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1

Electrothermal Defect Detection in Powder Metallurgy Compacts  

NASA Astrophysics Data System (ADS)

Faced with increasing market pressures, metal part manufacturers have turned to new processes and fabrication technologies. One of these processes is powder metallurgy (P/M), which is employed for low-cost, high-volume precision part manufacturing. Despite many advantages, the P/M process has created a number of challenges, including the need for high-speed quality assessment and control, ideally for each compact. Consequently, sophisticated quality assurance is needed to rapidly detect flaws early in the manufacturing cycle and at minimal cost. In this paper we will discuss our progress made in designing and refining an active infrared (IR) detection system for P/M compacts. After discussing the theoretical background in terms of underlying equations and boundary conditions, analytical and numerical solutions are presented that are capable of predicting temperature responses for various defect sizes and orientations of a dynamic IR testing system. Preliminary measurements with controlled and industrial samples have shown that this active IR methodology can successfully be employed to test both green-state and sintered P/M compacts. The developed system can overcome many limitations observed with a standard IR testing methodology such as emissivity, background calibration, and contact resistance.

Benzerrouk, Souheil; Ludwig, Reinhold; Apelian, Diran

2006-03-01

2

Ultrasonic Characterization of Iron Powder Metallurgy Compacts during and after Compaction  

Microsoft Academic Search

Ultrasonic measurements in powder metallurgy (PM) compacts at various stages of production are presented both as a practical means of improving PM production and as a method of providing a fuller understanding of PM materials. Ultrasonic monitoring during powder compaction, a novel process instrumentation technique to follow powder densification, is reviewed. Measurements taken during the compaction of simple PM disk

Andrew Lerossignol Dawson; Jean Franois Bussire

1998-01-01

3

On the mechanics of cold die compaction for powder metallurgy  

Microsoft Academic Search

The main object of this paper is to present a theoretical model for the cold die compaction of powder materials based on the axisymmetric solution of large deformation. The model produces an expression relating the green density of the compact to the applied pressure. The analysis takes into account the internal (restricted movements) coefficient of friction between the particles and

H. A. Al-Qureshi; A. Galiotto; A. N. Klein

2005-01-01

4

Acoustic harmonic generation measurement applications: Detection of tight cracks in powder metallurgy compacts  

NASA Astrophysics Data System (ADS)

Standard linear ultrasonic testing techniques have long been employed for locating and characterizing relatively open cracks in a wide variety of materials, from metallic alloys and ceramics to composites. In all these materials, the detection of open cracks easily accomplished because the void between the two crack surfaces provides sufficient acoustic impedance mismatch to reflect the incident energy. Closed or partially closed cracks, however, may often go undetected because contacting interfaces allow transmission of ultrasound. In the green (unsintered) state, powder metallurgy compacts typically contain high residual stresses that have the ability to close cracks formed during the compaction process, a result of oxide films, improper powder lubricant, mold design, etc. After sintering, the reduction of residual stresses may no longer be sufficient to close the crack. Although the crack may be more easily detected, it is obvious most desirable to discover defects prior to sintering. It has been shown that the displacements of an interface may be highly nonlinear if a stress wave of sufficient intensity propagates across it, a result of the stress wave either opening or closing the interface. Current efforts involve the application of nonlinear acoustic techniques, in particular acoustic harmonic generation measurements, for the detection and characterization of tightly closed cracks in powder metallurgy parts. A description of the equipment and the measurement technique will be discussed and initial experimental results on sintered and green compacts will be presented.-This work was performed at the Ames Laboratory, Iowa State University under USDOE Contract No. W-7405-ENG-82. .

Barnard, D. J.; Foley, J. C.

2000-05-01

5

Powder Metallurgy Production of Structural Shapes.  

National Technical Information Service (NTIS)

This program has involved an integrated and concurrent study of closely-related topics representing major critical steps and/or problem areas in powder metallurgy processing. The areas of major concern have been: quench atomization; powder compaction; pow...

A. Lawley M. J. Koczak R. M. Koerner H. A. Kuhn H. C. Rogers

1973-01-01

6

POWDER METALLURGY. STAINLESS STEEL-BORON CARBIDE AND ZIRCONIUM-BORON- CARBIDE COMPACTS. Progress Report  

Microsoft Academic Search

Powder metallurgical compacts were prepared consisting of varying boron ; carbide-to-base metal ratios, the base metals in these investigations being types ; 347 and 302 stainless steels and zirconium. Systematic studies of the effects of ; sintering and reheat temperatures on the physical properties of compacts are ; described and the resultant data presented in tabular form. Thermal differential ;

P. G. Herold; T. J. Planje; J. M. ed. Cisar

1955-01-01

7

Powder metallurgy of superalloys  

Microsoft Academic Search

Powder metallurgy superalloys were developed in the mid-1960's when stronger aircraft turbine disk materials were needed. Their characteristics of greatly reduced segregation, better hot-workability, improved mechanical properties, and cost-effective manufacturing processes made P\\/M superalloys highly desirable in high-temperature applications. This book deals with prealloyed superalloys including rapidly solidified (RSR) alloys and oxide-dispersion strengthened alloys, as well as processing techniques such

Gessinger

1984-01-01

8

Powder metallurgy of superalloys  

SciTech Connect

Powder metallurgy superalloys were developed in the mid-1960's when stronger aircraft turbine disk materials were needed. Their characteristics of greatly reduced segregation, better hot-workability, improved mechanical properties, and cost-effective manufacturing processes made P/M superalloys highly desirable in high-temperature applications. This book deals with prealloyed superalloys including rapidly solidified (RSR) alloys and oxide-dispersion strengthened alloys, as well as processing techniques such as sintering, hot isostatic pressing, extrusion, and isothermal forging. The large range of microstructures possible are correlated with mechanical properties at intermediate and elevated temperatures. Methods of powder production and consolidation are detailed, as are thermomechanical processing principles by which different microstructures can be created. Non-destructive testing techniques, and problems and advances relating to mechanical properties and processing are also covered.

Gessinger, G.H.

1984-01-01

9

Metallography of powder metallurgy materials  

Microsoft Academic Search

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

Alan Lawley; Thomas F. Murphy

2003-01-01

10

Powder metallurgy of titanium alloys  

Microsoft Academic Search

The powder metallurgy of titanium alloys is studied with attention given to blended elemental and prealloyed (PA) approaches. The PA method leads to mechanical behavior in all respects at least at ingot metallurgy levels. The use of the PA method in the aerospace industry is discussed. 230 refs.

F. H. Froes; D. Eylon

1990-01-01

11

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

12

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

13

Electro-thermographic detection of cracks in green-state powder metallurgy compacts  

NASA Astrophysics Data System (ADS)

In this paper we investigate the suitability of direct electric heating in an effort to conduct infrared NDE for various low conductivity metallic materials. Both DC and AC electric currents can be used to create the necessary Joule's power density in the metallic samples. Even low-conducting media such as composites and rubber can be thermally stimulated with high-frequency fields due to their high penetration depths. The reported research describes analytically and experimentally how this active electric heating approach can be utilized to conduct thermal NDE to characterize surface defects of green-state powder metal samples. The electric current is applied through two disk electrodes located on either side of the sample under test. An infrared camera subsequently records the transient thermal temperature profile, converts it into digital form, and displays the results as an image on a computer screen. .

Ludwig, Reinhold; Makarov, Sergey

2001-04-01

14

Aluminum powder metallurgy processing.  

National Technical Information Service (NTIS)

The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from a...

J. F. Flumerfelt

1999-01-01

15

Properties of Prealloyed Steel Powder Metallurgy Products.  

National Technical Information Service (NTIS)

The applicability of conventional powder metallurgy fabrication procedures to prealloyed steel powders was investigated. Fifteen lots of steel powder, representing six different major alloy types (4130, 1040, 8620, 4650, 8650, and 9450), have been formed ...

K. R. Sump R. E. Westerman

1971-01-01

16

Powder metallurgy repair of turbine components  

Microsoft Academic Search

An advanced powder metallurgy repair process called Liburdi Powder Metallurgy (LPM) has been developed for the repair, overlay or joining of nickel and cobalt-based high-temperature alloys. This process involves mechanical cleaning, followed by the application and consolidation of a filler metal powder, which has substantially the same composition as the base metal, and producer joints with mechanical properties similar to

K. A. Ellison; P. Lowden; J. Liburdi

1994-01-01

17

Low Porosity Powder Metallurgy Produced Components.  

