chemical analysis was done to investigate the interactions between Ni-Cr and BaF2-CaF2 and between Cr2O3 and BaF2-CaF2 at high temperature. To observe this, the two compounds that were being analyzed were mixed in a crucible in varied weight percentages and heated to 1100 C in a furnace for approximately two hours. Then the product was allowed to cool and was then analyzed by X-ray diffraction. Interpretation of the results is in progress.

Ward, LaNita D.

2004-01-01

53

Shock compaction of molybdenum nitride powder  

NASA Astrophysics Data System (ADS)

Molybdenum nitride has a potential application in multi layer capacitors. Since this material is not readily available in bulk form, molybdenum nitride powder, consisting of a mixture of the nitrides Mo2N and MoN has been compacted to 12 mm circular, 1-2 mm thick discs utilizing shock-compression technique. Powders were packed to 55-67 percent of the crystal density and shock compacted using a plate impact shock recovery system at 1.35 to 1.81 km/s impact velocity. The recovered compacts were characterized by scanning electron microscope, x-ray diffraction and cyclic voltammetry to evaluate its electrochemical stability in sulphuric acid. This paper presents the optimization technique used for compaction and the characteristics of the recovered compacts.

Roberson, S.; Davis, R. F.; Joshi, V. S.; Fienello, D.

1998-07-01

54

Compaction Stress in Fine Powders  

SciTech Connect

A vexing feature in granular materials compaction is density extrema interior to a compacted shape. Such inhomogeneities can lead to weaknesses and loss of dimensional control in ceramic parts, unpredictable dissolution of pharmaceuticals, and undesirable stress concentration in load-bearing soil. As an example, the centerline density in a cylindrical compact often does not decrease monotonically from the pressure source but exhibits local maxima and minima. Two lines of thought in the literature predict, respectively, diffusive and wavelike propagation of stress. Here, a general memory function approach has been formulated that unifies these previous treatments as special cases; by analyzing a convenient intermediate case, the telegrapher's equation, one sees that local density maxima arise via semidiffusive stress waves reflecting from the die walls and adding constructively at the centerline.

Hurd, A.J.; Kenkre, V.M.; Pease, E.A.; Scott, J.E.

1999-04-01

55

Fabrication of Powder Metallurgy Pure Ti Material by Using Thermal Decomposition of TiH2  

NASA Astrophysics Data System (ADS)

Titanium (Ti) and titanium alloys have been interested as an engineering material because they are widely used across various industrial applications, for example, motorcycle, automotive and aerospace industries, due to their light weight, high specific strength and superior corrosion resistance. Ti materials are particularly significant for the aircraft using carbon/carbon (C/C) composites, for example, carbon fiber reinforced plastics (CFRP), because Ti materials are free from the problem of contact corrosion between C/C composites. However, the applications of Ti materials are limited because of their high cost. From a viewpoint of cost reduction, cost effective process to fabricate Ti materials is strongly required. In the present study, the direct consolidation of titanium hydride (TiH2) raw powders in solid-state was employed to fabricate pure Ti bulk materials by using thermal decomposition of TiH2. In general, the production cost of Ti components is expensive due to using commercially pure (CP) Ti powders after dehydrogenation. On the other hand, the novel process using TiH2 powders as starting materials is a promising low cost approach for powder metallurgy (P/M) Ti products. Furthermore, this new process is also attractive from a viewpoint of energy saving because the dehydrogenation is integrated into the sintering process. In this study, TiH2 raw powders were directly consolidated by conventional press technique at 600 MPa to prepare TiH2 powder compacted billets. To thermally decompose TiH2 and obtain sintered pure Ti billets, the TiH2 powder billets were heated in the integrated sintering process including dehydrogenation. The hot-extruded pure Ti material, which was heat treated at 1273 K for 180 min in argon gas atmosphere, showed tensile strength of 701.8 MPa and elongation of 27.1%. These tensile properties satisfied the requirements for JIS Ti Grade 4. The relationship between microstructures, mechanical properties response and heat treatment temperature is discussed in detail.

Mimoto, Takanori; Nakanishi, Nozomi; Umeda, Junko; Kondoh, Katsuyoshi

56

An analysis of hot deformation of an Al–Cu–Mg alloy produced by powder metallurgy  

Microsoft Academic Search

The high-temperature plasticity of a 2014 aluminium alloy produced by powder metallurgy was investigated in a wide range of temperatures and strain rates. When the strain rate was plotted as a function of stress (either peak flow stress in torsion, or applied stress in tensile creep), the alloy exhibited the same threshold-like behaviour observed in similar materials. The microstructure of

F Bardi; M Cabibbo; E Evangelista; S Spigarelli; M Vuk?evi?

2003-01-01

57

Powder metallurgy approaches to high temperature components for gas turbine engines  

NASA Technical Reports Server (NTRS)

Research is reported for the tensile strength, ductility, and heat performance characterisitics of powder metallurgy (p/m) superalloys. Oxide dispersion strengthened alloys were also evaluated for their strength during thermal processing. The mechanical attributes evident in both p/m supperalloys and dispersion strengthened alloys are discussed in terms of research into their possible combination.

Probst, H. B.

1974-01-01

58

A powder metallurgy austenitic stainless steel for application at very low temperatures  

Microsoft Academic Search

The Large Hadron Collider to be built at CERN will require 1232 superconducting dipole magnets operating at 1.9 K. By virtue of their mechanical properties, weldability and improved austenite stability, nitrogen enriched austenitic stainless steels have been chosen as the material for several of the structural components of these magnets. Powder Metallurgy (PM) could represent an attractive production technique for

Stefano Sgobba; F Savary; J Liimatainen; M Kumpula

2000-01-01

59

Some aspects on workability of aluminium–iron powder metallurgy composite during cold upsetting  

Microsoft Academic Search

Workability is a measure of the extent of deformation that a powder metallurgy materials can withstand prior to fracture occurred in the forming or upsetting processes. Ductile fracture is the most common mode of failure in bulk forming process. The formability is a complicated phenomenon, dependent upon the process as well as the material parameters. A complete experimental investigation on

R. Narayanasamy; T. Ramesh; K. S. Pandey

2005-01-01

60

Mechanical properties of modified low cobalt powder metallurgy Udimet 700 type alloys  

NASA Technical Reports Server (NTRS)

Eight superalloys derived from Udimet 700 were prepared by powder metallurgy, hot isostatically pressed, heat treated and their tensile and creep rupture properties determined. Several of these alloys displayed properties superior to those of Udimet 700 similarly prepared, in one case exceeding the creep rupture life tenfold. Filter clogging by extracted gamma prime, its measurement and significance are discussed in an appendix.

Harf, Fredric H.

1989-01-01

61

Production of Titanium Alloys for Advanced Aerospace Systems by Powder Metallurgy  

Microsoft Academic Search

Titanium alloys parts are ideally suited for advanced aerospace systems because of their unique combination of high specific strength at both room temperature and moderately elevated temperature, in addition to excellent corrosion resistance. Despite these features, use of titanium alloys in engines and airframes is limited by cost. The alloys processing by powder metallurgy eases the obtainment of parts with

Vinicius André; Rodrigues Henriques; Pedro Paulo de Campos; José Carlos Bressiani

62

Copper matrix SiC and Al 2O 3 particulate composites by powder metallurgy technique  

Microsoft Academic Search

Copper matrix reinforced with either Ni-coated or uncoated SiC and Al2O3 particulate composites were made by means of the powder metallurgy route. The reinforcement particles of SiC and Al2O3 were coated with a thin layer of nickel by electroless method. The coated or uncoated reinforcement particles of either SiC or Al2O3 were added to copper metal powders with nominal loading

S. F Moustafa; Z Abdel-Hamid; A. M Abd-Elhay

2002-01-01

63

The benefits of commercially pure wrought powder metallurgy alloy strip in lithium battery and nickel cadmium energy systems  

SciTech Connect

This paper describes high purity wrought powder metallurgy alloys which conform to the general compositional description of commercially pure nickel (99% min. Ni+Co) yet offer property advantages for battery applications which are not available in conventional cast and wrought commercially pure alloy grades. In particular, the powder metallurgy approach enables use of very low level alloy additions with favorable impact on mechanical, welding, and other properties without detracting significantly from the high electrical and thermal conductivity achievable for high purity materials. Application details requiring special properties are noted and property comparisons are given between powder metallurgy and melted materials.

Smith, R.A.

1984-08-01

64

Application of superalloy powder metallurgy for aircraft engines  

NASA Technical Reports Server (NTRS)

The results of the Materials for Advanced Turbine Engines (MATE) program initiated by NASA are presented. Mechanical properties comparisons are made for superalloy parts produced by as-HIP powder consolidation and by forging of HIP consolidated billets. The effect of various defects on the mechanical properties of powder parts are shown.

Dreshfield, R. L.; Miner, R. V., Jr.

1980-01-01

65

Powder and compaction characteristics of pregelatinized starches.  

PubMed

Pregelatinized starch is widely used as a pharmaceutical aid, especially as a filler-binder. It is known that the tableting performance of excipients could be affected by their source. The aim of this study was to evaluate the powder and tableting properties of pregelatinized starches obtained from yucca, corn and rice and compare those properties with those of Starch 1500. This material had the lowest particle size, and porosity and largest density and best flow. However, yucca starch and corn starch showed an irregular granule morphology, better compactibility and compressibility than Starch 1500. Their onset of plastic deformation and their strain rate sensitivity was comparable to that of Starch 1500. These two materials showed compact disintegration slower that Starch 1500. Conversely, rice starch showed a high elasticity, and friability, low compactibility, which are undesirable for direct compression. This study demonstrated the potential use of pregelatinized starches, especially those obtained from yucca and corn as direct compression filler-binders. PMID:22822539

Rojas, J; Uribe, Y; Zuluaga, A

2012-06-01

66

Causal Factors of Weld Porosity in Gas Tungsten Arc Welding of Powder Metallurgy Produced Titanium Alloys  

SciTech Connect

ORNL undertook an investigation using gas tungsten arc (GTA) welding on consolidated powder metallurgy (PM) titanium (Ti) plate, to identify the causal factors behind observed porosity in fusion welding. Tramp element compounds of sodium and magnesium, residual from the metallothermic reduction of titanium chloride used to produce the titanium, were remnant in the starting powder and were identified as gas forming species. PM-titanium made from revert scrap where sodium and magnesium were absent, showed fusion weld porosity, although to a lesser degree. We show that porosity was attributable to hydrogen from adsorbed water on the surface of the powders prior to consolidation. The removal / minimization of both adsorbed water on the surface of titanium powder and the residues from the reduction process prior to consolidation of titanium powders, are critical to achieve equivalent fusion welding success similar to that seen in wrought titanium produced via the Kroll process.

Muth, Thomas R [ORNL; Yamamoto, Yukinori [ORNL; Frederick, David Alan [ORNL; Contescu, Cristian I [ORNL; Chen, Wei [ORNL; Lim, Yong Chae [ORNL; Peter, William H [ORNL; Feng, Zhili [ORNL

2013-01-01

67

Recent development in the fabrication of metal matrix-particulate composites using powder metallurgy techniques  

Microsoft Academic Search

It is advantageous to fabricate metal matrix-particulate composites (MMPCs) using powder metallurgy (PM) because the fabricated composites possess a higher dislocation density, a small sub-grain size and limited segregation of particles, which, when combined, result in superior mechanical properties. The various PM-related processes currently in use in the fabrication of MMPCs, are reviewed, outlining the common problems encountered in each

Y. B. Liu; S. C. Lim; L. Lu; M. O. Lai

1994-01-01

68

An experimental determination of the thermal conductivity of a 304L stainless steel powder metallurgy material  

Microsoft Academic Search

The thermal conductivity of a 304L stainless steel powder metallurgy (P\\/M) material was experimentally determined to support research aimed at understanding the poor machining characteristics of P\\/M austenitic stainless steels. Thermal conductivity measurements were made on samples having relative densities ranging between 64 and 90% of theoretical density since workpieces requiring machining are often fabricated in that density range. The

J. S. Agapiou; M. F. DeVries

1989-01-01

69

Development of novel carbon nanotube reinforced magnesium nanocomposites using the powder metallurgy technique  

Microsoft Academic Search

Carbon nanotube (CNT) reinforced magnesium was synthesized using the powder metallurgy technique followed by hot extrusion. Up to 0.3wt% of CNTs were added as reinforcements. The effects of the carbon nanotubes on the physical and mechanical properties of Mg were investigated. The thermo-mechanical property results show an increase in thermal stability with increasing amount of CNTs in the Mg nanocomposites.

C S Goh; J Wei; L C Lee; M Gupta

2006-01-01

70

High strain rate superplasticity in powder metallurgy processed Al-16Si-5Fe alloy  

SciTech Connect

In the present paper, new additional experimental results for these aluminum alloys with a very fine grain structure are demonstrated over a strain range of 10{sup {minus}4} {approximately} 10{sup {minus}1} s{sup {minus}1} in the temperature range of 673 {approximately} 793 K, to analyze the possible mechanisms of superplasticity at high strain rates in very fine grained aluminum alloys produced by powder metallurgy method.

Cho, H.S.; Jeong, H.G.; Kim, M.S.; Yamagata, H.

2000-01-01

71

Hydrogen halide cleaning of powder metallurgy nickel-20 chromium-3 thoria.  

NASA Technical Reports Server (NTRS)

The Cr2O3 content of powder metallurgy nickel-20 chromium-3 thoria was reduced with atmospheres consisting of hydrogen plus hydrogen chloride (HCl) or hydrogen bromide (HBr). The nonthoria oxygen content or 'oxygen excess' was reduced from an initial amount of greater than 50,000 ppm to less than 100 ppm. Low temperatures were effective, but lowest oxygen levels were achieved with the highest cleaning temperature of 1200 C.

Herbell, T. P.

1972-01-01

72

A Nonvolume Preserving Plasticity Theory with Applications to Powder Metallurgy  

NASA Technical Reports Server (NTRS)

A plasticity theory has been developed to predict the mechanical response of powder metals during hot isostatic pressing. The theory parameters were obtained through an experimental program consisting of hydrostatic pressure tests, uniaxial compression and uniaxial tension tests. A nonlinear finite element code was modified to include the theory and the results of themodified code compared favorably to the results from a verification experiment.

Cassenti, B. N.

1983-01-01

73

Making Self-Lubricating Parts By Powder Metallurgy  

NASA Technical Reports Server (NTRS)

Compositions and parameters of powder-metallurgical fabrication processes determined for new class of low-friction, low-wear, self-lubricating materials. Used in oxidizing or reducing atmospheres in bearings and seals, at temperatures from below 25 degrees C to as high as 900 degrees C. Thick parts made with minimal waste.

Sliney, Harold E.; Dellacorte, Christopher

1990-01-01

74

Micro powder metallurgy for the replicative production of metallic microstructures  

Microsoft Academic Search

Reproductive techniques like injection molding or embossing of feedstock provide microstructures of a wide variety of materials\\u000a for a reasonable price to micro system technology. In this paper, the dependencies and barriers to produce high aspect ratio\\u000a structures by micro metal injection molding are described; some results of embossing of metal powder based feedstocks are\\u000a presented, too. The investigations show

A. Rota; T. V. Duong; T. Hartwig

2002-01-01

75

Advances in powder metallurgy - 1991. Vol. 6 - Aerospace, refractory and advanced materials; Proceedings of the Powder Metallurgy Conference and Exhibition, Chicago, IL, June 9-12, 1991  

SciTech Connect

Various papers on aerospace, refractory, and advanced materials are presented. Individual topics addressed include: nonequilibrium processing of powder alloys for aerospace applications, chemical conditioning of rapidly solidified aluminum alloy particulate, fabrication of rapidly solidified high temperature aluminum alloys, fatigue and fracture of an advanced PM-aluminum alloy, thermal and mechanical properties of extruded 7075-Al P/M alloys, reactive sintering and reactive hot isostatic pressing of iron aluminides, P/M processing and applications of Fe3Al-based intermetallics, properties of plasma atomized NiAl powders, processing of continuous fiber reinforced NiAl matrix composite. Also discussed are: powder forging process on an alumimum alloy, P/M magnesium particle composites, P/M short-fiber-reinforced magnesium, mechanical properties of a TiAl6V4 alloy processed by powder metallurgy, porous core/Be Ti-6-4 development for aerospace structures, consolidation and plasticity of Bi-Sr-Ca-Cu-O superconductors, development of a new W-Ni-Mn heavy alloy.

Pease, L.F. III; Sansoucy, R.J.

1991-01-01

76

A maraging steel produced by the powder metallurgy method  

Microsoft Academic Search

1.In a study into the effect of sintering temperature and duration on the density, microhardness, and martensite lattice constant of a powder metallurgical maraging steel and also on the character of formation of its micro structure, the following mechanical properties were attained after sintering and aging: sB=101 kg\\/mm2, s0.2=98 kg\\/mm2, d=4%, ?=12%, aH=7.9 kg-m\\/cm2, and HRC=25–27.2.The influence exerted by plastic

V. N. Antsiferov; Yu. M. Kolbenev

1972-01-01

77

Net-Shape HIP Powder Metallurgy Components for Rocket Engines  

NASA Technical Reports Server (NTRS)

True net shape consolidation of powder metal (PM) by hot isostatic pressing (HIP) provides opportunities for many cost, performance and life benefits over conventional fabrication processes for large rocket engine structures. Various forms of selectively net-shape PM have been around for thirty years or so. However, it is only recently that major applications have been pursued for rocket engine hardware fabricated in the United States. The method employs sacrificial metallic tooling (HIP capsule and shaped inserts), which is removed from the part after HIP consolidation of the powder, by selective acid dissolution. Full exploitation of net-shape PM requires innovative approaches in both component design and materials and processing details. The benefits include: uniform and homogeneous microstructure with no porosity, irrespective of component shape and size; elimination of welds and the associated quality and life limitations; removal of traditional producibility constraints on design freedom, such as forgeability and machinability, and scale-up to very large, monolithic parts, limited only by the size of existing HIP furnaces. Net-shape PM HIP also enables fabrication of complex configurations providing additional, unique functionalities. The progress made in these areas will be described. Then critical aspects of the technology that still require significant further development and maturation will be discussed from the perspective of an engine systems builder and end-user of the technology.

Bampton, Cliff; Goodin, Wes; VanDaam, Tom; Creeger, Gordon; James, Steve

2005-01-01

78

Powder metallurgy processing of high strength turbine disk alloys  

NASA Technical Reports Server (NTRS)

Using vacuum-atomized AF2-1DA and Mar-M432 powders, full-scale gas turbine engine disks were fabricated by hot isostatically pressing (HIP) billets which were then isothermally forged using the Pratt & Whitney Aircraft GATORIZING forging process. While a sound forging was produced in the AF2-1DA, a container leak had occurred in the Mar-M432 billet during HIP. This resulted in billet cracking during forging. In-process control procedures were developed to identify such leaks. The AF2-1DA forging was heat treated and metallographic and mechanical property evaluation was performed. Mechanical properties exceeded those of Astroloy, one of the highest temperature capability turbine disk alloys presently used.

Evans, D. J.

1976-01-01

79

Properties of boride-added powder metallurgy magnesium alloys  

NASA Astrophysics Data System (ADS)

Magnesium alloys with metallic borides, magnesium diboride (MgB2) or aluminum diboride (AlB2), were investigated regarding their mechanical properties, transverse rupture strength (TRS) and micro Vickers hardness (HV). The alloys were made from pure Mg, Al and B powders by mechanical alloying and hot pressing to have boride content of between 2.0 and 20 vol%. The alloy with AlB2 exhibited an obvious improvement of HV around a boride content of 6 vol% though the other alloy, with MgB2, did not. TRS showed moderate maxima around the same boride content region for the both alloys. X-ray diffraction measurements indicated an intermetallic compound, Mg17Al12, formed in the alloy with AlB2, which was consistent with its higher hardness.

Tanaka, Atsushi; Yoshimura, Syota; Fujima, Takuya; Takagi, Ken-ichi

2009-06-01

80

Fabrication and characterization of americium, neptunium and curium bearing MOX fuels obtained by powder metallurgy process  

NASA Astrophysics Data System (ADS)

MOX fuel pellets containing up to 1.4 wt% of Minor Actinides (MA), i.e. Am, Np and Cm, were fabricated to demonstrate the technical feasibility of powder metallurgy process involving, pelletizing and sintering in controlled atmosphere. The compounds were then characterized using XRD, SEM and EDX/EPMA. Dense pellets were obtained which closed porosity mean size is equal to 7 ?m. The results indicate the formation of (U, Pu)O 2 solid solution. However, microstructure contains some isolated UO 2 grains. The distribution of Am and Cm appears to be homogeneous whereas Np was found to be clustered at some locations.

Lebreton, Florent; Prieur, Damien; Jankowiak, Aurélien; Tribet, Magaly; Leorier, Caroline; Delahaye, Thibaud; Donnet, Louis; Dehaudt, Philippe

2012-01-01

81

Joining of rapidly solidified powder metallurgy Al-Fe-Ce alloys  

SciTech Connect

Joining of rapidly-solidified powder metallurgy (RS/PM) Al-Fe-Ce alloys by capacitor-discharge and inertia-friction welding investigated from a metallurgical perspective. Capacitor-discharge welding was effective in the joining of 6.4 mm diameter Al-8Fe-4Ce rod. The application of pressure simultaneously with fusion zone solidification suppressed the formation of fusion zone porosity in this high-hydrogen PM product. In addition, extremely rapid cooling rates promoted RS fusion zone microstructures and prevented heat-affected zone (HAZ) formation, thereby providing joint efficiencies up to 100%. 4 references, 9 figures, 2 tables.

Baeslack, W.A. III

1989-01-01

82

Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy  

NASA Technical Reports Server (NTRS)

Hot isostatically pressed powder metallurgy Astroloy was obtained which contained 1.4 percent fine porosity at the grain boundaries produced by argon entering the powder container during pressing. This material was tested at 650 C in fatigue, creep fatigue, tension, and stress-rupture and the results compared with previous data on sound Astroloy. The pores averaged about 2 micrometers diameter and 20 micrometers spacing. They did influence fatigue crack initiation and produced a more intergranular mode of propagation. However, fatigue life was not drastically reduced. A large 25 micrometers pore in one specimen resulting from a hollow particle did not reduce life by 60 percent. Fatigue behavior of the porous material showed typical correlation with tensile behavior. The plastic strain range life relation was reduced proportionately with the reduction in tensile ductility, but the elastic strain range-life relation was little changed reflecting the small reduction in sigma sub u/E for the porous material.

Miner, R. V., Jr.; Dreshfield, R. L.

1980-01-01

83

Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy  

NASA Technical Reports Server (NTRS)

Hot-isostatically-pressed powder-metallurgy Astroloy was obtained which contained 1.4 percent porosity at the grain boundaries produced by argon entering the powder container during pressing. This material was tested at 650 C in fatigue, creep-fatigue, tension, and stress-rupture and the results compared with data on sound Astroloy. They influenced fatigue crack initiation and produced a more intergranular mode of propagation but fatigue life was not drastically reduced. Fatigue behavior of the porous material showed typical correlation with tensile behavior. The plastic strain range-life relation was reduced proportionately with the reduction in tensile ductility, but the elastic strain range-life relation was changed little.

Miner, R. V.; Dreshfield, R. L.

1980-01-01

84

Microstructure and mechanical behavior of 6061Al reinforced with silicon nitride particles, processed by powder metallurgy  

SciTech Connect

A critical step in the processing of Metal Matrix Composites (MMCs) reinforced with ceramic particles is the insertion of these particles into the metal matrix alloy. This greatly influences the strength of the composite since it is controlled by the metal-particle interfacial bond strength. Because of the difficulty in wetting ceramic particles with molten metal, the Powder Metallurgy or PM route was developed. Powder Extrusion consolidates the composite to over 98% dense, and can be carried out below the Solidus Temperature of the alloy. The most important aspect of the microstructure is the distribution of the reinforcing particles, and this depends on the processing and fabrication routes involved, as well as the relative size of the matrix and reinforcing particles. Extrusion can homogenize the structure to some extent, but minimizing reinforcement inhomogeneity during initial processing is important to achieve optimum properties.

Amigo, V.; Ortiz, J.L.; Salvador, M.D.

2000-01-31

85

Microstructural and mechanical characteristics of porous iron prepared by powder metallurgy.  

PubMed

The demand for porous biodegradable load-bearing implants has been increasing recently. Based on investigations of biodegradable stents, porous iron may be a suitable material for such applications. In this study, we prepared porous iron samples with porosities of 34-51vol.% by powder metallurgy using ammonium bicarbonate as a space-holder material. We studied sample microstructure (SEM-EDX and XRD), flexural and compressive behaviors (universal loading machine) and hardness HV5 (hardness tester) of the prepared samples. Sample porosity increased with the amount of spacer in the initial mixtures. Only the pore surfaces had insignificant oxidation and no other contamination was observed. Increasing porosity decreased the mechanical properties of the samples; although, the properties were still comparable with human bone and higher than those of porous non-metallic biomaterials and porous magnesium prepared in a similar way. Based on these results, powder metallurgy appears to be a suitable method for the preparation of porous iron for orthopedic applications. PMID:25175241

Capek, Jaroslav; Vojt?ch, Dalibor

2014-10-01

86

Development of an extra-high strength powder metallurgy nickel-base superalloy  

NASA Technical Reports Server (NTRS)

A program was conducted to optimize the composition of NASA IIb-11, an alloy originally developed as a wrought material, for thermal stability and to determine the feasibility for producing the alloy using powder metallurgy techniques. Seven compositions were melted and atomized, hot isostatically pressed, cross rolled to disks and heat treated. Tensile and stress rupture properties from room temperature to 870 C (1600 F) were determined in addition to thermal stability characteristics. Processing variables included hot isostatic pressing parameters and handling, cross rolling procedures and heat treatment cycles. NASA IIb-11E displayed the best combination of overall properties for service as a 760 C (1400 F) disk material. Its composition is 0.06 C, 8.5 Cr, 9.0 Co, 2.0 Mo, 7.1 W, 6.6 Ta, 4.5 Al, 0.75 Ti, 0.5 V, 0.7 Hf, 0.01 B, 0.05 Zr and balance Ni. While the alloy exhibits the highest 760 C (1400 F) rupture strength reported for any powder metallurgy disk alloy to date, additional studies to further evaluate the effects of heat treatment may be required. The alloy is not susceptible to topologically close-packed phase formation during thermal exposure at 870 C (1600 F) for 1,500 hours, but its mechanical property levels are lowered due to grain boundary carbide formation.

Kent, W. B.

1977-01-01

87

Modelling the plastic deformation during high-temperature creep of a powder-metallurgy coarse-grained superalloy  

Microsoft Academic Search

The study of creep deformation in a coarse-grained Udimet 720 superalloy obtained by powder-metallurgy reveals a good resistance associated to a dislocational deformation mechanism. A model is proposed for simulating creep and tensile curves. This model is used to understand the effect of microstructural changes on the deformation mechanisms.

Sofiane Terzi; Raphael Couturier; Laure Guétaz; Bernard Viguier

2008-01-01

88

Particles into 410L Stainless Steel by a Powder Metallurgy Route  

NASA Astrophysics Data System (ADS)

Addition of yttria to steels has been proposed for the fabrication of oxide-dispersion-strengthened materials for nuclear power applications. We have investigated materials prepared from 12 Cr martensitic stainless steel, AISI 410L, produced by powder metallurgy. Materials were produced with and without yttria addition, and two different sizes of yttria were used, 0.9 µm and 50 nm. Tensile and mini-creep tests were performed to determine mechanical properties. Optical microscopy, SEM, TEM, and EDX analysis were used to investigate the microstructures and deformation mechanisms and to obtain information about non-metallic inclusion particles. SiO2, MnS, and Y2Si2O7 inclusion particles were observed. An SiO2 and Y2O3 interaction was seen to have occurred during the ball milling, which impaired the final mechanical properties. Small-angle neutron scattering experiments showed that the matrix chemistry prevented effective dissolution of the yttria.

Zeybek, A.; Barroso, S. Pirfo; Chong, K. B.; Edwards, L.; Fitzpatrick, M. E.

2014-06-01

89

A powder metallurgy austenitic stainless steel for application at very low temperatures  

E-print Network

The Large Hadron Collider to be built at CERN will require 1232 superconducting dipole magnets operating at 1.9 K. By virtue of their mechanical properties, weldability and improved austenite stability, nitrogen enriched austenitic stainless steels have been chosen as the material for several of the structural components of these magnets. Powder Metallurgy (PM) could represent an attractive production technique for components of complex shape for which dimension tolerances, dimensional stability, weldability are key issues during fabrication, and mechanical properties, ductility and leak tightness have to be guaranteed during operation. PM Hot Isostatic Pressed test plates and prototype components of 316LN-type grade have been produced by Santasalo Powdermet Oy. They have been fully characterized and mechanically tested down to 4.2 K at CERN. The fine grained structure, the absence of residual stresses, the full isotropy of mechanical properties associated to the low level of Prior Particle Boundaries oxides ...

Sgobba, Stefano; Liimatainen, J; Kumpula, M

2000-01-01

90

Applied mechanics modeling of granulated ceramic powder compaction  

SciTech Connect

In ceramic manufacturing processes such as dry-pressing, correlations between applied compacting pressure and resultant powder compact density are essential for defining reliable process conditions for ceramic components. Pressure-density diagrams have been developed as a tool for both process control and for understanding the compaction behavior of different powders. These types of diagrams, however, pertain only to the averag@ properties of a powder compact and do not address a significant issue in powder compaction processes: the formation of density gradients within the compact. Continuum-based mechanics models of varying complexity have addressed the influence of frictional forces acting at the powder-die wall interface which dissipate the applied pressure throughout the compact. Resulting pressure distribution models are then typically coupled with empirical functions relating pressure and density to obtain a green density distribution in the compact. All of these models predict similar trends; however, none predict the distribution with sufficient accuracy to be considered as a design tool for industrial applications.

Mahoney, F.M.; Readey, M.J.

1995-08-01

91

Analysis of powder compaction process through equal channel angular extrusion  

E-print Network

A thermodynamic framework was presented for the development of powderconstitutive models. The process of powder compaction through Equal ChannelAngular Extrusion (ECAE) at room temperature was modeled using the finiteelement analysis package ABAQUS...

Kaushik, Anshul

2009-05-15

92

Green strength of zirconium sponge and uranium dioxide powder compacts  

SciTech Connect

Zirconium metal sponge is compacted into rectangular or cylindrical shapes using hydraulic presses. These shapes are stacked and electron beam welded to form a long electrode suitable for vacuum arc melting and casting into solid ingots. The compact electrodes should be sufficiently strong to prevent breakage in handling as well as during vacuum arc melting. Usually, the welds are strong and the electrode strength is limited by the green strength of the compacts, which constitute the electrode. Green strength is also required in uranium dioxide (UO{sub 2}) powder compacts, to withstand stresses during de-tensioning after compaction as well as during ejection from the die and for subsequent handling by man and machine. The strengths of zirconium sponge and UO{sub 2} powder compacts have been determined by bending and crushing respectively, and Weibul moduli evaluated. The green density of coarse sponge compact was found to be larger than that from finer sponge. The green density of compacts from lightly attrited UO{sub 2} powder was higher than that from unattrited category, accompanied by an improvement in UO{sub 2} green crushing strength. The factors governing green strength have been examined in the light of published literature and experimental evidence. The methodology and results provide a basis for quality control in metal sponge and ceramic powder compaction in the manufacture of nuclear fuel.

Balakrishna, Palanki [Nuclear Fuel Complex, Hyderabad 500 062 (India)], E-mail: bpalanki@rediffmail.com; Murty, B. Narasimha; Sahoo, P.K.; Gopalakrishna, T. [Nuclear Fuel Complex, Hyderabad 500 062 (India)

2008-07-15

93

Powder Metallurgy of Uranium Alloy Fuels for TRU-Burning Reactors Final Technical Report  

SciTech Connect

Overview Fast reactors were evaluated to enable the transmutation of transuranic isotopes generated by nuclear energy systems. The motivation for this was that TRU isotopes have high radiotoxicity and relatively long half-lives, making them unattractive for disposal in a long-term geologic repository. Fast reactors provide an efficient means to utilize the energy content of the TRUs while destroying them. An enabling technology that requires research and development is the fabrication metallic fuel containing TRU isotopes using powder metallurgy methods. This project focused upon developing a powder metallurgical fabrication method to produce U-Zr-transuranic (TRU) alloys at relatively low processing temperatures (500ºC to 600ºC) using either hot extrusion or alpha-phase sintering for charecterization. Researchers quantified the fundamental aspects of both processing methods using surrogate metals to simulate the TRU elements. The process produced novel solutions to some of the issues relating to metallic fuels, such as fuel-cladding chemical interactions, fuel swelling, volatility losses during casting, and casting mold material losses. Workscope There were two primary tasks associated with this project: 1. Hot working fabrication using mechanical alloying and extrusion • Design, fabricate, and assemble extrusion equipment • Extrusion database on DU metal • Extrusion database on U-10Zr alloys • Extrusion database on U-20xx-10Zr alloys • Evaluation and testing of tube sheath metals 2. Low-temperature sintering of U alloys • Design, fabricate, and assemble equipment • Sintering database on DU metal • Sintering database on U-10Zr alloys • Liquid assisted phase sintering on U-20xx-10Zr alloys Appendices Outline Appendix A contains a Fuel Cycle Research & Development (FCR&D) poster and contact presentation where TAMU made primary contributions. Appendix B contains MSNE theses and final defense presentations by David Garnetti and Grant Helmreich outlining the beginning of the materials processing setup. Also included within this section is a thesis proposal by Jeff Hausaman. Appendix C contains the public papers and presentations introduced at the 2010 American Nuclear Society Winter Meeting. Appendix A—MSNE theses of David Garnetti and Grant Helmreich and proposal by Jeff Hausaman A.1 December 2009 Thesis by David Garnetti entitled “Uranium Powder Production Via Hydride Formation and Alpha Phase Sintering of Uranium and Uranium-Zirconium Alloys for Advanced Nuclear Fuel Applications” A.2 September 2009 Presentation by David Garnetti (same title as document in Appendix B.1) A.3 December 2010 Thesis by Grant Helmreich entitled “Characterization of Alpha-Phase Sintering of Uranium and Uranium-Zirconium Alloys for Advanced Nuclear Fuel Applications” A.4 October 2010 Presentation by Grant Helmreich (same title as document in Appendix B.3) A.5 Thesis Proposal by Jeffrey Hausaman entitled “Hot Extrusion of Alpha Phase Uranium-Zirconium Alloys for TRU Burning Fast Reactors” Appendix B—External presentations introduced at the 2010 ANS Winter Meeting B.1 J.S. Hausaman, D.J. Garnetti, and S.M. McDeavitt, “Powder Metallurgy of Alpha Phase Uranium Alloys for TRU Burning Fast Reactors,” Proceedings of 2010 ANS Winter Meeting, Las Vegas, Nevada, USA, November 7-10, 2010 B.2 PowerPoint Presentation Slides from C.1 B.3 G.W. Helmreich, W.J. Sames, D.J. Garnetti, and S.M. McDeavitt, “Uranium Powder Production Using a Hydride-Dehydride Process,” Proceedings of 2010 ANS Winter Meeting, Las Vegas, Nevada, USA, November 7-10, 2010 B.4. PowerPoint Presentation Slides from C.3 B.5 Poster Presentation from C.3 Appendix C—Fuel cycle research and development undergraduate materials and poster presentation C.1 Poster entitled “Characterization of Alpha-Phase Sintering of Uranium and Uranium-Zirconium Alloys” presented at the Fuel Cycle Technologies Program Annual Meeting C.2 April 2011 Honors Undergraduate Thesis by William Sames, Research Fellow, entitled “Uranium Metal Powder Production, Particle Dis

Sean M. McDeavitt

2011-04-29

94

Hot Isostatic Pressing of Ceramic Powder Compacts.  

National Technical Information Service (NTIS)

The effect of temperature, pressure and time on the rate of densification of submicron alumina powder during hot isostatic pressing has been determined using a dilatometer to continuously monitor volumetric changes. A Fortran computer program is used to m...

J. K. McCoy, R. R. Wills

1984-01-01

95

Dense and Homogeneous Compaction of Fine Ceramic and Metallic Powders: High-Speed Centrifugal Compaction Process  

SciTech Connect

High-Speed Centrifugal Compaction Process (HCP) is a variation of colloidal compacting method, in which the powders sediment under huge centrifugal force. Compacting mechanism of HCP differs from conventional colloidal process such as slip casting. The unique compacting mechanism of HCP leads to a number of characteristics such as a higher compacting speed, wide applicability for net shape formation, flawless microstructure of the green compacts, etc. However, HCP also has several deteriorative characteristics that must be overcome to fully realize this process' full potential.

Suzuki, Hiroyuki Y. [Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiayma, Higashi-Hiroshima, Hiroshima, 739-8527 (Japan)

2008-02-15

96

Effect of ECAP on microstructure and mechanical properties of a commercial 6061 Al alloy produced by powder metallurgy  

Microsoft Academic Search

The 6061 (Al–1.01 wt% Mg–1.07 wt% Si) Al alloy was fabricated by powder metallurgy, and then subjected to equal channel angular pressing. The microstructure and mechanical properties such as microhardness and tensile properties of the equal channel angular pressed P\\/M 6061 Al alloy were investigated. The P\\/M 6061 Al alloy had an initial grain size of approximately 20 ?m. After

Si-Young Chang; Ki-Seung Lee; Seung-Hoe Choi; Dong Hyuk Shin

2003-01-01

97

Dry wear behaviour and its relation to microstructure of novel 6092 aluminium alloy–Ni 3Al powder metallurgy composite  

Microsoft Academic Search

Novel aluminium alloy matrix composites reinforced by 15vol.% Ni3Al intermetallic particles were prepared by a powder metallurgy route. The 6092 aluminium alloy was produced by gas atomisation, followed by blending with Ni3Al particles. Consolidation by extrusion at 515°C, with an extrusion ratio of 30:1, produced a uniform distribution of Ni3Al in the Al alloy matrix. The wear properties of the

Y. Wang; W. M. Rainforth; H. Jones; M. Lieblich

2001-01-01

98

Microstructures of a powder metallurgy-hot-isostatically pressed super duplex stainless steel forming in industrial heat treatments  

Microsoft Academic Search

The microstructures of a powder metallurgy\\/hot-isostatically pressed super duplex stainless steel, designed and manufactured\\u000a for massive components of paper machines, were studied after heat treatments simulating the industrial production. It was\\u000a shown that copper precipitates in the ferrite phase as ? phase. Morphologically, the copper precipitates are of two types—nearly spherical particles of typical size from 30 to 50\\u000a nm,

O. Smuk; P. Nenonen; H. Hänninen; J. Liimatainen

2004-01-01

99

Fundamentals of Powder Compression. I. The Compactibility and Compressibility of Pharmaceutical Powders  

Microsoft Academic Search

In spite of the widespread use of tablets, the theoretical understanding of the tableting process has been limited. During the last decades considerable research has been done in the field of powder technology and compaction. A survey of the literature and compression equations reveals many studies on the characterization of powder properties, most of which relate to volume reduction under

Hans Leuenberger; Bhagwan Dass Rohera

1986-01-01

100

A Novel Ni-Containing Powder Metallurgy Steel with Ultrahigh Impact, Fatigue, and Tensile Properties  

NASA Astrophysics Data System (ADS)

The impact toughness of powder metallurgy (PM) steel is typically inferior, and it is further impaired when the microstructure is strengthened. To formulate a versatile PM steel with superior impact, fatigue, and tensile properties, the influences of various microstructures, including ferrite, pearlite, bainite, and Ni-rich areas, were identified. The correlations between impact toughness with other mechanical properties were also studied. The results demonstrated that ferrite provides more resistance to impact loading than Ni-rich martensite, followed by bainite and pearlite. However, Ni-rich martensite presents the highest transverse rupture strength (TRS), fatigue strength, tensile strength, and hardness, followed by bainite, pearlite, and ferrite. With 74 pct Ni-rich martensite and 14 pct bainite, Fe-3Cr-0.5Mo-4Ni-0.5C steel achieves the optimal combination of impact energy (39 J), TRS (2170 MPa), bending fatigue strength at 2 × 106 cycles (770 MPa), tensile strength (1323 MPa), and apparent hardness (38 HRC). The impact energy of Fe-3Cr-0.5Mo-4Ni-0.5C steel is twice as high as those of the ordinary high-strength PM steels. These findings demonstrate that a high-strength PM steel with high-toughness can be produced by optimized alloy design and microstructure.

Wu, Ming-Wei; Shu, Guo-Jiun; Chang, Shih-Ying; Lin, Bing-Hao

2014-08-01

101

Tribological properties of PM212 - A high temperature, self-lubricating, powder metallurgy composite  

NASA Technical Reports Server (NTRS)

This paper describes a research program to develop and evaluate a new high temperature, self-lubricating powder metallurgy composite, PM212. PM212 has the same composition as the plasma-sprayed coating, PS212, which contains 70 wt percent metal-bonded chromium carbide, 15 wt percent silver and 15 wt percent barium fluoride/calcium fluoride eutectic. The carbide acts as a wear resistant matrix and the silver and fluorides act as low and high temperature lubricants, respectively. The material is prepared by sequential cold press, cold isostatic pressing and sintering techniques. In this study, hemispherically tipped wear pins of PM212 were prepared and slid against superalloy disks at temperatures from 25 to 850 C in air in a pin-on-disk tribometer. Friction coefficients range from 0.29 to 0.38 and the wear of both the composite pins and superalloy disks was moderate to low in the 10(exp -5) to 10(exp -6) cubic mm/N-m range. Preliminary tests indicate that the material has a compressive strength of at least 130 MPa over the entire temperature range of 25 to 900 C. This material has promise for use as seal inserts, bushings, small inside diameter parts and other applications where plasma-sprayed coatings are impractical or too costly.