National Technical Information Service (NTIS)

Components produced by powder metallurgy techniques are described herein. Embodiments of these components have little or no porosity therein after processing. Embodiments of these components are created by creating a preform from a powder; creating a comp...

G. Das

2004-01-01

18

Powder Metallurgy Production of Structural Shapes.  

National Technical Information Service (NTIS)

The program involves an integrated and concurrent study of closely-related topics which represent major critical steps and/or problem areas in a wide variety of powder metallurgy processes. Areas of study include atomization, powder characteristics (and t...

A. Lawley H. L. Gaigher R. H. Haase R. W. Heckel M. J. Koczak

1971-01-01

19

Powder metallurgy of vanadium and its alloys (review)  

SciTech Connect

This article reviews the current powder metallurgy technology of vanadium and its alloys. Data are given on sintering, compacting, electrowinning and other current production techniques, as well as on the corrosion behavior and mechanical and physical properties of alloys produced by these different methods. The use of vanadium alloys as reactor and jet engine materials is also briefly discussed.

Radomysel'skii, I.D.; Solntsev, V.P.; Evtushenko, O.V.

1987-10-01

20

The technologies of titanium powder metallurgy  

Microsoft Academic Search

Titanium alloys exhibit attractive mechanical properties but they are expensive. This paper reviews the current status of\\u000a titanium powder metallurgy which offers near-net shape cost-effective approaches to the fabrication of components.

F. H. Froes; S. J. Mashl; J. C. Hebeisen; V. S. Moxson; V. A. Duz

2004-01-01

21

The technologies of titanium powder metallurgy  

NASA Astrophysics Data System (ADS)

Titanium alloys exhibit attractive mechanical properties but they are expensive. This paper reviews the current status of titanium powder metallurgy which offers near-net shape cost-effective approaches to the fabrication of components.

Froes, F. H.; Mashl, S. J.; Hebeisen, J. C.; Moxson, V. S.; Duz, V. A.

2004-11-01

22

Composite metal foams processed through powder metallurgy  

Microsoft Academic Search

A new closed cell composite metal foam has been produced using a powder metallurgy technique. The composite foams are processed by filling the vacancies between densely packed steel hollow spheres with steel powder and sintering them into a solid cellular structure. Three sets of samples have been processed, two of carbon steel and one of stainless steel. The relative densities

B. P. Neville; A. Rabiei

2008-01-01

23

Milling and Drilling Evaluation of Stainless Steel Powder Metallurgy Alloys.  

National Technical Information Service (NTIS)

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 ...

L. J. Lazarus

2001-01-01

24

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

25

APPLICATION OF ULTRASONIC VIBRATION TO THE COMPACTION OF METAL POWDERS  

Microsoft Academic Search

Although powder metallurgy has lent impetus to the fabrication of high-; performance materials for nuclear reactor components, problems are associated ; with the technique; and the feasibility of applying ultrasonics as a means of ; improving and simplifying powder metallurgy procedures was investigated. ; Consideration was given to the possible influence of ultrasonic vibratory motion ; on mold filling, compact

J. G. Thomas; J. B. Jones

1958-01-01

26

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

27

Advances in powder metallurgy - 1991. Vol. 5 - P/M materials; Proceedings of the Powder Metallurgy Conference and Exhibition, Chicago, IL, June 9-12, 1991  

SciTech Connect

The present volume powder metallurgy materials discusses the state of the PM industry, a metallurgical evaluation of new steel powders, design criteria for the manufacturing of low-alloy steel powders, and homogenization processing of a PM maraging steel. Attention is given to the corrosion resistance of full density sintered 316 SS, the performance characteristics of a new sinter-hardening low-alloy steel, wear performance of compositions made by low alloy iron/high alloy powder mixtures, and the strengthening of an AISI 1020 steel by aluminum-microalloying during liquid dynamic compaction. Topics addressed include the influence of alloying on the properties of water-atomized copper powders, fundamentals of high pressure gas atomization process control, advanced sensors and process control of gas atomization, and bimetallic tubulars via spray forming. Also discussed are factors affecting the delamination of PM molybdenum during stamping, applications of powder metallurgy molybdenum in the 1990s, and powder processing of high-temperature oxides.

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

1991-01-01

28

An application of powder metallurgy to dentistry.  

PubMed

Generally, the dental casting method is used to fabricate dental prostheses made with metal. The method of fabricating dental prostheses from sintered titanium alloy has certain advantages: the elimination of casting defects, a sintering temperature that is lower than the melting point, and a shorter processing time. By examining (1) the properties of green, sintered compacts of titanium powder, (2) the effects of adding aluminum powder on the properties of green, sintered compacts of Ti-Al compound, and (3) the effects of adding copper powder on the properties of green, sintered compacts of Ti-Al-Cu compound, the authors developed a sintered titanium alloy on a trial basis. Because the properties satisfied the requirements of dental restorations, a powder metallurgical method of making dental restorations from this sintered titanium alloy was devised. Applications of such sintered titanium alloys for the metal coping of metal-ceramic crowns and denture base plates were discussed. PMID:8689755

Oda, Y; Ueno, S; Kudoh, Y

1995-11-01

29

FATIGUE CRACK INITIATION AND PROPAGATION IN FERROUS POWDER METALLURGY ALLOYS  

Microsoft Academic Search

Many of the targeted applications for powder metallurgy materials, particularly in the automotive industry, undergo cyclic loading. It is, therefore, essential to examine the fatigue mechanisms in these materials. The mechanisms of fatigue crack initiation and propagation in ferrous powder metallurgy components have been investigated. The fatigue mechanisms are controlled primarily by the inherent porosity present in these materials. Since

S. J. Polasik; J. J. Williams; N. Chawla; K. S. Narasimhan

30

Compaction of Titanium Powders  

SciTech Connect

Accurate modeling of powder densification has been an area of active research for more than 60 years. The earliest efforts were focused on linearization of the data because computers were not readily available to assist with curve-fitting methods. In this work, eight different titanium powders (three different sizes of sponge fines <150 ?m, <75 ?m, and < 45 ?m; two different sizes of a hydride-dehydride [HDH] <75 ?m and < 45 ?m; an atomized powder; a commercially pure [CP] Ti powder from International Titanium Powder [ITP]; and a Ti 6 4 alloy powder) were cold pressed in a single-acting die instrumented to collect stress and deformation data during compaction. From these data, the density of each compact was calculated and then plotted as a function of pressure. The results show that densification of all the powders, regardless of particle size, shape, or chemistry, can be modeled accurately as the sum of an initial density plus the sum of a rearrangement term and a work-hardening term. These last two terms are found to be a function of applied pressure and take the form of an exponential rise.

Stephen J. Gerdemann; Paul D. Jablonski

2010-11-01

31

Compaction of Titanium Powders  

NASA Astrophysics Data System (ADS)

Accurate modeling of powder densification has been an area of active research for more than 60 years. The earliest efforts were focused on linearization of the data because computers were not readily available to assist with curve-fitting methods. In this work, eight different titanium powders (three different sizes of sponge fines <150 ?m, <75 ?m, and < 45 ?m; two different sizes of a hydride-dehydride [HDH] <75 ?m and < 45 ?m; an atomized powder; a commercially pure [CP] Ti powder from International Titanium Powder [ITP]; and a Ti 6 4 alloy powder) were cold pressed in a single-acting die instrumented to collect stress and deformation data during compaction. From these data, the density of each compact was calculated and then plotted as a function of pressure. The results show that densification of all the powders, regardless of particle size, shape, or chemistry, can be modeled accurately as the sum of an initial density plus the sum of a rearrangement term and a work-hardening term. These last two terms are found to be a function of applied pressure and take the form of an exponential rise.

Gerdemann, Stephen J.; Jablonski, Paul D.

2011-05-01

32

Method for Refining Microstructures of Prealloyed Powder Metallurgy Titanium Articles.  

National Technical Information Service (NTIS)

A method for improving the microstructure of an article made by powder metallurgy of prealloyed titanium powder which comprises beta-solution heat treating the article at a temperature approximately equal to the beta-transus of the equivalent alloy, rapid...

D. Eylon

1984-01-01

33

Fatigue behavior of diffusion bonded powder metallurgy steel with heterogeneous microstructure  

Microsoft Academic Search

Fatigue is an important field for the application of powder metallurgy steels in service conditions. The fatigue performance of as-sintered powder metallurgy steel depends on microstructure and density. This concept requires a deep understanding of materials microstructure. Various microstructures in powder metallurgy steels, depending on alloying methods, have different responses against cyclic loading. Focus of this article is to quantify

H. Abdoos; H. Khorsand; A. R. Shahani

2009-01-01

34

[Hygienic evaluation of risk factors on powder metallurgy production].  

PubMed

Complex hygienic, clinical, sociologic and epidemiologic studies revealed reliable relationship between work conditions and arterial hypertension, locomotory system disorders, monocytosis in powder metallurgy production workers. Findings are more probable cardiovascular and respiratory diseases, digestive tract diseases due to influence of lifestyle factors. PMID:22288182

2011-01-01

35

Recrystallization in a powder metallurgy nickel-base superalloy  

Microsoft Academic Search

In an extruded powder metallurgy superalloy, carbide particles are precipitated at the previous article boundaries. The role of these particles in the recrystallization behaviour has been studied by electron microscopy and hardness measurements. It was found that these carbide particles act as nucleation sites for recrystallization and inhibit growth of new grains.

L. Winberg; M. Dahln

1978-01-01

36

Design of powder metallurgy titanium alloys and composites  

Microsoft Academic Search

Low cost and good performance are two major factors virtually important for Ti alloy development. In this paper, we have studied the effects of alloying elements, thermo-mechanical treatment and particle reinforcement on microstructures and mechanical properties of powder metallurgy (PM) Ti alloys and their composites. Our results indicate that low cost PM Ti alloys and their composites with attractive properties

Y. Liu; L. F. Chen; H. P. Tang; C. T. Liu; B. Liu; B. Y. Huang

2006-01-01

37

Scaleup of powder metallurgy processed Nb-Al multifilamentary wire  

Microsoft Academic Search

Power metallurgy processed Nb-Al superconducting wires were fabricated from billets up to 45 mm o.d. with nominal areal reduction ratios, R, up to 2 X 10⁵, Nb powder sizes from 40 to 300 ..mu..m from various sources, Al powder sizes from 9 to 75 ..mu..m, Al concentrations from 3 to 25 wt % Al and with a wide range of

C. Thieme; H. Zhang; J. Otubo; S. Pourrahimi; B. Schwartz; S. Foner

1983-01-01

38

Microstructures and properties of powder metallurgy TiAl alloys  

Microsoft Academic Search

The microstructures and properties of powder metallurgy (PM) TiAl alloys fabricated by hot-extrusion of gas-atomized powder at different temperatures (1150, 1250 and 1400C) have been investigated. Microstructure of the alloy fabricated at 1150C consists of fine grains of ? and ?2 phases in association with coarse grains of B2 (ordered bcc) phase. Metastable ? particles of ordered hexagonal phase were

L. M Hsiung; T. G Nieh

2004-01-01

39

Properties of Prealloyed Steel Powder Metallurgy Products.  

National Technical Information Service (NTIS)

A program to evaluate the properties of prealloyed steel powders, consolidated by various fabrication techniques, was conducted. Sixteen lots of low-alloy prealloyed steel powder, representing seven different major alloys (4130, 1040, 8620, 4640, 4650, 86...

R. E. Westerman K. R. Sump

1972-01-01

40

Use of Cement Copper in an Iron-Copper-Carbon Powder Metallurgy Alloy.  

National Technical Information Service (NTIS)

An investigation was made of the substitution of cement copper powder for commercial copper powder in an Fe-7 pct Cu-1 pct C powder metallurgy alloy. Copper powders from six different commercial cementation operations were separately upgraded by screening...

R. L. Crosby D. H. Desy R. M. Doerr

1970-01-01

41

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

42

Powder compaction with ultrasonic assistance  

Microsoft Academic Search

The compaction behaviour of a ceramic powder can be improved by ultrasonic assistance, only when ultrasounds are used at pressures lower than a critical value,PC. This critical pressure is connected with the limit of mobility of the powder grains under ultrasonic vibrations. Its value depends on the characteristics of the powder, as well as those of the ultrasounds: frequency, amplitude,

E. Emeruwa; J. Jarrige; J. Mexmain; M. Billy; K. Bouzouita

1990-01-01

43

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

44

Fatigue behavior of a high density powder metallurgy steel  

Microsoft Academic Search

Rotating bending fatigue tests were carried out on a high density Fe2%Ni based powder metallurgy steel at 50 Hz frequency and at room temperature. The material was subjected to high cycle fatigue to evaluate endurance\\/fatigue limit and its influence on heat treatment\\/microstructure. The fractured fatigue surfaces were examined using scanning electron microscope to study the mechanism\\/s associated with crack propagation.

K. V Sudhakar

2000-01-01

45

Powder Metallurgy Alloys: Proceedings of the Symposium Held at I.I.T. Bombay on October 11, 1980.  

National Technical Information Service (NTIS)

Powder Metallurgy is a rapidly growing manufacturing process for forming precision components and shapes from metal powders. The powder metallurgy technology is expanding into more demanding application and has led to the development of a variety of powde...

1982-01-01

46

Compaction of Titanium Powders  

Microsoft Academic Search

Accurate modeling of powder densification has been an area of active research for more than 60 years. The earliest efforts were focused on linearization of the data because computers were not readily available to assist with curve-fitting methods. In this work, eight different titanium powders (three different sizes of sponge fines <150 mum, <75 mum, and < 45 mum; two

Stephen J. Gerdemann; Paul D. Jablonski

2011-01-01

47

Compaction of Titanium Powders  

Microsoft Academic Search

Accurate modeling of powder densification has been an area of active research for more than 60years. The earliest efforts\\u000a were focused on linearization of the data because computers were not readily available to assist with curve-fitting methods.\\u000a In this work, eight different titanium powders (three different sizes of sponge fines ?m, ?m, and ?m; two different sizes of a hydride-dehydride

Stephen J. Gerdemann; Paul D. Jablonski

2011-01-01

48

MESOSCALE SIMULATIONS OF POWDER COMPACTION  

SciTech Connect

Mesoscale 3D simulations of shock compaction of metal and ceramic powders have been performed with an Eulerian hydrocode GEODYN. The approach was validated by simulating a well-characterized shock compaction experiment of a porous ductile metal. Simulation results using the Steinberg material model and handbook values for solid 2024 aluminum showed good agreement with experimental compaction curves and wave profiles. Brittle ceramic materials are not as well studied as metals, so a simple material model for solid ceramic (tungsten carbide) has been calibrated to match experimental compaction curves. Direct simulations of gas gun experiments with ceramic powders have been performed and showed good agreement with experimental data. The numerical shock wave profile has same character and thickness as that measured experimentally using VISAR. The numerical results show reshock states above the single-shock Hugoniot line as observed in experiments. We found that for good quantitative agreement with experiments 3D simulations are essential.

Lomov, Ilya; Fujino, Don; Antoun, Tarabay; Liu, Benjamin [Lawrence Livermore National Laboratory, P. O. Box 808, Livermore CA 94551 (United States)

2009-12-28

49

Ti matrix syntactic foam fabricated by powder metallurgy: Particle breakage and elastic modulus  

NASA Astrophysics Data System (ADS)

Titanium matrix syntactic foams have potential for orthopedic applications because of their good biocompatibility, corrosion resistance and ability of varying the elastic modulus. This paper studies the fabrication of Ti matrix syntactic foams embedded with ceramic microspheres (CMs) by a powder metallurgy method. The percentage of the crushed CMs during compaction was measured by the volume measurement and water absorption methods, and the elastic modulus of the Ti matrix syntactic foam was measured by compression tests. The effects of the Ti volume percentage and the compaction pressure on the percentage of crushed CMs and the elastic modulus were studied. For a given Ti volume percentage, the percentage of crushed CMs increases with increasing compaction pressure; for a given compaction pressure, the percentage of crushed CMs decreases with increasing Ti volume percentage. At a compaction pressure lower than 100 MPa, the elastic modulus increases with increasing Ti volume percentage and compaction pressure; at a compaction pressure above 100 MPa, further increases in Ti volume percentage and compaction pressure decrease the elastic modulus.

Xue, Xiaobing; Zhao, Yuyuan

2011-02-01

50

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

51

Shock compaction of molybdenum powder  

SciTech Connect

Shock recovery experiments carried out in the 9 to 12 GPa range on 1.4 distension Mo appear adequate to compact to full density (< 45 ..mu..m) powders. However, the stress levels 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 ..mu..m particles. The present model predicts that for powders 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 ..mu..m range.