Dellacorte, Christopher; Sliney, Harold E.

1990-01-01

102

Characterization of the carbides and the martensite phase in powder-metallurgy high-speed steel  

SciTech Connect

A microstructural characterization of the powder-metallurgy high-speed-steel S390 Microclean was performed based on an elemental distribution of the carbide phase as well as crystallographic analyses. The results showed that there were two types of carbides present: vanadium-rich carbides, which were not chemically homogeneous and exhibited a tungsten-enriched or tungsten-depleted central area; and chemically homogeneous tungsten-rich M{sub 6}C-type carbides. Despite the possibility of chemical inhomogenities, the crystallographic orientation of each of the carbides was shown to be uniform. Using electron backscatter diffraction the vanadium-rich carbides were determined to be either cubic VC or hexagonal V{sub 6}C{sub 5}, while the tungsten-rich carbides were M{sub 6}C. The electron backscatter diffraction results were also verified using X-ray diffraction. Several electron backscatter diffraction pattern maps were acquired in order to define the fraction of each carbide phase as well as the amount of martensite phase. The fraction of martensite was estimated using band-contrast images, while the fraction of carbides was calculated using the crystallographic data.

Godec, Matjaz, E-mail: matjaz.godec@imt.si [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Batic, Barbara Setina; Mandrino, Djordje; Nagode, Ales; Leskovsek, Vojteh [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Skapin, Sreco D. [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Jenko, Monika [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia)

2010-04-15

103

Superplastic behavior in a powder-metallurgy TiAl alloy with a metastable microstructure  

SciTech Connect

Superplasticity in a powder-metallurgy TiAl alloy (Ti-47Al-2Cr-2Nb) with a metastable microstructure has been studied. Samples were tested at temperatures ranging from 650 to 1100{degrees}C, and at strain rate ranging from 10{sup -6} to 10{sup -4} s{sup -1}. An elongation value of over 300 obtained at a strain rate of 2 x 10{sup -5} s{sup -1} and at a temperature as lo as 800{degrees}C, which is close to the ductile-to-brittle-transition temperature. This is in contrast to the prior major observations of superplastic behaviors in TiAl in which typical temperatures of 1000{degrees}C have usually been required for superplasticity. It is proposed that the occurrence of superplasticity at 8000{degrees}C in the present alloy is caused by the presence of a B2 phase. During superplastic deformation (grain boundary sliding), the soft P grains accommodate sliding strains to reduce the propensity for cavitation at grain triple junctions and, thus, delays the fracture process. The final microstructure consists of stable, equiaxed y+a{sub 2} grains.

Nieh, T.G.; Hsiung, L.M.; Wadsworth, J.

1997-12-01

104

Application of powder metallurgy techniques to produce improved bearing elements for liquid rocket engines  

NASA Technical Reports Server (NTRS)

The objective was to apply powder metallurgy techniques for the production of improved bearing elements, specifically balls and races, for advanced cryogenic turbopump bearings. The materials and fabrication techniques evaluated were judged on the basis of their ability to improve fatigue life, wear resistance, and corrosion resistance of Space Shuttle Main Engine (SSME) propellant bearings over the currently used 440C. An extensive list of candidate bearing alloys in five different categories was considered: tool/die steels, through hardened stainless steels, cobalt-base alloys, and gear steels. Testing of alloys for final consideration included hardness, rolling contact fatigue, cross cylinder wear, elevated temperature wear, room and cryogenic fracture toughness, stress corrosion cracking, and five-ball (rolling-sliding element) testing. Results of the program indicated two alloys that showed promise for improved bearing elements. These alloys were MRC-2001 and X-405. 57mm bearings were fabricated from the MRC-2001 alloy for further actual hardware rig testing by NASA-MSFC.

Moracz, D. J.; Shipley, R. J.; Moxson, V. S.; Killman, R. J.; Munson, H. E.

1992-01-01

105

Application of powder metallurgy technique to produce improved bearing elements for cryogenic aerospace engine turbopumps  

NASA Technical Reports Server (NTRS)

Traditionally, vacuum melted 440C stainless steel is used for high performance bearings for aerospace cryogenic systems where corrosion due to condensation is a major concern. For the Space Shuttle Main Engine (SSME), however, 440C performance in the high-pressure turbopumps has been marginal. A basic assumption of this study was that powder metallurgy, rather than cast/wrought, processing would provide the finest, most homogeneous bearing alloy structure. Preliminary testing of P/M alloys (hardness, corrosion resistance, wear resistance, fatigue resistance, and fracture toughness) was used to 'de-select' alloys which did perform as well as baseline 440C. Five out of eleven candidate materials (14-4/6V, X-405, MRC-2001, T-440V, and D-5) based on preliminary screening were selected for the actual rolling-sliding five-ball testing. The results of this test were compared with high-performance vacuum-melted M50 bearing steel. The results of the testing indicated outstanding performance of two P/M alloys, X-405 and MRC-2001, which eventually will be further evaluated by full-scale bearing testing.

Moxson, V. S.; Moracz, D. J.; Bhat, B. N.; Dolan, F. J.; Thom, R.

1987-01-01

106

The substitution of nickel for cobalt in hot isostatically pressed powder metallurgy UDIMET 700 alloys  

NASA Technical Reports Server (NTRS)

Nickel was substituted in various proportions for cobalt in a series of five hot-isostatically-pressed powder metallurgy alloys based on the UDIMET 700 composition. These alloys were given 5-step heat treatments appropriate for use in turbine engine disks. The resultant microstructures displayed three distinct sizes of gamma-prime particles in a gamma matrix. The higher cobalt-content alloys contained larger amounts of the finest gamma-prime particles, and had the lowest gamma-gamma-prime lattice mismatch. While all alloys had approximately the same tensile properties at 25 and 650 gamma C, the rupture lives at 650 and 760 C peaked in the alloys with cobalt contents between 12.7 and 4.3 pct. Minimum creep rates increased as cobalt contents were lowered, suggesting their correlation with the gamma-prime particle size distribution and the gamma-gamma-prime mismatch. It was also found that, on overaging at temperatures higher than suitable for turbine disk use, the high cobalt-content alloys were prone to sigma phase formation.

Harf, F. H.

1985-01-01

107

Factors Influencing Dwell Fatigue Cracking in Notches of Powder Metallurgy Superalloys  

NASA Technical Reports Server (NTRS)

The influences of heat treatment and cyclic dwells on the notch fatigue resistance of powder metallurgy disk superalloys were investigated for low solvus high refractory (LSHR) and ME3 disk alloys. Disks were processed to produce material conditions with varied microstructures and associated mechanical properties. Notched specimens were first subjected to baseline dwell fatigue cycles having a dwell at maximum load, as well as tensile, stress relaxation, creep rupture, and dwell fatigue crack growth tests at 704 C. Several material heat treatments displayed a bimodal distribution of fatigue life with the lives varying by two orders-of-magnitude, while others had more consistent fatigue lives. This response was compared to other mechanical properties, in search of correlations. The wide scatter in baseline dwell fatigue life was observed only for material conditions resistant to stress relaxation. For selected materials and conditions, additional tests were then performed with the dwells shifted in part or in total to minimum tensile load. The tests performed with dwells at minimum load exhibited lower fatigue lives than max dwell tests, and also exhibited early crack initiation and a substantial increase in the number of initiation sites. These results could be explained in part by modeling evolution of peak stresses in the notch with continued dwell fatigue cycling. Fatigue-environment interactions were determined to limit life for the fatigue cycles with dwells.

Gabb, T. P.; Telesman, J.; Ghosn, L.; Garg, A.; Gayda, J.

2011-01-01

108

Distribution of Inclusion-Initiated Fatigue Cracking in Powder Metallurgy Udimet 720 Characterized  

NASA Technical Reports Server (NTRS)

In the absence of extrinsic surface damage, the fatigue life of metals is often dictated by the distribution of intrinsic defects. In powder metallurgy (PM) alloys, relatively large defects occur rarely enough that a typical characterization with a limited number of small volume fatigue test specimens will not adequately sample inclusion-initiated damage. Counterintuitively, inclusion-initiated failure has a greater impact on the distribution in PM alloy fatigue lives because they tend to have fewer defects than their cast and wrought counterparts. Although the relative paucity of defects in PM alloys leads to higher mean fatigue lives, the distribution in observed lives tends to be broader. In order to study this important failure initiation mechanism without expending an inordinate number of specimens, a study was undertaken at the NASA Glenn Research Center where known populations of artificial inclusions (seeds) were introduced to production powder. Fatigue specimens were machined from forgings produced from the seeded powder. Considerable effort has been expended in characterizing the crack growth rate from inclusion-initiated cracks in seeded PM alloys. A rotating and translating positioning system, with associated software, was devised to map the surface inclusions in low-cycle fatigue (LCF) test bars and to monitor the crack growth from these inclusions. The preceding graph illustrates the measured extension in fatigue cracks from inclusions on a seeded LCF test bar subjected to cyclic loading at a strain range of 0.8 percent and a strain ratio (max/min) of zero. Notice that the observed inclusions fall into three categories: some do not propagate at all (arrest), some propagate with a decreasing crack growth rate, and a few propagate at increasing rates that can be modeled by fracture mechanics. The following graph shows the measured inclusion-initiated crack growth rates from 10 interrupted LCF tests plotted against stress intensities calculated for semi-elliptical cracks with the observed surface lengths. The expected scatter in the crack growth rates for stress intensity ranges near threshold is observed. These data will be used to help determine the distribution in growth rates of cracks emanating from inclusions as well as the proportion of cracks that arrest under various loading conditions.

Bonacuse, Peter J.; Kantzos, Pete T.; Barrie, Robert; Telesman, Jack; Ghosn, Louis J.; Gabb, Timothy P.

2004-01-01

109

Static and Dynamic Compaction of CL-20 Powders  

NASA Astrophysics Data System (ADS)

Hexanitrohexaazaisowurtzitane (CL-20) powders were compacted under quasi-static and dynamic loading conditions. A uniaxial compression apparatus quasi-statically compressed the powders to 90% theoretical maximum density with applied stresses up to 0.4 GPa. Dynamic compaction measurements using low-density pressings approximately 64% theoretical maximum density (TMD) were obtained in a single-stage gas gun at impact velocities between 0.17-0.95 km/s. Experiments were conducted in a reverse ballistic arrangement in which the projectile contained the CL-20 powder bed and impacted a target consisting of an aluminized window. VISAR-measured particle velocities at the explosive-window interface determined the shock Hugoniot states for pressures up to 1.3 GPa. Approved for public release, SAND2009-4810C.

Cooper, Marcia A.; Brundage, Aaron L.; Dudley, Evan C.

2009-12-01

110

Processing and development of aluminum-silicon powder metallurgy alloys for hot forging technologies  

NASA Astrophysics Data System (ADS)

The growing field of aluminum powder metallurgy (PM) brings promise to an economical and environmental demand for the production of high strength, light weight aluminum engine components. To tackle the limited selection of readily available light alloy blends, an experimental hypoeutectic AlSi alloy was chosen for study. The optimal processing route for this alloy was determined and the mechanical properties were examined. In an effort to further enhance the mechanical properties of the alloys, post sinter forging was investigated. This body of work consists of an introduction to relevant topics in PM, aluminum alloys, and forging followed by three sections of results and discussion. Each represents an accepted or submitted Journal Manuscript intended for journal publication. These sections deliver detailed experimental procedures, results and discussion for the development of the experimental PM alloy Al-65i, a comparison of hot deformation behaviours of Al-65i and Alumix-231 Al5i PM alloys, and their mechanical properties observed upon hot densification. A final section was added to summarize the important findings from each experiment. In the development of Al-65i, the alloy was able to achieve a high sintered density approaching 98%, and a yield strength of 232 MPa in the T6 condition. Upon hot upset forging, the experimental alloy achieved an average density of 99.6% (+/- 0.2%) while the commercial alloy (Alumix-231) achieved 98.3% (+/- 0.6%) of its theoretical density. It was found that the experimentally obtained peak flow stresses for each material studied could be very closely approximated using the semi-empirical Zener-Hollomon models. Upon hot densification it was found that all the mechanical properties of the Al-65i alloy were significantly enhanced. However, due to the fracturing of 5i particles during deformation, Alumix-231 experienced a reduction in density and UT5, while making improvements in ductility.

Mosher, Winston G. E.

111

Study of alumina-trichite reinforcement of a nickel-based matric by means of powder metallurgy  

NASA Technical Reports Server (NTRS)

Research was conducted on reinforcing nickel based matrices with alumina trichites by using powder metallurgy. Alumina trichites previously coated with nickel are magnetically aligned. The felt obtained is then sintered under a light pressure at a temperature just below the melting point of nickel. The halogenated atmosphere technique makes it possible to incorporate a large number of additive elements such as chromium, titanium, zirconium, tantalum, niobium, aluminum, etc. It does not appear that going from laboratory scale to a semi-industrial scale in production would create any major problems.

Walder, A.; Hivert, A.

1982-01-01

112

Compact, Non-Pneumatic Rock-Powder Samplers  

NASA Technical Reports Server (NTRS)

Tool bits that automatically collect powdered rock, permafrost, or other hard material generated in repeated hammering action have been invented. The present invention pertains to the special case in which it is desired to collect samples in powder form for analysis by x-ray diffraction and possibly other techniques. The present invention eliminates the need for both the mechanical collection equipment and the crushing chamber and the pneumatic collection equipment of prior approaches, so that it becomes possible to make the overall sample-acquisition apparatus more compact.

Sherrit, Stewart; Bar-Cohen, Yoseph; Badescu, Mircea; Bao, Xiaoqi; Chang, Zensheu; Jones, Christopher; Aldrich, Jack

2008-01-01

113

Compaction of fine powders: from fluidized agglomerates to primary particles  

Microsoft Academic Search

In previous works it has been shown that fine powders (particle size 7 ?m \\u000a$$\\\\lesssim d_{p}$ $\\\\lesssim 20 \\\\mu$$m) exhibit two well differentiated behaviors in the compaction regime at low consolidation stresses ?\\u000a c\\u000a . At very low stresses\\u000a$$(\\\\sigma_{c} \\\\lesssim10 Pa)$$ the compaction process is governed by a critical-like dynamics of fractal agglomerates previously formed in the fluid-like regime, undergoing

Jose Manuel Valverde; Antonio Castellanos

2007-01-01

114

Preparation of Cu and Fly Ash Composite by Powder Metallurgy Technique  

SciTech Connect

Cu and Fly Ash (FA) mixtures with different weight percentages were prepared. Pellets of the mixture powder were produced with the dimension of 17.7 mm in diameter and 10-15 mm in height. These different composites were compacted at a constant pressure of 280 MPa. One of the selected weight percentages was then compacted to form into pellet and sintered at different temperatures which were at 900, 950 and 1000 deg. C respectively for 2 hours. Density of green pellet was measured before sintered in furnace. After sintering, all the pellets with different temperatures were re-weighed and sintered density were calculated. The densification of the green and sintered pellets was required to be measured as one of the parameter in selection of the best material properties. Porosity of the pellet shall not be ignored in order to analyze the close-packed particles stacking in the pellet. SEM micrograph had been captured to observe the presence of pores and agglomeration of particles in the sample produced.

Chew, P. Y.; Lim, P. S.; Ng, M. C. [Infineon Technologies (M) Sdn Bhd, Batu Berendam, 75450 Melaka (Malaysia); Zahi, S.; You, A. H. [Faculty of Engineering and Technology, Multimedia University, Jalan Ayer Keroh Lama, 75450 Melaka (Malaysia)

2011-03-30

115

Modelling and Simulation of Tensile Fracture in High Velocity Compacted Metal Powder  

Microsoft Academic Search

In cold uniaxial powder compaction, powder is formed into a desired shape with rigid tools and a die. After pressing, but before sintering, the compacted powder is called green body. A critical property in the metal powder pressing process is the mechanical properties of the green body. Beyond a green body free from defects, desired properties are high strength and

P. Jonse´n

2007-01-01

116

Static and Dynamic Compaction of CL-20 Powders  

NASA Astrophysics Data System (ADS)

Hexanitrohexaazaisowurtzitane (CL-20) powders were compacted under quasi-static and dynamic loading conditions. A uniaxial compression apparatus quasi-statically compressed the powders to 90% theoretical maximum density with applied stresses up to 0.5 GPa. Dynamic compaction measurements using low-density pressings (62-70% theoretical maximum density) were obtained in a single-stage gas gun at impact velocities between 0.17-0.70 km/s. Experiments were conducted in a reverse ballistic arrangement in which the CL-20 ladened projectile impacted a target consisting of an aluminized window. VISAR-measured particle velocities at the explosive-window interface determined the shock Hugoniot states for pressures up to 0.9 GPa. The powder compaction behavior is found to be stiffer under dynamic loading than under quasi-static loading. Additional gas gun tests were conducted in which the low-density CL-20 pressings were confined within a target cup by the aluminized window. This arrangement enabled temporal measurement of the transmitted wave profiles in which elastic wave precursors were observed.

Cooper, Marcia; Brundage, Aaron; Dudley, Evan

2009-06-01

117

Studies on the sintering behaviour of uranium dioxide powder compacts  

NASA Astrophysics Data System (ADS)

Uranium dioxide fuel pellets are normally made from their precursor ammonium diuranate, followed by calcination, subsequent reduction to sinterable grade powders and a post operation treatment of pressing and sintering. The low temperature calcined powders, usually exhibiting non-crystalline behaviour (under X-ray diffraction studies) progressively transforms into a crystalline variety on subsequent heat treatment at higher temperature. It is observed however that powders calcined between 800 to 900°C exhibit enhanced densification behaviour when sintered at higher temperatures. The isothermal shrinkage versus time plot of the sintered compacts are well described by a hyperbolic relationship which takes care of the observed shrinkage (?) as caused due to a cumulative effect from the initial sintering of the powder compacts at zero time (?) and that caused due to the structural transformation from a non-crystalline modification with increased thermal treatment (?). The derived equation is a modification of the sintering mechanism of the viscous flow type proposed by Frenkel, involving sintering of an amorphous phase, the viscosity of the latter is presumed to increase with increasing thermal treatment to assume the final modified form as ? = {t}/{(? +?t)}, where t = time, ? = shrinkage and ? and ? are the unknown parameters.

Das, Pranab; Chowdhury, Ranjit

1988-09-01

118

Interparticle van der Waals force in powder flowability and compactibility.  

PubMed

Particle flowability and compactibility are the two critical process parameters tested when a pharmaceutical material is formulated for a tabletting process. These behavioral descriptions are strongly affected by geometrical, physical, chemical and mechanical particle properties, as well as operational conditions. The property influences are broadly known in a qualitative sense, but have largely escaped fundamental quantitative description. Various measurement methods have been separately developed for each of these properties which provide comparative indices to assist in process and formulation design. This paper seeks to establish the connections between interparticle van der Waals force and both flowability and compactibility, and therefore also the inter-relations between the two apparently distinct properties. Paracetamol and the excipients often associated with it for tabletting are used as test materials to provide an initial validation of the theoretical development. These powders are well-characterized and known to be particularly difficult with respect to flowability and compactibility. PMID:15265549

Li, Qin; Rudolph, Victor; Weigl, Bernhard; Earl, Alan

2004-08-01

119

Two methods for characterizing the compaction and ejection behavior of metal powders in a die  

E-print Network

Compaction Curve of Atomized Copper Powder Showing the Effect of Lubricant Addition 23 Dimensionless Compaction Curve of CuPbSn Powder Showing the Effect of Lubricant Addition 24 Dimensionless Compaction Curve of Sponge Iron Powder Showing the Effect... Level of Lubricant Added Force of Electrolytic Iron 31 13 Relationship and Ejection Between Level of Lubricant Added Force of Sponge Iron Powder . . . . 32 viii Figure Page 14 Relationship Between Level of Lubricant Added and Ejection Force...

Sajdak, Richard James

2012-06-07

120

In situ preparation of titanium base composites reinforced by TiB single crystals using a powder metallurgy technique  

Microsoft Academic Search

The feasibility of Ti\\/TiB composite by in situ precipitation of the reinforcement have been investigated. The titanium monoboride can be obtained by the chemical reaction between TiB2 and Ti powders. The fabrication method requires two stages: the first stage corresponds to the compacting of the pre-blended powders and the second one to the nucleation and growth of the TiB needles.

S Gorsse; J. P Chaminade; Y Le Petitcorps

1998-01-01

121

A novel powder metallurgy-based method for the recycling of aluminum adapted to a small island developing state in the  

E-print Network

developing state in the Pacific Shivendra Kumar1* , Fabrice Mathieux2,3 , Godfrey Onwubolu1 and Vineet volume scrap aluminum, the application of the powder metallurgy process is proposed. Its methodology in which more research will be carried out. * Corresponding author hal-00186366,version1-8Nov2007 Author

Boyer, Edmond

122

The most important tendencies in the development of powder metallurgy. II. Progress in the area of development of new materials (review)  

Microsoft Academic Search

The last decade has been characterized by progress in the area of development of new types of powder metallurgy materials including constructional, tribotechnical, composite, dispersion strengthened, fiber reinforced, tool, magnetic, corrosion-resistant, ceramic, aluminum- and titanium-base, and others. The volume of their use has been broadened in agricultural machinery, the machine tool industry, the automobile industry, the instrument industry, microelectronics, atomic

I. M. Fedorchenko

1989-01-01

123

An Investigation of Microstructure and Phase Transformation Behavior of Cu40Zn-1.0 wt.% Ti Brass Via Powder Metallurgy  

NASA Astrophysics Data System (ADS)

The effects of Ti addition on phase transformation, precipitation behavior, and microhardness response of Cu40Zn brass were investigated at elevated heat treatment (HT) temperatures using the powder metallurgy method. The volume fraction of the ? phase increased with the elevated temperatures, which showed an equal value as that of the ? phase at 400 °C, and reached a maximum value of 55.9% at 500 °C. The solid solubility of Ti in Cu40Zn brass matrix decreased as the HT temperature increased. Supersaturated Ti showed high chemical potential for precipitates' reaction in Cu40Zn brass. Lower HT temperature retained higher Ti solid solubility and fine precipitates. The precipitates presented in form of Cu2TiZn intermetallic compound, distributing uniformly in brass matrix which suppressed the phase and grain growth. After HT at elevated temperature, the precipitates coalesced, grew coarser, and segregated at the primary particle boundaries. The microhardness of the BS40-1.0Ti compact was primarily not only dependent on the solid solubility of Ti, but also dependent on the phase volume fraction of the ? and ? phases.

Li, Shufeng; Imai, Hisashi; Atsumi, Haruhiko; Kondoh, Katsuyoshi

2013-10-01

124

X-ray tensometry for study stress distribution and mechanical behavior of components of silumin fabricated by powder metallurgy  

NASA Astrophysics Data System (ADS)

Aluminium-silicon alloy or silurnin fabricated by powder metallurgy is a material widely used in aircraft and precision mechanics industries because of homogeneous composition and high mechanical properties. Residual stresses arising in this kind of composite material caused by the difference of thermal expansion coefficients of components have negative influence on the working of Al-Si parts and equipments. X-ray diffraction method of stress measurements is unique method allowing study the individual stresses acting in each component of composite material. In the present paper the stress distribution and mechanical behavior of aluminum matrix and silicon particles have been studied by X-ray diffraction method. Interpretation of experiment stress measurements was made on position of mechanics of composite materials.

de Assis, Joaquim T.; Monin, Vladimir I.; Filipov, Sergei A.; Iglesias, S. M.; Gurova, Tatiana

2006-04-01

125

Effects of Thermocapillary Forces during Welding of 316L-Type Wrought, Cast and Powder Metallurgy Austenitic Stainless Steels  

E-print Network

The Large Hadron Collider (LHC) is now under construction at the European Organization for Nuclear Research (CERN). This 27 km long accelerator requires 1248 superconducting dipole magnets operating at 1.9 K. The cold mass of the dipole magnets is closed by a shrinking cylinder with two longitudinal welds and two end covers at both extremities of the cylinder. The end covers, for which fabrication by welding, casting or Powder Metallurgy (PM) was considered, are dished-heads equipped with a number of protruding nozzles for the passage of the different cryogenic lines. Structural materials and welds must retain high strength and toughness at cryogenic temperature. AISI 316L-type austenitic stainless steel grades have been selected because of their mechanical properties, ductility, weldability and stability of the austenitic phase against low-temperature spontaneous martensitic transformation. 316LN is chosen for the fabrication of the end covers, while the interconnection components to be welded on the protrud...

Sgobba, Stefano; 10.1016/S0924-0136(03)00373-X

2003-01-01

126

A Novel Powder Metallurgy Processing Approach to Prepare Fine-Grained Cu-Al-Ni Shape-Memory Alloy Strips from Elemental Powders  

NASA Astrophysics Data System (ADS)

The current work describes the experimental results related to the successful preparation of fine-grained, Cu-Al-Ni, high-temperature shape-memory alloy (SMA) strips from elemental Cu, Al, and Ni powders via a novel powder metallurgy (P/M) processing approach. This route consists of short time period ball milling of elemental powder mixture, preform preparation from milled powder, sintering of preforms, hot-densification rolling of unsheathed sintered powder preforms under protective atmosphere, and postconsolidation homogenization treatment of the hot-rolled strips. It has been shown that it is possible to prepare chemically homogeneous Cu-Al-Ni SMA strips consisting of equiaxed grains of average size approximately 6 ?m via the current processing approach. It also has been shown that fine-grained microstructure in the finished Cu-Al-Ni SMA strips resulted from the pinning effect of nanosized alumina particles present on the grain boundaries. The finished SMA strips were almost fully martensitic in nature, consisting of a mixture of ?1^' } - and ?1^' } -type martensites. The Cu-Al-Ni SMA strips had 677 MPa average fracture strength, coupled with 13 pct average fracture strain. The fractured surfaces of the specimens exhibited primarily dimpled ductile type of fracture, together with some transgranular mode of fracture. The Cu-Al-Ni strips exhibited an almost 100 pct one-way shape recovery after bending followed by unconstrained heating at 1, 2, and 4 pct applied deformation prestrain. The two-way shape-memory strain was found approximately 0.35 pct after 15 training cycles at 4 pct applied training prestrain.

Vajpai, S. K.; Dube, R. K.; Chatterjee, P.; Sangal, S.

2012-07-01

127

Application of powder X-ray diffraction in studying the compaction behavior of bulk pharmaceutical powders.  

PubMed

This study investigates the effects of crystal lattice deformation on the powder X-ray diffraction (PXRD) patterns of compressed polycrystalline specimen (compacts/tablets) made from molecular, crystalline powders. The displacement of molecules and the corresponding adjustment of interplanar distances (d-spacings) between diffracting planes of PNU-288034 and PNU-177553, which have crystal habits with a high aspect ratio favoring preferred orientation during tableting, are demonstrated by shifts in the diffracted peak positions. The direction of shift in diffracted peak positions suggests a reduction of interplanar d-spacing in the crystals of PNU-288034 and PNU-177553 following compaction. There is also a general reduction of peak intensities following compression at the different compressive loads. The lattice strain representing the reduction in d-spacing is proportional to the original d-spacing of the uncompressed sample suggesting that, as with systems that obey a simple Hooke's law relationship, the further apart the planes of atoms/molecules within the lattice are, the easier it is for them to approach each other under compressive stresses. For a third model compound comprising more equant-shaped crystals of PNU-141659, the shift in diffracted peak positions are consistent with an expansion of lattice spacing after compression. This apparent anomaly is supported by the PXRD studies of the bulk powder consisting of fractured crystals where also, the shift in peak position suggests expansion of the lattice planes. Thus the crystals of PNU-141659 may be fracturing under the compressive loads used to produce the compacts. Additional studies are underway to relate the PXRD observations with the bulk tableting properties of these model compounds. PMID:16200547

Bandyopadhyay, Rebanta; Selbo, Jon; Amidon, Gregory E; Hawley, Michael

2005-11-01

128

Cohesion and dilatation of powder compacts containing hard phase particles under highly deviatoric stress states  

Microsoft Academic Search

The effect of hard particles in compacted powders is studied under highly deviatoric stress states. The soft matrix powder is pure aluminum while the hard particles are W2C particles. The behavior of compacts with volume fractions of hard particles up to 60% is investigated. Diametral compression and simple compression tests are carried out both at room temperature and at 450?C.

C. L. Martin; O. Lame; D. Bouvard

2000-01-01

129

Dry sliding wear behaviour of powder metallurgy Al–Mg–Si alloy-MoSi 2 composites and the relationship with the microstructure  

Microsoft Academic Search

The effect of the microstructure on the dry sliding wear of six aluminium alloy 6061 matrix composites reinforced with 15vol.% of MoSi2 particles and two monolithic 6061 alloys processed by powder metallurgy with and without ball milling has been studied. Wear testing was undertaken using pin-on-ring configuration against an M2 steel counterface at 0.94m\\/s and normal load of 42, 91

J. Corrochano; J. C. Walker; M. Lieblich; J. Ibáñez; W. M. Rainforth

2011-01-01

130

The influence of punch curvature on the mechanical properties of compacted powders  

Microsoft Academic Search

The influence of changing the overall thickness and face curvature of compacted microcrystalline cellulose powder (a direct compression excipient used extensively in the pharmaceutical industry) prepared at different compaction pressures has been assessed by the diametral compression test. For specimens that failed in tension, the tensile strength of the compacts was calculated from formulae derived from stress analysis. The values

J. Michael Newton; Ismael Haririan; Fridrun Podczeck

2000-01-01

131

Microstructure and Strengthening Mechanisms in an Ultrafine Grained Al-Mg-Sc Alloy Produced by Powder Metallurgy  

NASA Astrophysics Data System (ADS)

Additions of Sc to an Al-Mg matrix were investigated, paying particular attention to the influence of Al3Sc precipitates and other dispersoids, as well as grain size, on mechanical behavior. Prior studies have shown that Sc significantly increases the strength of coarse-grained Al-Mg alloys. Prompted by these findings, we hypothesized that it would be of fundamental and technological interest to study the behavior of Sc additions to an ultrafine-grained (UFG) microstructure ( e.g., 100's nm). Accordingly, we investigated the microstructural evolution and mechanical behavior of a cryomilled ultrafine grained Al-5Mg-0.4Sc (wt pct) and compared the results to those of an equivalent fine-grained material (FG) produced by powder metallurgy. Experimental materials were consolidated by hot isostatic pressing (HIP'ing) followed by extrusion or dual mode dynamic forging. Under identical processing conditions, UFG materials generate large Al3Sc precipitates with an average diameter of 154 nm and spaced approximately 1 to 3 ?m apart, while precipitates in the FG materials have a diameter of 24 nm and are spaced 50 to 200 nm apart. The strengthening mechanisms are calculated for all materials and it is determined that the greatest strengthening contributions for the UFG and FG materials are Mg-O/N dispersion strengthening and precipitate strengthening, respectively.

Harrell, Tammy J.; Topping, Troy D.; Wen, Haiming; Hu, Tao; Schoenung, Julie M.; Lavernia, Enrique J.

2014-12-01

132

The Effect of Forging Variables on the Supersolvus Heat-Treatment Response of Powder-Metallurgy Nickel-Base Superalloys  

NASA Astrophysics Data System (ADS)

The effect of subsolvus forging temperature and strain rate on the grain size developed during final supersolvus heat treatment (SSHT) of two powder-metallurgy, gamma-gamma prime superalloys, IN-100 and LSHR, was established. For this purpose, isothermal, hot compression tests were performed at temperatures ranging from 1144 K (871 °C) and 22 K (22 °C) below the respective gamma-prime solvus temperatures ( T ?') and strain rates between 0.0003 and 10 s-1. Deformed samples were then heat treated 20 K (20 °C) above the solvus for 1 h with selected additional samples exposed for shorter and longer times. For both alloys, the grain size developed during SSHT was in the range of 15 to 30 ?m, except for those processing conditions consisting of pre-deformation at the highest temperature, i.e., T ?'—22 K ( T ?'—22 °C), and strain rates in the range of ~0.001 to 0.1 s-1. In these latter instances, the heat-treated grain size was approx. four times as large. The observations were interpreted in terms of the mechanisms of deformation during hot working and their effect on the driving forces for grain-boundary migration which controls the evolution of the gamma-grain size.

Semiatin, S. L.; Shank, J. M.; Shiveley, A. R.; Saurber, W. M.; Gaussa, E. F.; Pilchak, A. L.

2014-12-01

133

Microstructure and Strengthening Mechanisms in an Ultrafine Grained Al-Mg-Sc Alloy Produced by Powder Metallurgy  

NASA Astrophysics Data System (ADS)

Additions of Sc to an Al-Mg matrix were investigated, paying particular attention to the influence of Al3Sc precipitates and other dispersoids, as well as grain size, on mechanical behavior. Prior studies have shown that Sc significantly increases the strength of coarse-grained Al-Mg alloys. Prompted by these findings, we hypothesized that it would be of fundamental and technological interest to study the behavior of Sc additions to an ultrafine-grained (UFG) microstructure (e.g., 100's nm). Accordingly, we investigated the microstructural evolution and mechanical behavior of a cryomilled ultrafine grained Al-5Mg-0.4Sc (wt pct) and compared the results to those of an equivalent fine-grained material (FG) produced by powder metallurgy. Experimental materials were consolidated by hot isostatic pressing (HIP'ing) followed by extrusion or dual mode dynamic forging. Under identical processing conditions, UFG materials generate large Al3Sc precipitates with an average diameter of 154 nm and spaced approximately 1 to 3 ?m apart, while precipitates in the FG materials have a diameter of 24 nm and are spaced 50 to 200 nm apart. The strengthening mechanisms are calculated for all materials and it is determined that the greatest strengthening contributions for the UFG and FG materials are Mg-O/N dispersion strengthening and precipitate strengthening, respectively.

Harrell, Tammy J.; Topping, Troy D.; Wen, Haiming; Hu, Tao; Schoenung, Julie M.; Lavernia, Enrique J.

2014-09-01

134

The Effect of Forging Variables on the Supersolvus Heat-Treatment Response of Powder-Metallurgy Nickel-Base Superalloys  

NASA Astrophysics Data System (ADS)

The effect of subsolvus forging temperature and strain rate on the grain size developed during final supersolvus heat treatment (SSHT) of two powder-metallurgy, gamma-gamma prime superalloys, IN-100 and LSHR, was established. For this purpose, isothermal, hot compression tests were performed at temperatures ranging from 1144 K (871 °C) and 22 K (22 °C) below the respective gamma-prime solvus temperatures (T ?') and strain rates between 0.0003 and 10 s-1. Deformed samples were then heat treated 20 K (20 °C) above the solvus for 1 h with selected additional samples exposed for shorter and longer times. For both alloys, the grain size developed during SSHT was in the range of 15 to 30 ?m, except for those processing conditions consisting of pre-deformation at the highest temperature, i.e., T ?'—22 K (T ?'—22 °C), and strain rates in the range of ~0.001 to 0.1 s-1. In these latter instances, the heat-treated grain size was approx. four times as large. The observations were interpreted in terms of the mechanisms of deformation during hot working and their effect on the driving forces for grain-boundary migration which controls the evolution of the gamma-grain size.

Semiatin, S. L.; Shank, J. M.; Shiveley, A. R.; Saurber, W. M.; Gaussa, E. F.; Pilchak, A. L.

2014-09-01

135

Development of superalloys by powder metallurgy for use at 1000 - 1400 F  

NASA Technical Reports Server (NTRS)

Consolidated powders of four nickel-base superalloys were studied for potential application as compressor and turbine discs in jet engines. All of the alloys were based on the Rene' 95 chemistry. Three of these had variations in carbon and A12O3 contents, and the fourth alloy was chemically modified to a higher volume fraction. The A12O3 was added by preoxidation of the powders prior to extrusion. Various levels of four experimental factors (1) alloy composition, (2) grain size, (3) thermomechanical processing, and (4) room temperature deformation plus final age were evaluated by tensile and stress rupture testing at 1200 F. Various levels of the four factors were assumed in order to construct the statistically-designed experiment, but the actual levels investigated were established in preliminary studies that preceded the statistical process development study.

Calhoun, C. D.

1971-01-01

136

Thermal and Electrical Conductivity of Porous Metals made by Powder Metallurgy Methods  

Microsoft Academic Search

Measurements are reported of the thermal conductivity and electrical resistivity over the range of 20° c to 200° c on several specimens of a sintered porous bronze material (89% Cu, 11% Sn). The constituent powder particles were substantially spherical in shape and the specimens studied covered particle diameters ranging from 0.00133 to 0.040 cm and had densities from 5.27 to

P Grootenhuis; R W Powell; R P Tye

1952-01-01

137

Chloride-Induced Stress Corrosion Cracking of Powder Metallurgy Duplex Stainless Steels  

Microsoft Academic Search

The chloride-induced stress corrosion cracking (SCC) resistance of nitrogen-alloyed, powder metallurgically (P\\/M) produced and hot isostatically pressed (HIP) duplex stainless steels (DSS) was investigated and compared to the SCC resistance of two commercial wrought (forged) DSS. Constant-strain (deflection) SCC tests with four-point, loaded-bend specimens were performed in aerated 50 wt% calcium chloride solution at 100 C with pH = 6.5

A. Laitinen; H. Haenninen

1996-01-01

138

The role of heat treatment on wear behavior of powder metallurgy low alloy steels  

Microsoft Academic Search

The influence of manufacturing parameters such as compacting pressure, heat treatment and microstructure on the static and dynamic properties of Fe–1.75 Ni–1.5 Cu–0.5 Mo–0.6 C was investigated. Wear and fatigue tests were carried out on reciprocate wearing and tension compression mode, respectively. The results show that delamination wear mechanism of sintered steel is similar to that of conventional wrought or

H Khorsand; S. M Habibi; H Yoozbashizadea; K Janghorban; S. M. S Reihani; H Rahmani Seraji; M Ashtari

2002-01-01

139

Characteristics of complicated AISI316L automobile components manufactured by powder\\/metallurgy  

Microsoft Academic Search

Indirect Selective Laser Sintering\\/Isostatic Pressing (SLS\\/IP), with Cold Isostatic Pressing (CIPing) and Hot Isostatic Pressing\\u000a (HIPing) IPs, is adopted for the manufacture of complicated automobile components. The preparation of PA12-coated AISI316L\\u000a powder and airproof plastic canning during CIPing are also investigated. The influence of technology parameters on the performances\\u000a of AISI316L specimens during SLS\\/IP is likewise analyzed. Results show that

L. Zhong Liang; L. Jin Hui; S. Yu Sheng; Y. Chun Ze

2009-01-01

140

Effect of reduced cobalt contents on hot isostatically pressed powder metallurgy U-700 alloys  

NASA Technical Reports Server (NTRS)

The effect of reducing the cobalt content of prealloyed powders of UDIMET 700 (U-700) alloys to 12.7, 8.6, 4.3, and 0% was examined. The powders were hot isostatically pressed into billets, which were given heat treatments appropriate for turbine disks, namely partial solutioning at temperatures below the gamma prime solvus and four step aging treatments. Chemical analyses, metallographic examinations, and X-ray diffraction measurements were performed on the materials. Minor effects on gamma prime content and on room temperature and 650 C tensile properties were observed. Creep rupture lives at 650 C reached a maximum at the 8.4% concentration, while at 760 C a maximum in life was reached at the 4.3% cobalt level. Minimum creep rates increased with decreasing cobalt content at both test temperatures. Extended exposures at 760 and 815 C resulted in decreased tensile strengths and rupture lives for all alloys. Evidence of sigma phase formation was also found.

Harf, F. H.

1982-01-01

141

Thermodynamic analysis of compact formation; compaction, unloading, and ejection. I. Design and development of a compaction calorimeter and mechanical and thermal energy determinations of powder compaction.  

PubMed

The aim of this investigation was to determine and evaluate the thermodynamic properties, i.e. heat, work, and internal energy change, of the compaction process by developing a 'Compaction Calorimeter'. Compaction of common excipients and acetaminophen was performed by a double-ended, constant-strain tableting waveform utilizing an instrumented 'Compaction Simulator.' A constant-strain waveform provides a specific quantity of applied compaction work. A calorimeter, built around the dies, used a metal oxide thermistor to measure the temperature of the system. A resolution of 0.0001 degrees C with a sampling time of 5 s was used to monitor the temperature. An aluminum die within a plastic insulating die, in conjunction with fiberglass punches, comprised the calorimeter. Mechanical (work) and thermal (heat) calibrations of the elastic punch deformation were performed. An energy correction method was outlined to account for system heat effects and mechanical work of the punches. Compaction simulator transducers measured upper and lower punch forces and displacements. Measurements of the effective heat capacity of the samples were performed utilizing an electrical resistance heater. Specific heat capacities of the samples were determined by differential scanning calorimetry. The calibration techniques were utilized to determine heat, work, and the change in internal energies of powder compaction. Future publications will address the thermodynamic evaluation of the tablet sub-processes of unloading and ejection. PMID:10722955

DeCrosta, M T; Schwartz, J B; Wigent, R J; Marshall, K

2000-03-30

142

Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2  

NASA Technical Reports Server (NTRS)

Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

Ray, Ranjan; Jha, Sunil C.

1987-01-01

143

Application of rapid solidification powder metallurgy to the fabrication of high-strength, high-ductility Mg–Al–Zn–Ca–La alloy through hot extrusion  

Microsoft Academic Search

The microstructure and mechanical properties of hot extruded Mg–7Al–1Zn–1Ca powder alloys with an addition of 1.5% La or 3.3% La were investigated. Both rapidly solidified powders, produced via spinning water atomization process, and cast billets were extruded at 573, 623 and 673K to optimize the processing conditions for obtaining better mechanical response. Powders were consolidated using both cold compaction and

Elsayed Ayman; Umeda Junko; Kondoh Katsuyoshi

2011-01-01

144

High strain rate superplasticity of a powder metallurgy SiC particulate reinforced 6061 Al composite (6061/SiC/17. 5p)  

SciTech Connect

One of the major drawbacks of conventional superplastic forming is that the phenomenon is only found at relatively low strain rates, typically about 10[sup [minus]4] to 10[sup [minus]3] s[sup [minus]1]. Recent studies have demonstrated that superlasticity can exist at considerably higher strain rates than 10[sup [minus]3] s[sup [minus]1]. This high-strain-rate superplasticity (HSRS) phenomenon has now been observed principally in metal matrix composites and mechanically alloyed materials, but it has also been observed in more conventionally produced metallic alloys. Metal matrix composites can be fabricated by various techniques, e.g., squeeze casting, vortex methods, compocasting, powder metallurgical (PM) methods, and spray deposition. However, metal matrix composites that show HSRS are fabricated primarily by PM methods. Recently, Hikosaka et al. demonstrated that an ingot metallurgy (IM) 20 vol% SiC[sub p]-reinforced 6061 Al can also exhibit the HSRS phenomenon. The purpose of this study is to investigate the HSRS behavior of a SiC particulate-reinforced 6061 Al prepared by a powder metallurgy method and to compared its behavior with that of the composites produced by IM methods. The effect of thermomechanical processing and testing temperature will be discussed.

Nieh, T.G.; Wadsworth, J. (Lawrence Livermore National Lab., CA (United States)); Imai, T. (National Industrial Research Inst. of Nagoya (Japan)); Kojima, S. (Nagoya Municipal Industrial Research Inst. (Japan))

1994-12-15

145

Cold Compaction of Copper Powders Under Mechanical Vibration and Uniaxial Compression  

NASA Astrophysics Data System (ADS)

Physical experiments were carried out to study the cold compaction of copper powders under uniaxial compression using our self-designed equipment. Two kinds of copper powders with different particle sizes and distributions were considered. One-dimensional vibrations were utilized before compaction to systematically study the effect of parameters such as vibration frequency ?, amplitude A, and vibration intensity ? on the initial packing density. The macro-property and corresponding microstructures of compacts obtained from initial packings with and without vibrations were compared and analyzed. The results show that higher packing density can be obtained in the compaction of coarse powders with broad size distribution when other experimental conditions are fixed. For each powder, the evolution of packing density vs pressure takes on exponential correlation with high R 2 value. Much denser and more uniform compacts can be realized with the aid of vibration which can improve the particle rearrangement and result in the filling of macro pores formed in initial packing, and the characterization on the microstructure identifies that the particles inside the compact become polyhedrons with regular shape and uniformly distributed.

An, Xizhong; Xing, Zhitao; Jia, Chengchang

2014-04-01

146

Towards an improved understanding of strength and anisotropy of cold compacted powder  

NASA Astrophysics Data System (ADS)

The strength of powder compacts after cold compaction is known to be anisotropic, which comes from the directionality of microstructure resulting from initial particle morphology and/or from particle deformation during compaction. Current work focuses on multi-scale numerical analysis of powder compaction with emphasis on the role of interparticle cohesion on post-compaction mechanical properties. At macroscopic level, we applied phenomenological model to describe the mechanical behavior of powder, in which the material is considered to be continuum medium. A user subroutine (VUMAT) was successfully developed for ABAQUS/Explicit analysis, in which one of the popular phenomenological models for powder compaction---Drucker Prager/Cap model---is implemented. By studying of pharmaceutical powder die compaction and subsequent diametrical compression test via finite element analysis, the capabilities and limitations of current constitutive models are evaluated on predicting such as density, stress and tool force evolution, as well as the strength and fracture tendency. Our results illustrate that current model has good predictive capability of powder densification (e.g. density evolution) but can not predict post-compaction strength well. The following studies focus on evaluating the physics and mechanics occurring at particle level. The compaction of granular media was explored by using MPFEM approach. In the new model, individual particles discretized with a finite element mesh allow for a full description of contact mechanics and local and global particle kinematics. The introduction of a layer of degrading material on the surface of each particle provides the means of introducing variable cohesion and its effect on the final strength of compacts. The simulations show that the unloading creates tensile stresses at the root of the contact necks, which may cause partial or full separation of contact interface when the cohesion developed during loading is not strong enough. These results, which are in agreement with recent strength anisotropy data for cold compaction, bring a new perspective on understanding the interparticle behavior and the origin of the strength and failure of cold compacts.

Wang, Wenhai

147

Sintering studies of urania powder compacts — Analysis of a flow model  

NASA Astrophysics Data System (ADS)

An attempt has been made to analyse the sintering data of urania powder compacts prepared form its precursor ammonium diuranate calcined and sintered in hydrogen atmosphere for various soaking times and temperatures. Better sintering behaviour was observed in compacts prepared from powders calcined below 800 ° C, which were non-crystalline under X-ray diffraction study. Frenkel's sintering mechanism as applicable for the non-crystalline powders was applied to understand the densification behaviour in which the viscosity term was linearly related to shear stress and strain rate as also its relationship with time was assumed to be either linear or exponential in nature. A plot between shear stress (to induce densification) and time indicated that (i) a critical time ( Tcrit) is necessary to induce any observable sintering stress in these powders and Tcrit, values increased with decrease in calcination temperature and (ii) the amount of shear stress increased with higher sintering temperatures and was related to time, exponentially.

Das, P.; Choudhury, R.

1990-03-01

148

Surface Area, and Oxidation Effects on Nitridation Kinetics of Silicon Powder Compacts  

NASA Technical Reports Server (NTRS)

Commercially available silicon powders were wet-attrition-milled from 2 to 48 hr to achieve surface areas (SA's) ranging from 1.3 to 70 sq m/g. The surface area effects on the nitridation kinetics of silicon powder compacts were determined at 1250 or 1350 C for 4 hr. In addition, the influence of nitridation environment, and preoxidation on nitridation kinetics of a silicon powder of high surface area (approximately equals 63 sq m/g) was investigated. As the surface area increased, so did the percentage nitridation after 4 hr in N2 at 1250 or 1350 C. Silicon powders of high surface area (greater than 40 sq m/g) can be nitrided to greater than 70% at 1250 C in 4 hr. The nitridation kinetics of the high-surface-area powder compacts were significantly delayed by preoxidation treatment. Conversely, the nitridation environment had no significant influence on the nitridation kinetics of the same powder. Impurities present in the starting powder, and those accumulated during attrition milling, appeared to react with the silica layer on the surface of silicon particles to form a molten silicate layer, which provided a path for rapid diffusion of nitrogen and enhanced the nitridation kinetics of high surface area silicon powder.

Bhatt, R. T.; Palczer, A. R.

1998-01-01

149

Superconducting and microstructural properties of shock-compacted highT sub c oxide powders  

Microsoft Academic Search

Shock compacted specimens of YBa2Cu3O(7-delta) and HoBa2Cu3O(7-delta) high-T(sub c) oxide powder mixed with 30 percent (vol) Ag powder were prepared using the LLNL two-stage light-gas gun in the 30 to 200 kbar range. We report the experimental technique and results of an investigation of the microstructural and superconducting properties of these composite specimens. Measurements of magnetic susceptibility show that bulk

C. L. Seaman; E. A. Early; M. B. Maple; W. J. Nellis; J. B. Holt; M. Kamegai; G. S. Smith

1989-01-01

150

Preparation and Electrical Properties of LaFeO3 Compacts Using Chemically Synthesized Powders  

Microsoft Academic Search

Pure, single-phase, crystalline LaFeO3 powders are formed by the thermal decomposition of a metal-nitrate-tartrate gel complex at 500-700 °C. The complex is prepared by dissolving nitrates of lanthanum and iron in an aqueous solution in the presence of nitric and tartaric acids. The powder can be densified at 1050 °C, and the resulting compacts exhibit ionic conduction above 300 °C

Sheng-Heng Chung; Kuo-Chuang Chiu; Jau-Ho Jean

2008-01-01

151

The effect of hydrogenation on the ECAP compaction of Ti–6Al–4V powder and the mechanical properties of compacts  

Microsoft Academic Search

The effect of hydrogen content on the compaction of Ti–6Al–4V powder at low temperatures, namely 500°C, using equal channel angular pressing (ECAP) with back pressure has been investigated. The properties of the compacts before and after a heat treatment and de-hydrogenation cycle have been determined. Compaction of powder by ECAP (500°C and 260MPa) has shown maximum levels of relative density

R. Lapovok; D. Tomus; V. M. Skripnyuk; M. R. Barnett; M. A. Gibson

2009-01-01

152

Modelling and Simulation of Tensile Fracture in High Velocity Compacted Metal Powder  

SciTech Connect

In cold uniaxial powder compaction, powder is formed into a desired shape with rigid tools and a die. After pressing, but before sintering, the compacted powder is called green body. A critical property in the metal powder pressing process is the mechanical properties of the green body. Beyond a green body free from defects, desired properties are high strength and uniform density. High velocity compaction (HVC) using a hydraulic operated hammer is a production method to form powder utilizing a shock wave. Pre-alloyed water atomised iron powder has been HVC-formed into circular discs with high densities. The diametral compression test also called the Brazilian disc test is an established method to measure tensile strength in low strength material like e.g. rock, concrete, polymers and ceramics. During the test a thin disc is compressed across the diameter to failure. The compression induces a tensile stress perpendicular to the compressed diameter. In this study the test have been used to study crack initiation and the tensile fracture process of HVC-formed metal powder discs with a relative density of 99%. A fictitious crack model controlled by a stress versus crack-width relationship is utilized to model green body cracking. Tensile strength is used as a failure condition and limits the stress in the fracture interface. The softening rate of the model is obtained from the corresponding rate of the dissipated energy. The deformation of the powder material is modelled with an elastic-plastic Cap model. The characteristics of the tensile fracture development of the central crack in a diametrically loaded specimen is numerically studied with a three dimensional finite element simulation. Results from the finite element simulation of the diametral compression test shows that it is possible to simulate fracturing of HVC-formed powder. Results from the simulation agree reasonably with experiments.

Jonsen, P.; Haeggblad, H.-A. [Division of Solid Mechanics, Department of Applied Physics and Mechanical Engineering, Luleaa University of Technology, 971 87 Luleaa (Sweden)

2007-05-17

153

Modelling and Simulation of Tensile Fracture in High Velocity Compacted Metal Powder  

NASA Astrophysics Data System (ADS)

In cold uniaxial powder compaction, powder is formed into a desired shape with rigid tools and a die. After pressing, but before sintering, the compacted powder is called green body. A critical property in the metal powder pressing process is the mechanical properties of the green body. Beyond a green body free from defects, desired properties are high strength and uniform density. High velocity compaction (HVC) using a hydraulic operated hammer is a production method to form powder utilizing a shock wave. Pre-alloyed water atomised iron powder has been HVC-formed into circular discs with high densities. The diametral compression test also called the Brazilian disc test is an established method to measure tensile strength in low strength material like e.g. rock, concrete, polymers and ceramics. During the test a thin disc is compressed across the diameter to failure. The compression induces a tensile stress perpendicular to the compressed diameter. In this study the test have been used to study crack initiation and the tensile fracture process of HVC-formed metal powder discs with a relative density of 99%. A fictitious crack model controlled by a stress versus crack-width relationship is utilized to model green body cracking. Tensile strength is used as a failure condition and limits the stress in the fracture interface. The softening rate of the model is obtained from the corresponding rate of the dissipated energy. The deformation of the powder material is modelled with an elastic-plastic Cap model. The characteristics of the tensile fracture development of the central crack in a diametrically loaded specimen is numerically studied with a three dimensional finite element simulation. Results from the finite element simulation of the diametral compression test shows that it is possible to simulate fracturing of HVC-formed powder. Results from the simulation agree reasonably with experiments.

Jonsén, P.; Häggblad, H.-A.?.

2007-05-01

154

Study on effects of powder and flake chemistry and morphology on the properties of Al-Cu-Mg-X-X-X powder metallurgy advanced aluminum alloys  

NASA Technical Reports Server (NTRS)

The effects of alloy chemistry and particulate morphology on consolidation behavior and consolidated product properties in rapid solidification processed, powder-metallurgical Al-3Li-1.5Cu-1Mg-0.5Co-0.2Zr and Al-4.4Cu-1.5Mg-Fe-Ni-0.2Zr extrusions and forgings were studied. Microstructures and mechanical properties of both alloys are largely unaffected by particulate production method (vacuum atomization, ultrasonic atomization, or twin-roller quenching) and by particulate solidification rates between 1000 and 100,000 K/s. Consolidation processing by canning, cold compaction, degassing, and hot extrusion is sufficient to yield mechanical properties in the non-Li-containing alloy extrusions which are similar to those of 7075-Al, but ductilities and fracture toughnesses are inferior owing to poor interparticle bonding caused by lack of a vacuum-hot-pressing step during consolidation. Mechanical properties of extrusions are superior to those of forgings owing to the stronger textures produced by the more severe hot working during extrusion. The effects on mechanical properties of dispersoid size and volume fraction, substructural refinement, solid solution strengthening by Mg, and precipitate size and distribution are elucidated for both alloy types.

Meschter, P. J.; Lederich, R. J.; Oneal, J. E.; Pao, P. S.

1985-01-01

155

Cooling of Er(3+) with Tm(3+) for accurate temperature sensing using yttrium silicate compact powders.  

PubMed

Er(3+) doped nanocrystalline powders are extensively used for thermometry based on luminescence spectral analysis. The luminescence from Er(3+) is produced by a nonlinear (two-photon) absorption process which may generate strong internal heat by activation of nonradiative relaxation channels. If the heat dissipation is not efficient, as is the case for compact powders, there will be inaccurate readings of the temperature. Our proposed solution is to cool down Er(3+) by transferring part of its accumulated energy to another rare-earth element in the lattice. Here, we show our results for Er(3+)-Tm(3+) co-doped yttrium silicate powders prepared by combustion synthesis. PMID:25232991

Rakov, Nikifor; Maciel, Glauco S

2014-10-01

156

Investigation of Conventional- and Induction-Sintered Iron and Iron-Based Powder Metal Compacts  

NASA Astrophysics Data System (ADS)

Induction sintering was developed as an alternative method to conventional sintering to sinter iron-based powder metal (PM) compacts. Several compositions of compact such as pure iron, 3 wt.% copper mixed iron, or 3 wt.% bronze mixed iron were sintered by using induction sintering machines with 12 kW power and 30 kHz frequency. The mechanical properties, microstructural properties, densities, and microhardness values were investigated for both processes. Iron-based PM compacts sintered at 1120°C by induction in 8.33 min (500 s) were found to be similar to those sintered conventionally in 30 min. The results were compared with the experimental studies.

Çavdar, U?ur; Atik, Enver

2014-06-01

157

The effect of polymorphism on powder compaction and dissolution properties of chemically equivalent oxytetracycline hydrochloride powders.  

PubMed

In South Africa, oxytetracycline is identified as an essential drug; many generic products are on the market, and many more are being developed. In this study, six oxytetracycline hydrochloride powders were obtained randomly from manufacturers, and suppliers were compared. It was found that compliance to a pharmacopoeial monograph was insufficient to ensure the optimum dissolution performance of a simple tablet formulation. Comparative physicochemical raw material analysis showed no major differences with regard to differential scanning calorimetry (DSC), infrared (IR) spectroscopy, powder dissolution, and particle size. However, the samples could be divided into two distinct types with respect to X-ray powder diffraction (XRD) and thus polymorphism. The two polymorphic forms had different dissolution properties in water or 0.1 N hydrochloride acid. This difference became substantial when the dissolution from tablets was compared. The powders containing form A were less soluble than that containing form B. PMID:10518242

Liebenberg, W; de Villiers, M M; Wurster, D E; Swanepoel, E; Dekker, T G; Lötter, A P

1999-09-01

158

Densification mechanisms during hot isostatic pressing of stainless steel powder compacts  

Microsoft Academic Search

In order to analyse the densification behaviour of powder compacts during hot isostatic pressing (HIP) at elevated temperatures, a power-law creep constitutive model based on the plastic deformation theory for porous materials was applied to the densification. Various densification mechanisms including interparticle boundary diffusion, grain boundary diffusion and lattice diffusion mechanisms were incorporated in the constitutive model. The power-law creep

Hyoung Seop Kim

2002-01-01

159

Time-resolved studies of impact-initiated combustion in aluminum powder compacts  

NASA Astrophysics Data System (ADS)

The mechanisms of combustion reaction occurring under impact loading of aluminum powder compacts are studied using UV/Vis spectroscopy to gain time-resolved chemical information. Impact experiments performed on aluminum powder compacts reveal light emission due to reaction at velocities greater than 400m/s in air, while no reaction is observed in a vacuum (50mTorr). Light emission and reaction occurrence is also sensitive to the density of the Al powder compacts. Upon combustion, wavelengths indicative of the well-known reaction Al+O2->AlO+O, a sharp doublet at 398nm and multiple broad peaks between 420 and 500nm, are observed. Microsecond time-resolved chemical information is gained through analysis of these wavelengths using a spectrometer coupled with an electron multiplier CCD camera. The impact initiated reaction is also monitored by high speed imaging of transient deformation profiles which are compared to those predicted using numerical simulations employing ANSYS-AUTODYN-3D computer code. The insight obtained from the combination of these analyses of impact-initiated combustion reaction in aluminum powder compacts will be presented.

Breidenich, Jennifer; Dixon, Sean; Aydelotte, Brady; Thadhani, Naresh

2011-06-01

160

Thermal behavior of supersolidus bronze powder compacts during heating by hollow cathode discharge  

E-print Network

is very different from that of conventional heating (e.g., resistive, flame and induction). KnowledgeThermal behavior of supersolidus bronze powder compacts during heating by hollow cathode discharge were heated either by plasma or by a resistive furnace technique. The plasma heating was performed

dos Santos, C.A.

161

High damping Al-Fe-Mo-Si/Zn-Al composites produced by rapidly solidified powder metallurgy process  

SciTech Connect

The metallic materials commonly used in aircraft and aerospace fields, such as aluminum and titanium alloys, steels, etc., show extremely low damping capacity (usually of the order of or less than 10{sup {minus}3}). Thus, some problems related to vibration may emerge and influence the reliability, safety and life of airplanes, satellites, etc. It has been reported that almost two thirds of errors for rockets and satellites are related to vibration and noise. One effective way to solve these vibration-related problems is to adopt high damping metallic materials. Conventional high damping alloys exhibit damping capacity above 10{sup {minus}2}, however, their densities are usually great than 5 x 10{sup 3} kg m{sup {minus}3}, or their strengths are less than 200 MPa (for alloys based on dislocation damping), making them impossible to be applied to aircraft and aerospace areas. Recently, some low-density high-damping metal/metal composites based on aluminum and high damping alloys have been developed in Beijing Institute of Aeronautical Materials (BIAM) by the rapidly solidified power metallurgy process. This paper aims to report the properties of the composites based on a high temperature Al-Fe-Mo-Si alloy and a high damping Zn-Al alloy, and compare them with that of 2618-T61 alloy produced by the ingot metallurgy process.

Li, P.Y.; Dai, S.L.; Chai, S.C.; Li, Y.R.

2000-05-10

162

Compressibility of binary powder formulations: investigation and evaluation with compaction equations.  

PubMed

The purpose of this work was to investigate and evaluate the powder compressibility of binary mixtures containing a well-compressible compound (microcrystalline cellulose) and a brittle active drug (paracetamol and mefenamic acid) and its progression after a drug load increase. Drug concentration range was 0%-100% (m/m) with 10% intervals. The powder formulations were compacted to several relative densities with the Zwick material tester. The compaction force and tensile strength were fitted to several mathematical models that give representative factors for the powder compressibility. The factors k and C (Heckel and modified Heckel equation) showed mostly a nonlinear correlation with increasing drug load. The biggest drop in both factors occurred at far regions and drug load ranges. This outcome is crucial because in binary mixtures the drug load regions with higher changeover of plotted factors could be a hint for an existing percolation threshold. The susceptibility value (Leuenberger equation) showed varying values for each formulation without the expected trend of decrease for higher drug loads. The outcomes of this study showed the main challenges for good formulation design. Thus, we conclude that such mathematical plots are mandatory for a scientific evaluation and prediction of the powder compaction process. PMID:22081488

Gentis, Nicolaos D; Betz, Gabriele

2012-02-01

163

Tungsten and tungsten alloy powder metallurgy. (Latest citations from the EI Compendex*plus database). Published Search  

SciTech Connect

The bibliography contains citations concerning tungsten powder preparation and processing. Studies include sintering, densification, shrinkage, phase analysis, and heat treatment. The physical and mechanical properties of tungsten powder metal products are included. The effects of additives and particle size on the sintering and sintered articles are also described. (Contains 250 citations and includes a subject term index and title list.)

Not Available

1994-12-01

164

Preparation and Electrical Properties of LaFeO3 Compacts Using Chemically Synthesized Powders  

NASA Astrophysics Data System (ADS)

Pure, single-phase, crystalline LaFeO3 powders are formed by the thermal decomposition of a metal-nitrate-tartrate gel complex at 500-700 °C. The complex is prepared by dissolving nitrates of lanthanum and iron in an aqueous solution in the presence of nitric and tartaric acids. The powder can be densified at 1050 °C, and the resulting compacts exhibit ionic conduction above 300 °C with an apparent activation energy of electrical conduction of 20-30 kJ/mol.

Chung, Sheng-Heng; Chiu, Kuo-Chuang; Jean, Jau-Ho

2008-11-01

165

Oxidation behavior in reaction-bonded aluminum-silicon alloy/alumina powder compacts  

SciTech Connect

Goal of this research is to determine the feasibility of producing low-shrinkage mullite/alumina composites by applying the reaction-bonded alumina (RBAO) process to an aluminum-silicon alloy/alumina system. Mirostructural and compositional changes during heat treatment were studied by removing samples from the furnace at different steps in the heating schedule and then using optical and scanning electron microscopy, EDS and XRD to characterize the powder compacts. Results suggest that the oxidation behavior of the alloy compact is different from the model proposed for the pure Al/alumina system.

Yokota, S.H.

1992-12-01

166

Effect of Mass Fraction of Dolomite on the Foaming Behavior of AlSiCu Alloy Foam by Powder Metallurgy Route  

NASA Astrophysics Data System (ADS)

Metallic foams are commonly produced using hydride foaming agents. Carbonates are safer to handle than hydrides; furthermore, a fine and homogenous cell structure can be obtained by carbonates in the powder metallurgy route. In this study, the principle of foaming by dolomite, which is a carbonate, for AlSiCu alloy was investigated by observing foaming with a high-temperature transmission X-ray system and identifying the foaming gas with a gas chromatography-mass spectrometry technique. During foaming by dolomite, two stages of expansion were observed. The first stage of expansion was induced by the water vapor absorbed onto the AlSiCu powder surface, and the second stage of expansion was induced by the decomposition of dolomite. The coarse cells of the first stage of expansion were filled with H2, and the fine cells of the second stage of expansion were filled with CO. A fine and homogenous cell structure was achieved by controlling the mass fraction of dolomite with the fraction of adsorbed water, which induced cell coarsening.

Koizumi, Takuya; Kido, Kota; Kita, Kazuhiko; Mikado, Koichi; Gnyloskurenko, Svyatoslav; Nakamura, Takashi

2012-11-01

167

Application of powder metallurgy to an advanced-temperature nickel-base alloy, NASA-TRW 6-A  

NASA Technical Reports Server (NTRS)

Bar stock of the NASA-TRW 6-A alloy was made by prealloyed powder techniques and its properties evaluated over a range of temperatures. Room temperature ultimate tensile strength was 1894 MN/sq m (274 500 psi). The as-extruded powder product showed substantial improvements in strength over the cast alloy up to 649 C (1200 F) and superplasticity at 1093 C (2000 F). Both conventional and autoclave heat treatments were applied to the extruded powder product. The conventional heat treatment was effective in increasing rupture life at 649 and 704 C (1200 and 1300 F); the autoclave heat treatment, at 760 and 816 C (1400 and 1500 F).

Freche, J. C.; Ashbrook, R. L.; Waters, W. J.

1971-01-01

168

Tensile fracture characteristics of double convex-faced cylindrical powder compacts  

Microsoft Academic Search

Doubly-convex cylindrical tablets compacted uniaxially from different particle-size fractions of “Di-Pac-Sugar” powder, have been fractured under diametral loading conditions employing the standard diametral compression test. The ratio of cylinder length to diameter (W\\/D) ranged from 0.476–1.06; the ratio of cylinder diameter to radius of curvature of the tablet faces (D\\/R) was varied from 0.0–1.184. An equation based on geometrical volume

M. H. H. Es-Saheb

1996-01-01

169

Effect of Extrusion Temperature on the Microstructural Development of Powder Metallurgy Ti-47A1-2Cr-1Nb-1Ta Alloy  

SciTech Connect

Effect of extrusion temperatures on the microstructural development of a powder metallurgy (PM) Ti-47Al-2Cr-1Nb-1Ta (at. %) alloy has been investigated. Microstructure of the PM alloy extruded at 1150 C consists of a fine-grained ({gamma} + {alpha}{sub 2}) two-phase structure in association with coarse grains of metastable B2 (ordered bcc) phase. In addition, fine {omega} (ordered hexagonal) particles are also found within some B2 grains. The PM alloy containing the metastable B2 grains displays a low-temperature superplastic behavior, in which a tensile elongation of 310% is obtained at 800 C under a strain rate of 2 x 10{sup -5} s{sup -1}. It is suggested that the decomposition of metastable B2 phase and microstructural evolution during the deformation play a crucial role in the low-temperature superplasticity of the PM TiAl alloy. A refined fully-lamellar (FL) microstructure with alternating {gamma} and {alpha}{sub 2} lamellae is developed within the PM alloy extruded at 1400 C. The creep resistance of the refined FL-TiAl alloy is found to be superior to those of the TiAl alloys fabricated by conventional processing techniques. Creep mechanisms for the PM alloy with a refined FL microstructure are critically discussed according to TEM examination of deformation substructure.

Hsiung, L.; Nieh, T.G.

2000-06-29

170

Influence of foreign particles on fatigue behavior of Ti-6Al-4V prealloyed powder compacts  

NASA Astrophysics Data System (ADS)

The effect of three types of contaminants on the fatigue life of prealloyed Plasma Rotating Electrode Process (PREP) Ti-6A1-4V hot isostatically pressed (HIP’d) powder compacts was studied. Ultraclean powder was seeded separately with SiO2, A12O3, and 316 stainless steel (SS) contaminants of 50 ?m, 150 ?, and 350 ?m nominal size, a total of nine conditions. Seeded compacts were fatigue tested at room temperature and the results were compared to those of an unseeded baseline compact. It was found that a substantial loss in fatigue life occurred even at the smallest seeded contaminants used in this work. Angular nonmetallic SiO2 and A12O3 contaminants were found to be more detrimental to fatigue strength than spherical metallic 316 SS contaminants of the same size range also indicating a shape effect. The loss of fatigue life suggests that at the high stress levels there is almost no crack initiation period and fatigue lives are controlled mainly by crack growth.

Schwenker, S. W.; Eylon, D.; Froes, F. H.

1986-02-01

171

Fabrication of Al-Fe Alloys by Repeated Compaction and Extrusion of Mixture of Elemental Powders  

NASA Astrophysics Data System (ADS)

Al-Fe alloys with composition 1.0, 2.5, 5.0at.%Fe are fabricated by repeated compaction and backward extrusion in a closed die set using raw materials as elemental powder mixture. This process is done in solid state at room temperature. The produced alloyed preforms are further consolidated by hot forging to achieve high density billet. Alloyed preforms are tested for thermal stability by using differential thermal analysis. Phase changes during heating are investigated by using x-ray diffraction, and confirmed by scanning electron microscope using EDS line scan mode. The alloyed billets are subjected to tensile test.

Luangvaranunt, Tachai; Threrujirapapong, Thotsaphon; Danchaivijit, Sawai; Kondoh, Katsuyoshi

172

The Reactive Stabilisation of Aluminum-Zinc-X Foams via the Formation of a Transient Liquid Phase Using the Powder Metallurgy Approach  

NASA Astrophysics Data System (ADS)

During the past few decades, aluminum foam research has focused on the improvement of properties. These properties include pore structure and process reproducibility. High energy absorption capacity, lightweight and high stiffness to weight ratio are some of the properties that make these foams desirable for a number of diverse applications. The use of a transient liquid phase and melting point depressant was studied in order to improve aluminum foam manufactured through the powder metallurgy process and to create reactive Stabilisation. The transient liquid phase reacts with aluminum and helps encapsulate higher levels of hydrogen, simultaneously reducing the difference between the melting point of the alloy and the gas release temperature of the blowing agent (TiH2). A large difference is known to adversely affect foam properties. The study of pure aluminum foam formation was undertaken to understand the basic foaming mechanisms related to crack formations under in-situ conditions. Elemental zinc powder at various concentrations (Al-10wt%Zn, Al-33wt%Zn and Al-50wt%Zn) was added to produce a transient liquid phase. Subsequently, an Al-12wt%Si pre-alloyed powder was added to the Al-Zn mixture in order to further reduce the melting point of the alloy and to increase the amount of transient liquid phase available (Al-3.59wtSi-9.6%Zn and Al-2.4wt%Si-9.7wt%Zn). The mechanical properties of each system at optimal foaming conditions were assessed and compared. It was determined that pure aluminum foam crack formation could be suppressed at higher heating rates, improving the structure through the nucleation of uniform pores. The Al-10wt%Zn foams generated superior pore properties, post maximum expansion stability and mechanical properties at lower temperatures, compared to pure aluminum. The Al-Si-Zn foams revealed remarkable stability and pore structure at very low temperatures (640 to 660°C). Overall, the Al-10wt%Zn and Al-3.59wt%Si-9.6wt%Zn foams offer superior properties compared to pure aluminum.

Lafrance, Maxime

173

Effects of C and Hf concentration on phase relations and microstructure of a wrought powder-metallurgy superalloy  

NASA Technical Reports Server (NTRS)

NASA IIB-11, a candidate alloy for advanced temperature turbine engine disks, and four modifications with varying C and Hf concentrations were produced from prealloyed powders. Several notable effects of C and Hf concentration in the alloys were observed. Both the amount of the gamma-prime phase and its solvus temperature increased with decreasing C, but only the gamma-prime solvus was affected by Hf, increasing with increasing Hf. Hf also promoted a cellular gamma-prime precipitation. Hf was, however, about equally distributed between gamma-prime and gamma. Hf and C both affected the carbides formed. Increasing both promoted formation of an MC relative to that of an M6C.

Miner, R. V., Jr.

1977-01-01

174

A Numerical Study of Material Parameter Sensitivity in the Production of Hard Metal Components Using Powder Compaction  

NASA Astrophysics Data System (ADS)

Modeling of hard metal powder inserts is analyzed based on a continuum mechanics approach. In particular, one commonly used cutting insert geometry is studied. For a given advanced constitutive description of the powder material, the material parameter space required to accurately model the mechanical behavior is determined. These findings are then compared with the corresponding parameter space that can possibly be determined from a combined numerical/experimental analysis of uniaxial die powder compaction utilizing inverse modeling. The analysis is pertinent to a particular WC/Co powder and the finite element method is used in the numerical investigations of the mechanical behavior of the cutting insert.

Andersson, Daniel C.; Lindskog, Per; Staf, Hjalmar; Larsson, Per-Lennart

2014-06-01

175

The Influence of Sc and Zr Additions on the Microstructure and Mechanical Behavior of Ultrafine Grained Al-Mg Alloys Processed by Powder Metallurgy  

NASA Astrophysics Data System (ADS)

Additions of Sc and Zr to an Al-Mg matrix were investigated, paying particular attention to the influence of Al3Sc precipitates and other dispersoids, as well as grain size, on mechanical behavior. Prior studies have shown that Sc and Zr significantly increase the strength of coarse-grained Al-Mg alloys. Prompted by these findings, we hypothesized that it would be of fundamental and technological interest to study the behavior of Sc additions to an ultra-fine-grained (UFG) microstructure (e.g., 100's nm). Accordingly, we investigate the microstructural evolution and mechanical behavior of four powder metallurgy UFG Al-Mg-Sc-(Zr) compositions and compared the results to those of equivalent fine-grained (FG) compositions - Al-5Mg-0.1Sc, Al-3Mg-0.5Sc, Al-5Mg-0.4Sc and Al-5Mg-0.2Sc-0.2Zr (wt.%). Experimental materials were consolidated by hot isostatic pressing (HIP'ing) followed by extrusion or dual mode dynamic (DMD) forging. Under identical processing conditions, UFG ternary Al-5Mg-0.4Sc materials generate large Al3Sc precipitates with an average diameter of 154 nm and spaced approximately 1 - 3 ?m apart, while precipitates in the FG materials have an average diameter of 24 nm and are spaced 50 - 200 nm apart. The strengthening mechanisms are quantitatively evaluated for all materials and it is determined that the greatest strengthening contributions for the UFG and FG materials are dispersion strengthening due to the presence of Mg-rich oxides/nitrides and precipitate strengthening, respectively. Preliminary results suggest that replacing 0.2 wt% Sc with Zr results in higher strength, lower ductility and a change in precipitate distribution.

Harrell, Tammy Jeanne

176

The influence of morphology on the low- and high-strain-rate compaction response of CeO2 powders  

NASA Astrophysics Data System (ADS)

The low- and high-strain-rate compaction response of three distinct morphology CeO2 powders was measured experimentally. At low-strain-rates, the compression path was found to vary with initial particle morphology as a result of differences in initial packing structure and particle rearrangement at low stresses. However, similar compression responses were observed at higher stresses under low-strain-rate loading. Dynamic experiments were performed at impact velocities between 0.15 and 0.78 km/s, and resulted in compaction stresses of 0.51-4.59 GPa in the powders. In contrast to the behavior observed at low stresses and low-strain-rates, dynamic loading resulted in a similar compaction response for all morphology powders. The dynamic results were treated with a Hayes equation of state augmented with a P-? compaction model, and good agreement between experimental and theoretical results was achieved. From the observed similarities in compressibility for the three morphology powders at elevated stresses at both low- and high-strain-rates, a relationship is proposed linking the measured strength properties at low-strain-rates to those controlling the compaction response under dynamic loading.

Fredenburg, D. A.; Koller, D. D.; Coe, Joshua D.; Kiyanda, C. B.

2014-03-01

177

Density and plastic strain evaluations using small-angle X-ray scattering and finite element simulations for powder compacts  

E-print Network

direction within powder compacts, which arise due to the effects of friction and die shape. In order to test by true density). Analysis of data from different locations across diametral cross-section revealed elements of volume being compressed along the direction of applied stress, into ellipsoids [3

Elliott, James

178

Use of X-ray micro tomography to study the microstructure of loose-packed and compacted milk powders.  

PubMed

The use of X-rays to evaluate food microstructure has developed considerably in recent years. In this work we used X-ray micro tomography (XMT) to visualize the microstructure of loose-packed and compacted samples of spray-dried skim milk powder (SMP) and whole milk powder (WMP) and to quantify the proportion of both interstitial and occluded air voids in each sample. Visual scrutiny of the acquired XMT images showed details of the microstructure of the milk powders such as the spherical morphology of the particles, the size of the particles and internal air voids of various sizes. Within loose-packed powders, the proportion of air voids was higher (13% average) in WMP than in SMP. This was reversed in the compacted powders, in which the proportion of air voids was higher in SMP. The disparity in the proportion of air voids in both loose-packed and compacted samples of SMP and WMP was attributed to the size, shape and surface properties of the particles. PMID:22897706

Chawanji, A S; Baldwin, A J; Brisson, G; Webster, E

2012-10-01

179

Low temperature production of glass ceramics in the anorthite–diopside system via sintering and crystallization of glass powder compacts  

Microsoft Academic Search

The production of glass ceramics (GCs) with theoretical anorthite–diopside (An–Di) weight ratios of 60\\/40, 50\\/50 and 45\\/55 via sintering and crystallization of glass powder compacts was investigated at different temperatures between 800 and 950°C. The investigated compositions are located in the cross-section of the ternary fluorapatite–An–Di system close to An–Di binary joint, with constant fluorapatite content of 4.8wt.%. Two different

V. M. F. Marques; D. U. Tulyaganov; S. Agathopoulos; J. M. F. Ferreira

2008-01-01

180

Investigation of the effects of pressure on the compaction and subsequent sintering of nanosize powders. Final report  

SciTech Connect

With current technology and available raw materials, one knows that it is very difficult, if not impossible, to produce a monolithic ceramic material with an average grain size of less than 100 nm. The grains of ceramic materials cannot be refined by cold working as is typically done in metals. Hence, the starting ceramic powder must be of a smaller or similar particle size as the desired grain size for the final product. The availability of nanosize (<100 nm) ceramic powders, however, is limited. In many cases, the powders consist of polymorphic mixtures, precursors, or amorphous phases of the desired material. Phase transformation during sintering is difficult to control, and when it does occur it usually is accompanied by significant microstructural changes and grain growth. An example of such a powder is Al{sub 2}O{sub 3}. To the best of the authors` knowledge, high purity nanosize {alpha}-Al{sub 2}O{sub 3} powder is unavailable commercially. However, a variety of nanosize transitional forms of Al{sub 2}O{sub 3}, including the {gamma} and {delta} polymorphs, are commercially available in large quantities as mixtures. Results on the compaction and sintering of nanosize {gamma}-Al{sub 2}O{sub 3} powder are reported here.

Gonzalez, E.J.; Piermarini, G.J.; Hockey, B.; Malghan, S.G. [National Inst. of Standards and Technology, Gaithersburg, MD (United States). Ceramics Div.

1996-02-26

181

Massing in high shear wet granulation can simultaneously improve powder flow and deteriorate powder compaction: A double-edged sword  

Microsoft Academic Search

The influence of massing during high shear wet granulation (HSWG) process on granule properties and performance was investigated using microcrystalline cellulose (MCC). Massing time varied from 0 to 40min while other factors were fixed. Granule physical properties, including morphology, size, porosity, and specific surface area (SSA), were characterized. Changes in powder properties were profound in the first 10min of massing

Limin Shi; Yushi Feng; Changquan Calvin Sun

2011-01-01

182

Plutonium Metallurgy  

SciTech Connect

Due to its nuclear properties, Pu will remain a material of global interest well into the future. Processing, Structure, Properties and Performance remains a good framework for discussion of Pu materials science Self-irradiation and aging effects continue to be central in discussions of Pu metallurgy Pu in its elemental form is extremely unstable, but alloying helps to stabilize Pu; but, questions remain as to how and why this stabilization occurs. Which is true Pu-Ga binary phase diagram: US or Russian? Metallurgical issues such as solute coring, phase instability, crystallographic texture, etc. result in challenges to casting, processing, and properties modeling and experiments. For Ga alloyed FCC stabilized Pu, temperature and pressure remain as variables impacting phase stability.

Freibert, Franz J. [Los Alamos National Laboratory

2012-08-09

183

Pressing device for producing compacts from source material in powder form in particular pulverized nuclear reactor fuel  

SciTech Connect

Pressing device for producing compacts from source material in powder form, in particular pulverized nuclear reactor fuel having a die-plate contained in platen and a bore associated with a ram, for receiving source material powder, a filling shoe, and a reservoir for powder connected by a hose to the filling shoe. The device is characterized by a passing wheel in the filling shoe as filling aid means; a tube containing a feedscrew disposed between the reservoir and hose as metering means; the reservoir having a bottom part with a can type place-on part with an opening eccentric to the axis; a coupling part and a cover part are placed on the open part of the can, these parts are also provided with a passageway to the feedscrew eccentric to the longitudinal axis.

Heller, G.; Adelmann, M.; Konigs, W.; Wendorf, W.