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

1983-09-01

52

Shock Compaction of Molybdenum Powder.  

National Technical Information Service (NTIS)

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 a...

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

1983-01-01

53

Compaction of Amorphous Ferromagnetic Metal Powders.  

National Technical Information Service (NTIS)

The attractive magnetic properties of certain amorphous metal powders might be exploited in the electrical industry if the powders can be consolidated into relatively dense compacts. The production of integral bodies of an amorphous powder was attempted u...

R. D. Caligiuri

1982-01-01

54

Shock compaction of molybdenum powder  

Microsoft Academic Search

Shock recovery experiments carried out in the 9 to 12 GPa range on 1.4 distension Mo appear adequate to compact to full density (< 45 ..mu..m) powders. However, the stress levels 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 ..mu..m particles. The

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

1983-01-01

55

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

PubMed

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 a sacrificial wax template, fabricated using a commercial 3D-printer. Powder metallurgy processes were employed to generate the titanium scaffolds by filling around the wax template with titanium slurry. In the attempt to optimise the powder metallurgy technique, variations in slurry concentration, compaction pressure and sintering temperature were investigated. By altering the wax design template, pore sizes ranging from 200 to 400 microm were achieved. Scaffolds with porosities of 66.8 +/- 3.6% revealed compression strengths of 104.4+/-22.5 MPa in the axial direction and 23.5 +/- 9.6 MPa in the transverse direction demonstrating their anisotropic nature. Scaffold topography was characterised using scanning electron microscopy and microcomputed tomography. Three-dimensional reconstruction enabled the main architectural parameters such as pore size, interconnecting porosity, level of anisotropy and level of structural disorder to be determined. The titanium scaffolds were compared to their intended designs, as governed by their sacrificial wax templates. Although discrepancies in architectural parameters existed between the intended and the actual scaffolds, overall the results indicate that the porous titanium scaffolds have the properties to be potentially employed in orthopaedic applications. PMID:18556060

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

2008-06-16

56

The Making of Titanium and Titanium-Alloy Shapes by Casting, Powder Metallurgy, and Other Processes.  

National Technical Information Service (NTIS)

The state of the art of making titanium and titanium-alloy shapes by methods other than machining from wrought materials is reviewed. The methods covered are casting, powder metallurgy, metal spraying, electroforming and chemical vapor deposition. Of thes...

J. G. Kura V. D. Barth H. McCurdy W. H. Safranek E. T. Hall

1966-01-01

57

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 1340C-1350C 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

58

Thixoforming of Stellite Powder Compacts  

SciTech Connect

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 deg. C-1350 deg. 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. [Institute of PolymerTechnology and Materials Engineering, Loughborough University, Loughborough, LE11 3TU (United Kingdom); Atkinson, H. V. [Department of Engineering, University of Leicester, University Rd., Leicester LE1 7RH (United Kingdom); Kapranos, P. [Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

2007-04-07

59

Worn surface characteristics of Cu-based powder metallurgy bake materials for aircraft  

Microsoft Academic Search

Cu-based powder metallurgy brake materials are used for aircraft widely and successfully. The characteristics of worn surface of Cu-based powder metallurgy brake materials for aircraft after working under service condition were studied, and two main wear mechanisms were discussed. The results show that the main components of worn surface are graphite. SiO2, Fe, Cu and oxide of Fe (Fe3O4 and

Ping-ping YAO; Hong-chao SHENG; Xiang XIONG; Bai-yun HUANG

2007-01-01

60

Fatigue crack initiation and propagation of binder-treated powder metallurgy steels  

Microsoft Academic Search

Many of the targeted applications for powder-metallurgy materials, particularly in the automotive industry, undergo cyclic\\u000a loading. It is, therefore, essential to examine the fatigue mechanisms in these materials. The mechanisms of fatigue-crack\\u000a initiation and propagation in ferrous powder-metallurgy components have been investigated. The fatigue mechanisms are controlled\\u000a primarily by the inherent porosity present in these materials. Since most, if not

S. J. Polasik; J. J. Williams; N. Chawla

2002-01-01

61

A study on the development of a substitution process by powder metallurgy in automobile parts  

Microsoft Academic Search

Powder metallurgy processes using sintering are able to form net-shaped products and have been used widely in the production of automobile parts to improve productivity. However, the toughness of powder products is generally poor because they contain pores. Therefore, forged products are used in parts subjected to severe fatigue loads, but in the case of powder products having high toughness,

G. B Jang; M. D Hur; S. S Kang

2000-01-01

62

Compacting of various metal, alloy and ceramic powder using 20 kHz ultrasonic vibration compacting equipments with upper and lower vibration punches  

Microsoft Academic Search

-20 kHz ultrasonic vibration compacting system with 15-mm-diameter upper and lower vibration punches and a radial vibration die, and 20 kHz vibration compacting system using 5-mm-diameter upper and lower vibration punches are studied. Compacting of metal, alloy and ceramics powder is important process for powder metallurgy which is used for producing small and precise mechanical parts and required for various

J. Tsujino; N. Shimada; Y. Saotome; E. Sugimoto

2009-01-01

63

A new apparatus for non-destructive evaluation of green-state powder metal compacts using the electrical-resistivity method  

Microsoft Academic Search

This paper presents a new apparatus developed for non-destructive evaluation (NDE) of green-state powder metal compacts. A green-state compact is an intermediate step in the powder metallurgy (PM) manufacturing process, which is produced when a metal powder-lubricant mixture is compacted in a press. This compact is subsequently sintered in a furnace to produce the finished product. Non-destructive material testing is

Gene Bogdanov; Reinhold Ludwig; William R. Michalson

2000-01-01

64

An integrated approach to the characterization of powder metallurgy components performance during green machining  

Microsoft Academic Search

Green machining of powder metallurgy (P\\/M) components appears as an interesting procedure to solve the eternal problems associated with the poor machining behaviour of porous metallic samples. With the increasing usage of sinter-hardenable powders for high performance applications, green machining is an attractive method to lower production costs and compete against other shaping processes. Green machining is not a straightforward

Etienne Robert-Perron; Carl Blais; Yannig Thomas; Sylvain Pelletier; Martin Dionne

2005-01-01

65

Powder Metallurgy Processing of Dual Phase Al Rich Fe-Al Intermetallics.  

National Technical Information Service (NTIS)

A powder metallurgy technique was used to fabricate two different dual-phase Al-rich Fe-Al intermetallics, namely, FeAl2-Fe2Al5 and FeAl3-Fe2Al5. Powders were first produced by inert gas atomization, and then subsequently consolidated by hot pressing at 1...

Y. L. Jeng R. Hayes J. Wolfenstine E. J. Lavernia

1995-01-01

66

Microstructure and Mechanical Behavior of Powder Metallurgy Mg98.5Gd1Zn0.5 Alloy  

NASA Astrophysics Data System (ADS)

The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 C and 400 C). The microstructure of extruded materials was characterized by ?-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 ?m in the extruded ingot, down to 1.6 ?m for powders extruded at 623 K (350 C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

Cabeza, Sandra; Garcs, Gerardo; Prez, Pablo; Adeva, Paloma

2013-10-01

67

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

68

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

National Technical Information Service (NTIS)

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 -...

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

1997-01-01

69

[Concomitant influence of occupational and social risk factors on health of workers engaged into powder metallurgy].  

PubMed

Results of health risk evaluation in workers engaged into powder metallurgy, using complex of hygienic, medical, epidemiologic and sociologic studies, enable to define priority occupational and social risk factors, to assess degree of their influence on the workers' health and to identify occupationally induced diseases. PMID:23461181

Shur, P Z; Za?tseva, N V; Kostarev, V G; Lebedeva-Nesevria, N A; Shliapnikov, D M

2012-01-01

70

Knowledge based and adaptive computational techniques for concurrent design of powder metallurgy parts  

Microsoft Academic Search

The practice of concurrent engineering (CE) is adopted widely to facilitate integrated design and manufacture by industry in order to maintain competitiveness in the market place. Use of near net-shape processes like powder metallurgy (PM) within a CE environment can give added benefits in terms of material utilisation and environmental considerations. A system for concurrent design of PM parts is

R. P Cherian; P. S Midha; L. N Smith; A. G Pipe

2001-01-01

71

Characterization of the microstructure and phase equilibria calculations for the powder metallurgy superalloy IN100  

Microsoft Academic Search

The microstructure of the Ni-based superalloy IN100 processed by a powder metallurgy route was evaluated to reveal the structures, volume fractions, distributions, and chemistries of the various phases present. These data were compared with those predicted by computational thermodynamics. It is shown that the microstructural parameters expected on the basis of global equilibrium conditions differ significantly from those measured experimentally.