1984-04-17

184

On the applicability of the P-? and P-? models to describe the dynamic compaction response of highly heterogeneous powder mixtures  

NASA Astrophysics Data System (ADS)

The shock consolidation response of recently obtained data for a powder mixture of Ta + Bi2O3 with previously published results for mixtures of Ni + Al, Mo + Si, and Ti + Si are investigated within the context of the P-? and P-? models to determine the applicability of these models to highly heterogeneous powder mixtures. The mixtures were found to vary significantly in densification path and crush strength (pressures required to reach full density), and no one model offers the best fit for all the mixtures. The static spherical P-? model, which uses mechanical properties of the solid materials to predict the compaction response for the powder mixtures, was found to provide the greatest disagreement with experimental data. By modifying the yield parameter to reflect measured yield properties from quasi-static densification tests, better agreement between the model and experimental data was obtained. For the empirical fitting models, the ability of a model to separate compaction into elastic and plastic components had minimal influence on goodness of fit. Conversely, homogeneity in deformation of the constituent particles was found to promote model agreement, specifically for the Mo + Si and Ti + Si powder mixtures where dynamically recovered microstructures were available for inspection.

Fredenburg, D. A.; Thadhani, N. N.

2013-01-01

185

Development and characterization of Powder Metallurgy (PM) 2XXX series Al alloy products and Metal Matrix Composite (MMC) 2XXX Al/SiC materials for high temperature aircraft structural applications  

NASA Technical Reports Server (NTRS)

The results of a series of material studies performed by the Lockheed Aeronautical Systems Company over the time period from 1980 to 1991 are discussed. The technical objective of these evaluations was to develop and characterize advanced aluminum alloy materials with temperature capabilities extending to 350 F. An overview is given of the first five alloy development efforts under this contract. Prior work conducted during the first five modifications of the alloy development program are listed. Recent developments based on the addition of high Zr levels to an optimum Al-Cu-Mg alloy composition by powder metallurgy processing are discussed. Both reinforced and SiC or B4C ceramic reinforced alloys were explored to achieve specific target goals for high temperature aluminum alloy applications.

Chellman, D. J.; Gurganus, T. B.; Walker, J. A.

1992-01-01

186

Fabrication and properties of rapidly solidified powder-based high-temperature application light-alloy composites  

Microsoft Academic Search

Particulate-reinforced composites based on Al-Fe-Ce and SiC were fabricated by conventional powder metallurgy techniques, namely powder mixing, cold compaction and hot extrusion. Static mechanical properties at ambient temperature and at elevated temperature after prolonged exposure to the test temperature were measured and related to process parameters and the volume fraction of the reinforcement. The addition of SiC particles in considerable

N. Raghunathan; H. B. Mcshane; C. Davies; T. Sheppard

1990-01-01

187

Structure and mechanical properties of compacts produced from rapidly solidified VT6S-alloy powders in hydrogen-containing atmosphere  

Microsoft Academic Search

The state of the surface of compacts produced from rapidly solidified (RS) titanium-alloy powders determined by the presence of an oxide film is an important factor affecting their quality. A decrease in its thickness results in increased reliability of diffusion welding between particles during hot isostatic pressing (HIP) and, as a consequence, in improved mechanical properties of the compacts, their

Yu. I. Ponomaryov; M. A. Golub; T. I. Barmina; A. Yu. Krivospitsky; T. V. Tulaeva; A. V. Popov

1997-01-01

188

Investigation on the effect of lubrication and forming parameters to the green compact generated from iron powder through warm forming route  

Microsoft Academic Search

In order to generate green compacts of iron ASC 100.29 powder at above ambient temperature and below its recrystallization temperature, a warm compaction rig is designed and fabricated which can be operated at various temperature and load. The aim of this paper is to present the outcomes of an investigation on the effect of lubrication and forming parameters, i.e., load

M. M. Rahman; S. S. M. Nor; H. Y. Rahman

2011-01-01

189

Massing in high shear wet granulation can simultaneously improve powder flow and deteriorate powder compaction: a double-edged sword.  

PubMed

The influence of massing during high shear wet granulation (HSWG) process on granule properties and performance was investigated using microcrystalline cellulose (MCC). Massing time varied from 0 to 40 min while other factors were fixed. Granule physical properties, including morphology, size, porosity, and specific surface area (SSA), were characterized. Changes in powder properties were profound in the first 10 min of massing but negligible beyond 10 min. With 10 min of massing, granule tabletability decreased by 75% while flowability increased by 75%. The significantly deteriorated tabletability and improved flowability resulted from dramatic changes in granule morphology, porosity, and SSA. The results confirm that massing time is a key process parameter in HSWG, and it must be carefully evaluated and controlled during process development, scale up, and manufacturing. PMID:21443948

Shi, Limin; Feng, Yushi; Sun, Changquan Calvin

2011-05-18

190

A homogenization approach to the yield strength of spherical powder compacts  

SciTech Connect

Optimal external estimates of the macroscopic strength criteria of a hexagonal array of identical spherical grains, under isostatic and closed die compaction, have been obtained through the use of the kinematic approach of the yield design homogenization method. Two appropriate unit cells, one for each stage compaction (I and II), and eight relevant failure mechanisms are considered. For comparison purposes, numerical simulations based on FEA similar to those of Ogbana and Fleck [1] have also been carried out. The shapes and sizes of the macroscopic yield surfaces are determined at various stages of compaction and it has been found in particular that they depend upon the loading history as well as the relative density of the compact.

Benabbes, A.; Siad, L. [URCA/GRESPI, Universite de Reims, UFR SEN, B.P. 1039, 51687 Reims cedex 2 (France); Dormieux, L. [LMSGC, Ponts ParisTech, cite Descartes, Champs-sur-Marne, F-77455 (France); Liu, W. K. [Northwestern University, DME, Evanston (United States) and SKKU (Korea, Republic of)

2010-06-15

191

High strength-high conductivity Cu-Fe composites produced by powder compaction/mechanical reduction  

DOEpatents

A particulate mixture of Cu and Fe is compacted and mechanically reduced to form an ''in-situ'' Cu-Fe composite having high strength and high conductivity. Compaction and mechanical reduction of the particulate mixture are carried out at a temperature and time at temperature selected to avoid dissolution of Fe into the Cu matrix particulates to a harmful extent that substantially degrades the conductivity of the Cu-Fe composite. 5 figures.

Verhoeven, J.D.; Spitzig, W.A.; Gibson, E.D.; Anderson, I.E.

1991-08-27

192

Investigation of a high pressure implosive technique for metal powder compaction  

E-print Network

ball bearing introduced into the test to study mode of fai. lure. Figure 22 shows the fracture patterns. Figure 23 shows an ampoule of non-metallic material de- posited in the powdered iron specimen. 28 5. 90 g~ 7. M AQQK8. 22* PFSCCVX8 32... ball bearing introduced into the test to study mode of fai. lure. Figure 22 shows the fracture patterns. Figure 23 shows an ampoule of non-metallic material de- posited in the powdered iron specimen. 28 5. 90 g~ 7. M AQQK8. 22* PFSCCVX8 32...

Garrett, Donald Richard

2012-06-07

193

Fracture energy based constitutive models for tensile fracture of metal powder compacts  

Microsoft Academic Search

Diametral compression test or the Brazilian disc test is commonly used to characterise the tensile strength of brittle materials. A general fracture model based on energy assumptions is proposed for simulation of the discrete and localised tensile fracturing process in metal powder. The characteristics of the tensile fracture development of the central crack in diametral tested specimen is numerically studied.

P. Jonsén; H.-Å. Häggblad

2007-01-01

194

Interaction of Tournemire argillite (Aveyron, France) with hyperalkaline fluids: Batch experiments performed with powdered and/or compact materials  

NASA Astrophysics Data System (ADS)

Argillaceous rocks and concrete matrix are considered as potential host rocks and engineered barrier, respectively for radioactive waste repositories. The concrete matrix could react with the groundwater of the geological site, inducing a drastic change in its chemical composition and pH. Consequently, the physico-chemical properties of the rock in contact with this hyperalkaline fluid may be modified. Therefore, an experimental programme has been developed for examining the physico-chemical changes of claystone in contact with alkaline fluids: batch experiments undertaken as a preliminary step followed by diffusion and percolation experiments in order to describe and to assess the physico-chemical phenomena observed under repository conditions. The first series of batch experiments are carried out in order to study the degradation of the Tournemire argillite properties caused by a fluid resulting from a contact with fresh concrete, considered as the most aggressive in relation to its hyper alkaline pH (?13). Thus, the influence of several parameters is tested, such as liquid/rock ratio (L/R 3-30 g/g), contact time (1-3 months), temperature (25-70 °C) and oxygen concentration. To compare the effect of the concrete maturity on the argillite physico-chemical damage, the second series of batch experiments are performed with a fluid resulting from a contact with moderately degraded concrete. Experiments are carried out on powdered and compact samples in order to identify structural and geochemical modifications. Before and after contact with simplified concrete fluids, powdered solids were mainly characterised by XRD (with measurements of specific surface area and SEM observations for a selection of samples) whereas compact materials were only observed by SEM. The chemical composition of the recovered solutions was also determined for their major anions and cations with their carbon content and pH values. Interpretations are based on solid analyses and aqueous chemistry. The comparison of results obtained with powdered and compact solids is only feasible for short time experiments. Aqueous chemistry and solid analyses indicate the dissolution of pyrite, dolomite and organic carbon with the precipitation of calcite. Precipitations of zeolites and K-feldspars occur sometimes and are only evidenced by SEM analyses. Nevertheless, silicates dissolution or precipitation is unclear through XRD analyses. Experimental conditions influence widely the intensity/nature of processes and prevent the transposition of data obtained in given conditions to other ones.

Devol-Brown, I.; Tinseau, E.; Bartier, D.; Mifsud, A.; Stammose, D.

195

Warm Compaction Forming of a Binder-Treated Fe-Base Material  

Microsoft Academic Search

It is well known that increasing density is the best way to increase the performance of powder metallurgy (PM) parts. Conventional PM processing can produce iron-base parts with density less than 7.2 g\\/cm3. Their mechanical properties are substantially less than their full density counterpart. With minor modification on the conventional PM equipment, green compact density of 7.4 g\\/cm3 can be

Tungwai Leo NGAI; Ying-huan KUANG; Yuan-yuan LI

2007-01-01

196

NON-MELT PROCESSING OF "LOW-COST", ARMSTRONG TITANIUM AND TITANIUM ALLOY POWDERS  

SciTech Connect

In the last decade, a considerable effort has been made to develop new methods for producing low cost titanium and titanium powders. The Armstrong process is a new method of producing titanium powder via reducing TiCl4 vapor in molten sodium. The process is scalable, and can be used to produce pre-alloyed powders. Non-melt processing and powder metallurgy approaches are economically viable with the commercially pure powders. In this investigation, several non-melt processing technologies, including vacuum hot pressing, extrusion, roll compaction, and forging techniques, will be evaluated using the Armstrong titanium powders. The metallurgical, chemical, and mechanical properties of the processed titanium samples will be discussed.

Peter, William H [ORNL; Blue, Craig A [ORNL; Clive, Scorey [Ametek, Inc.; Ernst, Bill [International Titanium Powder; McKernan, John [Ametek, Inc.; Kiggans, Jim [ORNL; Rivard, John D [ORNL; Yu, Dr. Charlie [Ametek, Inc.

2007-01-01

197

Improvement of the Dimensional Stability of Powder Injection Molded Compacts by Adding Swelling Inhibitor into the Debinding Solvent  

NASA Astrophysics Data System (ADS)

Defects are frequently found in powder injection molded (PIM) compacts during solvent debinding due to the swelling of the binders. This problem can be alleviated by adjusting the composition of the debinding solvent. In this study, 10 vol pct swelling inhibitors were added into heptane, and the in-situ amounts of swelling and sagging of the specimen in the solvent were recorded using a noncontacting laser dilatometer. The results show that the addition of ethanol, 2-propanol, 1-butanol, and 1-pentanol reduced the amounts of swelling by 31, 21, 17, and 11 pct, respectively. This was because the small molecule alcohols, which do not dissolve paraffin wax (PW) or stearic acid (SA) in the binder system, could diffuse easily into the specimen and increased the portion of the swelling inhibitor inside. The amount of the extracted PW and SA also decreased, but only by 8.3, 6.1, 4.3, and 2.4 pct, respectively. The solubility parameters of 1-bromopropane (n-PB) and ethyl acetate (EA) are between those of heptane and alcohols, and they also yielded a slight reduction in the amounts of swelling by 6 and 11 pct, respectively. These results suggest that to reduce defects caused by binder swelling during solvent debinding, alcohols with high solubility parameters can be added into heptane without sacrificing significantly on the debinding rate.

Fan, Yang-Liang; Hwang, Kuen-Shyang; Su, Shao-Chin

2008-02-01

198

Metastable structures in metallurgy  

Microsoft Academic Search

Metastable structures or, more accurately, configurationally frozen metastable structures are no novelty in metallurgy. Indeed,\\u000a much of the traditional practice of metallurgy has centered on the formation, characterization, understanding and control\\u000a of structures which are either compositionally, topologically and\\/or morphologically metastable. However, in the past two\\u000a to three decades we have seen a great upsurge in the production and study

David Turnbull

1981-01-01

199

Superplasticity in a powder metallurgy magnesium composite  

SciTech Connect

Metal-matrix composites (MMC) have great potential to be used in high-performance aerospace and automobile applications. It is important, therefore, to develop secondary processing for MMCs which can effectively produce complex engineering components directly from wrought products. Many studies now have been performed that demonstrate superplasticity can be developed in MMCs. Superplasticity has been reported in some Mg alloys, including ZK60, AZ31, AZ61, and Mg-Li alloys. But, none of these alloys showed superplasticity at high strain rates. Although HSRS has been extensively demonstrated in Al-base MMCs, both in PM and IM products, neither conventional superplasticity nor HSRS has yet been shown in any Mg-base composite. The purpose of this paper is to present, for the first time, the observation of HSRS in a 17 vol% SiC particulate-reinforced ZK60A magnesium composite (ZK60/SiC/17p).

Nieh, T.G.; Wadsworth, J. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States)

1995-04-15

200

High gamma prime superalloys by powder metallurgy  

Microsoft Academic Search

A series of superalloy compositions are described, which when processed according to a described processing sequence, produce homogeneous superalloy articles which contain an exceptionally high amount of the gamma prime phase. These alloys contain large amounts of aluminum and chromium and hence are quite oxidation resistant. The processing sequence includes rapid solidification to suppress the formation of the low melting

R. G. Bourdeau; A. R. Cox; P. R. Holiday

1980-01-01

201

Metallurgy Department Progress Report for  

E-print Network

Risø-R-444 Metallurgy Department Progress Report for the Period l January to 31 December 1980 "Stiffness Based Fatigue Damage Characterization of Fibrous Composites" (page 53). #12;Risø-R-444 METALLURGY of the Metallurgy Departnent at Risø during 1980 are described. The work is presented in four chap- ters: General

202

Synthesis and characterization of the NiFe2O4/Ni3Fe nanocomposite powder and compacts obtained by mechanical milling and spark plasma sintering  

NASA Astrophysics Data System (ADS)

Nanocomposite powder and compacts of NiFe2O4/Ni3Fe type were synthesized using mechanical milling and spark plasma sintering (SPS) techniques. The samples have been investigated by X-ray diffraction (XRD), laser particles size analysis, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The nanocomposite powder was obtained by mechanical milling in a high planetary ball mill of nanocrystalline NiFe2O4 and nanocrystalline Ni3Fe powders. The nanocomposite powder consists from Ni3Fe particles covered at the surface with a layer of NiFe2O4 fine particles and NiFe2O4 particles. The nanocomposite particles have the median diameter d50 of 1.6 ?m. The sintering in 400-600 °C temperature range preserve the nanocomposite phases but lead to a high porosity. The nanocomposite compacts consist in Ni3Fe clusters surrounded by NiFe2O4. A sintering temperature of 800 °C leads to a good density for the nanocomposite compacts and to the new phase formation. The new phase is a wustite type (Fe1-xNixO) and is formed at the metal/ceramic interface. A change in the Ni/Fe ratio, in the spinel structure, was evidenced during sintering. Sintering at a temperature of 800 °C, leads to the formation of a mixed iron-nickel ferrite with a very small amount of nickel, Ni1-xFexFe2O4.

Marinca, T. F.; Neam?u, B. V.; Popa, F.; Tar?a, V. F.; Pascuta, P.; Takacs, A. F.; Chicina?, I.

2013-11-01

203

Microstructure and mechanical properties of Nb-Al-N and Nb-Si-B powder compacts produced by spark plasma sintering  

SciTech Connect

Nb-Al-N and Nb-Si-B powder compacts were prepared by spark plasma sintering, and their microstructure, mechanical properties and oxidation behavior were investigated. Adding nitrogen was easily done by blending or mechanically alloying Nb and AlN powders and then sintering them. The addition of nitrogen caused the formation of Nb{sub 2}N in all the Nb-Al-N compacts and Nb{sub 2}N and Nb{sub 3}Al{sub 2}N in compacts with high aluminum and nitrogen contents. The highest room-temperature hardness and the highest yield stress at 1,473K were observed for compacts consisting of Nb{sub 2}N and Nb{sub 3}Al{sub 2}N and those consisting of Nb{sub 2}N and Nb{sub 2}Al, respectively. Nb-Si-B compacts were prepared from elemental powders. Two or three of NbB{sub 2}, Nb{sub 5}Si{sub 3}, Nb{sub 5}Si{sub 3}B{sub 2} and NbSi{sub 2} phases were identified as constituent phases of Nb-Si-B compacts depending on composition unless a large amount of silicon is consumed by forming SiO{sub 2}. Contributions of NbB{sub 2}, Nb{sub 5}Si{sub 3} and Nb{sub 5}Si{sub 3}B{sub 2} phases to room-temperature hardness and yield stress at 1,973K were much larger than those of NbSi{sub 2}. However, the oxidation resistance of Nb-Si-B compacts increased with increasing the volume fraction of NbSi{sub 2}. The oxidation resistance of Nb{sub 5}Si{sub 3}B{sub 2} was better than that of Nb{sub 5}Si{sub 3}, but was not as good as that of NbSi{sub 2}.

Murakami, T.; Kitahara, A.; Kawahara, M.; Takahashi, Y.; Inui, H.; Yamaguchi, M.

1999-07-01

204

Power metallurgy tool electrodes for electrical discharge machining  

Microsoft Academic Search

Electrodes in electrical discharge machining (EDM) can be compared with cutting tools in conventional machining. Tool performance is one of the important factors that determine the quality of the machined component. Due to the ease of manufacturing and control over the properties of electrodes, the powder metallurgy (P\\/M) technique has an advantage over other methods of electrode fabrication. P\\/M electrodes

M. P. Samuel; P. K. Philip

1997-01-01

205

Process Metallurgy Course Outline  

E-print Network

MATS4003 Process Metallurgy Advanced Course Outline Session 1, 2014 School of Materials Science Kinetics of homogeneous and heterogeneous reactions 2-3 4 Mechanisms of carbothermal reduction 3 5 Types;4 Timetable Lectures and Tutorials Day Time Location Wednesday 9:00-11:00am Webster 256 Thursday 12:00-2:00pm

New South Wales, University of

206

Consolidation of aluminum 6061 powder by equal channel angular extrusion  

E-print Network

Equal channel angular extrusion is a promising approach to obtaining full density in powder metallurgy applications. This method can impose large effective deformations through uniform shear strain. Aluminum alloy 6061 powder is used as a test...

Pearson, John Montgomery

2012-06-07

207

The effect of hot isostatic pressing parameters on microstructure and mechanical properties of Eurofer powder HIPed material  

NASA Astrophysics Data System (ADS)

The production of reduced activation ferritic/martensitic (RAFM) steel by powder metallurgy and high isostatic pressing (HIP) offers numerous advantages for different nuclear applications. The objective of this work is to optimise the Eurofer powder HIP process in order to obtain RAFM solid HIPed steel with similar mechanical properties to those of a forged material. Starting from the forged solid Eurofer steel batch, the material is atomized and the Eurofer powder is characterized in terms of granulometry, chemical composition, surface oxides, etc. Different compaction HIP cycle parameters in the temperature range (950-1100 °C) are tested. The chemical composition of the HIPed material is comparable to the initial forged Eurofer. All the obtained materials are fully dense and the microstructure of the compacted material is well martensitic. The prior austenite grain size seems to be constant in this temperature range. The mechanical tests performed at room temperature reveal acceptable hardness, tensile and Charpy impact properties regarding the ITER specification.

Gentzbittel, J. M.; Chu, I.; Burlet, H.

2002-12-01

208

Enhanced Densification of Carbonyl Iron Powder Compacts by the Retardation of Exaggerated Grain Growth through the Use of High Heating Rates  

NASA Astrophysics Data System (ADS)

An investigation of the effect of heating rates on the densification behavior of carbonyl iron powder compacts, particularly on the exaggerated grain growth during the ?- ? phase transformation, was carried out in this study. Compacts heated at 1200 °C/min and then sintered for 90 minutes at 1200 °C attained 7.14 g/cm3, while those heated at 10 °C/min reached only 6.61 g/cm3. Dilatometer curves using heating rates of 2 °C/min, 5 °C/min, 10 °C/min, 30 °C/min, and 90 °C/min demonstrate that 90 °C/min yields the highest sintered density. The microstructure analysis shows that high heating rates inhibit exaggerated grain growth during the phase transformation by keeping the interparticle neck size small and pinning the grain boundaries. This explanation is supported by the calculation that shows that the energy barrier preventing the grain boundary from breaking away from the neck is reduced hyperbolically as the neck size and the amount of shrinkage increase. The high heating rate, however, shows little beneficial effect for materials that have no allotropic phase transformation or have less drastic grain growth during heating, such as nickel and copper. Thus, bypassing the low temperatures to suppress the surface diffusion mechanism, which does not contribute to densification, is ruled out as the main reason for the enhanced densification of carbonyl iron powders.

Hwang, Kuen-Shyang; Lu, Yung-Chung; Shu, Guo-Jiun; Chen, Bor-Yuan

2009-12-01

209

Electrical Discharge Surface Alloying of Ti and Fe Workpiece Materials Using Refractory Powder Compact Electrodes and Cu Wire  

Microsoft Academic Search

The paper reviews the use of metal powders dispersed in the dielectric fluid and refractory PM electrodes, to initiate workpiece surface modification during EDM. Experimental work details the effects of EDM parameters (up to 270 V) on the hardness\\/composition of the white layer following die sink machining of AISI H13 tool steel and roll texturing of 2% Cr steel using

D. K. Aspinwall; R. C. Dewes; H. G. Lee; J. Simao; P. A. McKeown

2003-01-01

210

International Powder Metallurgy Conference September 4-8, 2002, Turkish Powder Metallurgy Association  

E-print Network

., Budapest, P.O.Box 32, H-1518, Hungary b Dept. of Materials Sci. and Eng., Faculty of Pet. and Mining, Suez Canal Univ., Suez, Egypt, mkassem54@yahoo.com c Dept. of General Physics, Eötvös University, Budapest, P

Gubicza, Jenõ

211

Dustiness behaviour of loose and compacted Bentonite and organoclay powders: What is the difference in exposure risk?  

Microsoft Academic Search

Single-drop and rotating drum dustiness testing was used to investigate the dustiness of loose and compacted montmorillonite\\u000a (Bentonite) and an organoclay (Nanofil®5), which had been modified from montmorillonite-rich Bentonite. The dustiness was analysed based on filter measurements as\\u000a well as particle size distributions, the particle generation rate, and the total number of generated particles. Particle monitoring\\u000a was completed using a

Keld Alstrup Jensen; Ismo Kalevi Koponen; Per Axel Clausen; Thomas Schneider

2009-01-01

212

Engineering in Process Metallurgy  

E-print Network

flow in process vessels. 9 Gas-liquid flow in packed bed reactors, gas-solid flow in fluid bed reactors Modelling of mass and heat flow in packed/fluidised beds 7 Plant Visit (BlueScope Steelworks - Wollongong) 8 10 Multiphase flow: gas-powder-liquid flow in moving bed 11 Powder flow in packed beds, pulverised

New South Wales, University of

213

Enery Efficient Press and Sinter of Titanium Powder for Low-Cost Components in Vehicle Applications  

SciTech Connect

This is the final technical report for the Department of Energy NETL project NT01931 Energy Efficient Press and Sinter of Titanium Powder for Low-Cost Components in Vehicle Applications. Titanium has been identified as one of the key materials with the required strength that can reduce the weight of automotive components and thereby reduce fuel consumption. Working with newly developed sources of titanium powder, Webster-Hoff will develop the processing technology to manufacture low cost vehicle components using the single press/single sinter techniques developed for iron based powder metallurgy today. Working with an automotive or truck manufacturer, Webster-Hoff will demonstrate the feasibility of manufacturing a press and sinter titanium component for a vehicle application. The project objective is two-fold, to develop the technology for manufacturing press and sinter titanium components, and to demonstrate the feasibility of producing a titanium component for a vehicle application. The lowest cost method for converting metal powder into a net shape part is the Powder Metallurgy Press and Sinter Process. The method involves compaction of the metal powder in a tool (usually a die and punches, upper and lower) at a high pressure (up to 60 TSI or 827 MPa) to form a green compact with the net shape of the final component. The powder in the green compact is held together by the compression bonds between the powder particles. The sinter process then converts the green compact to a metallurgically bonded net shape part through the process of solid state diffusion. The goal of this project is to expand the understanding and application of press and sinter technology to Titanium Powder applications, developing techniques to manufacture net shape Titanium components via the press and sinter process. In addition, working with a vehicle manufacturer, demonstrate the feasibility of producing a titanium component for a vehicle. This is not a research program, but rather a project to develop a process for press and sinter of net shape Titanium components. All of these project objectives have been successfully completed.

Thomas Zwitter; Phillip Nash; Xiaoyan Xu; Chadwick Johnson

2011-03-31

214

Use of Cation Exchange Resins for Production of U{sub 3}O{sub 8} Suitable for the Al-U{sub 3}O{sub 8} Powder Metallurgy Process  

SciTech Connect

This report describes the production of U{sub 3}O{sub 8} powders from three types of cation exchange resins: Dowex 50W, a strong acid, sulfonate resin; AG MP-50, a macroporous form of sulfonate resin; and Bio-Rex 70, a weak acid, carboxylic resin.

Mosley, W.C.

2001-09-17

215

Metallurgy Department Progress Report for the Period  

E-print Network

Dlcfc^ooWS imsm "-"' Metallurgy Department Progress Report for the Period 1 January to 31 December 1962 (Uw National Laboratory, DK-4000 Roskilde, Denmark July 1963 #12;Risø-R-486 METALLURGY DEPARTMENT PROGRESS REPORT FOR THE PERIOD 1 JANUARY TO 31 DECEMBER 1982 Abstract. The activities of the Metallurgy

216

Ris-M-2888 Metallurgy Department  

E-print Network

©KC^OOO-»9 å Risø-M-2888 Metallurgy Department Publications 1989 Risø National Laboratory, DK-4000 Roskilde, Denmark August 1990 #12;Metallurgy Department Publications 1989 Edited by A. Horsewell Risø of the Metallurgy Department during 1989 are listed. This list is divided into three sections asfollows

217

Application of X-ray Microtomography and Image Processing to the Investigation of a Compacted Granular System  

E-print Network

Insti- tute for Pharmaceutical Materials Science, Department of Materials Science and Metallurgy to the pharmaceutical, food and powder metallurgy industries. In order to produce a uniform, high quality end product distributions within pharmaceutical tablets, and Yang and Fu [9] used XMT to characterize powder processing

Elliott, James

218

Influence of Powder Metallurgical Processing Routes on Phase Formations in a Multicomponent NbSi-Alloy  

NASA Astrophysics Data System (ADS)

Refractory metal silicide composites on the basis of Nbss-Nb5Si3 have been investigated as potential alternatives for nickel-base superalloys for years because of their low densities and good high-temperature strengths. NbSi-based composites are typically produced by arc-melting or casting. Samples in this study, however, were produced by powder metallurgy because of the potential for near net-shape component fabrication with very homogeneous microstructures. Either gas atomized powder or high-energy mechanically alloyed elemental powders were compacted by powder injection molding or hot isostatic pressing. Heat treatments were applied for phase stability evaluation. Slight compositional changes (oxygen, nitrogen, or iron) introduced by the processing route, i.e., powder production and consolidation, can affect phase formations and phase transitions during the process. Special focus is put on the distinction between different silicides (Nb5Si3 and Nb3Si) and silicide modifications (?-, ?-, and ?-Nb5Si3), respectively. These were evaluated by x-ray diffraction and energy-dispersive spectroscopy measurements with the additional inclusion of thermodynamic calculations using the calculated phase diagram method.

Seemüller, C.; Hartwig, T.; Mulser, M.; Adkins, N.; Wickins, M.; Heilmaier, M.

2014-08-01

219

Influence of Powder Metallurgical Processing Routes on Phase Formations in a Multicomponent NbSi-Alloy  

NASA Astrophysics Data System (ADS)

Refractory metal silicide composites on the basis of Nbss-Nb5Si3 have been investigated as potential alternatives for nickel-base superalloys for years because of their low densities and good high-temperature strengths. NbSi-based composites are typically produced by arc-melting or casting. Samples in this study, however, were produced by powder metallurgy because of the potential for near net-shape component fabrication with very homogeneous microstructures. Either gas atomized powder or high-energy mechanically alloyed elemental powders were compacted by powder injection molding or hot isostatic pressing. Heat treatments were applied for phase stability evaluation. Slight compositional changes (oxygen, nitrogen, or iron) introduced by the processing route, i.e., powder production and consolidation, can affect phase formations and phase transitions during the process. Special focus is put on the distinction between different silicides (Nb5Si3 and Nb3Si) and silicide modifications (?-, ?-, and ?-Nb5Si3), respectively. These were evaluated by x-ray diffraction and energy-dispersive spectroscopy measurements with the additional inclusion of thermodynamic calculations using the calculated phase diagram method.

Seemüller, C.; Hartwig, T.; Mulser, M.; Adkins, N.; Wickins, M.; Heilmaier, M.

2014-09-01

220

University of Cambridge Department of Materials Science & Metallurgy  

E-print Network

University of Cambridge Department of Materials Science & Metallurgy Modelling of Microstructural and Metallurgy, University of Cambridge, between May 2007 and August 2007. Except where acknowledgements

Cambridge, University of

221

Powder metal matrix composites: selection and processing  

Microsoft Academic Search

There has been growing interest in the last decade in the development of metal matrix composites (MMCs) for the aerospace industry because of their attractive physical and mechanical properties and enhanced elevated temperature capabilities. However, some of the fabrication techniques (e.g. using powder metallurgy) for this new class of MMCs are hampered by (i) the poor distribution of the reinforcements,

M. J Tan; X Zhang

1998-01-01

222

A NUMERICAL STUDY ON THE MECHANICAL BEHAVIOUR OF PHARMACEUTICAL POWDERS DURING COMPRESSION  

E-print Network

for Pharmaceutical Materials Science, Department of Materials Science and Metallurgy, University of CambridgeA NUMERICAL STUDY ON THE MECHANICAL BEHAVIOUR OF PHARMACEUTICAL POWDERS DURING COMPRESSION C-Y. Wu1 of pharmaceutical powders. The effects of kinematics of punch movements and the friction between powder and die wall

de Gispert, Adrià

223

The Rules of Ferrous Metallurgy  

PubMed Central

The ways in which the sciences have been delineated and categorized throughout history provide insights into the formation, stabilization, and establishment of scientific systems of knowledge. The Dresdener school’s approach for explaining and categorizing the genesis of the engineering disciplines is still valid, but needs to be complemented by further-reaching methodological and theoretical reflections. Pierre Bourdieu’s theory of social practice is applied to the question of how individual agents succeed in influencing decisively a discipline’s changing object orientation, institutionalisation and self-reproduction. Through the accumulation of social, cultural and economic capital, they succeed in realising their own organisational ideas and scientific programs. Key concepts for the analysis include the struggle for power and resources, monopolies of interpretation, and the degree of autonomy. A case study from the Aachener Technische Hochschule shows that the consolidation of ferrous metallurgy can be conceived as a symbolical struggle between Fritz Wüst, professor for ferrous metallurgy, and the German Iron and Steel Institute, leading to a construction of a system of differences in which scientists accepted being scientists rather than entrepreneurs, and entrepreneurs accepted becoming entrepreneurs and renounced science.

2010-01-01

224

Dual-Alloy Disks are Formed by Powder Metallurgy  

NASA Technical Reports Server (NTRS)

High-performance disks have widely varying properties from hub to rim. Dual property disk is fabricated using two nickel-base alloys, AF-115 for rim and Rene 95 for hub. Dual-alloy fabrication may find applications in automobiles, earth-moving equipment, and energy conversion systems as well as aircraft powerplants. There is potential for such applications as shafts, gears, and blades.

Harf, F. H.; Miner, R. V.; Kortovich, C. S.; Marder, J. M.

1982-01-01

225

Powder metallurgy Rene 95 rotating turbine engine parts, volume 2  

NASA Technical Reports Server (NTRS)

A Rene 95 alloy as-HIP high pressure turbine aft shaft in the CF6-50 engine and a HIP plus forged Rene 95 compressor disk in the CFM56 engine were tested. The CF6-50 engine test was conducted for 1000 C cycles and the CFM56 test for 2000 C cycles. Post test evaluation and analysis of the CF6-50 shaft and the CFM56 compressor disk included visual, fluorescent penetrant, and dimensional inspections. No defects or otherwise discrepant conditions were found. These parts were judged to have performed satisfactorily.

Wilbers, L. G.; Redden, T. K.

1981-01-01

226

Powder and particulate production of metallic alloys  

NASA Technical Reports Server (NTRS)

Developments of particulate metallurgy of alloyed materials where the final products is a fully dense body are discussed. Particulates are defined as powders, flakes, foils, silvers, ribbons and strip. Because rapid solidification is an important factor in particulate metallurgy, all of the particulates must have at least one dimension which is very fine, sometimes as fine as 10 to 50 microns, but move typically up to several hundred microns, provided that the dimension permits a minimum solidification rate of at least 100 K/s.

Grant, N. J.

1982-01-01

227

Materials for Advanced Turbine Engines. Volume 1; Power Metallurgy Rene 95 Rotating Turbine Engine Parts  

NASA Technical Reports Server (NTRS)

An attempt was made to improve methods for producing powder metallurgy aircraft gas turbine engine parts from the nickel base superalloy known as Rene 95. The parts produced were the high pressure turbine aft shaft for the CF6-50 engine and the stages 5 through 9 compressor disk forgings for the CFM56/F101 engines. A 50% cost reduction was achieved as compared to conventional cast and wrought processing practices. An integrated effort involving several powder producers and a major forging source were included.

Pfouts, W. R.; Shamblen, C. E.; Mosier, J. S.; Peebles, R. E.; Gorsler, R. W.

1979-01-01

228

Fabrication of metal matrix composite by semi-solid powder processing  

SciTech Connect

Various metal matrix composites (MMCs) are widely used in the automotive, aerospace and electrical industries due to their capability and flexibility in improving the mechanical, thermal and electrical properties of a component. However, current manufacturing technologies may suffer from insufficient process stability and reliability and inadequate economic efficiency and may not be able to satisfy the increasing demands placed on MMCs. Semi-solid powder processing (SPP), a technology that combines traditional powder metallurgy and semi-solid forming methods, has potential to produce MMCs with low cost and high efficiency. In this work, the analytical study and experimental investigation of SPP on the fabrication of MMCs were explored. An analytical model was developed to understand the deformation mechanism of the powder compact in the semi-solid state. The densification behavior of the Al6061 and SiC powder mixtures was investigated with different liquid fractions and SiC volume fractions. The limits of SPP were analyzed in terms of reinforcement phase loading and its impact on the composite microstructure. To explore adoption of new materials, carbon nanotube (CNT) was investigated as a reinforcing material in aluminum matrix using SPP. The process was successfully modeled for the mono-phase powder (Al6061) compaction and the density and density distribution were predicted. The deformation mechanism at low and high liquid fractions was discussed. In addition, the compaction behavior of the ceramic-metal powder mixture was understood, and the SiC loading limit was identified by parametric study. For the fabrication of CNT reinforced Al6061 composite, the mechanical alloying of Al6061-CNT powders was first investigated. A mathematical model was developed to predict the CNT length change during the mechanical alloying process. The effects of mechanical alloying time and processing temperature during SPP were studied on the mechanical, microstructural and compositional properties of the Al6061-CNT composites. A shear lag model was applied to predict the mechanical property (hardness) of the composite. This work demonstrated the promising potential of SPP in the fabrication of particle/fiber (nanotube) reinforced MMCs.

Wu, Yufeng [Ames Laboratory

2012-11-28

229

Ultrafast Powder Diffraction  

NASA Astrophysics Data System (ADS)

An overview is given of the use of powder synchrotron-X-ray and neutron diffraction to study very fast physical or chemical processes that require time resolution of 500 ms or less. The experimental requirements to obtain data of good quality are considered, including the incident flux, detector characteristics, and the different strategies possible for irreversible and reversible processes. The latter are accessible via a stroboscopic approach whereas the former require the maximum rates of data acquisition. Some recent studies are described, drawn from the areas of combustion synthesis, metallurgy and catalysis. The exploitation of the bunch structure of a synchrotron ring to obtain time resolution in the sub-ns range with the pump-probe stroboscopic approach is also illustrated.

Fitch, Andy; Curfs, Caroline

230

-OK 8>00jigLi Metallurgy Department  

E-print Network

-OK 8°>00jigLi 00 tf) Risø-M-28B Metallurgy Department Publications 1988 Risø National Laboratory, DK-4000 Roskilde, Denmark August 1989 #12;Metallurgy Department Publications 1988 Edited by A by the staffof the Metallurgy Department during 1988 is given. The list comprises journal papers, conference

231

* TOTT(^/Oi\\ Riso-R-402 Metallurgy Department  

E-print Network

o o o o 00 U *· TOTT(^/Oi\\ Riso-R-402 ^ Metallurgy Department Progress Report for the period l METALLURGY DEPARTMENT PROGRESS REPORT FOR THE PERIOD 1 JANUARY TO 31 DECEMBER 1978 Abstract. The activities of the Metallurgy Department at Risø during 1978 are described. The work is presented in four chap- ters: General

232

Characterization and prediction of abrasive wear of powder composite materials  

Microsoft Academic Search

Composite materials produced by powder metallurgy provide a solution in many engineering applications where materials with high abrasion and erosion resistance are required. The actual wear behaviour of the material is associated with many external factors (particle size, velocity, angularity, etc.) and intrinsic material properties (hardness, toughness, Young modulus, etc.). Hardness and toughness properties of such tribomaterials are highly dependent

R. Veinthal; P. Kulu; J. Pirso; H. Käerdi

2009-01-01

233

African metallurgy in the Atlantic world  

Microsoft Academic Search

This paper examines the history of African metallurgy in the era of Atlantic trade. It reports on excavations at the John Reeder foundry site in St Thomas, Jamaica. The transfer of African technologies to the Caribbean reveals the plantation economy's dependence on African technical expertise, not merely slave labour. The comprehensive focus on the Atlantic world also informs archaeological investigations

Candice L. Goucher

1993-01-01

234

DlcSsoo |LI Metallurgy Department  

E-print Network

chap- ters: General Materials Research, Technology and Materials De- velopment, and Fuel Elements 1984 is included. INIS-descriptors; FUEL ELEMENTS, METALLURGY, NONDESTRUCTIVE TESTING, RESEARCH recrystallization of commercially pure aluminium 9 2.4. Calorimetric studies of recrystallization 9 2.5. Small angle

235

The effect of high density electric pulses on sintered aluminum 201AB silicon carbide MMC PM compacts during plastic deformation  

NASA Astrophysics Data System (ADS)

The effect of high-density electrical pulses on mechanical and structural properties of sintered aluminum SiC metal-matrix composites, fabricated by standard powder-metallurgy compaction and sintering, was investigated. Three types of phenomena where investigated during transverse rupture testing of the samples: a consolidation effect (increasing of the transverse rupture strength (TRS)), an electroplastic effect (decreasing of the flow stresses), and an increasing of the stress intensity factor by electric pulse application. It was observed, that an increase in the TRS strength of sintered powder metallurgy (PM) aluminum and aluminum metal matrix composite (MMC) compacts is a result of the electric pulse consolidation effect due to non-uniform temperature distribution around the grain boundaries. Three analytical models of the thermal effect of electric pulses on aluminum samples where considered: total temperature change of the sample due to a one electric pulse, one-dimensional steady state model and transient 2D thermal analysis of the temperature distribution around the grain boundary. The 2D transient analysis shows that the temperature rise in the grain boundary of a sintered PM aluminum sample due to an electric pulse can exceed the melting point. At the same time the temperature of the bulk material has an insignificant (<28°C) change. It was found that the electroplastic effect, due to electric pulse application, can account for up to a 40% load drop in aluminum MMC PM compacts. Reduction of flow stresses during plastic deformation could reduce the risk of structural damage, micro-cracks, SiC particle fracture and delamination of the aluminum MMC. These results may find practical application for manufacturing processes such as forging, extrusion, rolling, which involve plastic deformation. It was experimentally proven that a non-uniform temperature distribution around the crack could re-melt the crack tip and increase the strength of the damaged material. The experimental study shows an increase in the stress intensity factor up to 76% for sintered aluminum PM compacts and up to 116% for sintered aluminum MMC PM compacts due to application of high-density electric pulses during transverse rapture testing.