Am. Wusatowska-Sarnek; Gautam Ghosh; Gregory B. Olson; Mj. Blackburn; M. Aindow

2003-01-01

72

Fabrication of TiB 2 particulate reinforced magnesium matrix composites by powder metallurgy  

Microsoft Academic Search

Magnesium metal matrix composites (MMCs) reinforced with 10, 20 and 30 vol.% TiB2 particulates, respectively, were fabricated by powder metallurgy. The microstructure, porosity, hardness and abrasive wear behavior of the composites were evaluated. Microstructural characterization of Mg MMCs showed generally uniform reinforcement distribution. As compared with pure Mg, the hardness (HB) values of Mg MMCs reinforced with 10, 20 and

H. Y. Wang; Q. C. Jiang; Y. Wang; B. X. Ma; F. Zhao

2004-01-01

73

NEW B OHLER POWDER METALLURGY HIGH SPEED STEEL WITH EXCELLENT HOT HARDNESS  

Microsoft Academic Search

High Performance Cutting - that means reducing production costs by using higher cutting speeds and by reducing the amount of coolant and lubricant (for example using dry cutting). For the cutting tools this means a much higher requirement for strength and hot hardness than under normal cutting conditions. Bhler has therefore developed a new super-hard powder metallurgy high speed steel

I. Maili; R. Rabitsch; W. Liebfahrt; H. Makovec; E. Putzgruber

74

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 Andr; Rodrigues Henriques; Pedro Paulo de Campos; Jos Carlos Bressiani

75

Processing of M2 powder metallurgy high-speed steel by means of starch consolidation  

Microsoft Academic Search

A study is made of a new method called starch consolidation (SC) for the production of powder metallurgy (P\\/M) high-speed steel (HSS) components. Samples of a commercial HSS, M2, were shaped by using 1.5, 3.5 and 5vol% of starch and up to 60vol% of powder. The high solids loading was made possible by a small addition (0.03wt%) of dispersant (polyacrylic

P. Romano; F. J. Velasco; J. M. Torralba; N. Candela

2006-01-01

76

Production of a Low Young Modulus Titanium Alloy by Powder Metallurgy  

Microsoft Academic Search

Titanium alloys have several advantages over ferrous and non-ferrous metallic materials, such as high strength-to- weight ratio and excellent corrosion resistance. A blended elemental titanium powder metallurgy process has been developed to offer low cost commercial products. The process employs hydride-dehydride (HDH) powders as raw material. In this work, results of the Ti-35Nb alloy sintering are presented. This alloy due

Dalcy Roberto dos Santos; Vinicius Andr; Rodrigues Henriques; Carlos Alberto; Alves Cairo

2005-01-01

77

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

PubMed

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, alpha-Ti and a TiP-like phase. When the composite is immersed in the simulated body fluid for a certain time, a poor-crystallized, calcium-deficient, carbonate-containing apatite film will form on the surface of the composite. The time required to induce apatite nucleation is within 2 h. In addition, the apatite is also incorporated with a little magnesium and chlorine element. It is found that Ti2O has the ability to induce the formation of bone-like apatite in the SBF. And a dissolve of the CaO phase could also provide favorable conditions for the apatite formation, by forming open pores on the surface of the composite and increasing the degree of supersaturation of the SBF with respect to the apatite. PMID:12069332

Ning, C Q; Zhou, Y

2002-07-01

78

Explosive-powder compaction system  

Microsoft Academic Search

Sandia National Laboratories has developed a pressure-control system and a test fixture to study the behavior of explosive materials during compaction. Both the pressure-control system and the test fixture are self-contained and portable. Explosive materials are compacted in a bridged header charge holder assembly by means of a test fixture and a pneumatic cylinder arrangement. Forces are measured with load

A. P. Montoya; M. L. Reichenbach

1981-01-01

79

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

PubMed

Mg/Ca (1 wt.%, 5 wt.%, 10 wt.% Ca) composites were prepared from pure magnesium and calcium powders using the powder metallurgy method, aiming to enlarge the addition of Ca content without the formation of Mg(2)Ca. The microstructures, mechanical properties and cytotoxicities of Mg/Ca composite samples were investigated. The corrosion of Mg/Ca composites in Dulbecco's modified Eagle's medium (DMEM) for various immersion intervals was studied by electrochemical impedance spectroscopy measurements and environmental scanning electron microscope, with the concentrations of released Mg and Ca ions in DMEM for various immersion time intervals being measured. It was shown that the main constitutional phases were Mg and Ca, which were uniformly distributed in the Mg matrix. The ultimate tensile strength (UTS) and elongation of experimental composites decreased with increasing Ca content, and the UTS of Mg/1Ca composite was comparable with that of as-extruded Mg-1Ca alloy. The corrosion potential increased with increasing Ca content, whereas the current density and the impedance decreased. It was found that the protective surface film formed quickly at the initial immersion stage. With increasing immersion time, the surface film became compact, and the corrosion rate of Mg/Ca composites slowed down. The surface film consisted mainly of CaCO(3), MgCO(3)x3H(2)O, HA and Mg(OH)(2) after 72 h immersion in DMEM. Mg/1Ca and Mg/5Ca composite extracts had no significant toxicity (p>0.05) to L-929 cells, whereas Mg/10Ca composite extract induced approximately 40% reduced cell viability. PMID:19815098

Zheng, Y F; Gu, X N; Xi, Y L; Chai, D L

2009-10-06

80

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

81

Explosive-Powder Compaction System.  

National Technical Information Service (NTIS)

Sandia National Laboratories has developed a pressure-control system and a test fixture to study the behavior of explosive materials during compaction. Both the pressure-control system and the test fixture are self-contained and portable. Explosive materi...

A. P. Montoya M. L. Reichenbach

1981-01-01

82

Press Molds for Powder Metallurgy. Design and Construction.  

National Technical Information Service (NTIS)

The technological principles and classification of the methods of formation of cermet articles are presented, the principles of constructing press molds for cold and hot pressing of articles from metallic powders are stated, and also the repressing and ca...

E. L. Pechentkovskii G. G. Serdyuk I. D. Radomyselskii

1971-01-01

83

Apparent Electrical Conductivity of Porous Titanium Prepared by the Powder Metallurgy Method  

NASA Astrophysics Data System (ADS)

Porous titanium is produced by the powder metallurgy method. Dependence of the electrical conductivity on the porosity and pore size is investigated and the experimental results are compared with a number of models. It is found that the minimum solid area model could be successfully applied to describe the relationship between the electrical conductivity and the porosity of porous titanium. This kind of conductivity increases with increasing pore sizes.

Li, Cheng-Feng; Zhu, Zhen-Gang

2005-10-01

84

Wear behavior of a ferritic stainless steel with carbides manufactured through powder metallurgy  

Microsoft Academic Search

A ferritic stainless steel has been manufactured through the powder metallurgy (P\\/M) route: uniaxial pressing and sintering.\\u000a The sintering process was carried out in vacuum, at 1215 C for 30 min. After sintering, materials showed nearly 90% of density.\\u000a A complete metallographic study was carried out using optical microscopy and scanning electron microscopy (SEM). Wear behavior\\u000a was evaluated using a

E. M. Ruiz-Navas; N. Antn; E. Gordo; R. Navalpotro; F. Velasco

2001-01-01

85

Heat treatment effects on mechanical behavior of copper-nickel-tin produced via powder metallurgy  

Microsoft Academic Search

Certain spring applications require a material with a combination of high strength, stiffness, and electrical conductivity. An alloy, Cu-15wt%Ni-8wt%Sn, formed via a powder metallurgy process, is one of several copper-based alloys which can be heat treated\\/processed to form a metallic nano-structured alloy with good combinations of yield strength and electrical conductivity. For certain heat treatment conditions, this alloy decomposes spinodally

Joshua Benjamin Caris

2007-01-01

86

Environmentally assisted, sustained-load crack growth in powder metallurgy nickel-based superalloys  

Microsoft Academic Search

To examine the influence of niobium (Nb) on sustained-load crack growth (SLCG) in oxygen, three powder metallurgy (P\\/M) nickel-based\\u000a superalloys, with nominal compositions similar to IN100, but with 0, 2.5, and 5 wt pct of Nb, are used. These alloys are gamma-prime\\u000a (?) strengthened and have comparable volume fractions (53 vol pct) of ? precipitates. The SLCG experiments are conducted

Zhifan Huang; Carl Iwashita; Irene Chou; Robert P. Wei

2002-01-01

87

Metal foaming by a powder metallurgy method: Production, properties and applications  

Microsoft Academic Search

A method for fabricating metal foams based on the powder metallurgy process is presented. This foaming process allows for\\u000a the production of complex-shaped foam parts, metal foam sandwich panels and foam filled hollow profiles. A range of alloys\\u000a can be foamed using this method including aluminum, zinc, tin, lead and steel. The as-produced part has a closed-cell microstructure\\u000a and a

C.-J. Yu; Harald H. Eifert; John Banhart; Joachim Baumeister

1998-01-01

88

Fabrication of B 4C particulate reinforced magnesium matrix composite by powder metallurgy  

Microsoft Academic Search

Magnesium metal matrix composites (MMCs) reinforced with various fractions of 10, 15 and 20vol.% B4C particulates fabricated by powder metallurgy (P\\/M) technique were investigated. Microstructure characterization of the composites revealed necklace distribution of B4C particulates in the matrix material and the presence of minimal micro-porosity. The X-ray diffraction (XRD) showed the formation of MgO and MgB2 in B4C\\/Mg composites. Moreover,

Q. C. Jiang; H. Y. Wang; B. X. Ma; Y. Wang; F. Zhao

2005-01-01

89

Cooling precipitation and strengthening study in powder metallurgy superalloy U720LI  

Microsoft Academic Search

The excellent mechanical properties of powder metallurgy (P\\/M) superalloys strongly depend on the microstructure, such as\\u000a grain size, and morphology and size distribution of the ? precipitates. The microstructure is, in turn, determined by the heat treatment, viz., solution annealing, quenching, and subsequent aging. To study the effect of the quenching process, two types of quenching\\u000a methods were used to

Jian Mao; Keh-Minn Chang; Wanhong Yang; Koushik Ray; Suhas P. Vaze; David U. Ferrer

2001-01-01

90

Strength and microstructure of powder metallurgy processed restacked Cu-Nb microcomposites  

Microsoft Academic Search

Powder metallurgy (PM) was used to fabricate Cu-Nb microcomposites both at the laboratory and intermediate industrial scales.\\u000a Ultimate tensile strengths (UTSs) of 1.6 and 1.035 GPa were obtained for the laboratory-and intermediate-scale composites,\\u000a respectively. Filament morphology and the microstructure of various microcomposites were examined with transmission electron\\u000a microscopy (TEM), scanning electron microscopy (SEM), and optical microscopy. In the early stages

S. Pourrahimi; H. Nayeb-Hashemi; S. Foner

1992-01-01

91

Axial fatigue behavior of binder-treated versus diffusion alloyed powder metallurgy steels  

Microsoft Academic Search

A comparative study has been conducted on the microstructure, tensile, and axial fatigue behavior of two Fe0.5Mo1.5Cu1.75Ni alloys, made by binder-treated and diffusion alloying processes. The mechanical properties will be explained in terms of the pore size and morphology, as well as the heterogeneous microstructures typical of ferrous powder metallurgy materials. Binder treatment can provide a variety of advantages in

N. Chawla; T. F. Murphy; K. S. Narasimhan; M. Koopman; K. K. Chawla

2001-01-01

92

A PLASTICITY MODEL FOR POWDER COMPACTION PROCESSES  

Microsoft Academic Search

An endochronic constitutive model for cold powder compaction processes is developed. Although the concept of yield surface has not been explicitly assumed in the endochronic theory, it is demonstrated that the cone-cap yield surface can be derived as a special case of the proposed endochronic model. The plastic flow rule and the dilatancy condition of the model are derived and

A. Bakhshiani; M. Mofid; A. R. Khoei

93

Relationship between fractional porosity and tensile strength for high-porosity sintered ferrous powder compacts  

SciTech Connect

The current study examines the mechanical properties of pressed and sintered ferrous powder metallurgy compacts with low relative densities, between 0.6 and 0.8. Three different powder particle compositions were investigated: eutectoid steel, stainless steel, and stainless tool steel compacts. To obtain information concerning the tensile properties of these low-density compacts, simple tensile tests were performed. In addition, Vickers microhardness tests were performed on metallographic sections of the tensile bars. The results from these tests are used to compare the measured relative strength values with estimates generated by previously published models. Also, the fracture surfaces of selected compacts were examined in the scanning electron microscope to obtain information concerning the fracture process.

Baron, R.P.; Wawner, F.E.; Wert, J.A. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science and Engineering

1998-07-03

94

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

95

Proceedings of 1974 National powder metallurgy conference held at Boston, Massachusetts, April 9--10, 1974  

Microsoft Academic Search

Papers given at the conference on process variables in production of P\\/M ; parts, properties of 316L steel powder, compacts, properties of highly porous Al ; powder compacts, properties of Cu infiltrated steel powders, uses of P\\/M Ti and P\\/; M Al alloys, heat treatment of P\\/M parts, quality control, safety, ultrasonic ; testing of P\\/M parts, P\\/M sealing, cold

Halter

1974-01-01

96

Simulation of dynamic compaction of metal powders  

NASA Astrophysics Data System (ADS)

This article presents numerical studies on the deformation of particles during dynamic compaction of metal powders. The analysis of the process is based on a micromechanics approach using multiple particle configurations. The material considered is elastoviscoplastic with interparticle friction. Two-dimensional studies on particles in close packed arrangement were carried out using plane strain conditions for deformation and thermal response. The finite element method using an explicit dynamic analysis procedure was used for the simulations. The influence of speed of compaction, strain hardening, strain rate dependency, interparticle friction and size of the powder particles on the final shape and temperature variations within the particles were analyzed. The studies offer useful information on the shape and temperature variations within the particles. The results provide a better understanding of the dynamic compaction process at the micromechanics level.

Kumar, D. Roshan; Kumar, R. Krishna; Philip, P. K.

1999-01-01

97

Control of microstructure and component shape in rapidly solidified\\/powder metallurgy titanium alloys  

Microsoft Academic Search

Extensive use of titanium rapidly solidified\\/powder metallurgy (RS\\/PM) components requires not only careful control of the\\u000a microstructure for optimum mechanical properties but also cost-effective processing. A new direct reduction process for production\\u000a of titanium alloy powder will be presented. Control of the microstructure in conventional alloys such as Ti-6Al-4V and in\\u000a non-conventional dispersion strengthened terminal and intermetallic alloys will be

F H Froes; D Eylon; R G Rowe; C F Yolton

1989-01-01

98

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

99

Processing condition for the development of cube texture in Ni and Ni alloy tapes fabricated by powder metallurgy process  

NASA Astrophysics Data System (ADS)

Bi-axially textured Ni, Ni-W (1, 3 and 5 at.%) and Ni-Cu alloy tapes for YBCO coated conductors were fabricated by powder metallurgy process including powder compaction, cold isostatic pressing, cold rolling and recrystallization heat treatment. The rod-like Ni and Ni alloy compacts were sintered at 1100 C for 6 h in 96% Ar-4% H2 atmosphere. The sintered Ni and Ni-W rods were successfully cold-rolled into thin tapes of 80-100 ?m thickness with 5% reduction at each path, but the Ni-Cu alloy rods with Cu content less than 20 at.% were made into tapes. The Ni and Ni alloy tapes were heat-treated at 800-1200 C for the development of cube texture. The good (200) texture was obtained for both Ni and Ni-W alloy tapes, while it was obtained only for the Ni-Cu tapes with low Cu contents. The W and Cu addition to Ni improved the mechanical properties by solid solution hardening. Critical current density (Jc) of YBCO film deposited on the CeO2/YSZ/CeO2(CYC)/Ni template was 0.25 MA/cm2 at 77 K and self-field.