Dariavach, Nader Guseinovich

236

Comparison of processing properties and product properties of beta III titanium alloy powder metal (pm) and ingot metal (im). Final report, Feb 1975Feb 1976  

Microsoft Academic Search

United States Air Force interest in powder metallurgy stems largely from the potential benefits obtainable by use of metal powders, instead of ingot materials, for the production of metal products. These benefits include reduction in production costs and improved service performance of aerospace parts. Metal powder processing may furnish lower production costs by reduction of the number of processing operations

N. Birla; V. DePierre; A. M. Adair

1976-01-01

237

Shear consolidation of powders  

NASA Astrophysics Data System (ADS)

The manufacture of bulk parts from metastable powder materials requires new approaches to cold consolidation. One potential technique is equal-channel angular extrusion (ECAE), a simple shear process. This thesis describes an investigation into the effects of confining pressure (back-pressure) on single-pass, right-angled ECAE consolidation of copper and aluminum 6061 powders below 250°C, using an extrusion machine designed and constructed for this purpose. Empirical relationships for punch pressure requirements as a function of back-pressure and billet length are determined experimentally and compared with published theory. Powder particle boundaries are examined in extruded billets, revealing pores and regions of localized shear formed under low back-pressure conditions. This shear localization is considered with a visualization experiment involving wax spheres in a transparent die, and a linear stability analysis of simple shear of a thin strip of material described by a generalized powder yield function and flow rule. The back-pressures required to obtain homogeneous, pore-free microstructures are determined, and related to the response of the powders during the initial compaction stage of ECAE. Interparticle bond formation in cold powder processing is briefly discussed in the context of multi-pass extrusions.

Hanna, James A.

238

Compaction of Ductile and Fragile Grains  

NASA Astrophysics Data System (ADS)

The compaction of powders into tablets is widely used in several industries (cosmetics, food, pharmaceutics…). In all these industries, the composition of the initial powder is complex, and the behaviour under compaction is not well known, also the mechanical behaviour of the tablets. The aim of this paper is to understand the behaviour (pressure vs density) of a simplified media made of fragile and ductile powders, varying the relative ratio of each powder. Some compaction experiments were carried out with glass beads (fragile) and Polyethylen Glycol powder (ductile). We observe two typical behaviours, depending on the relative volumic fraction of each component. A transition is pointed out, observing the evolution of the slope of the curve pressure/density. This transition is explained by geometrical considerations during compaction. A model is proposed, based on the assumption that the studied media can be compare to a diphasic material with a continuous phase (the ductile powder) and a discrete phase (the fragile powder). The result of this model is compare to the experimental results of compaction, and give a good prediction of the behaviour of the different mixing, knowing the behaviour of the ductile and the fragile phase separately. These results were also interpreted in terms of Heckel parameter which characterizes the ability of the powder to deform plastically under compaction. Some mechanical tests were also performed to compare the mechanical resitance of the obtained tablets.

Creissac, S.; Pouliquen, O.; Dalloz-Dubrujeaud, B.

2009-06-01

239

Investigations into the mechanical strength anisotropy of Sorbitol Instant compacts made by uniaxial compression  

Microsoft Academic Search

Powder compacts manufactured by the pharmaceutical industry are usually produced by uniaxial compression of powders or granules. This process results in compacts that are anisotropic in their mechanical strength, but this hypothesis has received little attention in the past. In this work, compacts were produced from sorbitol granules using two distinctively different particle size fractions, two compaction speeds and a

F. Podczeck

2007-01-01

240

Discrete element modeling of powder consolidation and the formation of titanium-matrix composites from powder-fiber monotapes  

NASA Astrophysics Data System (ADS)

A three year research effort is completed with the development of the Discrete Element Consolidation Analyzer (DECA) for process modeling the formation of titanium composites from powder-fiber monotapes. The primary goal of the DECA process model is to provide a statistically realistic analysis of the various physical processes necessary to achieve higher quality composites from the powder-fiber technique. Over the course of this effort, research and code development was conducted in three distinct stages. The first stage focused on the simulation of initial geometry of the powder and fibers as well as the evolution of tape configuration during the pre-consolidation processing steps. The second stage developed the mechanics of the discrete element powder consolidation and the material characterization methods necessary to model the viscoplastic response of the powder to transient thermal and mechanical boundary conditions. The final stage incorporated the presence of fibers to evaluate the interaction mechanics and possible fibers damage resulting from discrete powder-fiber contacts. As a conclusion to the research, DECA model predictions of density versus time for various consolidation profiles are directly compared to actual consolidation test results and a DECA prescribed process profile is used to fabricate a 6sp{''} × 6sp{''} composite panel of Ti-6242/SCS-6. In completing this research, the discrete element modeling technique has proven to be a powerful tool for the analysis and simulation of metal powder consolidation as well as the consolidation of metal matrix composites. The DECA code orchestrates the use of particle kinetics, some simple aspects of gas dynamics, elasticity, plasticity, creep and various innovative material characterization methods to produce a seamless analysis for powder metallurgy processing of composites. Through the application of the DECA capability, many aspects of the processing stages have been elucidated for further investigation and possibly for optimization to in the end provide the underlying goal of increasing quality and reduce cost of producing composites from the powder-fiber monotape method. As a minimum, it was desired that the resulting code provide an accurate prediction of relative density as a function of applied pressure, temperature, and time. This goal was achieved. However, it was later realized that under specific conditions of pre-heat and unidirectional compaction, the rate change in relative density could be determined by the rate of applied load. With the appropriate control and load capacity, densification by plasticity and transient creep mechanisms can achieve complete void removal. Unfortunately, the real world doesn't work with 1sp{''} × 1sp{''} samples and the pressurization rates attained by most HIP units are several orders of magnitude below those specific conditions in which it is possible to essentially "hammer" the voids out of the composite. As a result, it was learned that under certain conditions Ti-6242/SCS-6 monotape (temperature between 1650sp°F and beta-transus with a loading rate greater than 10 kips/min.), it is possible to consolidate Ti-6242/SCS-6 monotape composite in a matter of minutes without damaging fibers. (Abstract shortened by UMI.)

Newell, Kenneth James

241

April 11, 2013 Powder Consolidation under Pressure  

E-print Network

Science and Technology. 2011;25:483-499 4. Alderborn G, Nystrom C. Pharmaceutical Powder Compaction generally formed by compression, is the most common pharmaceutical solid dosage form because of its economic Technology. 1996 5. Antikainen O, Yliruusi J. Determining the compression behavior of pharmaceutical powders

Thomas, David D.

242

A Millennium of Metallurgy Recorded by Lake Sediments from  

E-print Network

of metallurgy. Here, we combine a lake sediment record of pre-historic metal pollution from the Morococha regionA Millennium of Metallurgy Recorded by Lake Sediments from Morococha, Peruvian Andes C O L I N activity in the Peruvian Andes using the lake- sediment stratigraphy of atmospherically derived metals (Pb

Wolfe, Alexander P.

243

Metallurgy and Heat Treating. Welding Module 7. Instructor's Guide.  

ERIC Educational Resources Information Center

This guide is intended to assist vocational educators in teaching a three-unit module in metallurgy and heat treating. The module is part of a welding curriculum that has been designed to be totally integrated with Missouri's Vocational Instruction Management System. The basic principles of metallurgy and heat treatment and techniques for…

Missouri Univ., Columbia. Instructional Materials Lab.

244

Selective laser melting W–10 wt.% Cu composite powders  

Microsoft Academic Search

Tungsten–Copper (W–Cu) alloys are promising materials for electrical and thermal applications. However, its forming method\\u000a still remains limited in conventional powder metallurgy technique which is not suitable for manufacturing parts with intricate\\u000a shapes. In this work, selective laser melting technology was introduced for fabricating W–10 wt.% Cu alloys parts. The morphological\\u000a feature of a single molten track was analyzed. The results

Ruidi Li; Yusheng Shi; Jinhui Liu; Zhan Xie; Zhigang Wang

2010-01-01

245

Fluidized reduction of oxides on fine metal powders without sintering  

NASA Technical Reports Server (NTRS)

In the process of reducing extremely fine metal particles (av. particle size or = 1000 angstroms) covered with an oxide layer, the metal particles are fluidized by a gas flow contg. H, heated, and reduced. The method uniformly and easily reduces surface oxide layers of the extremely fine metal particles without causing sintering. The metal particles are useful for magnetic recording materials, conductive paste, powder metallurgy materials, chem. reagents, and catalysts.

Hayashi, T.

1985-01-01

246

Accretion of titanium carbide by electrical discharge machining with powder suspended in working fluid  

Microsoft Academic Search

A surface modification method by electrical discharge machining (EDM) with a green compact electrode has been studied to make thick TiC or WC layer. Titanium alloy powder or tungsten powder is supplied from the green compact electrode and adheres on a workpiece by the heat caused by discharge. To avoid the production process of the green compact electrode, a surface

Katsushi Furutania; Akinori Saneto; Hideki Takezawa; Naotake Mohri; Hidetaka Miyake

2001-01-01

247

Abrasive Wear Resistance of Powder Composites at Abrasive Erosion and Abrasive Impact Wear  

Microsoft Academic Search

Composite materials produced by powder metallurgy provide solution to many engineering applications where materials with high abrasive wear resistance are required. The actual wear behaviour of the material is associated with many external factors (the abrasive particle size, velocity and angularity) and the intrinsic material properties of wear (hardness, toughness, Young modulus, etc.). The hardness and toughness properties of wear

Priit KULU; Renno VEINTHAL; Helmo KÄERDI; Riho TARBE

248

Influence of consolidation method on structure/properties of rapidly solidified Type 304 SS powders  

SciTech Connect

The structure/properties of consolidated, centrifugally atomized (CA) Type 304 SS powders containing approx.8 appM helium entrapped during powder processing were evaluated. Three powder consolidation methods were used in the study: hot extrusion, hot isostatic pressing (HIPping), and dynamic (using explosives). In addition, cold-rolled 50% HIPped material was included in the evaluation. The four forms of consolidated powders were fully dense and possessed good bond strengths. The bond strength of the HIPped powders was the lowest. The consolidated materials were subjected to 1 h heat treatments and their grain growth, tensile, and creep behaviors were compared with those of wrought ingot metallurgy Type 304 SS materials. Grain growth of the CA Type 304 SS consolidated powders was substantially lower than for the wrought material. Similarly, significant strengthening was observed for the powder materials. The apparent microstructure stability and strengthening observed for the consolidated powder materials is attributed to the entrapped helium. 5 figs., 4 tabs.

Flinn, J.E.; Korth, G.E.; Wright, R.N.

1988-01-01

249

Electrodeposition in extractive metallurgy: An emerging technology?  

NASA Astrophysics Data System (ADS)

The electrowinning and electrorefining of metals from aqueous solutions continues to be one of the essential unit processes employed in nonferrous extractive metallurgy. Current processes effectively address both ohmic and mass transport of the primary metal ion in their design. Some deficiencies exist, however, in the basic understanding of the other two critical elements essential in cathodic deposition: activation kinetics and electrocrystallization. The understanding of the latter two must be elevated to the level of understanding of ohmic and mass transport if truly new and innovative advances are to occur. Because of the increasingly demanding standards for electrometallurgy processes and products, technical progress must be made if a competitive edge is to be maintained in the future.

O'Keefe, Thomas J.

1992-04-01

250

Physical metallurgy of direct-quenched steels  

SciTech Connect

This symposium was held during November 2-4, 1992 in Chicago as part of Materials Week '92''. This symposium focused on the metallurgy of steels containing martensitic or bainitic microstructures formed from thermomechanically processed austenite, and builds upon two recent topical meetings on the related subject of ferritic accelerated cooled steels. Papers in the first section deal with thermodynamics and kinetics of austenite transformation, the morphology of austenite transformation products, and alloy carbide precipitation. Results of investigations of relationships between processing variables, microstructure, and mechanical properties are contained in the following section. Section III is devoted specifically to boron hardenability effects. papers in the final section are concerned with product development; included here is a comprehensive overview of industrial accelerated cooling/direct quenching technology by researchers from the Nippon Steel Corporation.

Taylor, K.A. (ed.) (Bethlehem Steel Corp., PA (United States)); Thompson, S.W. (ed.) (Colorado School of Mines, Golden, CO (United States)); Fletcher, F.B. (ed.) (Lukens Steel Co., Coatesville, PA (United States))

1993-01-01

251

Development of a power metallurgy superalloy for use at 1800-2000 F (980-1090 C)  

NASA Technical Reports Server (NTRS)

A program was conducted to develop a powder metallurgy nickel-base superalloy for 1800-2000 F (980-1090 C) temperature applications. The feasibility of a unique concept for alloying carbon into a superalloy powder matrix and achieving both grain growth and a discrete particle grain boundary carbide precipitation was demonstrated. The process consisted of blending metastable carbides with a carbon free base alloy and consolidating this blend by hot extrusion. This was followed by heat treatment to grow a desired ASTM No. 2-3 grain size and to solution the metastable carbides to allow precipitation of discrete particle grain boundary carbides during subsequent aging heat treatments. The best alloy developed during this program was hydrogen-atomized, thermal-mechanically processed, modified MAR-M246 base alloy plus VC (0.28 w/o C). Although below those for cast MAR-M246, the mechanical properties exhibited by this alloy represent the best combination offered by conventional powder metallurgy processing to date.

Kortovich, C. S.

1973-01-01

252

Looking North into Lab Metallurgy Testing Area and Enrichment Motor ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Looking North into Lab Metallurgy Testing Area and Enrichment Motor within Recycle Recovery Building - Hematite Fuel Fabrication Facility, Recycle Recovery Building, 3300 State Road P, Festus, Jefferson County, MO

253

1. Photocopy from J. L. Bray, The Principles of Metallurgy, ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. Photocopy from J. L. Bray, The Principles of Metallurgy, Ginn & Company, New York, 1929 - International Smelting & Refining Company, Tooele Smelter, Sinter Plant, State Route 178, Tooele, Tooele County, UT

254

78 FR 8202 - Meeting of the Joint ACRS Subcommittees on Thermal Hydraulic Phenomena and Materials, Metallurgy...  

Federal Register 2010, 2011, 2012, 2013

...ACRS) Meeting of the Joint ACRS Subcommittees on Thermal Hydraulic Phenomena and Materials, Metallurgy and Reactor Fuels; Notice of Meeting The Joint ACRS Subcommittees on Thermal Hydraulic Phenomena and Materials, Metallurgy and Reactor...

2013-02-05

255

Investigation of particle packing in model pharmaceutical powders using X-ray microtomography and discrete element method  

E-print Network

. Cameron a , James A. Elliott a a Pfizer Institute for Pharmaceutical Materials Science, DepartmentInvestigation of particle packing in model pharmaceutical powders using X-ray microtomography of Materials, Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, UK b Pfizer

Elliott, James

256

Energetic powder  

DOEpatents

Fluoroalkylsilane-coated metal particles. The particles have a central metal core, a buffer layer surrounding the core, and a fluoroalkylsilane layer attached to the buffer layer. The particles may be prepared by combining a chemically reactive fluoroalkylsilane compound with an oxide coated metal particle having a hydroxylated surface. The resulting fluoroalkylsilane layer that coats the particles provides them with excellent resistance to aging. The particles can be blended with oxidant particles to form energetic powder that releases chemical energy when the buffer layer is physically disrupted so that the reductant metal core can react with the oxidant.

Jorgensen, Betty S. (Jemez Springs, NM); Danen, Wayne C. (Los Alamos, NM)

2003-12-23

257

Chemistry and Metallurgy Research Facility The Los Alamos National Laboratory (LANL) Chemistry and  

E-print Network

CMR Chemistry and Metallurgy Research Facility The Los Alamos National Laboratory (LANL) Chemistry analytical chemistry and metallurgy. In 1952, the first LANL CMR facility was completed. At that time chemistry and metallurgy. Upgrades to the original CMR were completed in 2002. In 2012, the CMR facility

258

On constructing a virtual museum of mining and metallurgy culture in Huangshi, China  

Microsoft Academic Search

This paper, through analyzing the development trend of heritage museums and the current situation of exhibiting mining and metallurgy heritages in Huangshi China, proposes scientific ideas and methods to guide the construction of a virtual museum of mining and metallurgy culture, and expresses the profound realistic and historical significance of it for the preservation and presentation of mining and metallurgy

Manzhong Liu

2010-01-01

259

Charpy Impact Testing University of Saskatchewan -Mechanical Engineering -Materials Science and Metallurgy  

E-print Network

and Metallurgy ID: Mat0020 Rev: 002 Date: Nov. 8, 2011 Page: 1 of 6 Impact Testing with the Charpy Impact Tester - Materials Science and Metallurgy ID: Mat0020 Rev: 002 Date: Nov. 8, 2011 Page: 2 of 6 1. SIGNATURES Science and Metallurgy ID: Mat0020 Rev: 002 Date: Nov. 8, 2011 Page: 3 of 6 2. VERSION HISTORY Handwritten

Saskatchewan, University of

260

Adventures in the physical metallurgy of steels H. K. D. H. Bhadeshia  

E-print Network

Preface Adventures in the physical metallurgy of steels H. K. D. H. Bhadeshia Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK, email hkdb a template for meetings of the future. Attendance at `Adventures in the physical metallurgy of steels' (APMS

Cambridge, University of

261

Microhardness Testing -Mitutoyo University of Saskatchewan -Mechanical Engineering -Materials Science and Metallurgy  

E-print Network

Science and Metallurgy ID: Mat0017 Rev: 002 Date: Nov. 8, 2011 Page: 1 of 5 Vickers Hardness Testing Engineering - Materials Science and Metallurgy ID: Mat0017 Rev: 002 Date: Nov. 8, 2011 Page: 2 of 5 1 of Saskatchewan - Mechanical Engineering - Materials Science and Metallurgy ID: Mat0017 Rev: 002 Date: Nov. 8

Saskatchewan, University of

262

C T D ) T T ( ^ / S ^ \\ / Ris-R-473 Metallurgy Department  

E-print Network

t C T D ) T T ( ^ / S ^ \\ / Ris»-R-473 Metallurgy Department Progress Report for tbe Period 1 of the Metallurgy Department at Risø during 1981 are described. The work is presented in three chap- ters: General-descriptors; FUEL ELEMENTS, METALLURGY, NONDESTRUCTIVE TESTING, RESEARCH PROGRAMS, RISOE NATIONAL LABORATORY. UDC

263

Mesoscale Simulations of Power Compaction  

SciTech Connect

Mesoscale 3D simulations of metal and ceramic powder compaction in shock waves have been performed with an Eulerian hydrocode GEODYN. The approach was validated by simulating shock compaction of porous well-characterized ductile metal using Steinberg material model. Results of the simulations with handbook values for parameters of solid 2024 aluminum have good agreement with experimental compaction curves and wave profiles. Brittle ceramic materials are not so well studied as metals, so material model for ceramic (tungsten carbide) has been fitted to shock compression experiments of non-porous samples and further calibrated to match experimental compaction curves. Direct simulations of gas gun experiments with ceramic powder have been performed and showed good agreement with experimental data. Numerical shock wave profile has same character and thickness as measured with VISAR. Numerical results show reshock states above the single-shock Hugoniot line also observed in experiments. They found that to receive good quantitative agreement with experiment it is essential to perform 3D simulations.

Lomov, I; Fujino, D; Antoun, T; Liu, B

2009-08-06

264

Exploring Baking Powder  

NSDL National Science Digital Library

In this activity, learners examine baking powder, a combination of three powders: baking soda, cream of tartar, and cornstarch. Learners use their data from the previous activity (see related resource) to identify these three powders as possible ingredients. Then, they test combinations of these powders to determine the active ingredients in baking powder.

Kessler, James H.; Galvan, Patricia M.

2007-01-01

265

Compact accelerator  

DOEpatents

A compact linear accelerator having at least one strip-shaped Blumlein module which guides a propagating wavefront between first and second ends and controls the output pulse at the second end. Each Blumlein module has first, second, and third planar conductor strips, with a first dielectric strip between the first and second conductor strips, and a second dielectric strip between the second and third conductor strips. Additionally, the compact linear accelerator includes a high voltage power supply connected to charge the second conductor strip to a high potential, and a switch for switching the high potential in the second conductor strip to at least one of the first and third conductor strips so as to initiate a propagating reverse polarity wavefront(s) in the corresponding dielectric strip(s).

Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Kirbie, Hugh C. (Los Alamos, NM)

2007-02-06

266

Electrophoretic deposition of nanosized ceramic powders  

SciTech Connect

For nanosized powders the forming of compacts by electrophoretic deposition is an interesting method. In aqueous suspensions high deposition rates can be achieved at low electric fields. The problems with the gas bubble formation at the electrodes which are caused by the decomposition of water can be solved by depositing the compact on a microporous membrane in front of the electrode. Thus, with nanosized zirconia powders made by the flame hydrolysis (BET-surface area approx. 50 M{sup 2}/g) the deposition rate was measured as a function of deposition time and electrolyte concentration. Furthermore, the deposition rate depends on the effective electric field inside the suspension, which is much lower in zirconia suspensions than in comparable silica suspensions. In spite of this, deposition rates up to 0.5 g/min {center_dot} CM{sup 2} were achieved. The deposited compacts showed a small pore size distribution (max. 25 nm) and a relative green density of 40%.

Clasen, R.; Janes, S.; Oswald, C.; Ranker, D. [Institut fuer Neue Materialien gem GmbH, Saarbruechek (Germany)

1995-09-01

267

Contribution to mechanical metallurgy behaviour of steel during continuous casting  

Microsoft Academic Search

The paper is devoted to the study of the mechanical metallurgy characteristics of the mushy zone. The basic parameters of the brittle temperature range (TB), the zero strength (ZST), the zero ductility temperature (ZDT) and the liquid impenetrable temperature (LIT) are used for explaining the possibility of cracking. This temperature range was defined in the following form: ZDT

Z Jonšta; A Hernas; K Mazanec

1998-01-01

268

PETROLEUM SOCIETY CANADIAN INSTITUTE OF MINING, METALLURGY & PETROLEUM  

E-print Network

1 PETROLEUM SOCIETY CANADIAN INSTITUTE OF MINING, METALLURGY & PETROLEUM PAPER 2002-092 Effects of Alberta This paper is to be presented at the Petroleum Society's Canadian International Petroleum of the meeting. This paper and any discussion filed will be considered for publication in Petroleum Society

Hossain, M. Enamul

269

PETROLEUM SOCIETY CANADIAN INSTITUTE OF MINING, METALLURGY & PETROLEUM  

E-print Network

1 PETROLEUM SOCIETY CANADIAN INSTITUTE OF MINING, METALLURGY & PETROLEUM PAPER 2002-074 Temperature Canada Ltd. This paper is to be presented at the Petroleum Society's Canadian International Petroleum of the meeting. This paper and any discussion filed will be considered for publication in Petroleum Society

Schramm, Laurier L.

270

Chemical and Metallurgy Research (CMR) Sample Tracking System Design Document  

SciTech Connect

The purpose of this document is to describe the system architecture of the Chemical and Metallurgy Research (CMR) Sample Tracking System at Los Alamos National Laboratory. During the course of the document observations are made concerning the objectives, constraints and limitations, technical approaches, and the technical deliverables.

Bargelski, C. J.; Berrett, D. E.

1998-09-01

271

Iron Metallurgy: Technical Terminology Bulletin. Terminotech, Vol. 2, No. 7.  

ERIC Educational Resources Information Center

This issue of a bulletin of technological terminology is devoted to iron metallurgy. Various aspects of iron production are described in both French and English. An English-French dictionary of terms comprises the bulk of the document. Explanatory illustrations are appended. (JB)

General Electric Co. of Canada, Ltd., Montreal, Quebec.

272

NSF: A "Populist" Pattern in Metallurgy, Materials Research?  

ERIC Educational Resources Information Center

Describes the testimony of a University of Virginia professor of applied science, who charged that the National Science Foundation grants disproportionately small funds to the best university departments in the field of metallurgy and materials, while preferentially funding middle-ranked departments. (MLH)

Shapley, Deborah

1975-01-01

273

Materials and Metallurgy Materials Science and Metallurgical Engineering  

E-print Network

Materials and Metallurgy Materials Science and Metallurgical Engineering Objective Students will learn about raw materials and where they come from. Standards and Objectives · 7th Grade Standard 1, Objective 3 · Chemistry Standard 4, Objective 1 Learning Outcomes Students will learn: · Where raw materials

Provancher, William

274

Powder treatment process  

DOEpatents

(1) A process comprising spray drying a powder-containing slurry, the slurry containing a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, while reducing the tendency for oxidation of the constituent by including as a liquid constituent of the slurry an organic liquid; (2) a process comprising spray drying a powder-containing slurry, the powder having been pretreated to reduce content of a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, the pretreating comprising heating the powder to react the constituent; and (3) a process comprising reacting ceramic powder, grinding the reacted powder, slurrying the ground powder, spray drying the slurried powder, and blending the dried powder with metal powder.

Weyand, John D. (Greensburg, PA)

1988-01-01

275

Simulation Study for Complex Shaped Pressing of Ceramic Powder  

NASA Astrophysics Data System (ADS)

The modified Drucker-Prager Cap elasto-plastic constitutive model is used for the calculation that performed using the finite element code ABAQUS 6.4 to simulate densification of alumina powder of complex shaped sample. Four-node axisymmetric elements were used for the powder compact and two-node axisymmetric rigid surface elements were used for the interfaces between powder and die and punches. Finite element result predicts very high density in the inner top region and relatively uniform density distribution is observed in the region far from the axisymmetric axis. The model developed can describe not only the compaction and decompression phases, but also the ejection phase.

Abdullah, Omed Gh.; Rasin, Fadhil Abd; Al-Dhahir, Tariq A.

2010-07-01

276

Processing of silicon nitride and alumina nanosize powders  

SciTech Connect

The effects of pressure on the compaction and subsequent processing of nanosize {gamma} alumina powders were studied. A 3 mm diameter piston/cylinder die was used to compact the nanosize powders to pressures of 1 and 2.5 GPa. The green bodies were sintered at temperatures up to 1600{degrees}C. Results show that green body density can be increased by higher compaction pressures. It appears that as a result of the {gamma}-to-{alpha} transformation in alumina, higher green density does not necessarily produce a higher density sintered alumina body. The microstructures of the sintered bodies are described in terms of porosity and phase content.

Gonzalez, E.J.; Piermarini, G.; Hockey, B.; Malghan, S.G. [National Inst. of Standard and Technology, Gaithersburg, MD (United States)

1995-08-01

277

Near-net-shape forming of 316L stainless steel powder under hot isostatic pressing  

Microsoft Academic Search

Near-net-shape forming of 316L stainless steel powder is investigated under hot isostatic pressing (HIPing). A stainless steel powder compact and an insert were encapsulated by a stainless steel container and hot isostatically pressed to produce an axisymmetric near-net-shape part. To simulate densification and deformation of a powder compact in the container during HIPing, the constitutive model of Abouaf et al.,

Y. C. Jeon; K. T. Kim

1999-01-01

278

Simultaneous Deposition of Powder in Three Parallel-Oriented Cylindrical Dies  

Microsoft Academic Search

The inhomogeneity of bulk density distribution created during the die filling process might cause quality problems for powder compacts, such as distortion, lamination, and cracking. To avoid these problems, understanding the die filling process and ensuring a uniform pre-compaction powder deposition are necessary. The second-generation pressure deposition tester (PDT-II) was developed to investigate simultaneous deposition of powder into multiple dies.

X. Xie; V. M. Puri

2007-01-01

279

Fracture toughness and thermal resistance of polycrystalline diamond compacts  

Microsoft Academic Search

Polycrystalline diamond compacts (PCD) are being used increasingly for oil and gas drilling and in machining of ceramics and hard non-ferrous materials. Average diamond grain size and its distribution are used as one of the means to tailor properties of PCD compacts. The diamond sintering process requires use of a tungsten carbide cobalt disc placed onto diamond powder followed by

D. Miess; G. Rai

1996-01-01

280

Compact magnetograph  

NASA Technical Reports Server (NTRS)

A compact magnetograph system based on solid Fabry-Perot interferometers as the spectral isolation elements was studied. The theory of operation of several Fabry-Perot systems, the suitability of various magnetic lines, signal levels expected for different modes of operation, and the optimal detector systems were investigated. The requirements that the lack of a polarization modulator placed upon the electronic signal chain was emphasized. The PLZT modulator was chosen as a satisfactory component with both high reliability and elatively low voltage requirements. Thermal control, line centering and velocity offset problems were solved by a Fabry-Perot configuration.

Title, A. M.; Gillespie, B. A.; Mosher, J. W.

1982-01-01

281

Claw pole armature permanent magnet machines exploiting soft iron powder metallurgy  

Microsoft Academic Search

This paper describes a novel permanent magnet machine which uses a claw pole topology in the armature to produce a high performance machine. This machine is almost impossible to construct from laminated material, therefore a soft magnetic composite has been employed throughout the stator. The paper gives details of the constructional features and presents performance measurements for this machine

Alan G. Jack; Barrie C. Mecrow; Chris P. Maddison; Norhasbi Abdul Wahab

1997-01-01

282

Wear resistant tools for reproduction technologies produced by micro powder metallurgy  

Microsoft Academic Search

Micro system technology (MST) needs cost effective production techniques and for the development of new MST products also\\u000a new materials are necessary. Reproduction technologies have been developed for large scale production which are allow processing\\u000a a broad scope of materials (plastic, ceramic and metal). For these, tools are needed which have to fulfil a lot of requirements.\\u000a In this paper

A. Rota; T.-V. Duong; T. Hartwig

2002-01-01

283

Development of powder metallurgy 2XXX series Al alloys for high temperature aircraft structural applications  

NASA Technical Reports Server (NTRS)

The objective of the present investigation was to improve the strength and fracture toughness combination of P/M 2124 Al alloys in accordance with NASA program goals for damage tolerance and fatigue resistance. Two (2) P/M compositions based on Al-3.70 Cu-1.85 Mg-0.20 Mn with 0.12 and 0.60 wt. pct. Zr were selected for investigation. The rapid solidification rates produced by atomization were observed to prohibit the precipitation of coarse, primary Al3Zr in both alloys. A major portion of the Zr precipitated as finely distributed, coherent Al3Zr phases during vacuum preheating and solution heat treatment. The proper balance between Cu and Mg contents eliminated undissolved, soluble constituents such as Al2CuMg and Al2Cu during atomization. The resultant extruded microstructures produced a unique combination of strength and fracture toughness. An increase in the volume fraction of coherent Al3Zr, unlike incoherent Al20Cu2Mn3 dispersoids, strengthened the P/M Al base alloy either directly by dislocation-precipitate interactions, indirectly by a retardation of recrystallization, or a combination of both mechanisms. Furthermore, coherent Al3Zr does not appear to degrade toughness to the extent that incoherent Al20Cu2Mn3 does. Consequently, the addition of 0.60 wt. pct. Zr to the base alloy, incorporated with a 774K (935 F) solution heat treatment temperature, produces an alloy which exceeds all tensile property and fracture toughness goals for damage tolerant and fatigue resistant applications in the naturally aged condition.

Chellman, D. J.

1984-01-01

284

The Making of Stainless Steel Shapes by Casting and Powder Metallurgy.  

National Technical Information Service (NTIS)

Contents: Production by casting; Designation and composition of alloys, Melting practice, Molding practice for static casting, Sand molds - methods, finish and tolerance, Ceramic molds - methods, finish and tolerance, Centrifugal casting, Casting characte...

J. G. Kura, V. D. Barth, E. T. Hall, W. H. Safranek, H. O. McIntire

1967-01-01

285

Porous titanium scaffolds fabricated using a rapid prototyping and powder metallurgy technique  

Microsoft Academic Search

One of the main issues in orthopaedic implant design is the fabrication of scaffolds that closely mimic the biomechanical properties of the surrounding bone. This research reports on a multi-stage rapid prototyping technique that was successfully developed to produce porous titanium scaffolds with fully interconnected pore networks and reproducible porosity and pore size. The scaffolds' porous characteristics were governed by

Garrett E. Ryan; Abhay S. Pandit; Dimitrios P. Apatsidis

2008-01-01

286

Effects of temperature on the superplastic characteristics of a powder metallurgy pure aluminum  

SciTech Connect

High Strain Rate Superplasticity (HSRS) is expected to establish an efficient near-net shape forming process for metal matrix composites and mechanically alloyed(MA) aluminum alloys. It is of interest to clarify the deformation mechanism, because the optimum strain rate at which a maximum elongation of 300--600% is obtained is larger by 10--1,000 times than that of conventional superplastic aluminum alloys. Thus, the deformation mechanism of HSRS materials is thought to be different from that of conventional alloys. The purpose of this study is to develop a thermomechanical process to produce superplasticity at high strain rate (HSRS) for 1N90 pure aluminum, and also to examine the deformation mechanism of the HSRS.

Imai, T [National Industrial Research Inst. (Japan)] [National Industrial Research Inst. (Japan); Kojima, S. [Nagoya Municipal Industrial Research Inst. (Japan)] [Nagoya Municipal Industrial Research Inst. (Japan); L`Esperance, G.; Hong, B.D. [Ecole Polytechnique de Montreal, Quebec (Canada)] [Ecole Polytechnique de Montreal, Quebec (Canada); Jiang, D. [Harbin Inst. of Tech. (China)] [Harbin Inst. of Tech. (China); Nieh, T.G. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States)

1996-11-15

287

In vitro degradation and cytotoxicity of Mg/Ca composites produced by powder metallurgy q  

E-print Network

in ultimate tensile strength (UTS), 0.2% yield tensile strength and elastic modulus, while the ductility System and Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, No. 5 Yi-He-Yuan Road, Hai-Dian District, Beijing 100871, China b Luoyang Ship Material Research

Zheng, Yufeng

288

Effect of thermally induced porosity on an as-HIP powder metallurgy superalloy  

NASA Technical Reports Server (NTRS)

The impact of thermally induced porosity on the mechanical properties of an as-hot-isostatically-pressed and heat treated pressing made from low carbon Astroloy was determined. Porosity in the disk-shape pressing studied ranged from 2.6 percent at the bore to 1.4 percent at the rim. Tensile, yield strength, ductility, and rupture life of the rim of the porous pressing was only slightly inferior to the rim of sound pressings. The strength, ductility, and rupture life of the bore of the porous pressing was severely degraded compared to sound pressings. At strain ranges typical of commercial jet engine designs, the rim of the porous pressing had slightly inferior fatigue life to sound pressings.

Dreshfield, R. L.; Miner, R. V., Jr.

1979-01-01

289

Effects of thermally induced porosity on an as-HIP powder metallurgy superalloy  

NASA Technical Reports Server (NTRS)

The effect of thermally induced porosity on the mechanical properties of an as-hot-isostatically pressed and heat-treated pressing made from low carbon Astroloy is examined. Tensile, stress-rupture, creep, and low cycle fatigue tests were performed and the results were compared with industrial acceptance criteria. It is shown that the porous pressing has a porosity gradient from the rim to the bore with the bore having 1-1/2% greater porosity. Mechanical properties of the test ring below acceptance level are tensile reduction in area at room temperature and 538 C and time for 0.1% creep at 704 C. It is also found that the strength, ductility, and rupture life of the rim are slightly inferior to those of the rim of the sound pressings, while those of the bore are generally below the acceptable level. At strain ranges typical of commercial aircraft engines, the low cycle fatigue life of the rim of the porous pressings is slightly lower than that of the sound pressings.

Dreshfield, R. L.; Miner, R. V., Jr.

1980-01-01

290

Stress corrosion evaluation of powder metallurgy aluminum alloy 7091 with the breaking load test method  

NASA Technical Reports Server (NTRS)

The stress corrosion behavior of the P/M aluminum alloy 7091 is evaluated in two overaged heat treatment conditions, T7E69 and T7E70, using an accelerated test technique known as the breaking load test method. The breaking load data obtained in this study indicate that P/M 7091 alloy is highly resistant to stress corrosion in both longitudinal and transverse orientations at stress levels up to 90 percent of the material yield strength. The reduction in mean breaking stress as a result of corrosive attack is smallest for the more overaged T7E70 condition. Details of the test procedure are included.

Domack, Marcia S.

1987-01-01

291

Utilization of Space Shuttle External Tank materials by melting and powder metallurgy  

NASA Technical Reports Server (NTRS)

The Crucible Melt Extraction Process was demonstrated to convert scraps of aluminum alloy 2219, used in the Space Shuttle External Tank, into fibers. The cast fibers were then consolidated by cold welding. The X-ray diffraction test of the cast fibers was done to examine the crystallinity and oxide content of the fibers. The compressive stress-strain behavior of the consolidated materials was also examined. Two conceptual schemes which would adapt the as-developed Crucible Melt Extraction Process to the microgravity condition in space were finally proposed.

Chern, T. S.

1985-01-01

292

Characterization of Properties of Cryogenically Treated Al–SiC Composites Fabricated by Powder Metallurgy  

Microsoft Academic Search

The basis of this research was an exploration of the fundamental phenomena that determine the response of silicon carbide-reinforced aluminium composite material to thermal cycling between cryogenic and ambient temperatures. This analysis began with a phenomenological approach that investigated the role of the production, processing, and machining of composite materials, and led to study of their mechanical behavior at cryogenic

S. Charles; V. P. Arunachalam

2006-01-01

293

Effect of the Machining Processes on Low Cycle Fatigue Behavior of a Powder Metallurgy Disk  

NASA Technical Reports Server (NTRS)

A study has been performed to investigate the effect of various machining processes on fatigue life of configured low cycle fatigue specimens machined out of a NASA developed LSHR P/M nickel based disk alloy. Two types of configured specimen geometries were employed in the study. To evaluate a broach machining processes a double notch geometry was used with both notches machined using broach tooling. EDM machined notched specimens of the same configuration were tested for comparison purposes. Honing finishing process was evaluated by using a center hole specimen geometry. Comparison testing was again done using EDM machined specimens of the same geometry. The effect of these machining processes on the resulting surface roughness, residual stress distribution and microstructural damage were characterized and used in attempt to explain the low cycle fatigue results.

Telesman, J.; Kantzos, P.; Gabb, T. P.; Ghosn, L. J.

2010-01-01

294

Metals for bone implants. Part 1. Powder metallurgy and implant rendering.  

PubMed

New metal alloys and metal fabrication strategies are likely to benefit future skeletal implant strategies. These metals and fabrication strategies were looked at from the point of view of standard-of-care implants for the mandible. These implants are used as part of the treatment for segmental resection due to oropharyngeal cancer, injury or correction of deformity due to pathology or congenital defect. The focus of this two-part review is the issues associated with the failure of existing mandibular implants that are due to mismatched material properties. Potential directions for future research are also studied. To mitigate these issues, the use of low-stiffness metallic alloys has been highlighted. To this end, the development, processing and biocompatibility of superelastic NiTi as well as resorbable magnesium-based alloys are discussed. Additionally, engineered porosity is reviewed as it can be an effective way of matching the stiffness of an implant with the surrounding tissue. These porosities and the overall geometry of the implant can be optimized for strain transduction and with a tailored stiffness profile. Rendering patient-specific, site-specific, morphology-specific and function-specific implants can now be achieved using these and other metals with bone-like material properties by additive manufacturing. The biocompatibility of implants prepared from superelastic and resorbable alloys is also reviewed. PMID:24956564

Andani, Mohsen Taheri; Shayesteh Moghaddam, Narges; Haberland, Christoph; Dean, David; Miller, Michael J; Elahinia, Mohammad

2014-10-01

295

A geometrical description of microstructure with application to Al powder metallurgy processing  

SciTech Connect

The spatial distribution of second-phase particles in materials, and inhomogeneities such as clusters of second-phase particles, are known to affect bulk properties of particle-containing materials. The lack of a convenient method for quantitative characterization of the spatial distribution of second-phase particles has limited understanding of the mechanisms underlying these effects. The Dirichlet tessellation, and the associated dual tessellation, provide a unique, geometrical description of the spatial distribution of second-phase particles. This dissertation describes a computerized analysis, based on the Dirichlet tessellation, for quantitative characterization of the spatial distribution of second-phase particles. The analysis was designed to operate on a PC in the interest of wide applicability. For reasons of computational simplicity, particle size and morphology are excluded from the analysis. The analysis provides statistical descriptions of several microstructural variables, including local particle density and nearest-neighbor distances. An analysis of particle clustering, based on the dual tessellation and an assumed particle interaction distance, provides a detailed description of clustering of second-phase particles. Analysis of computer-generated particle distributions provides insight into the effect of spatial inhomogeneities and plane-strain deformation on the tessellation and clustering characteristics of various types of particle distributions. The analysis method was applied to determining the effects of type and degree of deformation processing on the spatial distribution of oxide fragments in PM-Al alloy sheet. Forging with subsequent rolling, and cross-rolling, were found to produce significantly more effective fragmentation and dispersal of the oxide skin than direct-rolling, per unit effective strain.

Parse, J.B.

1992-01-01

296

Superplastic behavior at high strain rate of rapidly solidified powder metallurgy Al-Li alloy  

SciTech Connect

A number of studies which reveal that superplasticity can sometimes occur at an extremely high strain rate (> 10[sup [minus]1]s[sup [minus]1]) have been reported in several classes of materials, including metal-matrix composites and mechanically-alloyed (MA) materials. Since multiphase aluminum alloys processed by rapid solidification techniques can have fine stable grains, the interest in the superplastic behavior of these alloys increased sharply. Some tests indicated that rapid solidification processed (RSP) aluminum alloys can exhibit superplastic behavior, but nearly all optimum strain rate in above experiments are relatively low. In this paper, high strain rate superplasticity of rapid solidification processed Al-Li alloy has been researched. It is demonstrated that a maximum elongation of 250% is obtained at a high strain rate of 1.4 [times] 10[sup [minus]1]s[sup [minus]1] at 570 C, which is above the solidus temperature of 562 C.

Zhongqi Cui; Wang Zhong; Qingbin Wei (Harbin Inst. of Tech. (China). Dept. of Metals and Technology)

1994-01-01

297

Magnetic Properties of Amorphous Fe-Si-B Powder Cores Mixed with Pure Iron Powder  

NASA Astrophysics Data System (ADS)

Amorphous Fe-Si-B alloy was prepared by melt-spinning, and then the ribbons were pulverized and ball-milled to make the amorphous powder of ˜25 µm in size. Subsequently those were mixed with pure iron powders with an average particle size of 3 µm, and 1.5 wt % water glass diluted by distilled water at the ratio of 1:2. The powder mixtures were cold compacted at 650 MPa in toroid die, and heat treated at 430-440 °C under a nitrogen atmosphere for 1 h and 30 min, respectively. The soft magnetic properties of powder core were investigated using a B-H analyzer and a flux meter at the frequency range of ˜100 kHz. The microstructure was observed using scanning electron microscope (SEM), and the density of the core was measured using the principle of Archimedes. Based on the experimental results, the amorphous powder mixed with pure iron powder showed the improved powder compactability, which resulted in the increased permeability and the reduced core loss.

Kim, Hyeon-Jun; Nam, Seul Ki; Kim, Kyu-Sung; Yoon, Sung Chun; Sohn, Keun-Yong; Kim, Mi-Rae; Sul Song, Yong; Park, Won-Wook

2012-10-01

298

Magnetic Pulsed Compaction of Nanopowders Based on Lithium-Containing Spinels  

Microsoft Academic Search

This paper reports on the results of investigations into the compactibility and structure of powder materials based on lithium-containing spinels that have been considered promising candidates for electrodes of lithium-ion batteries. Dynamic compaction of the powders is accomplished using the uniaxial magnetic pulsed compaction technique, which seems to be an efficient tool for assembling flat and cylindrical lithium-ion batteries. Experiments

A. S. Kaigorodov; E. M. Kelder; J. Schoonman; V. V. Ivanov; A. V. Nikonov; A. I. Medvedev; Al. A. Rempel’; A. A. Nozdrin; O. F. Ivanova

2005-01-01

299

Polymer quenched prealloyed metal powder  

DOEpatents

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3 % Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Hajaligol, Mohammad R. (Midlothian, VA); Fleischhauer, Grier (Midlothian, VA); German, Randall M. (State College, PA)

2001-01-01

300

Preparation of titanium diboride powder  

DOEpatents

Finely-divided titanium diboride or zirconium diboride powders are formed by reacting gaseous boron trichloride with a material selected from the group consisting of titanium powder, zirconium powder, titanium dichloride powder, titanium trichloride powder, and gaseous titanium trichloride.

Brynestad, Jorulf (Oak Ridge, TN); Bamberger, Carlos E. (Oak Ridge, TN)

1985-01-01

301

Compact torus  

SciTech Connect

The objective of the compact torus approach is to provide toroidal magnetic-field configurations that are based primarily on plasma currents and can be freed from closely surrounding mechanical structures. Some familiar examples are the current-carrying plasma rings of reversed-field theta pinches and relativistic-electron smoke ring experiments. The spheromak concept adds an internal toroidal magnetic field component, in order to enhance MHD stability. In recent experiments, three different approaches have been used to generate spheromak plasmas: (1) the reversed-field theta pinch; (2) the coaxial plasma gun; (3) a new quasi-static method, based on the initial formation of a toroidal plasma sleeve around a mechanical ring that generates poloidal and toroidal fluxes, followed by field-line reconnection to form a detached spheromak plasma. The theoretical and experimental MHD stability results for the spheromak configuration are found to have common features.

Furth, H.P.

1980-10-01

302

The influence of metallurgy on the formation of welding aerosols.  

PubMed

Recent research has indicated that insoluble ultrafine aerosols (ie., particles whose physical diameters are less than 100 nm) may cause adverse health effects due to their small size, and that toxicological response may be more appropriately represented by particle number or particle surface area. Unfortunately, current exposure criteria and the associated air-sampling techniques are primarily mass-based. Welding processes are high-temperature operations that generate substantial number concentrations of ultrafine aerosols. Welding aerosols are formed primarily through the nucleation of metal vapors followed by competing growth mechanisms such as coagulation and condensation. Experimental results and mathematical tools are presented to illustrate how welding metallurgy influences the chemical aspects and dynamic processes that initiate and evolve the resultant aerosol. This research suggests that a fundamental understanding of metallurgy and aerosol physics can be exploited to suppress the formation of undesirable chemical species as well as the amount of aerosol generated during a welding process. PMID:12400906

Zimmer, Anthony T

2002-10-01

303

SteelMATTER: An Interactive Website for Ferrous Metallurgy  

NSDL National Science Digital Library

SteelMATTER is a "series of interactive educational software resources aimed at helping students understand the key concepts and relationships in ferrous metallurgy." Guided Study is the main section of the site, which describes the six stages of steel production. Starting the guided study can be slightly confusing because of poor site organization; instead of taking users directly to the first stage, an interactive quiz is presented before any material is covered. However, this can easily be bypassed by clicking the Raw Materials link at the bottom of the page. From this point, the site provides a good, step-by-step overview of the processes involved in making steel. There are also numerous Java applets accessible from the main page that simulate many metallurgy processes.

2000-01-01

304

The physical metallurgy of mechanically-alloyed, dispersion-strengthened Al-Li-Mg and Al-Li-Cu alloys  

NASA Technical Reports Server (NTRS)

Powder processing of Al-Li-Mg and Al-Li-Cu alloys by mechanical alloying (MA) is described, with a discussion of physical and mechanical properties of early experimental alloys of these compositions. The experimental samples were mechanically alloyed in a Szegvari attritor, extruded at 343 and 427 C, and some were solution-treated at 520 and 566 C and naturally, as well as artificially, aged at 170, 190, and 210 C for times of up to 1000 hours. All alloys exhibited maximum hardness after being aged at 170 C; lower hardness corresponds to the solution treatment at 566 C than to that at 520 C. A comparison with ingot metallurgy alloys of the same composition shows the MA material to be stronger and more ductile. It is also noted that properly aged MA alloys can develop a better combination of yield strength and notched toughness at lower alloying levels.

Gilman, P. S.

1984-01-01

305

Reliability comparison of two metallurgies for ceramic ball grid array  

Microsoft Academic Search

Surface-mountable ceramic ball grid array (CBGA) packages have proven to be attractive in a variety of applications as designers seek to maximize electrical performance, reduce card real estate, and improve manufacturing process yields. In support of the PowerPC family of microprocessors, 21 mm CBGA packages (256 leads) were used to evaluate two different ball metallurgies-90\\/10 Pb\\/Sn and 62\\/36\\/2 Sn\\/Pb\\/Ag. Test

D. R. Banks; T. E. Burnette; R. D. Gerke; E. Mammo; S. Mattay

1995-01-01

306

The Astrolabe Craftsmen of Lahore and Early Brass Metallurgy  

Microsoft Academic Search

A study of the metallurgy and manufacturing techniques of a group of eight astrolabes (seven from Lahore, one attributed to India) using non-destructive methods has produced the earliest evidence for systematic use of high-zinc (??+??) brass. To produce this alloy, the brass industry supplying the Lahore instrument makers must have co-melted metallic copper and zinc. This brass-making technology was previously

B. D. Newbury; M. R. Notis; B. Stephenson; G. S. Cargill III; G. B. Stephenson

2006-01-01

307

TT^T7Gs!rf5ft Riso-R-425 Metallurgy Department  

E-print Network

CM tf TT^T7Gs!rf5ft Riso-R-425 (O O o o o \\l O Metallurgy Department Progress Report for the Period-R-425 METALLURGY DEPARTMENT PROGRESS REPORT FOR THE PERIOD 1 JANUARY TO 31 DECEMBER 1979 Abstract. The activities of the Metallurgy Department at Risø during 1979 are described. The work is presented in four chap

308

ilvVJl!U)jXy Ris-R-503 Metallurgy Department  

E-print Network

CO GO ilvVJl!U)jXy Risø-R-503 Metallurgy Department Progress Report for the Period 1 January - 31 December 1983 Risø National Laboratory, DK-4000 Roskilde, Denmark June 1984 #12;1 Risø-R-503 METALLURGY of the Metallurgy Department at Risø during 1983 are described. The work is presented in three chap- ters: General

309

Effective temperature of an aging powder.  

PubMed

The aging dynamics and the fluctuation-dissipation relation between the spontaneous diffusion induced by a random noise and the drift motion induced by a small stirring force are numerically investigated in a 3D schematic model of compacting powder: a gravity-driven lattice-gas with purely kinetic constraints. The compaction dynamics is characterized by a super-aging behavior and, in analogy with glasses, exhibits a purely dynamical time-scale-dependent effective temperature. A simple experiment to measure this quantity is suggested. PMID:11415060

Sellitto, M

2001-06-01

310

3.40J / 22.71J Physical Metallurgy, Spring 2003  

E-print Network

Discusses structure-property relationships in metallic alloys selected to illustrate some basic concepts of physical metallurgy and alloy design. Fundamentals of annealing, spinodal decomposition, nucleation, growth, and ...

Russell, Kenneth

311

Welding metallurgy and toughness improvement for mild and low-alloyed steel electroslag weldments.  

E-print Network

??Fundamental aspects of welding metallurgy and microstructural relationships controlling fracture toughness improvement were studied during a series of experimental electroslag (ES) welding practices for joining… (more)

Yu, Dawei

1988-01-01

312

C-Fe Hardmetals with High Hardness Fabricated by Direct Current Arc In Situ Metallurgy  

NASA Astrophysics Data System (ADS)

Coarse-grained W p C-Fe ( P = 1,2) hardmetals were fabricated with tungsten and graphite powders by the direct current arc in situ metallurgy technique. Investigations on the microstructures, morphology evolution, and performance for the resultant materials were also carried out. It is found that with decreasing the applied current, the content of W2C decreases, but the content and grain size of WC increase. The largest WC grain can reach around 150 ?m. The shape of WC changes from hexangular prism to truncated triangle prism, and ultimately transforms into triangular prism due to the different growth rates of the prismatic planes. Furthermore, a layer by layer growth mode of the WC was observed. The performance tests indicate that the average microhardnesses of the WC and W2C are 2559 and 1916 HV0.2, respectively. For the WC grain, the microhardness of 2761 HV0.2 of the triangular basal plane is much higher than the 2357 HV0.2 of the prismatic plane.

Chi, Jing; Li, Huiqi; Zhao, Jian; Wang, Shufeng; Li, Min; Ji, Qiang; Li, Jiannan

2014-11-01

313

NanoComposite Stainless Steel Powder Technologies  

SciTech Connect

Oak Ridge National Laboratory has been investigating a new class of Fe-based amorphous material stemming from a DARPA, Defense Advanced Research Projects Agency initiative in structural amorphous metals. Further engineering of the original SAM materials such as chemistry modifications and manufacturing processes, has led to the development of a class of Fe based amorphous materials that upon processing, devitrify into a nearly homogeneous distribution of nano sized complex metal carbides and borides. The powder material is produced through the gas atomization process and subsequently utilized by several methods; laser fusing as a coating to existing components or bulk consolidated into new components through various powder metallurgy techniques (vacuum hot pressing, Dynaforge, and hot isostatic pressing). The unique fine scale distribution of microstructural features yields a material with high hardness and wear resistance compared to material produced through conventional processing techniques such as casting while maintaining adequate fracture toughness. Several compositions have been examined including those specifically designed for high hardness and wear resistance and a composition specifically tailored to devitrify into an austenitic matrix (similar to a stainless steel) which poses improved corrosion behavior.

DeHoff, R.; Glasgow, C. (MesoCoat, Inc.)

2012-07-25

314

Amorphous powders of Al-Hf prepared by mechanical alloying  

SciTech Connect

We synthesized amorphous Al/sub 50/Hf/sub 50/ alloy powder by mechanically alloying an equimolar mixture of crystalline powders of Al and Hf using hexane as a dispersant. We characterized the powder as a function of mechanical-alloying time by scanning electron microscopy, x-ray diffraction, and differential scanning calorimetry. Amorphous Al/sub 50/Hf/sub 50/ powder heated at 10 K s/sup /minus/1/ crystallizes polymorphously at 1003 K into orthorhombic AlHf (CrB-type structure). During mechanical alloying, some hexane decomposes and hydrogen and carbon are incorporated into the amorphous alloy powder. The hydrogen can be removed by annealing the powder by hot pressing at a temperature approximately 30 K below the crystallization temperature. The amorphous compacts have a diamond pyramidal hardness of 1025 DPH. 24 refs., 7 figs., 1 tab.

Schwarz, R.B.; Hannigan, J.W.; Sheinberg, H.; Tiainen, T.

1988-01-01

315

Shock compression response of magnetic nanocomposite powders  

Microsoft Academic Search

The shock compression response of magnetic Pr2Fe14B\\/?-Fe nanocomposite powders, pressed at different packing densities, was studied in the range of 11–23 GPa shock pressure, using a single-stage gas gun. Bulk compacts (97.5–99% dense) recovered in the form of 12 mm diameter by 4 mm thick disks, were analyzed to determine the structural changes occurring within the particles and at particle

Z. Q. Jin; K. H. Chen; J. Lia; H. Zeng; S.-F. Cheng; J. P. Liu; Z. L. Wang; N. N. Thadhani

2004-01-01

316

Composite powder particles  

NASA Technical Reports Server (NTRS)

A liquid coating composition including a coating vehicle and composite powder particles disposed within the coating vehicle. Each composite powder particle may include a magnesium component, a zinc component, and an indium component.

Parker, Donald S. (Inventor); MacDowell, Louis G. (Inventor)

2009-01-01

317

Precision powder feeder  

DOEpatents

A new class of precision powder feeders is disclosed. These feeders provide a precision flow of a wide range of powdered materials, while remaining robust against jamming or damage. These feeders can be precisely controlled by feedback mechanisms.

Schlienger, M. Eric (Albuquerque, NM); Schmale, David T. (Albuquerque, NM); Oliver, Michael S. (Sandia Park, NM)

2001-07-10

318

1.Answer the following questions: (a)& you have learned in your physical metallurgy class, diffusion rate in solid may be  

E-print Network

1.Answer the following questions: (a)& you have learned in your physical metallurgy class on the physical metallurgy principles, the student suggested two possibilities for the stress drop: 1) The stress

Huang, Haimei

319

Materials Science & Metallurgy Master of Philosophy, Materials Modelling, Course MP6, Kinetics and Microstructure Modelling, H. K. D. H. Bhadeshia  

E-print Network

Materials Science & Metallurgy Master of Philosophy, Materials Modelling, Course MP6, Kinetics in metallurgy. To form a complete design­technology, it is consequently necessary to re- sort to careful

Cambridge, University of

320

Materials Science & Metallurgy Master of Philosophy, Materials Modelling, Course MP10, Process Modelling, H. K. D. H. Bhadeshia  

E-print Network

Materials Science & Metallurgy Master of Philosophy, Materials Modelling, Course MP10, Process.­E. Svensson. The metallurgy of the welded joint can be categorised into two major regions, the fusion zone

Cambridge, University of

321

SGC tests for influence of material composition on compaction characteristic of asphalt mixtures.  

PubMed

Compaction characteristic of the surface layer asphalt mixture (13-type gradation mixture) was studied using Superpave gyratory compactor (SGC) simulative compaction tests. Based on analysis of densification curve of gyratory compaction, influence rules of the contents of mineral aggregates of all sizes and asphalt on compaction characteristic of asphalt mixtures were obtained. SGC Tests show that, for the mixture with a bigger content of asphalt, its density increases faster, that there is an optimal amount of fine aggregates for optimal compaction and that an appropriate amount of mineral powder will improve workability of mixtures, but overmuch mineral powder will make mixtures dry and hard. Conclusions based on SGC tests can provide basis for how to adjust material composition for improving compaction performance of asphalt mixtures, and for the designed asphalt mixture, its compaction performance can be predicted through these conclusions, which also contributes to the choice of compaction schemes. PMID:23818830

Chen, Qun; Li, Yuzhi

2013-01-01

322

SGC Tests for Influence of Material Composition on Compaction Characteristic of Asphalt Mixtures  

PubMed Central

Compaction characteristic of the surface layer asphalt mixture (13-type gradation mixture) was studied using Superpave gyratory compactor (SGC) simulative compaction tests. Based on analysis of densification curve of gyratory compaction, influence rules of the contents of mineral aggregates of all sizes and asphalt on compaction characteristic of asphalt mixtures were obtained. SGC Tests show that, for the mixture with a bigger content of asphalt, its density increases faster, that there is an optimal amount of fine aggregates for optimal compaction and that an appropriate amount of mineral powder will improve workability of mixtures, but overmuch mineral powder will make mixtures dry and hard. Conclusions based on SGC tests can provide basis for how to adjust material composition for improving compaction performance of asphalt mixtures, and for the designed asphalt mixture, its compaction performance can be predicted through these conclusions, which also contributes to the choice of compaction schemes. PMID:23818830

Chen, Qun

2013-01-01

323

SUMMARIES ON PHYSICAL RESEARCH IN METALLURGY, SOLID STATE PHYSICS, AND CERAMICS  

Microsoft Academic Search

The objectives and current status of the individual research projects ; supported by the Metallurgy and Materials Branch, Division of Research, in the ; fields of physical metallurgy, solid state physics, and physical ceramics are ; summarized. Included is the research conducted at the Commission's laboratories ; as well as that performed at university and other laboratories. The information ;

R. R. ed

1959-01-01

324

Rigorous investigations of piecewise linear circuits Department of Electrical Engineering, University of Mining and Metallurgy,  

E-print Network

, University of Mining and Metallurgy, al. Mickiewicza 30, 30­059 Krak´ow, POLAND e-mail: galias where the Poincar´e This work was supported by the University of Mining and Metallurgy, Krak´ow, grant

Galias, Zbigniew

325

Rigorous investigations of piecewise linear circuits # Department of Electrical Engineering, University of Mining and Metallurgy,  

E-print Network

Engineering, University of Mining and Metallurgy, al. Mickiewicza 30, 30--059 Krakâ??ow, POLAND e­mail: galias where the Poincarâ??e # This work was supported by the University of Mining and Metallurgy, Krakâ??ow, grant

Galias, Zbigniew

326

Powder material parameters establishment through warm forming route  

Microsoft Academic Search

This paper presents the establishment of the properties of powder materials through experimentation at elevated temperature ranging from room temperature (30°C) to 150°C. Uniaxial die compaction experiments were conducted to establish the powder properties such as densification, Young’s modulus, spring-back, plastic index, elastic index, and plastic hardening coefficient. Shearing experiments were conducted to establish the temperature dependent friction coefficient. Iron

M. M. Rahman; A. K. Ariffin; S. S. M. Nor; H. Y. Rahman

2011-01-01

327

Advances in Physical Metallurgy, edited by S. Banerjee and R. V. Ramanujan, Gordon and Breach Publishers, 1996  

E-print Network

Advances in Physical Metallurgy, edited by S. Banerjee and R. V. Ramanujan, Gordon and Breach into metallurgy. But this is where cre- ativity comes in. I recall someone saying that high TC superconductors are metallic. But how does "Metallurgy of ceramic cutting tools" qualify? I guess that even the ceramics

Cambridge, University of

328

Welding Metallurgy and Processing Issues for Joining of Power Sources  

SciTech Connect

Weldability issues with the pertinent alloys have been reviewed and preliminary results of our work on Haynes 25 have been presented. Further results on the mechanical properties and metallography on the EB welds are imminent. Hot-ductility experiments will commence within a few weeks. Aging studies on the effects of heat treatment using the Gleeble are also planned. MST-6 has extensive background in the welding metallurgy of the pertinent alloys. We also have considerable experience with the various welding processes to be used.

Lienert, Thomas J. [Los Alamos National Laboratory; Reardon, Patrick T. [Los Alamos National Laboratory

2012-08-14

329

Mechanical properties and shear failure surfaces of two alumina powders in triaxial compression  

SciTech Connect

In the manufacture of ceramic components, near-net-shape parts are commonly formed by uniaxially pressing granulated powders in rigid dies. Density gradients that are introduced into a powder compact during press-forming often increase the cost of manufacturing, and can degrade the performance and reliability of the finished part. Finite element method (FEM) modeling can be used to predict powder compaction response, and can provide insight into the causes of density gradients in green powder compacts; however, accurate numerical simulations require accurate material properties and realistic constitutive laws. To support an effort to implement an advanced cap plasticity model within the finite element framework to realistically simulate powder compaction, the authors have undertaken a project to directly measure as many of the requisite powder properties for modeling as possible. A soil mechanics approach has been refined and used to measure the pressure dependent properties of ceramic powders up to 68.9 MPa (10,000 psi). Due to the large strains associated with compacting low bulk density ceramic powders, a two-stage process was developed to accurately determine the pressure-density relationship of a ceramic powder in hydrostatic compression, and the properties of that same powder compact under deviatoric loading at the same specific pressures. Using this approach, the seven parameters that are required for application of a modified Drucker-Prager cap plasticity model were determined directly. The details of the experimental techniques used to obtain the modeling parameters and the results for two different granulated alumina powders are presented.

ZEUCH,DAVID H.; GRAZIER,J. MARK; ARGUELLO JR.,JOSE G.; EWSUK,KEVIN G.

2000-04-24

330

Grain growth behavior of extrusion consolidated centrifugally atomized Type 304 stainless steel powder  

SciTech Connect

A study was performed to assess the role of entrapped helium in stabilizing the microstructure. Type 304 stainless steel powders produced by centrifugal atomization (CA) were consolidated by hot extrusion. The powders contain approx.7 appM He which was retained during extrusion. Isothermal heat treatments were performed on the CA 304 SS extruded powder as well as on the attached wrought ingot metallurgy (I/M) can and a filler plug of Type 304 SS for comparisons. Compared with the wrought I/M Type 304 SS, the CA Type 304 SS extruded powder exhibited considerable grain growth retardation. Grain growth was shown to be independent of the means used for powder consolidation, including hot isostatic pressing and dynamic consolidation. Also, other CA consolidated alloy powders exhibited grain growth resistance equal to the CA Type 304 SS extruded powder. Results indicate that the entrapped helium in the CA consolidated powder materials plays a significant role in retarding grain growth. 23 figs., 5 tabs.

Flinn, J.E.; Wright, R.N.; Korth, G.E.

1987-11-01

331

The mysterious world of plutonium metallurgy: Past and future  

SciTech Connect

The first atomic bomb detonated at the Trinity Site in New Mexico on July 16, 1945, used plutonium, a man-made element discovered < 5 yr earlier. The story of how Manhattan Project scientists and engineers tackled the mysteries of this element and fabricated it into the first atomic bomb is one of the most fascinating in the history of metallurgy and materials. The authors are currently trying to generate renewed interest in plutonium metallurgy because of the challenge posed by President Clinton, i.e., to keep the nuclear stockpile of weapons safe and reliable without nuclear testing. The stockpile stewardship challenge requires either a lifetime extension of the plutonium components or a remanufacture--neither of which can be verified by testing. In turn, this requires that one achieve a better fundamental understanding of plutonium. Of special interest is the effect of self-irradiation on the properties and on the long-term stability of plutonium and its alloys. Additional challenges arise from long-term concerns about disposing of plutonium and dealing with its environmental legacy. It is imperative to interest the next generation of students in these plutonium challenges.

Hecker, S.S.; Hammel, E.F. [Los Alamos National Lab., NM (United States)

1998-12-31

332

Implications of elastic wave velocities for Apollo 17 rock powders  

NASA Technical Reports Server (NTRS)

Ultrasonic P- and S-wave velocities of lunar rock powders 172701, 172161, 170051, and 175081 were measured at room temperature and to 2.5 kb confining pressure. The results compare well with those of terrestrial volcanic ash and powdered basalt. P-wave velocity values up to pressures corresponding to a lunar depth of 1.4 km preclude cold compaction alone as an explanation for the observed seismic velocity structure at the Apollo 17 site. Application of small amounts of heat with simultaneous application of pressure causes rock powders to achieve equivalence of seismic velocities for competent rocks.

Talwani, P.; Nur, A.; Kovach, R. L.

1974-01-01

333

The rheology and hydrodynamics of dry powder lubrication  

NASA Technical Reports Server (NTRS)

This paper conceptualizes a powder lubrication mechanisms which closely resembles that of a hydrodynamic fluid film. Based on the observations of past investigations and on the author's experiments, it is postulated that a layered shearing of the compacted powder generates velocity, density, and temperature profiles akin to fluid film bearings. Thus, a lubricant consisting of a fine powder unserted either deliberately or one generated by the water of the mating surfaces, constitutes a viable lubricant that generates the required flows and pressures to prevent contact between the surfaces.

Heshmat, Hooshang

1991-01-01

334

Shock Consolidation of Nanocrystalline Aluminum Powders for Bulk Component Formation  

NASA Astrophysics Data System (ADS)

Shock compression is used to consolidate micron-size nanocrystalline metal particles formed from Al-6061 T6 stock through frequency modulated severe plastic deformation (SPD) machining methods. Compaction characteristics are developed in the quasi-static and dynamic regime. Shock recovery experiments are performed to determine the degree of densification, and the microstructure and mechanical properties of compacts following shock compression. At lower impact velocities compacts show slight increase in crystallite size and reduction in residual strain for bulk compacts reaching 85-92% theoretical density, with microstructures revealing a lack of mechanical bonding between neighboring particles. At higher impact velocity of 650 m/s compacts reach 95-96% theoretical density. Mesoscale simulations using real microstructures obtained from powder compacts are performed to examine the shock propagation characteristics through the simulated compacts and determine the effect of particle morphology on compaction characteristics. Simulations will also aid in design of the compaction experiments to ensure fabrication of bulk compacts with retention of nanocrystalline grain structure.

Fredenburg, David A.; Vogler, Tracy; Saldana, Christopher; Thadhani, Naresh

2007-06-01

335

Which Powder is It?  

NSDL National Science Digital Library

In this chemistry challenge, learners identify an unknown white powder by comparing it with common household powders. Learners first explore what happens when baking soda, baking powder, and washing soda are mixed with water, vinegar, and PHTH (the indicator phenolphthalein mixed with alcohol and water). Learners then work to identify the unknown based on how it reacts with the known solutions. This is a simplified form of "qualitative analysis," which was historically an important approach chemists used for identifying unknown samples.

Sciencenter

2014-08-27

336

Quantitative analysis of powder mixtures by Raman spectrometry: the influence of particle size and its correction.  

PubMed

Particle size distribution and compactness have significant confounding effects on Raman signals of powder mixtures, which cannot be effectively modeled or corrected by traditional multivariate linear calibration methods such as partial least-squares (PLS), and therefore greatly deteriorate the predictive abilities of Raman calibration models for powder mixtures. The ability to obtain directly quantitative information from Raman signals of powder mixtures with varying particle size distribution and compactness is, therefore, of considerable interest. In this study, an advanced quantitative Raman calibration model was developed to explicitly account for the confounding effects of particle size distribution and compactness on Raman signals of powder mixtures. Under the theoretical guidance of the proposed Raman calibration model, an advanced dual calibration strategy was adopted to separate the Raman contributions caused by the changes in mass fractions of the constituents in powder mixtures from those induced by the variations in the physical properties of samples, and hence achieve accurate quantitative determination for powder mixture samples. The proposed Raman calibration model was applied to the quantitative analysis of backscatter Raman measurements of a proof-of-concept model system of powder mixtures consisting of barium nitrate and potassium chromate. The average relative prediction error of prediction obtained by the proposed Raman calibration model was less than one-third of the corresponding value of the best performing PLS model for mass fractions of barium nitrate in powder mixtures with variations in particle size distribution, as well as compactness. PMID:22468859

Chen, Zeng-Ping; Li, Li-Mei; Jin, Jing-Wen; Nordon, Alison; Littlejohn, David; Yang, Jing; Zhang, Juan; Yu, Ru-Qin

2012-05-01

337

Dynamic consolidation of rapidly solidified titanium alloy powders by explosives  

Microsoft Academic Search

Consolidation of rapidly solidified titanium alloy powders employing explosively generated shock pressures was carried out successfully. The cylindrical explosive consolidation technique was utilized, and compacts with densities in the range 97 to 100% were produced. Better consolidation (with more interparticle melting regions and less cracking) was achieved by using a double tube design in which the outer tube (flyer tube)

H. L. Coker; M. A. Meyers; J. F. Wessels

1991-01-01

338

Thermodynamic analysis of compact formation; compaction, unloading, and ejection. II. Mechanical energy (work) and thermal energy (heat) determinations of compact unloading and ejection.  

PubMed

A compaction calorimeter, previously described (DeCrosta, M.T., Schwartz, J.B., Wigent, J.B., Marshall, K., 2000. Thermodynamic analysis of compact formation; compaction, unloading, and ejection. I. Design and development of a compaction calorimeter and mechanical and thermal energy determinations of powder compaction. Int. J. Pharm. 198, 113--134), was utilized to evaluate the thermodynamics of the unloading and ejection of compacts of Avicel pH102, Emcompress, Fast-Flo #316, Starch 1500, and acetaminophen (APAP). A constant strain waveform, applied by a compaction simulator, enabled the separate thermodynamic evaluation of unloading from compaction. The brittle materials, Fast-Flo #316 and Emcompress, displayed the most unloading work, and the plastic/self-lubricating materials, Avicel and Starch 1500, displayed the least. Unloading heat values were negative for all materials, except APAP. APAP's positive heat values indicated the breaking of bonds during unloading as a result of its highly elastic nature. Positive internal energy changes of unloading, which indicate the net breaking of bonds, were observed for APAP and Emcompress over the compaction forces tested. Negative energy changes for Starch 1500, Fast-Flo #316, and Avicel became positive with increasing compaction forces. Ejection work increased with increasing compaction force for the brittle materials, whereas smaller ejection work values for Avicel, Starch 1500, and APAP remained constant. Increasing negative heat values as a function of compaction force were observed for Fast-Flo #316 and Emcompress. Negative internal energy values for ejection were observed for Fast-Flo #316 and Emcompress, which indicates net bond formation as a result of high shear of the compact with the die wall. Internal energy changes for Starch 1500, Avicel, and APAP, were approximately zero, indicating the absence of net bonding or bond formation during the process. PMID:11165093

DeCrosta, M T; Schwartz, J B; Wigent, R J; Marshall, K

2001-02-01

339

Chem-Prep PZT 95/5 for Neutron Generator Applications: Powder Fractionation Study of Production-Scale Powders  

SciTech Connect

The Materials Chemistry Department 1846 has developed a lab-scale chem-prep process for the synthesis of PNZT 95/5, referred to as the ''SP'' process (Sandia Process). This process (TSP) has been successfully transferred to and scaled-up by Department 14192 (Ceramics and Glass Department), producing the larger quantities of PZT powder required to meet the future supply needs of Sandia for neutron generator production. The particle size distributions of TSP powders routinely have been found to contain a large particle size fraction that was absent in development (SP) powders. This SAND report documents experimental studies focused on characterizing these particles and assessing their potential impact on material performance. To characterize these larger particles, fractionation of several TSP powders was performed. The ''large particle size fractions'' obtained were characterized by particle size analysis, SEM, and ICP analysis and incorporated into compacts and sintered. Large particles were found to be very similar in structure and composition as the bulk of the powder. Studies showed that the large-size fractions of the powders behave similarly to the non-fractionated powder with respect to the types of microstructural features once sintered. Powders were also compared that were prepared using different post-synthesis processing (i.e. differences in precipitate drying). Results showed that these powders contained different amounts and sizes of porous inclusions when sintered. How this affects the functional performance of the PZT 95/5 material is the subject of future investigations.

MOORE, DIANA L.; VOIGT, JAMES A.; WATSON, CHAD S.; MCKENZIE, BONNIE B.; MOORE, ROGER H.; HUTCHINSON, MICHAEL A.; LOCKWOOD, STEVEN J.; RODMAN-GONZALES, EMILY D.

2003-06-01

340

Comparative study of high speed steels obtained through explosive compaction and hot isostatic pressing  

Microsoft Academic Search

Two grades of high speed steel (HSS) powders, T42 and M3II, were explosive compaced. The feasibility of shock compaction by explosives of HSSs using a cylindrical configuration and the microstructures of consolidated or compacted powders are analyzed. A comparison between their characteristics and some commercial hot isostatically pressed tool steels was also carried out.Since mechanical properties of HSSs depend strongly

L. E. G. Cambronero; E. Gordo; J. M. Torralba; J. M. Ruiz-Prieto

1996-01-01

341

Processing of a porous titanium alloy from elemental powders using a solid state isothermal foaming technique  

Microsoft Academic Search

The authors have conducted a preliminary investigation with regard to the potential to manufacture porous titanium alloys\\u000a for biomedical applications using toxic-free elemental powders, i.e., Ti, Nb, Ta, Zr, in combination with the pressurised\\u000a gas bubble entrapment method and in contrast to standard processing routes that generally utilise prealloyed powder containing\\u000a potentially toxic elements. Elemental powder compacts were either hot

Aris W. Nugroho; Garry Leadbeater; Ian J. Davies

2010-01-01

342

Iron-carbon compacts and process for making them  

DOEpatents

The present invention includes iron-carbon compacts and a process for making them. The process includes preparing a slurry comprising iron powder, furfuryl alcohol, and a polymerization catalyst for initiating the polymerization of the furfuryl alcohol into a resin, and heating the slurry to convert the alcohol into the resin. The resulting mixture is pressed into a green body and heated to form the iron-carbon compact. The compact can be used as, or machined into, a magnetic flux concentrator for an induction heating apparatus.

Sheinberg, Haskell (Santa Fe, NM)

2000-01-01

343

Evaluation of strength at early ages of self-compacting concrete with high volume fly ash  

Microsoft Academic Search

Self-compacting concrete (SCC) demands large amount of powder content and fines for its cohesiveness and ability to flow with out bleeding and segregation. In the present investigation, part of this powder is replaced with high volume fly ash based on a rational mix design method developed by the authors. Because of high fly ash content, it is essential to study

Binu Sukumar; K. Nagamani; R. Srinivasa Raghavan

2008-01-01

344

Optimization of aluminum oxynitride compaction process using a Gray-coded genetic algorithm  

Microsoft Academic Search

The densification process for the ceramic spinel aluminum oxinitride (ALON) has been analyzed using biologically inspired genetic algorithms. A micro-mechanical model for powder compaction is coupled with the available experimental data and the optimized parameter set for the densification process is obtained through genetic algorithms and the mechanism of compaction highlighted.

N Chakraborti; P Mishra; A Banerjee

2004-01-01

345

Analysis of cold and hot isostatic compaction of spherical particles  

SciTech Connect

Cold and hot isostatic compaction of monosized metal powders is analyzed within the framework of viscoplastic theory for particles packed both in a regular and a random manner. The problem of local contact between spherical particles is analyzed first by drawing upon recent detailed numerical studies of spherical indentation of power law plastic and creeping solids. The compaction process is then modelled as a self-similar contraction of unit (average) cells, in contrast to commonly used phenomenological assumptions, yielding a simple but rigorous relation between the densification density and center-to-center approach of adjacent powder particles. The resulting densification formulae are easy to apply and the influence of hardening and creep parameters appears in concise form. Predictions are compared with discriminating experimental data for a variety of different powder materials, both in the cold and a hot state, and the agreement is good for a relative density increase of up to 30%.

Larsson, P.L.; Biwa, S.; Storaakers, B. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid Mechanics] [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid Mechanics

1996-09-01

346

[Otologic diagnosis: powder technique].  

PubMed

The otologic diagnostic powder test with grape - sugar simple will be performed with a powder - blower. It permits a good differentiation between dry squamous epithelium and wet mucosa. In our opinion this test therefore is unrenouncable in microscopic differentiation between mucosa in central perforations on one hand and atrophic scars, retraction pockets or adhesive epithelium of the drum or complete atelectasis of the tympanic cavity on the other hand. PMID:21626473

Tolsdorff, P

2011-06-01

347

Process for synthesizing compounds from elemental powders and product  

DOEpatents

A process for synthesizing intermetallic compounds from elemental powders is described. The elemental powders are initially combined in a ratio which approximates the stoichiometric composition of the intermetallic compound. The mixed powders are then formed into a compact which is heat treated at a controlled rate of heating such that an exothermic reaction between the elements is initiated. The heat treatment may be performed under controlled conditions ranging from a vacuum (pressureless sintering) to compression (hot pressing) to produce a desired densification of the intermetallic compound. In a preferred form of the invention, elemental powders of Fe and Al are combined to form aluminide compounds of Fe[sub 3] Al and FeAl. 25 figures.

Rabin, B.H.; Wright, R.N.

1993-12-14

348

Phase transformations in shock compacted magnetic materials  

NASA Astrophysics Data System (ADS)

Shock compaction experiments were performed on soft magnetic phases Fe 4N and Fe16N2, and hard magnetic phases Nd 2Fe14B and Sm2Fe17N3 in order to determine their thermo-mechanical stability during shock loading and explore the possibility of fabricating a textured nanocomposite magnet. Gas gun experiments performed on powders pressed in a three capsule fixture showed phase transformations occurring in Fe4N, Fe16N 2, and Nd2Fe14B, while Sm2Fe17 N3 was observed to be relatively stable. Shock compaction of FCC Fe4N resulted in a partial transformation to HCP Fe3N, consistent with previous reports of the transition occurring at a static pressure of ~3 GPa. Shock compaction of Fe16N 2 produced decomposition products ?-Fe, Fe4N, and FeN due to a combination of thermal effects associated with dynamic void collapse and plastic deformation. Decomposition of Nd-Fe-B, producing ?-Fe and amorphous Nd-Fe-B, was observed in several shock consolidated samples and is attributed to deformation associated with shock compaction, similar to decomposition reported in ball milled Nd-Fe-B. No decomposition was observed in shock compacted samples of Sm-Fe-N, which is consistent with literature reports showing decomposition occurring only in samples compacted at a pressure above ~15 GPa. Nd-Fe-B and Sm-Fe-N were shown to accommodate deformation primarily by grain size reduction, especially in large grained materials. Hard/Soft composite magnetic materials were formed by mixing single crystal particles of Nd-Fe-B with iron nanoparticles, and the alignment-by-magnetic-field technique was able to introduce significant texture into green compacts of this mixture. While problems with decomposition of the Nd2Fe14B phase prevented fabricating bulk magnets from the aligned green compacts, retention of the nanoscale morphology of the ?-Fe particles and the high alignment of the green compacts shows promise for future development of textured nanocomposite magnets through shock compaction.

Wehrenberg, Christopher

349

Sol-gel synthesis and densification of aluminoborosilicate powders. Part 1: Synthesis  

NASA Technical Reports Server (NTRS)

Aluminoborosilicate powders high in alumina content were synthesized by the sol-gel process utilizing various methods of preparation. Properties and microstructural effects related to these syntheses were examined. After heating to 600 C for 2 h in flowing air, the powders were amorphous with the metal oxides comprising 87 percent of the weight and uncombusted organics the remainder. DTA of dried powders revealed a T(sub g) at approximately 835 C and an exotherm near 900 C due to crystallization. Powders derived from aluminum secbutoxide consisted of particles with a mean diameter 5 microns less than those from aluminum isopropoxide. Powders synthesized with aluminum isopropoxide produced agglomerates comprised of rod shaped particulates while powders made with the secbutoxide precursor produced irregular glassy shards. Compacts formed from these powders required different loadings for equivalent densities according to the method of synthesis.

Bull, Jeffrey; Selvaduray, Guna; Leiser, Daniel

1992-01-01

350

Hafnium- and titanium-coated tungsten powders for kinetic energy penetrators, Phase I, SBIR. Final report  

SciTech Connect

Depleted uranium (DU) is the state-of-the-art material for kinetic energy penetrators used to defeat steel and composite armors. DU alloys, however, are costly to fabricate, handle, and store because of their extremely complex metallurgy and the obvious health considerations associated with the use of uranium. Tungsten composite materials are also used in kinetic energy penetrators, offering easier and safer fabrication, handling, and storage but to date lacking the performance of DU. The mechanisms by which a penetrator defeats an armor are difficult to determine, either experimentally or from first principles. Recent experiments have identified the presence of an adiabatic shear mechanism that appears to be important in the penetration of rolled homogeneous armor (RHA) by DU penetrators. In this program, Ultramet proposed to apply hafnium and titanium coatings to tungsten powder (Wp) particles by chemical vapor deposition (CVD) using an established fluidized-bed powder coating technique. Both hafnium and titanium are known to exhibit the adiabatic shear phenomenon. High strain rate experiments (approx.10 to the 4th power/sec) were performed on Ti(6A1-4V) and hafnium materials in order to establish the presence or absence of this mode of deformation in small cylindrical specimens. In addition, specimens of 2 wt% CVD Hf/Wp and 2 wt% CVD Hf + 8 wt% powder-mixed Hf/Wp were tested at high strain rate conditions (approx. 10 to the 4th power/sec). Tungsten powders, Composites, Chemical Vapor Deposition(CVD), Microstructure, Hafnium, Titanium, Dynamic tests, Strain rate testing, Powder metallurgy.