Ji, Bong Ki; Lee, Dong-Wook; Kim, Min-Woo; Jun, Byung-Hyuk; Park, Pyeong Yeal; Jung, Kyu-Dong; Kim, Chan-Joong

2004-10-01

100

Compaction of amorphous ferromagnetic metal powders. Final report  

Microsoft Academic Search

The attractive magnetic properties of certain amorphous metal powders might be exploited in the electrical industry if the powders could be consolidated into relatively dense compacts. This work attempted to produce integral bodies of an amorphous powder using explosive compaction techniques. A disk-shaped compact 2.5 cm in diameter by 1 cm thick having a relative measured density of 91% was

Caligiuri

1982-01-01

101

Compaction mechanism as the function of atomized powder particle size  

Microsoft Academic Search

The cold compaction process of spray dried powder for ceramic floor\\/wall tiles production was followed by compaction response and compaction rate diagrams. Seven fractions of defined size, as well as the industrial powder batch, were compacted at pressures up to 31.5 MPa. The effect of particle size, textural and morphological characteristics on the consolidation mechanism was investigated. Both plastic deformation

M. Radeka; J. Ranogajec; R. Marinkovi?-Nedu?in; B. ivanovi?

1995-01-01

102

Compacting Plastic-Bonded Explosive Molding Powders to Dense Solids  

SciTech Connect

Dense solid high explosives are made by compacting plastic-bonded explosive molding powders with high pressures and temperatures for extended periods of time. The density is influenced by manufacturing processes of the powders, compaction temperature, the magnitude of compaction pressure, pressure duration, and number of repeated applications of pressure. The internal density variation of compacted explosives depends on method of compaction and the material being compacted.

B. Olinger

2005-04-15

103

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

104

Investigation of compaction, Young's modulus and tensile strength of binary powder mixtures using the multi-particle finite element method (MPFEM)  

Microsoft Academic Search

The compaction of particulate systems can be simulated using phenomenological elasto-plastic continuum models adopted from soil mechanics. These constitutive models, like the Drucker-Prager Cap (DPC) model, have been successfully implemented in a finite element method (FEM) framework to model compaction unit-operations in various powder processing industries such as powder metallurgy, ceramics and pharmaceuticals. The constitutive model parameters for these phenomenological

Tuhin Sinha

2011-01-01

105

Compaction and sintering characteristics of composite metal powders  

Microsoft Academic Search

The compaction and sintering characteristics of composite metal powders are examined using aluminium-copper, aluminium-iron and copper-iron powders. The density of a composite green compact is predicted based on the compacting pressure-density curve of each powder. The effects of the volume fraction of the mixed powders and the sintering temperature on the density and hardness of a sintered part are also

K. Yamaguchi; N. Takakura; S. Imatani

1997-01-01

106

Explosive compaction of Nd-Fe-B powder  

Microsoft Academic Search

The explosive compaction technique has been applied to consolidate Nd-Fe-B amorphous powder, and the microstructure and magnetic properties of the compacts have been investigated. Explosive compaction was performed using an improved direct method. Nd-Fe-B amorphous powder was filled in the upper part of a metal sleeve and SiC powder was filled up to a lower part of the powder to

S Ando; Y Mine; K Takashima; S Itoh; H Tonda

1999-01-01

107

Structure and properties of Nb-Al alloys prepared by powder metallurgy  

NASA Astrophysics Data System (ADS)

The structure and short-time strength of Nb-Al alloys of two compositions prepared by powder metallurgy are studied. The mechanical alloying of niobium with aluminum in a planetary ball mill in air is shown to result in simultaneous alloying of niobium with oxygen. During subsequent vacuum high-temperature sintering, disperse particles of a complex oxide, whose tentative composition is (AlNb)2O3, form in the alloy structure. The short-time strength at 1250C of the prepared alloys exceeds that of nickel-aluminum superalloys.

Karpov, M. I.; Korzhov, V. P.; Prokhorov, D. V.; Vnukov, V. I.; Kiiko, V. M.; Tolstun, A. N.; Kolobov, Yu. R.; Golosov, E. V.

2013-04-01

108

Low cycle fatigue improvement of powder metallurgy titanium alloy through thermomechanical treatment  

Microsoft Academic Search

A low-cost ? type Ti-1.5Fe-6.8Mo-4.8Al-1.2Nd (mass fraction, %)(T12LCC) alloy was produced by blended elemental powder metallurgy(P\\/M) method and subsequent thermomechanical treatment. Low cycle fatigue(LCF) behavior of P\\/M T12LCC alloy before and after thermomechanical treatment was studied. The results show that the LCF resistance of P\\/M titanium alloy is significantly enhanced through the thermomechanical treatment. The mechanisms for the improvement of

Bin LIU; Yong LIU; Xiao-yu HE; Hui-ping TANG; Li-fang CHEN

2008-01-01

109

Electrochemical study of Aluminum-Fly Ash composites obtained by powder metallurgy  

SciTech Connect

In this paper, two different ASTM C 618 Class C fly ashes (FA) were used for the production of aluminum metal matrix composites (MMCs) using powder metallurgy (PM) technology. Calcareous FAs were sampled from the electrostatic precipitators of two different lignite-fired power stations: from Megalopolis, Southern Greece (MFA) and from Kardia, Northen Greece (KFA), under maximum electricity load. FAs were milled in order to reduce the mean particle diameter and Aluminum-FA composites containing 10% and 20% of FA were then prepared and compacted. The green products were sintered for 2 h at 600 Degree-Sign C. Sintered Al-FA MMCs showed increased hardness and wear resistance suggesting their possible use in industrial applications for example in covers, casings, brake rotors or engine blocks. As most possible industrial applications of MMCs not only require wear resistance, but also corrosion resistance in different mild aggressive medias, this paper aims to study the electrochemical behavior of FA MMCs in order to evaluate their corrosion resistance. The morphology and chemical composition of the phases in the Aluminum-FA composite samples were investigated using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDXS). Moreover, topographic and Volta potential maps were acquired by Scanning Kelvin Probe Force Microscopy (SKP-FM). Volta potential maps provide information about the electrochemical behavior of the different phases in absence of electrolyte. The electrochemical behavior was investigated by Open Circuit Potential measurements and potentiodynamic polarization, while the corrosion mechanisms were studied by SEM observations after different times of immersion in a mild corrosive medium. In all cases it could be stated that the addition of the FA particles into the Al matrix might cause an increase of the hardness and mechanical properties of the pure aluminum but deteriorates the corrosion resistance. The degradation phenomena occurring on the FA containing samples might be related to the following mechanisms: 1) Partial detachment or dissolution of the FA soluble phases, in particular based on Si, Fe and Ca; 2) dissolution of the Al matrix surrounding the FA particles due to crevice corrosion; 3) Al localized dissolution due to galvanic coupling between the Fe-rich intermetallics and the matrix. - Highlights: Black-Right-Pointing-Pointer Aluminum metal matrix composites containing two types of fly ashes have been characterized. Black-Right-Pointing-Pointer The microstructure and the electrochemical behavior have been studied using different techniques. Black-Right-Pointing-Pointer The addition of FA deteriorates the corrosion resistance of the aluminum. Black-Right-Pointing-Pointer Degradation mechanisms: galvanic coupling, crevice corrosion, detachment of FA particles.

Marin, E. [Department of Chemistry, Physics and Environment, University of Udine, Via Cotonificio 108, 33100, Udine (Italy); Lekka, M., E-mail: maria.lekka@uniud.it [Department of Chemistry, Physics and Environment, University of Udine, Via Cotonificio 108, 33100, Udine (Italy); Andreatta, F.; Fedrizzi, L. [Department of Chemistry, Physics and Environment, University of Udine, Via Cotonificio 108, 33100, Udine (Italy); Itskos, G. [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechneiou 9, Zografou 15780, Athens (Greece); Centre for Research and Technology Hellas/Institute for Solid Fuels Technology and Applications, Mesogeion Avenue 357-359, Halandri 15231, Athens (Greece); Moutsatsou, A. [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechneiou 9, Zografou 15780, Athens (Greece); Koukouzas, N. [Centre for Research and Technology Hellas/Institute for Solid Fuels Technology and Applications, Mesogeion Avenue 357-359, Halandri 15231, Athens (Greece); Kouloumbi, N. [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechneiou 9, Zografou 15780, Athens (Greece)