Williams, B.E.; Stiglich, J.J.

1992-05-01

351

Indexation Rules for Metallurgy in PASCAL. Original Title: Regles d'Indexation de la Metallurgie'--Technical Note Issued by Informascience--January 1980. Translated by Marie Wallin.  

ERIC Educational Resources Information Center

The indexing rules presented are designed for use with a new French-German database on metallurgy being developed under an agreement by CNRS (Centre National de la Recherche Scientifique, Paris) and BAM (Bundesanstalt fur Materialprufung, Berlin). The new database, which will feature multilingual titles and index terms (French-German-English-) and…

Royal Inst. of Tech., Stockholm (Sweden). Library.

352

TRADITIONAL METALLURGY, NANOTECHNOLOGIES AND STRUCTURAL MATERIALS: A SORBY AWARD LECTURE  

SciTech Connect

Traditional metallurgical processes are among the many ''old fashion'' practices that use nanoparticles to control the behavior of materials. Many of these practices were developed long before microscopy could resolve nanoscale features, yet the practitioners learned to manipulate and control microstructural elements that they could neither see nor identify. Furthermore, these early practitioners used that control to modify microstructures and develop desired material properties. Centuries old colored glass, ancient high strength steels and medieval organ pipes derived many of their desirable features through control of nanoparticles in their microstructures. Henry Sorby was among the first to recognize that the properties of rocks, minerals, metals and organic materials were controlled by microstructure. However, Mr. Sorby was accused of the folly of trying to study mountains with a microscope. Although he could not resolve nanoscale microstructural features, Mr. Sorby's observations revolutionized the study of materials. The importance of nanoscale microstructural elements should be emphasized, however, because the present foundation for structural materials was built by manipulating those features. That foundation currently supports several multibillion dollar industries but is not generally considered when the nanomaterials revolution is discussed. This lecture demonstrates that using nanotechnologies to control the behavior of metallic materials is almost as old as the practice of metallurgy and that many of the emergent nanomaterials technologists are walking along pathways previously paved by traditional metallurgists.

Louthan, M

2007-07-17

353

Welding metallurgy of nickel alloys in gas turbine components  

SciTech Connect

Materials for gas turbine engines are required to meet a wide range of temperature and stress application requirements. These alloys exhibit a combination of creep resistance, creep rupture strength, yield and tensile strength over a wide temperature range, resistance to environmental attack (including oxidation, nitridation, sulphidation and carburization), fatigue and thermal fatigue resistance, metallurgical stability and useful thermal expansion characteristics. These properties are exhibited by a series of solid-solution-strengthened and precipitation-hardened nickel, iron and cobalt alloys. The properties needed to meet the turbine engine requirements have been achieved by specific alloy additions, by heat treatment and by thermal mechanical processing. A thorough understanding of the metallurgy and metallurgical processing of these materials is imperative in order to successfully fusion weld them. This same basic understanding is required for repair of a component with the added dimension of the potential effects of thermal cycling and environmental exposure the component will have endured in service. This article will explore the potential problems in joining and repair welding these materials.

Lingenfelter, A. C., LLNL

1997-05-21

354

Flow and compaction behaviour of ultrafine coated ibuprofen.  

PubMed

Good flow and compaction properties are prerequisites for successful compaction process. Apart from initial profile, mechanical properties of pharmaceutical powders can get modified during unit processes like milling. Milled powders can exhibit a wide range of particle size distribution. Further downstream processing steps like compaction can be affected by this differential particle size distribution. This has greatest implications for formulations like high dose drugs wherein the active pharmaceutical ingredient (API) contributes the maximum bulk in the final formulation. The present study assesses the impact of dry coating with ultrafine particles of same material, on the flow and compaction properties of the core material. Ibuprofen was selected as model drug as it has been reported to have poor mechanical properties. Ultrafine ibuprofen (average size 1.75 ?m) was generated by Dyno(®) milling and was dry coated onto the core ibuprofen particles (average size 180 ?m). Compaction studies were performed using a fully instrumented rotary tablet press. Compaction data was analyzed for compressibility, tabletability, compactibility profiles and Heckel plot. Dry coating of the ibuprofen exhibited greater compressibility and tabletability, at lower compaction pressure. However, at compaction pressure above 220 MPa, compressibility and tabletability of coated as well as uncoated materials were found to be similar. Heckel analysis also supported the above findings, as P(y) value of uncoated ibuprofen was found to be 229.49 MPa and for 2.0% ultrafine coated ibuprofen was found to be 158.53 MPa. Lower P(y) value of ultrafine coated ibuprofen indicated ease of plastic deformation. Superior compressibility and deformation behaviour of ultrafine coated ibuprofen attributed to increased interparticulate bonding area. This strategy can also be explored for improving tabletability of high dose poorly compressible drugs. PMID:23142495

More, Parth K; Khomane, Kailas S; Bansal, Arvind K

2013-01-30

355

Ultrafine hydrogen storage powders  

DOEpatents

A method of making hydrogen storage powder resistant to fracture in service involves forming a melt having the appropriate composition for the hydrogen storage material, such, for example, LaNi.sub.5 and other AB.sub.5 type materials and AB.sub.5+x materials, where x is from about -2.5 to about +2.5, including x=0, and the melt is gas atomized under conditions of melt temperature and atomizing gas pressure to form generally spherical powder particles. The hydrogen storage powder exhibits improved chemcial homogeneity as a result of rapid solidfication from the melt and small particle size that is more resistant to microcracking during hydrogen absorption/desorption cycling. A hydrogen storage component, such as an electrode for a battery or electrochemical fuel cell, made from the gas atomized hydrogen storage material is resistant to hydrogen degradation upon hydrogen absorption/desorption that occurs for example, during charging/discharging of a battery. Such hydrogen storage components can be made by consolidating and optionally sintering the gas atomized hydrogen storage powder or alternately by shaping the gas atomized powder and a suitable binder to a desired configuration in a mold or die.

Anderson, Iver E. (Ames, IA); Ellis, Timothy W. (Doylestown, PA); Pecharsky, Vitalij K. (Ames, IA); Ting, Jason (Ames, IA); Terpstra, Robert (Ames, IA); Bowman, Robert C. (La Mesa, CA); Witham, Charles K. (Pasadena, CA); Fultz, Brent T. (Pasadena, CA); Bugga, Ratnakumar V. (Arcadia, CA)

2000-06-13

356

Enhanced Green Strength Material System for Ferrous and Stainless P\\/M Processing  

Microsoft Academic Search

Strength limitations of green powder metallurgy compacts often present fabricators with processing problems. Increased part complexity, process automation and the need for reduced green scrap requires the P\\/M compact to attain higher green strength. Currently, several limitations restrict the ability to increase green strength in P\\/M compacts. Powder characteristics, such as particle size distribution and morphology, compressibility and common lubricant

Sydney H. Luk; Alan B. Davala; Howard M. Kopech

357

Molecular understanding of the compaction behavior of indomethacin polymorphs.  

PubMed

Polymorphs enable us to gain molecular insights into the compaction behavior of pharmaceutical powders. Two polymorphs (? and ?) of indomethacin (IMC) were investigated for in-die and out-of-die compaction behavior using compressibility, tabletability and compactibility (CTC) profile, stress-strain relationship, and Heckel, Kawakita and Walker equations. Compaction studies were performed on a fully instrumented rotary tabletting machine. CTC analysis revealed that the ?-form has increased compressibility while the ?-form showed greater compactibility. The ?-form also showed increased tabletability over the ?-form at all the compaction pressures. Lower values of Py (Heckel parameter) and 1/b (Kawakita parameter) indicated increased deformation behavior of ?-form. Stress-strain analysis also supports the increased compressibility of ?-form. In addition, Walker analysis showed higher compressibility coefficient (W) for ?-form, consistent with its greater tabletability. Thus, tabletability of IMC polymorphs was governed by the compactibility of the material. Detailed examination of crystallographic data revealed that the presence of a slip plane system in the ?-form offered it increased compressibility and deformation behavior. However, the ?-form showed greater compactibility by virtue of closer molecular packing (higher true density). Hence, although direct correlation between tabletability and the presence of slip planes in the crystals has been reported, prediction solely based on this crystallographic feature must be avoided. The present work reiterates the influence of the crystal packing on the tabletability of the pharmaceutical polymorphs. PMID:23301663

Khomane, Kailas S; More, Parth K; Raghavendra, Guru; Bansal, Arvind K

2013-02-01

358

[Atmospheric emission of PCDD/Fs from secondary aluminum metallurgy industry in the southwest area, China].  

PubMed

Five secondary aluminum metallurgy enterprises in the southwest area of China were measured for emissions of PCDD/Fs. The results indicated that the emission levels of PCDD/Fs (as TEQ) were 0.015-0.16 ng x m(-3), and the average was 0.093 ng x m(-3) from secondary aluminum metallurgy enterprises. Emission factors of PCDD/Fs (as TEQ) from the five secondary aluminum metallurgy enterprises varied between 0.041 and 4.68 microg x t(-1) aluminum, and the average was 2.01 microg x t(-1) aluminum; among them, PCDD/Fs emission factors from the crucible smelting furnace was the highest. Congener distribution of PCDD/F in stack gas from the five secondary aluminum metallurgies was very different from each other. Moreover, the R(PCDF/PCDD) was the lowest in the enterprise which was installed only with bag filters; the R(PCDF/PCDD) were 3.8-12.6 (the average, 7.7) in the others which were installed with water scrubbers. The results above indicated that the mechanism of PCDD/Fs formation was related to the types of exhaust gas treatment device. The results of this study can provide technical support for the formulation of PCDD/Fs emission standards and the best available techniques in the secondary aluminum metallurgy industry. PMID:24720181

Lu, Yi; Zhang, Xiao-Ling; Guo, Zhi-Shun; Jian, Chuan; Zhu, Ming-Ji; Deng, Li; Sun, Jing; Zhang, Qin

2014-01-01

359

JOURNAL DE PHYSIQUE Colloque C2, supplment au no6, Tome 39, Juin 1978,page C2-101 LES APPORTS DE LA METALLURGIE PHYSIQUE EN GOLOGIE  

E-print Network

LA METALLURGIE PHYSIQUE EN G�OLOGIE J.-C. DOUKHAN et J. PAQUET Laboratoire de structure et propriétés. The concepts of physical metallurgy are thus necessary to extra- polate the rheological laws obtained

Paris-Sud XI, Université de

360

Iowa Powder Atomization Technologies  

SciTech Connect

The same atomization effect seen in a fuel injector is being applied to titanium metal resulting in fine titanium powders that are less than half the width of a human hair. Titanium melts above 3,000°F and is highly corrosive therefore requiring specialized containers. The liquid titanium is poured through an Ames Laboratory - USDOE patented tube which is intended to increase the energy efficiency of the atomization process, which has the ability to dramatically decrease the cost of fine titanium powders. This novel process could open markets for green manufacturing of titanium components from jet engines to biomedical implants.

None

2012-01-01

361

Structure-property relations for monotonic and fatigue loading conditions for a powder metal steel  

NASA Astrophysics Data System (ADS)

Developing a multi-scale math-based model for powder metallurgy (PM) component design and performance prediction requires experimental calibration and validation. Monotonic tension, compression and torsion tests were performed at various porosity and temperatures to obtain the set of plasticity and damage constants required for model calibration. Uniaxial fatigue experiments were performed to determine the constants required for capturing the low cycle and high cycle fatigue characteristics of a PM steel. Optical microscopy of the material was performed prior to testing to quantify the initial state microstrucutral characteristics of each specimen. Tension tests on two different Bridgman notched specimens were undertaken to study the damage-triaxiality dependence for model validation. Validation of the model was further performed by monotonic component testing using PM bearing caps. Fracture surface analysis was performed using Scanning Electron Microscopy (SEM) to quantify the void nucleation and void sizes of the different specimens. The developed model will be used for optimizing component performance and design for PM parts. Key words: Powder Metallurgy, FC-0205, Mechanical Testing, Fatigue

Allison, Paul Galon

362

Production and properties of flat ceramic microfiltration membranes made of {alpha}-Al{sub 2}O{sub 3} powders  

SciTech Connect

Ceramic membranes are widely used to purify, separate, fractionate, and concentrate aggressive solutions and mixtures of components of different compositions and chemistry. Microfiltration membranes can be obtained by different methods in ceramics technology and powder metallurgy by varying the forming technique (pressing of powders, slip casting, etc.), the dispersity of the initial components, and production conditions. When relatively large flat ceramic microfiltration membranes are being made, it is difficult to attain a high porosity with a narrow pore-size distribution and achieve good permeability along with satisfactory mechanical properties. We have developed a technology for producing such membranes by using dispersed powders of aluminum oxide. Different forming methods are used in the process.

Bryk, M.T.; Volkova, A.P.; Klimenko, A.V. [Institute of Colloid and Water Chemistry, Kiev (Ukraine)]|[Institute of Problems of Materials Science, Kiev (Ukraine)] [and others

1995-03-01

363

High-temperature metallurgy of advanced borated stainless steels  

SciTech Connect

The high-temperature metallurgy of advanced borated stainless steels has been evaluated through differential thermal analysis, aging studies, quantitative metallography, and impact toughness measurements. Differential thermal analysis (DTA) was conducted on alloys containing a range of boron concentrations and was used to determine the temperatures associated with melting/solidification reactions. Aging studies, conducted at temperatures near the solidus, were used to determine the effects of elevated temperature exposures on impact properties and microstructure. Differential thermal analysis quantified the solidus and liquidus temperatures as a function of boron concentration. Impact testing of samples aged at temperatures near the solidus indicated only moderate reductions in toughness. Particle shape measurements indicated that the boride particles were initially nearly spherical and remained so during elevated temperature exposure, although some faceting and agglomeration of the borides did occur. Measurements of boride particle size distributions were used to define the time, temperature, and composition dependence of the boride coarsening. Coarsening data were analyzed in terms of current coarsening models. These analyses indicated that the boride particle coarsening followed the theoretically predicted t{sup 1/3} time dependence and that the coarsening rate increased with increasing volume fraction of the boride phase. Analysis of the particle size data for aging at various temperatures indicated that the boride coarsening was consistent with the activation energy for Cr diffusion in austenite. Scanning electron microscopy of the impact fracture surfaces showed that the failure mode in isothermally heat-treated samples was ductile and essentially identical to the failure mode for as-received material. The steels are important because of their use in the nuclear industry.

Robino, C.V.; Cieslak, M.J. [Sandia National Labs., Albuquerque, NM (United States). Physical and Joining Metallurgy Dept.

1995-07-01

364

4600 S. Ulster St. Suite 700 Denver, Colorado 80237 (303) 740-6750 Fax (303) 740-6789 Metallurgy and Corrosion Consulting  

E-print Network

Metallurgy and Corrosion Consulting Bruce Craig is the author and contributing author of more than seven metallurgy for projects ranging from Mobile Bay to the deep water GOM, the Rockies to Asia and the Middle independents. Dr Craig is the president of MetCorr, a corrosion and metallurgy consulting company located

Botte, Gerardine G.

365

Dielectric Constant of Powders  

Microsoft Academic Search

MEASUREMENTS have been made at 9,200 Mc\\/s to determine the dependence of dielectric constant of powder samples' packing densities. The net polarization P produced in a substance in an electric field consists of the contributions of electronic, atomic and dipolar polarizations. It is related to the dielectric constant by Clausius-Masotti relation: where K = (? - l)\\/(? + 2), M

Prem Swarup; R. P. Arora

1964-01-01

366

Spiral Powder Overlays  

E-print Network

Whether you encounter electron powder diffraction patterns everyday, or run across them only rarely, interpreting them may require a bit of preparation. But it's easy to lose track of the numbers for your microscope's camera constant, not to mention the bewildering array of lattice parameters and symmetries that one may encounter in the microscope. In that context, we describe

P. Fraundorf; Shuhan Lin

367

Sintering of Tin Powder  

Microsoft Academic Search

MOST powdered metals will sinter together appreciably when heated to a temperature which, in the absence of extraneous factors, is about three-quarters of their absolute melting point; metals of low melting point tend to be exceptions, however, to this generalization in that they can be heated nearly to their melting point before sintering takes place. There is no evidence, in

R. F. Smart; E. C. Ellwood

1958-01-01

368

Demystifying Mystery Powders.  

ERIC Educational Resources Information Center

Describes science activities which use simple chemical tests to distinguish between materials and to determine some of their properties. Explains the water, iodine, heat, acid, baking soda, acid/base indicator, glucose, and sugar tests. Includes activities to enhance chemical testing and a list of suggested powders for use. (RT)

Kotar, Michael

1989-01-01

369

Laser powder deposition  

Microsoft Academic Search

Purpose – The purpose of this paper is to review the state of the art of laser powder deposition (LPD), a solid freeform fabrication technique capable of fabricating fully dense functional items from a wide range of common engineering materials, such as aluminum alloys, steels, titanium alloys, nickel superalloys and refractory materials. Design\\/methodology\\/approach – The main R&D efforts and the

Lino Costa; Rui Vilar

2009-01-01

370

Ti(C,N) cermets — Metallurgy and properties  

Microsoft Academic Search

An overview of the metallurgical reactions during the vacuum sintering process of powder mixtures for the manufacture of cermets is presented. The relatively complex phase reactions in the multi-component system Ti\\/Mo\\/W\\/Ta\\/Nb\\/C,N-Co\\/Ni are discussed. The liquid binder phase reacts with titanium carbonitride by preferentially dissolving titanium carbide leaving titanium nitride undissolved. The compositions and the amounts of the gas species set

P. Ettmayer; H. Kolaska; W. Lengauer; K. Dreyer

1995-01-01

371

Processing map for controlling microstructure in hot working of hot isostatically pressed powder metallurgy NIMONIC AP-1 superalloy  

NASA Astrophysics Data System (ADS)

The hot deformation behavior of hot isostatically pressed (HIP) NIMONIC AP-1 superalloy is characterized using processing maps in the temperature range 950 °C to 1200 °C and strain rate range 0.001 to 100 s•1. The dynamic materials model has been used for developing the pro-cessing maps which show the variation of the efficiency of power dissipation given by [2m / ( m + 1)] with temperature and strain rate, with m being the strain rate sensitivity of flow stress. The processing map revealed a domain of dynamic recrystallization with a peak efficiency of 40 pct at 1125 °C and 0.3 s•1, and these are the optimum parameters for hot working. The microstructure developed under these conditions is free from prior particle boundary (PPB) de-fects, cracks, or localized shear bands. At 100 s•1 and 1200 °C, the material exhibits inter-crystalline cracking, while at 0.001 s•1, the material shows wedge cracks at 1200 °C and PPB cracking at 1000 °C. Also at strain rates higher than 10 s•1, adiabatic shear bands occur; the limiting conditions for this flow instability are accurately predicted by a continuum criterion based on the principles of irreversible thermodynamics of large plastic flow.

Somani, M. C.; Rao, E. S. Bhagiradha; Birla, N. C.; Bhatia, M. L.; Singh, Vakil; Prasad, Y. V. R. K.

1992-10-01

372

High-strain-rate superplasticity at low temperature in a ZK61 magnesium alloy produced by powder metallurgy  

Microsoft Academic Search

In the present study, superplastic behavior of a pseudo single phase magnesium alloy, ZK61, was investigated at about half the absolute melting point. The material was produced by the P\\/M route, and had a fine grain size of [approximately]500 nm. It is demonstrated that the P\\/M ZK61 alloy can behave in a superplastic manner at a high strain rate of

Hiroyuki Watanabe; Toshiji Mukai; Mamoru Mabuchi; Kenji Higashi

1999-01-01

373

Optimization of bond strength between gold alloy and porcelain through a composite interlayer obtained by powder metallurgy  

Microsoft Academic Search

The purpose of this study was to evaluate the influence of a composite interlayer (at the metal–ceramic interface) on the shear bond strength of a metal–ceramic composite when compared with a conventional porcelain fused to metal (PFM).Several metal–ceramic composites specimens were produced by hot pressing. To identify which was the best composition for the interlayer several composites, with different relations

B. Henriques; D. Soares; F. S. Silva

2011-01-01

374

Explosive reaction pressing of intermetallic compounds from stoichiometric powder mixtures  

SciTech Connect

Intermetallic NiAl, TiAl, and TiAl{sub 3} were synthesized by shock compression experiments from stoichiometric powder mixtures of nickel and aluminium as well as of titanium and aluminium. Good consolidation and complete intermetallic reaction were achieved by the direct method of explosive compaction. For each powder mixture, a certain individual threshold pressure has to be exceeded in order to initiate intermetallic reaction. The reacting compounds melted completely with subsequent rapid solidification during the passage of the shock wave. The new material shows high hardness. Pores are formed by gaseous reaction products in the NiAl and TiAl{sub 3} compacts. The TiAl structure is fully-dense and dendritic.

Kochsiek, D.; Pruemmer, R.; Brunold, A. [Ernst-Mach-Institut of the Fraunhofer Research Association, Freiburg (Germany)

1995-09-01

375

Compact turbidity meter  

NASA Technical Reports Server (NTRS)

Proposed monitor that detects back-reflected infrared radiation makes in situ turbidity measurements of lakes, streams, and other bodies of water. Monitor is compact, works well in daylight as at night, and is easily operated in rough seas.

Hirschberg, J. G.

1979-01-01

376

Compact Disc Interactive.  

ERIC Educational Resources Information Center

This overview of a digital optical storage medium with a multimedia capability includes a global description of specifications, current status, and elements required to make a CD-I (compact disk interactive) launch possible. (Author/CLB)

Valk, Anton

1987-01-01

377

Countable choice and compactness  

Microsoft Academic Search

We work in set-theory without choice ZF. Denoting by AC(N) the countable axiom of choice, we show in ZF+AC(N) that the closed unit ball of a uniformly convex Banach space is compact in the convex topology (an alternative to the weak topology in ZF). We prove that this ball is (closely) convex-compact in the convex topology. Given a set I,

Marianne Morillon

2008-01-01

378

A new approach for instruction in powder crystallography.  

SciTech Connect

A series of Internet-distributed audio/visual recordings for learning crystallographic analysis of powder diffraction data is discussed. These recordings provide a compact mechanism for distributing educational information. Such presentations provide hands-on discussion beyond what is usually presented in instructional texts. In some cases similar material can be presented with HTML text, but recordings can be created with significantly less effort and are superior for software demonstration.

Toby, B.; X-Ray Science Division

2007-03-01

379

Method to blend separator powders  

DOEpatents

A method for making a blended powder mixture, whereby two or more powders are mixed in a container with a liquid selected from nitrogen or short-chain alcohols, where at least one of the powders has an angle of repose greater than approximately 50 degrees. The method is useful in preparing blended powders of Li halides and MgO for use in the preparation of thermal battery separators.

Guidotti, Ronald A. (Albuquerque, NM); Andazola, Arthur H. (Albuquerque, NM); Reinhardt, Frederick W. (Albuquerque, NM)

2007-12-04

380

Powdering or spraying.  

PubMed

Application--especially in combination with the new camera--is so easy and advantageous that it has advanced to become the standard procedure in our practice. Potential for improvement still exists in the stiffness of the cannula, in a release mechanism located separately from the cannula and in the impudent demand to completely do away with powder and spray. Despite announcements to the contrary by alternative systems, the fulfilment of this desire appears to be a long way off. PMID:19213361

Reiss, B

2009-01-01

381

Sintering Behavior of Hypereutectic Aluminum-Silicon Metal Matrix Composites Powder  

NASA Astrophysics Data System (ADS)

Lightweight materials of Aluminum-Silicon P/M alloys offer the advantage of high-wear resistance, high strength, good temperature resistance, and a low coefficient of thermal expansion. An A359 MMC alloy was mixed together with Alumix 231 in this research. Powders were compacted with compaction pressure up to 700 MPa. Particle size and compaction pressure influenced green density. Compacted powders were sintered in a tube furnace under a flowing nitrogen gas. Sintering temperature, heating rate and sintering time were verified to determine best sintering conditions of the alloys. Chemical composition also contributed to gain higher sintered density. Precipitation strengthening method was used to improve mechanical properties of this materials.T6 heat treatment was carried out to produce fine precipitates to impede movement of dislocation. The chemical composition of this materials allow for the potential formation of several strengthening precipitates including ? (Al2Cu) and ? (Mg2Si).

Rudianto, Haris; Sun, Yang Sang; Jin, Kim Yong; Woo, Nam Ki

382

Cerium (IV) oxide synthesis and sinterable powders prepared by the polymeric organic complex solution method  

Microsoft Academic Search

Three processing methods making use of different cations complexant as citric acid (CA), polyvinylalcohol (PVA) or polyethylene glycol (PEG) have been used to prepare high purity fine CeO2 powder with different particle size and agglomeration degrees. Green compacts prepared from the differently agglomerated powders were studied by Hg-porosimetry, and pore-size distribution curves were taken to compare the uniformity of the

Pedro Durán; Francisco Capel; Dionisio Gutierrez; Jesús Tartaj; Carlos Moure

2002-01-01

383

Densification behavior of 316L stainless steel powder under high temperature  

Microsoft Academic Search

Densification behavior of 316L stainless steel powder was investigated during pressureless sintering, sinter forging and hot isostatic pressing. Experimental data were compared with finite element calculations by using the constitutive models of Abouaf and co-workers and of McMeeking and co-workers. Densification of a stainless steel powder compact in a stainless steel container was studied under hot isostatic pressing. Due to

K. T Kim; Y. C Jeon

1998-01-01

384

Physically Detached "Compact Groups"  

E-print Network

A small fraction of galaxies appear to reside in dense compact groups, whose inferred crossing times are much shorter than a Hubble time. These short crossing times have led to considerable disagreement about the dynamical state of these systems. We suggest that many of the observed groups are not physically bound but are chance projections of galaxies well-separated along the line of sight. Unlike earlier similar proposals, ours does not require that the galaxies in the compact group be members of a more diffuse, but physically bound entity. The probability of physically separated galaxies projecting into an apparent compact group is non-negligible if most galaxies are distributed, as observed, in thin filaments. We illustrate this general point with a specific example: a simulation of a cold dark matter universe, in which hydrodynamic effects are included to identify galaxies. The simulated galaxy distribution is filamentary, and end-on views of these filaments produce apparent galaxy associations that have sizes and velocity dispersions similar to those of observed compact groups. The frequency of such projections can explain the observed space-density of groups in the Hickson catalog. We discuss the implications of our proposal for the formation and evolution of groups and elliptical galaxies. The proposal can be tested by using redshift-independent distance estimators to measure the line-of-sight spatial extent of nearby compact groups.

Lars Hernquist; Neal Katz; David Weinberg

1994-07-20

385

The Application of Thermal Plasma to Extraction Metallurgy and Related Fields  

NASA Technical Reports Server (NTRS)

Various applications of thermal plasma to extraction metallurgy and related fields are surveyed, chiefly on the basis of documents published during the past two or three years. Applications to melting and smelting, to thermal decomposition, to reduction, to manufacturing of inorganic compounds, and to other fields are considered.

Akashi, K.

1980-01-01

386

The Origins of Metallurgy: Distinguishing Stone from Metal Cut-marks on Bones from Archaeological Sites  

Microsoft Academic Search

This paper presents an analytical procedure for identifying and mapping the introduction and spread of metallurgy to regions based upon the relative frequency of metal versus stone tool slicing cut-marks in butchered animal bone assemblages. The author conducted experiments to establish the relationship between the edge characteristics of metal and stone tools that create slicing cut-marks and the marks they

Haskel J. Greenfield

1999-01-01

387

Conversion of the under bump metallurgy into intermetallics: the impact on flip chip reliability  

Microsoft Academic Search

In high temperature applications, the conversion of the under bump metallurgy (UBM) into UBM-Sn intermetallics can ultimately limit the reliability of flip chip components. Here, an intermetallic growth model characterizing the rate of electrical failure to the rate of UBM consumption is developed which derives a relationship between field reliability and accelerated temperature tests. For a flip chip structure employing

Frank Stepniak

2001-01-01

388

Intensive Pre-Incan Metallurgy Recorded by Lake Sediments from the Bolivian Andes  

Microsoft Academic Search

The history of pre-Columbian metallurgy in South America is incomplete be- cause looting of metal artifacts has been pervasive. Here, we reconstruct a millennium of metallurgical activity in southern Bolivia using the stratigraphy of metals associated with smelting (Pb, Sb, Bi, Ag, Sn) from lake sediments deposited near the major silver deposit of Cerro Rico de Potosi ´. Pronounced metal

Mark B. Abbott; Alexander P. Wolfe

2003-01-01

389

University of Cambridge, Materials Science & Metallurgy H. K. D. H. Bhadeshia Other Techniques  

E-print Network

University of Cambridge, Materials Science & Metallurgy H. K. D. H. Bhadeshia Other Techniques Thermogravimetry Thermogravimetry (TG) is a technique by which the weight of a substance, in an environment heated recording system. The assembly has to be capable of continuously registering any weight changes in the test

Cambridge, University of

390

Biomimetic scaling of mechanical behavior of thin films, coatings, and surfaces by Laser Interference Metallurgy  

Microsoft Academic Search

Biological solutions to enhance strength and stability often use hierarchical composite structures. The effect is not based on large chemical variations, but instead is realized by structural composites with long-range order. Laser Interference Metallurgy is a newly developed technique that utilizes this biological approach to optimize the mechanical properties of surfaces and thin films. The possibility of scaling mechanical properties

Claus Daniel; Thomas John Balk; Thomas Wobben; Frank Mcklich

2005-01-01

391

A Guide for Planning Facilities for Occupational Preparation Programs in Metallurgy Technology. Interim Report. Research 28.  

ERIC Educational Resources Information Center

The major purpose of this guide is to elicit the information necessary for writing educational specifications for facilities to house technical education programs in metallurgy. It is organized in these parts: (1) Part I discusses the major purpose, underlying assumptions, recent instructional trends, and guiding principles utilized in the…

German, Carl, Jr.

392

Part II Materials Science and Metallurgy Example of a Literature Survey  

E-print Network

. Property References Damage summation [1] Hardness [2] Tensile test [3] Interparticle spacing [4] CavitationPart II Materials Science and Metallurgy Example of a Literature Survey Power Plant Steels enough to describe the steel with all requisite completeness. However, the present survey is confined

Cambridge, University of

393

Preparation of superconductor precursor powders  

DOEpatents

A process for the preparation of a precursor metallic powder composition for use in the subsequent formation of a superconductor. The process comprises the steps of providing an electrodeposition bath comprising an electrolyte medium and a cathode substrate electrode, and providing to the bath one or more soluble salts of one or more respective metals which are capable of exhibiting superconductor properties upon subsequent appropriate treatment. The bath is continually energized to cause the metallic and/or reduced particles formed at the electrode to drop as a powder from the electrode into the bath, and this powder, which is a precursor powder for superconductor production, is recovered from the bath for subsequent treatment. The process permits direct inclusion of all metals in the preparation of the precursor powder, and yields an amorphous product mixed on an atomic scale to thereby impart inherent high reactivity. Superconductors which can be formed from the precursor powder include pellet and powder-in-tube products.

Bhattacharya, Raghunath (Littleton, CO)

1998-01-01

394

Soil compaction verification  

SciTech Connect

While conducting their maintenance activities, utilities must break and restore pavement. During pavement restoration it is vitally important to ensure adequate compaction of the soil. To ensure that specified standards are met, tests have evolved that are well-suited to highway construction, but poorly suited to utility operations. A novel approach that attempts to address this problem is being tested. In the course of an intensive experimental effort it was found that relatively simple, inexpensive devices could be used to verify compaction in a wide variety of soils. Further confirmatory work has been scheduled.

Todres, H.A.

1986-01-01

395

Nanocrystalline TiAl compacts prepared by HDDR and hot pressing  

SciTech Connect

Nanocrystalline TiAl powder was formed by the modified HDDR (hydrogenation-disproportion-dehydrogenation-recombination) method utilizing ball milling in a hydrogen atmosphere. That is, TiAl compound powder decomposed into TiH{sub 2} and Al-rich TiAl powders by mechanical grinding in a hydrogen atmosphere (HD process). Dehydrogenation-recombination (realloying) resulted in the formation of nanocrystalline TiAl powder when heated to about 700 K in an argon atmosphere (DR process). Almost fully dense nanocrystalline TiAl compacts were prepared by a combination of HDDR and hot-pressing at 873 K which is lower than the usual consolidation temperature by about 300 K. The TiAl compact thus made was brittle in the as-pressed state but showed compressive ductility after annealing.

Aoki, K.; Itoh, Y.; Kawamura, Y.; Inoue, A.; Masumoto, T. [Tohoku Univ., Sendai (Japan)

1997-12-31

396

Powder Processing of High Temperature Cermets and Carbides at Marshall Space Flight Center  

NASA Technical Reports Server (NTRS)

The Materials and Processing Laboratory at NASA Marshall Space Flight Center is developing Powder Metallurgy (PM) processing techniques for high temperature cermet and carbide material consolidation. These new group of materials would be utilized in the nuclear core for Nuclear Thermal Rockets (NTR). Cermet materials offer several advantages for NTR such as retention of fission products and fuels, better thermal shock resistance, hydrogen compatibility, high thermal conductivity, and high strength. Carbide materials offer the highest operating temperatures but are sensitive to thermal stresses and are difficult to process. To support the effort, a new facility has been setup to process refractory metal, ceramic, carbides and depleted uranium-based powders. The facility inciudes inert atmosphere glove boxes for the handling of reactive powders, a high temperature furnace, and powder processing equipment used for blending, milling, and sieving. The effort is focused on basic research to identify the most promising compositions and processing techniques. Several PM processing methods including Cold and Hot Isostatic Pressing are being evaluated to fabricate samples for characterization and hot hydrogen testing.

Salvail, Pat; Panda, Binayak; Hickman, Robert R.

2007-01-01

397

Spatio-temporal dynamics behind the shock front from compacted metal nanopowders.  

PubMed

Laser ablated shock waves from compacted metal nanoenergetic powders of Aluminum (Al), Nickel coated Aluminum (Ni-Al) was characterized using shadowgraphy technique and compared with that from Boron Potassium Nitrate (BKN), Ammonium Perchlorate (AP) and Potassium Bromide (KBr) powders. Ablation is created by focused second harmonic (532 nm, 7 ns) of Nd:YAG laser. Time resolved shadowgraphs of propagating shock front and contact front revealed dynamics and the precise time of energy release of materials under extreme ablative pressures. Among the different compacted materials studied, Al nanopowders have maximum shock velocity and pressure behind the shock front compared to others. PMID:24922235

Leela, Ch; Venkateshwarlu, P; Singh, Raja V; Verma, Pankaj; Kiran, P Prem

2014-03-10

398

Bend strengths of reaction bonded silicon nitride prepared from dry attrition milled silicon powder  

NASA Technical Reports Server (NTRS)

Dry attrition milled silicon powder was compacted, sintered in helium, and reaction bonded in nitrogen-4 volume percent hydrogen. Bend strengths of bars with as-nitrided surfaces averaged as high as 210 MPa at room temperature and 220 MPa at 1400 C. Bars prepared from the milled powder were stronger than those prepared from as-received powder at both room temperature and at 1400 C. Room temperature strength decreased with increased milling time and 1400 C strength increased with increased milling time.

Herbell, T. P.; Glasgow, T. K.

1979-01-01

399

Compact Ultradense Matter Impactors  

NASA Astrophysics Data System (ADS)

We study interactions of meteorlike compact ultradense objects (CUDO), having nuclear or greater density, with Earth and other rocky bodies in the Solar System as a possible source of information about novel forms of matter. We study the energy loss in CUDO puncture of the body and discuss differences between regular matter and CUDO impacts.

Rafelski, Johann; Labun, Lance; Birrell, Jeremiah

2013-03-01

400

Threads in compact semigroups  

Microsoft Academic Search

In this note we show that if S is a compact connected topological semigroup with unit, in which each subgroup is totally disconnected, then S contains a standard thread which meets the minimal ideal K and contains the unit. This is an extension of a previous result of the author [5] in which threads are constructed in partially ordered semigroups

Robert J. Koch

1964-01-01

401

NSTX LTXPEGASUS Compact CTF  

E-print Network

ST-PoP NSTX LTXPEGASUS ST-DEMO ARIES-ST Compact CTF ST-CTF ST-PE NHTX Spherical Torus Fusion;Investigating Innovative Solutions for NHTX/CTF and DEMO NSTX with ITER-level heat flux PEGASUS Gun Start-ST) at 3 - 4 MA range provides cost effective physics / technology basis in support for CTF and DEMO

Princeton Plasma Physics Laboratory

402

Limestone compaction: an enigma  

USGS Publications Warehouse

Compression of an undisturbed carbonate sediment core under a pressure of 556 kg/cm2 produced a “rock” with sedimentary structures similar to typical ancient fine-grained limestones. Surprisingly, shells, foraminifera, and other fossils were not noticeably crushed, which indicates that absence of crushed fossils in ancient limestones can no longer be considered evidence that limestones do not compact.

Shinn, Eugene A.; Halley, Robert B.; Hudson, J. Harold; Lidz, Barbara H.

1977-01-01

403

Compact fusion reactors  

SciTech Connect

Compact, high-power-density approaches to fusion power are proposed to improve economic viability through the use of less-advanced technology in systems of considerably reduced scale. The rationale for and the means by which these systems can be achieved are discussed, as are unique technological problems.

Krakowski, R.A.; Hafenson, R.L.

1983-09-01

404

Compact fusion reactors  

SciTech Connect

Compact, high-power-density approaches to fusion power are proposed to improve economic viability through the use of less-advanced technology in systems of considerably reduced scale. The rationale for and the means by which these systems can be achieved are discussed, as are unique technological problems.

Krakowski, R.A.; Hagenson, R.L.

1983-01-01

405

Fuel assembly skeleton compaction  

Microsoft Academic Search

The fuel assembly skeleton compaction system provides a means for remotely dismantling an irradiated nuclear fuel assembly skeleton once the nuclear fuel rods have been removed therefrom while the skeleton remains submerged in a coolant. The system comprises a feed chamber for holding the spent fuel assembly skeleton and for feeding a spent fuel assembly skeleton into a shear chamber

J. J. Wilhelm; R. F. Antol; A. Kapoor; R. M. Kobuck; G. W. Norris

1985-01-01

406

Artificial stone slab production using waste glass, stone fragments and vacuum vibratory compaction  

Microsoft Academic Search

In this research, waste glass and stone fragments from stone slab processing are recycled as raw materials for making artificial stone slabs using vibratory compaction in a vacuum environment. Waste glass powder (40%) and fine granite aggregates (60%) are mixed with unsaturated polymer resins (8%) as binder. Under compaction pressure of 14.7MPa, vibration frequency of 33.3Hz and vacuum condition at

Ming-Yu Lee; Chun-Han Ko; Fang-Chih Chang; Shang-Lien Lo; Jyh-Dong Lin; Ming-Yang Shan; Jeng-Ching Lee

2008-01-01

407

COMPACT FACTORS IN FINALLY COMPACT PRODUCTS OF TOPOLOGICAL SPACES  

E-print Network

COMPACT FACTORS IN FINALLY COMPACT PRODUCTS OF TOPOLOGICAL SPACES Paolo Lipparini We present that if a product is regu- lar and Lindel¨of then all but at most countably many factors are compact. We generalize that if a product of topological spaces is Lindel¨of then each factor is Lindel¨of. What is relevant to the present

Lipparini, Paolo

408

MAZUR INTERSECTION PROPERTIES FOR COMPACT AND WEAKLY COMPACT CONVEX SETS  

Microsoft Academic Search

Various authors have studied when a Banach space can be renormed so that every weakly compact convex, or less restrictively every compact convex set is an intersection of balls. We first observe that each Banach space can be renormed so that every weakly compact convex set is an intersection of balls, and then we introduce and study properties that are

JON VANDERWERFF

1998-01-01

409

Preliminary attempt at sintering an ultrafine alumina powder using microwaves. Master's thesis  

SciTech Connect

A commercially available microwave oven was used to sinter ultrafine alumina powders (0.02 - 0.05 micrometers particle size) with and without CaO sintering aid. The oven was modified by inserting a thermocouple probe through the bottom housing, and thoroughly insulating the interior with insulating material. The oven was placed in a glove box and filled with argon to prevent degradation of the thermocouple, and oxidation of the powdered graphite susceptor. Heating rates of 50-75 Deg C/sec with a maximum temperature of 1575 Deg C were obtained. Limited success in sintering of the the powder compacts was achieved in this preliminary effort. The microstructures of the sintered products were examined by scanning electron microscopy. It was concluded that further work is necessary to develop this technique into one which can be used for the routine sintering of fine powdered ceramic material. A review of the literature on microwave sintering of ceramic powders is also reported.

Alhambra, E.M.

1994-09-01

410

Polymer powder prepregging: Scoping study  

NASA Technical Reports Server (NTRS)

Early on, it was found that NEAT LARC-TPI thermoplastic polyimide powder behaved elastoplastically at pressures to 20 ksi and temperatures to 260 degrees celcius (below MP). At high resin assay, resin powder could be continuously cold-flowed around individual carbon fibers in a metal rolling mill. At low resin assay (2:1, C:TPI), fiber breakage was prohibitive. Thus, although processing of TPI below MP would be quite unique, it appears that the polymer must be melted and flowed to produce low resin assay prepreg. Fiber tow was spread to 75 mm using a venturi slot tunnel. This allowed intimate powder/fiber interaction. Two techniques were examined for getting room temperature powder onto the room temperature fiber surface. Electrostatic powder coating allows the charged powder to cling tenaciously to the fiber, even while heated with a hot air gun to above its melt temperature. A variant of the wet slurry coating process was also explored. The carbon fibers are first wetted with water. Then dry powder is sprinkled onto the wet tow and doctor-rolled between the fibers. The wet structure is then taken onto a heated roll, with hot air guns drying and sinter-melting the powder onto the fiber surfaces. In both cases SEM shows individual fibers coated with powder particles that have melted in place and flowed along the fiber surface via surface tension.

Throne, James L.

1988-01-01

411

A pedagogical history of compactness  

E-print Network

This paper traces the history of compactness from the original motivating questions, through the development of the definition, to a generalization of sequential compactness in terms of nets and filters.

Sundstrom, Manya Raman

2010-01-01

412

Super-Compact Laser  

NASA Technical Reports Server (NTRS)

Microcosm, Inc. produced the portable Farfield-2 laser for field applications that require high power pulsed illumination. The compact design was conceived through research at Goddard Space Flight Center on laser instruments for space missions to carry out geoscience studies of Earth. An exclusive license to the key NASA patent for the compact laser design was assigned to Microcosm. The FarField-2 is ideal for field applications, has low power consumption, does not need water cooling or gas supplies, and produces nearly ideal beam quality. The properties of the laser also make it effective over long distances, which is one reason why NASA developed the technology for laser altimeters that can be toted aboard spacecraft. Applications for the FarField-2 include medicine, biology, and materials science and processing, as well as diamond marking, semiconductor line-cutting, chromosome surgery, and fluorescence microscopy.

1997-01-01

413

Compact spreader schemes  

NASA Astrophysics Data System (ADS)

This paper describes beam distribution schemes adopting a novel implementation based on low amplitude vertical deflections combined with horizontal ones generated by Lambertson-type septum magnets. This scheme offers substantial compactness in the longitudinal layouts of the beam lines and increased flexibility for beam delivery of multiple beam lines on a shot-to-shot basis. Fast kickers (FK) or transverse electric field RF Deflectors (RFD) provide the low amplitude deflections. Initially proposed at the Stanford Linear Accelerator Center (SLAC) as tools for beam diagnostics and more recently adopted for multiline beam pattern schemes, RFDs offer repetition capabilities and a likely better amplitude reproducibility when compared to FKs, which, in turn, offer more modest financial involvements both in construction and operation. Both solutions represent an ideal approach for the design of compact beam distribution systems resulting in space and cost savings while preserving flexibility and beam quality.

Placidi, M.; Jung, J.-Y.; Ratti, A.; Sun, C.

2014-12-01

414

Near-net-shape forming of alumina powder under hot pressing and hot isostatic pressing  

Microsoft Academic Search

Densification and deformation of alumina powder under hot pressing and hot isostatic pressing were investigated. Finite element calculations were performed by implementing constitutive equations for grain growth, power law creep and diffusional creep in the user defined subroutine CREEP of ABAQUS. An alumina compact of valve head shape was produced under hot pressing and its forming process was predicted by

K. T. Kim; Y. S. Kwon; H. G. Kim

1997-01-01

415

Apollo 12 Seismic Signal: Indication of a Deep Layer of Powder  

Microsoft Academic Search

The seismic signal caused by the Apollo 12 lunar module is interpreted in terms of propagation between source and receiver through a layer of powder in which sound velocity increases with depth. This increase, which is due to compaction, extends over several kilometers and leads to a concentration of seismic waves toward the surface. Computer simulations with the use of

Thomas Gold; Steven Soter

1970-01-01

416

Predicting the shock compression response of heterogeneous powder mixtures  

NASA Astrophysics Data System (ADS)

A model framework for predicting the dynamic shock-compression response of heterogeneous powder mixtures using readily obtained measurements from quasi-static tests is presented. Low-strain-rate compression data are first analyzed to determine the region of the bulk response over which particle rearrangement does not contribute to compaction. This region is then fit to determine the densification modulus of the mixture, ?D, an newly defined parameter describing the resistance of the mixture to yielding. The measured densification modulus, reflective of the diverse yielding phenomena that occur at the meso-scale, is implemented into a rate-independent formulation of the P-? model, which is combined with an isobaric equation of state to predict the low and high stress dynamic compression response of heterogeneous powder mixtures. The framework is applied to two metal + metal-oxide (thermite) powder mixtures, and good agreement between the model and experiment is obtained for all mixtures at stresses near and above those required to reach full density. At lower stresses, rate-dependencies of the constituents, and specifically those of the matrix constituent, determine the ability of the model to predict the measured response in the incomplete compaction regime.

Fredenburg, D. A.; Thadhani, N. N.

2013-06-01

417

Compact toroid formation experiments  

Microsoft Academic Search

Summary form only given, as follows. A compact toroid (CT) formation experiment is discussed. The device has coaxial electrode diameters of 0.9 m (inner) and 1.25 m (outer) and an electrode length of ~1.2 m, including an expansion drift section. The CT is formed by a 0.1-0.2-T initial radial magnetic field embedded coaxial puff gas discharge. The gas puff is

J. H. Degnan; G. P. Baca; J. D. Beason; M. E. Dearborn; D. Dietz; K. E. Hackett; J. L. Holmes; B. W. Mullins; J. L. Mullins; E. L. Ruden; D. W. Price; C. R. Sovinec; D. Gale; J. D. Graham; D. Ralph; M. Scott; W. Sommars; G. Bird; S. K. Coffey; S. W. Seiler; G. F. Kiuttu; R. E. Peterkin; N. F. Roderick; P. Turchi

1990-01-01

418

Compact infrared detector  

NASA Technical Reports Server (NTRS)

Broadband IR detector integrated into compact package for pollution monitoring and weather prediction is small, highly responsive, and immune to high noise. Sensing material is transparent sheet metalized with reflecting coating and overcoated with black material on same side. Pulse produced by chopping of infrared source beam creates transient "thermal lens" that temporarily defocuses laser beam probe. Detector monitoring beam measures defocusing which parallels infrared intensity.

Gupta, A.; Hong, S.; Moacanin, J.

1981-01-01

419

Estimation and characterization of polycyclic aromatic hydrocarbons from magnesium metallurgy facilities in China.  

PubMed

Field monitoring was conducted to develop a polycyclic aromatic hydrocarbon (PAH) emission inventory for the magnesium (Mg) metallurgy industry in China. PAH emissions in stack gas and fly/bottom ash samples from different smelting units of a typical Mg smelter were measured and compared. Large variations of concentrations, congener patterns, and emission factors of PAHs during the oxidation and reduction stages in the Mg smelter were observed. The measured average emission factor (166,487 ?g/t Mg) was significantly higher than those of other industrial sources. Annual emission from Mg metallurgy in 2012 in China was estimated at 116 kg (514 g BaPeq) for PAHs. The results of this study suggest that PAH emission from Mg industries should be considered by local government agencies. These data may be helpful for understanding PAH levels produced by the Mg industry and in developing a PAH inventory. PMID:24958530

Nie, Zhiqiang; Yang, Yufei; Tang, Zhenwu; Liu, Feng; Wang, Qi; Huang, Qifei

2014-11-01

420

Powdered resin for condensate polishing  

Microsoft Academic Search

Powdered resin systems have a lot to offer in the deionization of low TDS waters, as can be seen in the wide use of this process for the treatment of condensate in the electric power industry. I believe that as new ion-exchange resins are developed, we will see the powdered ion-exchange resin process adopted in other industries. At this time,

Richard Hetherington

1997-01-01

421

Baking powder pica mimicking preeclampsia.  

PubMed

We report a case of baking powder pica during pregnancy that was associated with maternal hypertension, hypokalemia, and elevated liver function tests. After discontinuation of baking powder ingestion and correction of electrolyte abnormalities, the blood pressure and the liver function tests normalized. PMID:1442966

Barton, J R; Riely, C A; Sibai, B M

1992-07-01

422

Characterization of lead-free solders and under bump metallurgies for flip-chip package  

Microsoft Academic Search

A variety of Pb-free solders and under bump metallurgies (UBMs) was investigated for flip chip packaging applications. The result shows that the Sn-0.7Cu eutectic alloy has the best fatigue life and it possess the most desirable failure mechanism in both thermal and isothermal mechanical tests regardless of UBM type. Although the electroless Ni-P UBM has a much slower reaction rate

Jong-Kai Lin; Ananda De Silva; Darrel Frear; Yifan Guo; Jin-Wook Jang; Li Li; D. Mitchell; B. Yeung; C. Zhang

2001-01-01

423

Characterization of lead-free solders and under bump metallurgies for flip-chip package  

Microsoft Academic Search

A variety of Pb-free solders and under bump metallurgies (UBMs) was investigated for flip chip packaging applications. The result shows that the Sn-0.7Cu eutectic alloy has the best fatigue life and it possess the most desirable failure mechanism in both thermal and isothermal mechanical tests regardless of UBM type. Although the electroless Ni-P UBM has a much slower reaction rate

Jong-Kai Lin; Ananda De Silva; Darrel Frear; Yifan Guo; Scott Hayes; Jin-Wook Jang; Li Li; Dianne Mitchell; Betty Yeung; Charles Zhang

2002-01-01

424

Contrasting lead speciation in forest and tilled soils heavily polluted by lead metallurgy  

Microsoft Academic Search

The concentration trends and chemical fractionation of Pb was studied in eight tilled and forest soil profiles heavily polluted by Pb metallurgy in the P?íbram district, Czech Republic. The highest Pb concentrations were observed in surface and subsurface horizons attaining 35300mgkg?1 in forest soils and 1233mgkg?1 in tilled soils. Total Pb concentrations were one order of magnitude lower in tilled

Vojt?ch Ettler; Aleš Van?k; Martin Mihaljevi?; Petr Bezdi?ka

2005-01-01

425

The welding metallurgy of HASTELLOY alloys C-4, C-22, and C-276  

Microsoft Academic Search

The welding metallurgy (solidification and solid state transformations) of HASTELLOY* Alloys C-4, C-22, and C-276 has been\\u000a determined. Varestraint hot-cracking tests performed on commercial alloys revealed a weldability ranking as follows: C-4 >\\u000a C-22 > C-276. All alloys would be expected to have good weldability, with Alloy C-4 having a very low hot-cracking tendency,\\u000a comparable to 304L stainless steel. Microstructures

M. J. Cieslak; T. J. Headley; A. D. Romig

1986-01-01

426

The role of metallurgy in the NIST investigation of the World Trade Center towers collapse  

Microsoft Academic Search

On August 21, 2002, on the direction of the U.S. Congress, the National Institute of Standards and Technology (NIST) initiated\\u000a an investigation into the collapse of the World Trade Center (WTC) towers. In support of the overall investigation goals,\\u000a the NIST Metallurgy and Materials Reliability Divisions pursued three objectives: assess the quality of the steel used in\\u000a the construction of

S. W. Banovic; T. Foecke; W. E. Luecke; J. D. McColskey; C. N. McCowan; T. A. Siewert; F. W. Gayle

2007-01-01

427

A millennium of metallurgy recorded by lake sediments from Morococha, Peruvian Andes.  

PubMed

To date, information concerning pre-Colonial metallurgy in South America has largely been limited to the archaeological record of artifacts. Here, we reconstruct a millennium of smelting activity in the Peruvian Andes using the lake-sediment stratigraphy of atmospherically derived metals (Pb, Zn, Cu, Ag, Sb, Bi, and Ti) and lead isotopic ratios (206Pb/ 207Pb) associated with smelting from the Morococha mining region in the central Peruvian Andes. The earliest evidence for metallurgy occurs ca. 1000 A.D., coinciding with the fall of the Wari Empire and decentralization of local populations. Smelting during this interval appears to have been aimed at copper and copper alloys, because of large increases in Zn and Cu relative to Pb. A subsequent switch to silver metallurgy under Inca control (ca. 1450 to conquest, 1533 A.D.) is indicated by increases in Pb, Sb, and Bi, a conclusion supported by further increases of these metals during Colonial mining, which targeted silver extraction. Rapid development of the central Andes during the 20th century raised metal burdens by an order of magnitude above previous levels. Our results represent the first evidence for pre-Colonial smelting in the central Peruvian Andes, and corroborate the sensitivity of lake sediments to pre-Colonial metallurgical activity suggested by earlier findings from Bolivia. PMID:17547165

Cooke, Colin A; Abbott, Mark B; Wolfe, Alexander P; Kittleson, John L

2007-05-15

428

*Correspondence to: Zbigniew Galias, Department of Electrical Engineering, University of Mining and Metallurgy, al. Mickiewicza 30, 30-059 KrakoH w, Poland.  

E-print Network

and Metallurgy, al. Mickiewicza 30, 30-059 KrakoH w, Poland. Contract/grant sponsor: University of Mining and Metallurgy, KrakoH w Contract/grant number: 10.10.120.133 CCC 0098}9886/99/060589}16$17.50 Received September and Metallurgy, al. Mickiewicza 30, 30-059 KrakoH w, Poland SUMMARY In this paper we consider the problem

Galias, Zbigniew

429

21 CFR 73.2645 - Aluminum powder.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Aluminum powder. 73.2645 Section 73...CERTIFICATION Cosmetics § 73.2645 Aluminum powder. (a) Identity and specifications. The color additive aluminum powder shall conform in...

2012-04-01

430

21 CFR 73.1645 - Aluminum powder.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Aluminum powder. 73.1645 Section 73.1645...CERTIFICATION Drugs § 73.1645 Aluminum powder. (a) Identity. (1) The color additive aluminum powder shall be composed of finely...

2012-04-01

431

30 CFR 56.6901 - Black powder.  

...Resources 1 2014-07-01 2014-07-01 false Black powder. 56.6901 Section 56.6901 Mineral... Explosives General Requirements § 56.6901 Black powder. (a) Black powder shall be used for blasting only when a...

2014-07-01

432

Behaviour of colloidal silicas during uniaxial compaction Franoise Ehrburger and Jacques Lahaye  

E-print Network

1349 Behaviour of colloidal silicas during uniaxial compaction Françoise Ehrburger and Jacques > 2). Abstract. 2014 The pressure P transmitted by colloidal silica samples during low speed a percolation law E '" ( f - f,)'. The percolation threshold te obtained for silver powder beams [1] is 0

Paris-Sud XI, Université de

433

Fully compact anechoic chamber using the pyramidal ferrite absorber for immunity test  

Microsoft Academic Search

A new generation of electromagnetic wave absorber, which has a pyramidal shape and 10 cm in height and excellent absorbing characteristics, was developed to satisfy the required characteristics of a fully compact anechoic chamber in the wide frequency range. The material of the new absorber is composed of a ferrite powder and polypropylene. When the new absorber was cascaded on

Kazuo Shimada; Toshikatsu Hayashi; Masamitsu Tokuda

2000-01-01

434

powder in water  

NASA Astrophysics Data System (ADS)

Submicron-sized NiAl2+ X O4 fragments and nanocondensates of Ni-doped ?-Al2O3, Al-doped NiO and ?-Ni(OH)2 were synthesized simultaneously by pulsed laser ablation of NiAl2O4 powder in water and characterized using X-ray/electron diffraction and optical spectroscopy. The NiAl2+ X O4 is Al-enriched spinel with dislocations and subgrains. The Ni-doped ?-Al2O3 spinel has paracrystalline distribution (i.e., with fair constant longitudinal spacing, but variable relative lateral translations) of defect clusters and intimate intergrowth of ?-Al2O3 and 2x(3) commensurate superstructure. The Al-doped NiO has perfect cubo-octahedron shape and as small as 5 nm in size. The ?-Ni(OH)2 and 1-D turbostratic hydroxide lamellae occurred as a matrix of these oxide nanoparticles. The colloidal suspension containing the composite phases has a minimum band gap of 5.3 eV for potential photocatalytic applications.

Chan, Ya-Ting; Wu, Chao-Hsien; Shen, Pouyan; Chen, Shuei-Yuan

2014-09-01

435

Preparation of superconductor precursor powders  

DOEpatents

A process for the preparation of a precursor metallic powder composition for use in the subsequent formation of a superconductor. The process comprises the steps of providing an electrodeposition bath comprising an electrolyte medium and a cathode substrate electrode, and providing to the bath one or more soluble salts of one or more respective metals which are capable of exhibiting superconductor properties upon subsequent appropriate treatment. The bath is continually energized to cause the metallic and/or reduced particles formed at the electrode to drop as a powder from the electrode into the bath, and this powder, which is a precursor powder for superconductor production, is recovered from the bath for subsequent treatment. The process permits direct inclusion of all metals in the preparation of the precursor powder, and yields an amorphous product mixed on an atomic scale to thereby impart inherent high reactivity. Superconductors which can be formed from the precursor powder include pellet and powder-in-tube products. 7 figs.

Bhattacharya, R.

1998-08-04

436

Effects of long-time elevated temperature exposures on hot-isostatically-pressed power-metallurgy Udimet 700 alloys with reduced cobalt contents  

NASA Technical Reports Server (NTRS)

Because almost the entire U.S. consumption of cobalt depends on imports, this metal has been designated "strategic'. The role and effectiveness of cobalt is being evaluated in commercial nickel-base superalloys. Udiment 700 type alloys in which the cobalt content was reduced from the normal 17% down to 12.7%, 8.5%, 4.3%, and 0% were prepared by standard powder metallurgy techniques and hot isostatically pressed into billets. Mechanical testing and microstructural investigations were performed. The mechanical properties of alloys with reduced cobalt contents which were heat-treated identically were equal or better than those of the standard alloy, except that creep rates tended to increase as cobalt was reduced. The effects of long time exposures at 760 C on mechanical properties and at 760 C and 845 C on microstructures were determined. Decreased tensile properties and shorter rupture lives with increased creep rates were observed in alloy modifications. The exposures caused gamma prime particle coarsening and formation of sigma phase in the alloys with higher cobalt contents. Exposure at 845 C also reduced the amount of MC carbides.

Hart, F. H.

1984-01-01

437

Compact Plasma Accelerator  

NASA Technical Reports Server (NTRS)

A plasma accelerator has been conceived for both material-processing and spacecraft-propulsion applications. This accelerator generates and accelerates ions within a very small volume. Because of its compactness, this accelerator could be nearly ideal for primary or station-keeping propulsion for spacecraft having masses between 1 and 20 kg. Because this accelerator is designed to generate beams of ions having energies between 50 and 200 eV, it could also be used for surface modification or activation of thin films.

Foster, John E.

2004-01-01

438

Shock compression of quartz and aluminum powder mixtures  

NASA Astrophysics Data System (ADS)

We report about the shock-compression response of highly porous (55% and 65% dense) mixtures of 4Al+3SiO2 powders having shock-induced phase transitions and chemical reactions. Shock recovery experiments were performed using the CETR/Sawaoka plate-impact system (P=40 to 100 GPa) and the Sandia Momma Bear A Comp B fixture (P=22 to 45 GPa). The recovered compacts contained the high pressure stishovite phase, products of chemical reaction, as well as unreacted constituents. The reaction products formed included Al2O3, metallic Si (ambient and high pressure phases), SiAl intermetallic, and kyanite (Al2SiO5). The shock-induced chemical reaction in 4Al+3SiO2 powder mixtures, appears to have been accompanied (or assisted) by the formation of stishovite, a high pressure phase of quartz.

Joshi, V. S.; Thadhani, N. N.; Graham, R. A.; Holman, G. T.

1996-05-01

439

Silica powders for powder evacuated thermal insulating panel and method  

DOEpatents

A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2/ g is described. The silica powders are prepared by reacting a tetraakyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders.

Harris, Michael T. (Knoxville, TN); Basaran, Osman A. (Oak Ridge, TN); Kollie, Thomas G. (Oak Ridge, TN); Weaver, Fred J. (Knoxville, TN)

1996-01-01

440

Silica powders for powder evacuated thermal insulating panel and method  

DOEpatents

A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2/ g is described. The silica powders are prepared by reacting a tetraakyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders.

Harris, Michael T. (Knoxville, TN); Basaran, Osman A. (Oak Ridge, TN); Kollie, Thomas G. (Oak Ridge, TN); Weaver, Fred J. (Knoxville, TN)

1995-01-01

441

Silica powders for powder evacuated thermal insulating panel and method  

DOEpatents

A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2 /g is described. The silica powders are prepared by reacting a tetraakyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders.

Harris, Michael T. (Knoxville, TN); Basaran, Osman A. (Oak Ridge, TN); Kollie, Thomas G. (Oak Ridge, TN); Weaver, Fred J. (Knoxville, TN)

1994-01-01

442

Pharmaceutical Powder Diffraction: Structure Solution from PXRD  

E-print Network

Pharmaceutical Powder Diffraction: Structure Solution from PXRD How reliable are our structures? Pharmaceutical Powder Diffraction: Structure Solution from PXRD How reliable are our structures? Maryjane

443

Silica powders for powder evacuated thermal insulating panel and method  

Microsoft Academic Search

A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g\\/cm³ and an external surface area in the range of about 90 to 600 m²\\/g is described. The silica powders are prepared by reacting a tetraalkyl silicate

M. T. Harris; O. A. Basaran; T. G. Kollie; F. J. Weaver

1996-01-01

444

Silica powders for powder evacuated thermal insulating panel and method  

Microsoft Academic Search

A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g\\/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2\\/ g is described. The silica powders are prepared by reacting a tetraakyl

Michael T. Harris; Osman A. Basaran; Thomas G. Kollie; Fred J. Weaver

1996-01-01

445

Silica powders for powder evacuated thermal insulating panel and method  

Microsoft Academic Search

A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g\\/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2\\/ g is described. The silica powders are prepared by reacting a tetraakyl

Michael T. Harris; Osman A. Basaran; Thomas G. Kollie; Fred J. Weaver

1995-01-01

446

Silica powders for powder evacuated thermal insulating panel and method  

Microsoft Academic Search

A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g\\/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2 \\/g is described. The silica powders are prepared by reacting a tetraakyl

Michael T. Harris; Osman A. Basaran; Thomas G. Kollie; Fred J. Weaver

1994-01-01

447

Edge-restraint deformation processing of aluminides and other powders  

NASA Technical Reports Server (NTRS)

The novel, 'edge-restraint rolling' method has been developed in order to facilitate the thickness reduction of brittle, high strength alloys to the degree of thin plates or sheets, by first hot-compacting the prealloyed powders into billets and conducting the thickness reduction in a series of reheats and roll passes. Attention is presently given to the cases of equiatomic aluminide FeAl, (Ni,Fe)3Al, and an Al-Fe alloy. The flat-rolled products thus obtained may lead to the development of components not otherwise formable for powerplant and other aerospace applications.

Bhattacharyya, S.

1986-01-01

448

A compact SADM family  

NASA Astrophysics Data System (ADS)

Alcatel Space has developed a new SADM family driven by cost, modularity, mass and performances. The modularity concept is based on separating the rotation drive function from the electrical transfer function. The drive actuator has been designed for various applications where pointing and reliability is needed. It can be associated with high dissipative rotary devices (SA collectors, RF joints..). The design goal was to minimize the number of parts in order to reach the most simple and compact mechanism. Mass reduction was achieved by reducing as much as possible the load path between the Solar Array interface and the spacecraft interface. Following these guidelines, the drive actuator was developed and qualified on ATV SADM (part od Alcatel Space Solar Array Drive Sub System for ATV). Further more a high power integrated collector was qualified inside the SADM for Geo-stationary telecom satellite (SPACEBUS platforms). Fine thermal and mechanical modeling was necessary to predict SADM behaviors for the numerous thermal environments over the missions (steady and transient cases). These modeling were well correlated through mechanical and thermal balances qualification tests. The challenging approach of thermal dissipation in a compact design leads to a family of 3 SADM capabilities form 2kW up to 15kW per SADM weighing less than 4.5 kg each.

Barbet, Vincent; Le Quintrec, Cyrille; Jeandot, Xavier; Chaix, Alain; Grain, Eric; Roux, Jerome

2005-07-01

449

Ceramic powder for sintering materials  

NASA Technical Reports Server (NTRS)

Surface activity of ceramic powders such as MgO and Al2O3, for use in sintering with sp. emphasis on their particle size, shape, particle size distribution, packing, and coexisting additives and impurities are reviewed.

Akiya, H.; Saito, A.

1984-01-01

450

Rotary powder feed through apparatus  

DOEpatents

A device for increasing the uniformity of solids within a solids fabrication system, such as a direct light fabrication (DLF) system in which gas entrained powders are passed through the focal point of a moving high-power light which fuses the particles in the powder to a surface being built up in layers. The invention provides a feed through interface wherein gas entrained powders input from stationary input lines are coupled to a rotating head of the fabrication system. The invention eliminates the need to provide additional slack in the feed lines to accommodate head rotation, and therefore reduces feed line bending movements which induce non-uniform feeding of gas entrained powder to a rotating head.

Lewis, Gary K. (Los Alamos, NM); Less, Richard M. (Los Alamos, NM)

2001-01-01

451

Neutron detectors comprising boron powder  

DOEpatents

High-efficiency neutron detector substrate assemblies comprising a first conductive substrate, wherein a first side of the substrate is in direct contact with a first layer of a powder material comprising .sup.10boron, .sup.10boron carbide or combinations thereof, and wherein a conductive material is in proximity to the first layer of powder material; and processes of making said neutron detector substrate assemblies.

Wang, Zhehui; Morris, Christopher; Bacon, Jeffrey Darnell; Makela, Mark F; Spaulding, Randy Jay

2013-05-21

452

Luminescence of powdered uranium glasses  

NASA Technical Reports Server (NTRS)

Measurement of cathodoluminescence and photoluminescence efficiencies in powdered borosilicate glasses having different particle size and different uranium content. Excitation with 100 to 350 keV electrons and with 253.7 nm light was found to produce identical absolute radiant exitance spectra in powdered samples. The most efficient glass was one containing 29.4 wt% B2O3, 58.8 wt% SiO2, 9.8 wt% Na2O and 2.0 wt% UO2.

Eubanks, A. G.; Mcgarrity, J. M.; Silverman, J.

1974-01-01

453

WEAKLY COMPACTLY GENERATED BANACH ALGEBRAS ASSOCIATED TO LOCALLY COMPACT GROUPS  

Microsoft Academic Search

Let G be a locally compact group, and let X be any one of the Banach algebras C (G), C0(G), B(G) or A(G). We characterize the property that X, as a Banach space, is weakly compactly generated in terms of conditions on G and its dual space.

E. KANIUTH; A. T. LAU; G. SCHLICHTING

1998-01-01

454

Compact artificial hand  

NASA Technical Reports Server (NTRS)

A relatively simple, compact artificial hand, is described which includes hooks pivotally mounted on first frame to move together and apart. The first frame is rotatably mounted on a second frame to enable "turning at the wrist" movement without limitation. The second frame is pivotally mounted on a third frame to permit 'flexing at the wrist' movement. A hook-driving motor is fixed to the second frame but has a shaft that drives a speed reducer on the first frame which, in turn, drives the hooks. A second motor mounted on the second frame, turns a gear on the first frame to rotate the first frame and the hooks thereon. A third motor mounted on the third frame, turns a gear on a second frame to pivot it.

Wiker, G. A.; Mann, W. A. (inventors)

1979-01-01

455

Compact vacuum insulation  

DOEpatents

An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially "point" or "line" contacts with the metal wall sheets. In the case of monolithic spacers that form "line" contacts, two such spacers with the line contacts running perpendicular to each other form effectively "point" contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included.

Benson, David K. (Golden, CO); Potter, Thomas F. (Denver, CO)

1993-01-01

456

Compact vacuum insulation embodiments  

DOEpatents

An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially "point" or "line" contacts with the metal wall sheets. In the case of monolithic spacers that form "line" contacts, two such spacers with the line contacts running perpendicular to each other form effectively "point" contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included.

Benson, David K. (Golden, CO); Potter, Thomas F. (Denver, CO)

1992-01-01

457

Atacama compact array antennas  

NASA Astrophysics Data System (ADS)

The ACA (Atacama Compact Array) system is an important element of ALMA and consists of four ACA 12-m antennas and twelve ACA 7-m antennas. The ACA system aims to acquire the total power data with four 12-m antennas and the short baseline interferometer data with 7-m antennas. The ACA system also increases reliability of the interferometer maps of astronomical sources larger than the field view of the 12-m antenna. The science performance of these antennas has been extensively verified at OSF (operation support facility) at an elevation of 2900 m in Atacama desert in northern Chile since 2007. The pointing performance has been verified with a dedicated optical pointing telescope, the servo performance is tested with angle encoders, and the surface accuracy has been measured with a radio holography method. Both ACA 12-m antennas and 7-m antennas have been successfully demonstrated to meet the very stringent ALMA specifications.

Saito, M.; Inatani, J.; Nakanishi, K.; Saito, H.; Iguchi, S.

2012-09-01

458

Compact acoustic refrigerator  

DOEpatents

A compact acoustic refrigeration system actively cools components, e.g., electrical circuits, in a borehole environment. An acoustic engine includes first thermodynamic elements for generating a standing acoustic wave in a selected medium. An acoustic refrigerator includes second thermodynamic elements located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements and a relatively hot temperature at a second end of the second thermodynamic elements. A resonator volume cooperates with the first and second thermodynamic elements to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements, first heat pipes transfer heat from the heat load to the second thermodynamic elements and second heat pipes transfer heat from first and second thermodynamic elements to the borehole environment. 18 figs.

Bennett, G.A.

1992-11-24

459

Compact acoustic refrigerator  

DOEpatents

A compact acoustic refrigeration system actively cools components, e.g., electrical circuits (22), in a borehole environment. An acoustic engine (12, 14) includes first thermodynamic elements (12) for generating a standing acoustic wave in a selected medium. An acoustic refrigerator (16, 26, 28) includes second thermodynamic elements (16) located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements (16) and a relatively hot temperature at a second end of the second thermodynamic elements (16). A resonator volume (18) cooperates with the first and second thermodynamic elements (12, 16) to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements (12, 16), first heat pipes (24, 26) transfer heat from the heat load (22) to the second thermodynamic elements (16) and second heat pipes (28, 32) transfer heat from first and second thermodynamic elements (12, 16) to the borehole environment.

Bennett, Gloria A. (Los Alamos, NM)

1992-01-01

460

Ceramic oxide powders and the formation thereof  

DOEpatents

Ceramic oxide powders and a method for their preparation. Ceramic oxide powders are obtained using a flame process whereby two or more precursors of ceramic oxides are introduced into a counterflow diffusion flame burner wherein said precursors are converted into ceramic oxide powders. The morphology, particle size, and crystalline form of the ceramic oxide powders are determined by process conditions. 14 figures.

Katz, J.L.; Chenghung Hung.

1993-12-07

461

Ceramic oxide powders and the formation thereof  

DOEpatents

Ceramic oxide powders and a method for their preparation. Ceramic oxide powders are obtained using a flame process whereby two or more precursors of ceramic oxides are introduced into a counterflow diffusion flame burner wherein said precursors are converted into ceramic oxide powders. The morphology, particle size, and crystalline form of the ceramic oxide powders are determined by process conditions.

Katz, Joseph L. (Baltimore, MD); Hung, Cheng-Hung (Baltimore, MD)

1993-01-01

462

The Beginnings of Metallurgy: A New Look: Arguments over diffusion and independent invention ignore the complex metallurgic crafts leading to iron.  

PubMed

In the 9 years since my first survey of early metallurgy appeared in this journal (65) metallurgy has become a major battleground between those who argue independent invention and those who argue diffusion in the evolution of urban civilization. In this new article I contend that: 1) The upland belt and debouching river valleys of southwestern Asia have a clear priority in the beginnings of copper metallurgy and extractive metallurgy generally, suggesting that the forces of urbanization contributing to the rise of metallurgy there were more massive, widespread, and better integrated than elsewhere. 2) The trend to polymetallism, against the background of pyrotechnology generally and the other important technologies of urbanism, established a necessary sequence to early metallurgy. This sequence was a prerequisite to the coming of the Iron Age, which was uniquely contained at first within the environment of Anatolia and the eastern Mediterranean and spread outward from there. 3) The course of metallurgy and possibly of the other urbanizing technologies can best be understood through a process of diffusion and multiple innovation interrelating metallurgical evolution over much of Eurasia, but with the area defined by the Black Sea, the Caspian Sea, the Red Sea, and the eastern Mediterranean as its center. Only in this fashion can we place metallurgy in its proper role as an important subsystem in the rise of civilization. PMID:17737520

Wertime, T A

1973-11-30

463

Hot deformation and wear resistance of P\\/M aluminium metal matrix composites  

Microsoft Academic Search

Hot compression and wear resistance as well as hardness of powder metallurgy (P\\/M) aluminium metal matrix composites (MMC) were investigated. Metal matrix composites were manufactured using powder metallurgy technique of ball milled mixing in a high energy attritor and cold compaction followed by hot extrusion at 500°C. Matrix of pure aluminium was used to which different weight fractions of Al2O3

G. Abouelmagd

2004-01-01

464

HOMOGENEITY PROPERTIES ON COMPACT SPACES  

E-print Network

HOMOGENEITY PROPERTIES ON COMPACT SPACES By Ramiro H. de la Vega A dissertation submitted) at the UNIVERSITY OF WISCONSIN -- MADISON 2005 #12; i Abstract A topological space X is said to be homogeneous show that under CH there exists a compact S­space which is homogeneous, thus answering a question of V

Miller, Joseph S.

465

Simulation of the particle misalignment of hard magnets after compaction  

NASA Astrophysics Data System (ADS)

The simulation of powder compaction for Nd-Fe-B, Sm-Co, and barium ferrite shows the influence of different static field strengths and different mold filling on particle misalignment. The final magnetization differs up to 20%. The processing determines the pressure activated processes in which the particle overcomes a volume barrier, characterized by elastic energy fluctuations. Isostatic compaction shows less pressure activated processes as compared to uniaxial mold pressing. However, an improved magnetization of about 10% owing to isostatic pressing was observed only for spherical particles. The pressure activated processes determine particle density defects such as cracks and pores, misalignment of c axes at the punch side, at corners and at particle density defects, and internal stress areas with cold plastic flow.

Zwick, H.; Schrefl, T.; Fidler, J.

1999-04-01

466

Eutectic Sn\\/Pb solder bump and under bump metallurgy: interfacial reactions and adhesion  

Microsoft Academic Search

In flip-chip interconnection on organic substrates using eutectic tin\\/lead solder bumps, a highly reliable under bump metallurgy (UBM) is required to maintain adhesion and solder wettability. Various UBM systems such as 1?m Al\\/0.2?m Ti\\/5?m Cu, 1?m Al\\/02?m Ti\\/1?m Cu, 1?m Al\\/0.2?m Ni\\/1?m Cu and 1?m Al\\/0.2?m Pd\\/1?m Cu, applied under eutectic tin\\/lead solder bumps, have been investigated with regard to

Se-Young Jang; Kyung-Wook Paik

1998-01-01

467

Process design applied to optimise a directly compressible powder produced via a continuous manufacturing process.  

PubMed

Manufacturing of 'ready-to-compress' powder mixtures for direct compression was performed by spray drying, without granulation, milling and/or blending steps in between spray drying and compaction. Powder mixtures containing acetaminophen, mannitol, erythritol, maltodextrin, crospovidone, colloidal silicon dioxide and polyoxyethylene 20 sorbitan monooleate were prepared via co-spray drying. A feed suspension having a solid content of 27.2% w/w was selected for further process optimisation because of its high process yield, excellent flowability and short tablet disintegration time. Experimental design was applied to evaluate processibility, physico-chemical properties and compactability of the spray dried powder mixtures. Significant and adequate regression models were developed for powder flowability, median particle size, bulk density, residual moisture content and process yield. An increasing inlet and outlet drying air temperature improved process yield. However, a higher inlet drying air temperature had a negative influence on density and moisture content, while the latter decreased at higher outlet drying air temperatures. Median particle size increased with a higher inlet temperature, while the outlet temperature had the opposite affect. Numerical optimisation determined the optimal spray drying process (inlet temperature: 221 degrees C, outlet temperature: 81 degrees C and atomisation pressure: 6 bar) in order to produce 'ready-to-compress' powder mixtures. PMID:17964129

Gonnissen, Y; Gonçalves, S I V; De Geest, B G; Remon, J P; Vervaet, C

2008-03-01

468

Etude des proprietes mecaniques statiques et dynamiques de pieces d'acier elaborees par metallurgie des poudres  

NASA Astrophysics Data System (ADS)

The main objective of this thesis ais to gain a better understanding of the effects of processing variables on the porosity and microstructure of powder metallurgy (P/M) steel and their effect on mechanical properties, both static and dynamic. The effects of processing variables on porosity and microstructure were evaluated by advanced microstructural characterization using both optical and electron microscopies. Then the impacts of porosity and microstructure on both static and dynamic properties were measured. Static mechanical properties were characterized by hardness measurements and by tensile tests while fatigue testing was used for evaluating dynamic properties. Fractographic observations were made on tensile and fatigue fracture samples to correlate the microstructural features to the mechanical performance of P/M steels. The experimental work covered in this Ph.D. thesis enables to further understand the mechanisms by which process variables affect the microstructure and the mechanical properties of samples. In the first paper, the effect of prealloying MnS up to 1.0 wt pct on the microstructural features of non-metallic inclusions and their impact on tensile and fatigue properties of a 7.0 g/cm3 P/M steel (Fe-2.0Cu-0.7C) have been investigated. As the MnS content increases, larger, more irregular and more closely spaced inclusions are obtained. Whilst no significant impact on both static and dynamic properties was observed when prealloying up to 0.65 wt pct MnS, a decrease of more than 15 pct of the ultimate tensile strength and of the endurance limit was found when the MnS content reaches 1.0 wt pct. The decrease in the ultimate tensile strength is attributed to a lower ductility of the sinternecks, as void initiation and void growth were promoted at lower stress levels by larger inclusions. The larger size of the MnS particles and the lower mean free path between non-metallic inclusions also favor microcrack initiation and their coalescence into cracks, leading to premature fatigue fracture. In the second paper, the improvement of performance that can be achieved by copper infiltration was quantified. Tensile and fatigue properties of a Fe-2.0Cu-0.7C PM steel were compared to the same alloy infiltrated with 8 wt-% copper. Microstructural characterization, using optical and electron microscopies, was carried out to understand the effect of copper infiltration on mechanical properties. Copper infiltration improves the ultimate tensile strength by 40% by increasing the load bearing section, decreasing the stress concentrations associated to open porosity and increasing the hardness of the steel matrix. Fractographic observations show the evidence of stress transmission from the sinternecks to the steel particles due to infiltrated copper. The beneficial effect of copper infiltration is less pronounced for fatigue properties as the endurance limit is increased by only 10%. This lower improvement is explained by crack initiation at the copper/steel matrix interface. In the last paper, the microstructural characterization of nickel rich areas and their influence on the endurance limit of a P/M steel was investigated. The addition of nickel powder to a P/M steel increases hardenability, enabling the formation of martensite directly after the sintering process. However, the slow diffusion rate of nickel into iron leads to the formation of nickel rich areas (NRA). Two steel alloys were studied, the first one is a Fe-6.4Ni-0.7Mo-0.7C with standard size nickel powder additions and the second one is a Fe-2.4-0.7Mo-0.7C where a finer size nickel powder was added. The influence of the size of the nickel powder used on hardenability and on the presence of NRA has been investigated by optical microscopy. A complete identification of the microstructural constituents and the effect of nickel concentration on their presence were achieved using X-ray energy dispersive spectrometry and electron diffraction in the transmission electron microscope. Results obtained by these techniques show the presence of austenite and martensite.

Bernier, Fabrice

469

Compact plasma accelerator  

NASA Technical Reports Server (NTRS)

A compact plasma accelerator having components including a cathode electron source, an anodic ionizing gas source, and a magnetic field that is cusped. The components are held by an electrically insulating body having a central axis, a top axial end, and a bottom axial end. The cusped magnetic field is formed by a cylindrical magnet having an axis of rotation that is the same as the axis of rotation of the insulating body, and magnetized with opposite poles at its two axial ends; and an annular magnet coaxially surrounding the cylindrical magnet, magnetized with opposite poles at its two axial ends such that a top axial end has a magnetic polarity that is opposite to the magnetic polarity of a top axial end of the cylindrical magnet. The ionizing gas source is a tubular plenum that has been curved into a substantially annular shape, positioned above the top axial end of the annular magnet such that the plenum is centered in a ring-shaped cusp of the magnetic field generated by the magnets. The plenum has one or more capillary-like orifices spaced around its top such that an ionizing gas supplied through the plenum is sprayed through the one or more orifices. The plenum is electrically conductive and is positively charged relative to the cathode electron source such that the plenum functions as the anode; and the cathode is positioned above and radially outward relative to the plenum.

Foster, John E. (Invento