2012-07-15

110

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

111

Stress-strain behavior and shape memory effect in powder metallurgy TiNi alloys  

Microsoft Academic Search

The shape memory properties of the TiNi alloy produced by a powder metallurgical method have been evaluated from tensile stress-strain curves. The contamination of the powders during atomization can be suppressed by applying the Plasma Rotating Electrode Process (P-REP), so that the compact made by Hot Isostatic Pressing (HIP) is expected to exhibit the shape memory effect identical to the

H. Kato; T. Koyari; S. Miura; M. Tokizane

1994-01-01

112

Study of Metallic Carbide (MC) in a Ni-Co-Cr-Based Powder Metallurgy Superalloy  

NASA Astrophysics Data System (ADS)

The evolution of carbides in a Ni-Cr-Co-based powder metallurgy (PM) superalloy in the as-atomized, as-atomized + annealed, hot isostatic pressed (HIPed) and HIPed + annealed conditions were systematically analyzed to understand the formation of blocky metallic carbide (MC) along the previous particle boundary (PPB). The results show that the carbides both on the powder surfaces and in the bulk of the powder particles are mainly fan-shaped MC whose decomposition temperatures are in the range of 1473 K to 1493 K (1200 C to 1220 C). PPB carbides in the HIPed alloy are mainly block-shaped MC, and the fan-shaped MC densely distributed in the area that have not been consumed by the recrystallized grains. The formation mechanism of PPB carbides can be described as follows: When the powders are HIPed at 1453 K (1180 C), the fan-shaped carbides are decomposed at the migrating boundaries of recrystallized grains, and the preferential precipitation of block-shaped MC at PPB is promoted by the carbide-forming elements released by the fan-shaped carbides. When the HIPed alloy is annealed at 1453 K (1180 C), the area fraction of PPB carbides increases with an increase in annealing time but that of the fan-shaped carbides exhibits opposite behavior. This proves the above formation mechanism of PPB carbides.

Ma, Wen-Bin; Liu, Guo-Quan; Hu, Ben-Fu; Hu, Peng-Hui; Zhang, Yi-Wen

2013-10-01

113

Analysis and experimental validation of performance for an axial flux permanent magnet brushless DC motor with powder iron metallurgy cores  

Microsoft Academic Search

A small axial flux permanent magnet (AFPM) brushless DC servomotor with powder iron metallurgy cores has been designed and built and its results are presented in this paper. To predict the motor performance, 2-D and 3-D finite element analyses have been performed respectively, and the results are compared in terms of computations of the no-load field and the cogging torque.

Z. Zhang; F. Profumo; A. Tenconi; M. Santamaria

1997-01-01

114

Sinterability of powder metallurgy tool steels produced with the application of heat-time treatment of the melt  

Microsoft Academic Search

Powder metallurgy tool steels prepared from the powders of gas-atomized melts subjected to heat-time treatment were studied.\\u000a Material containing above 1.2% carbon, in addition to tungsten and molybdenum, exhibited a porosity decrease of 612% after\\u000a vacuum sintering at a temperature 70?C lower than that of solid-phase sintering. The increased sinterability of the alloys\\u000a was related to the presence of a

L. A. Poznyak; Y. V. Sorokin; N. P. Korzhova; O. V. Datskevich

1997-01-01

115

A Neural Network Approach for Selection of Powder Metallurgy Process Parameter of Rapidly Solidified White Cast Iron  

Microsoft Academic Search

Powder Metallurgy (P\\/M) involves multiple input and output which are non-linearly related for which statistical optimization methods are not suitable. These considerations lead to adoption of neural network (NN) for proper selection of P\\/M process parameter. In the present work, white cast iron powder is taken as the work material and NN approach is employed which allows specification of multiple

G. Salwan; Debadutta Mishra; S. Pani

2009-01-01

116

Microstructure Evolution during Supersolvus Heat Treatment of a Powder Metallurgy Nickel-Base Superalloy  

NASA Astrophysics Data System (ADS)

Microstructure evolution during the supersolvus heat treatment of a powder-metallurgy, low-solvus, high-refractory (LSHR) superalloy was established. For this purpose, three lots of LSHR with varying initial carbon/boron composition and thermomechanical history were subjected to a series of short-time (induction) and long-time (furnace) heat treatments followed by scanning electron microscopy/electron backscatter diffraction and quantitative metallography. The size of the (pinned) gamma grains exhibited a limited dependence on heating rate and soak time at peak temperature, and it was generally smaller than the predictions based on the classic Smith-Zener model. The differences were rationalized in terms of stereological and pinning-particle location effects. Observations of limited coarsening of the carbide/boride pinning particles were interpreted in the context of prior experimental observations and a modified Lifshitz-Slyosov-Wagner model applied previously for the coarsening of compound phases in steels.

Semiatin, S. L.; McClary, K. E.; Rollett, A. D.; Roberts, C. G.; Payton, E. J.; Zhang, F.; Gabb, T. P.

2012-05-01

117

Corrosion properties in a simulated body fluid of Mg/?-TCP composites prepared by powder metallurgy  

NASA Astrophysics Data System (ADS)

Magnesium matrix composites (MMC) reinforced with 5wt% tricalcium phosphate (TCP) particles were prepared by powder metallurgy. Pure magnesium (CP-Mg) was fabricated by the same procedure for comparison. Scanning electron microscopy and energy- dispersive X-ray spectroscopy analyses revealed that TCP particles were distributed homogeneously in the MMC. In order to investigate the corrosion properties, MMC samples were immersed in a simulated body fluid (SBF) at 3100.5 K for 72 h. The mass loss of the samples in SBF and the pH values of the SBF were evaluated. Moreover, electrochemical measurements were conducted in the SBF. It was shown that the corrosion rate of the MMC decreased with the addition of TCP compared with CP-Mg. Hydroxyapatite was formed on the surface of MMC samples after immersion in the SBF for 72 h but not on the surface of CP-Mg.

Wang, Yong; Wu, Ze-hong; Zhou, Hong; Liao, Zhi-dong; Zhang, Heng-fei

2012-11-01

118

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

SciTech Connect

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 measurements were also made over a temperature range of 50 to 300C since workpiece temperatures can attain levels this high during the machining operation. The thermal conductivity was measured using an apparatus having a design based on the comparative method. The experimentally determined thermal conductivities were modeled by mathematical models found in the technical literature and modified for the present study. The thermal conductivity of this material increases with increasing relative density and temperature; it is also dependent on the matrix structure for a given porosity.

Agapiou, J.S. (General Motors Technical Center, Warren, MI (United States)); DeVries, M.F. (Univ. of Wisconsin, Madison (United States))

1989-05-01

119

Magnetic properties of dynamically compacted glassy metal powder cores  

Microsoft Academic Search

Dynamic compaction of glassy metal powder generally results in denser noncrystalline components than any other consolidation techniques. For example, a density of more than 90 % of the powder material can be achieved by dynamic compaction whereas it is typically about 70-80% for a component obtained by low temperature (below material's crystallization temperature) mechanical pressing. Bulk amorphous materials other than

R. Hasegawa; C. F. Cline

2008-01-01

120

Cleaner production of porcelain tile powders. Fired compact properties  

Microsoft Academic Search

A new ceramic powder preparation process, the droplet-powder granulation process (DPGP), was recently proposed for the cleaner production of ceramic tiles. The DPGP granules and resulting pressed compacts were characterized and compared with the granules and compacts obtained by spray-drying (SD) and dry granulation (G) processes in a previous paper. The results showed the feasibility of using the DPGP in

Z. Shu; J. Garcia-Ten; E. Monfort; J. L. Amoros; J. Zhou; Y. X. Wang

121

Effect of porosity on the thermal conductivity of copper processed by powder metallurgy  

NASA Astrophysics Data System (ADS)

Powder metallurgy is a preferred method of processing copper-carbon composites due to the non-wetting nature of these materials. Porosities are inherently introduced in these material systems, and adversely affect the thermal conductivity of the composite material, among other factors including interfaces and reinforcement distribution. In this work, we focus on the matrix material of pure copper and systematically analyzed the effect of volume fraction of porosities on the thermal conductivity. Spherical and dendritic copper powder materials were processed and it was found that the surface chemistry and morphology of particles affected the thermal conductivity apart from the porosity values. In order to study the effect of porosities alone, dentritic powder was used in the study. The thermal conductivity vs. porosity behavior showed three distinct domains. In all the domains the thermal conductivity decreases as volume fraction of porosities increases; however, in domain II, the decrease was much steeper than the other two. We are able to explain the variation based on the presence of interconnected and open pores in domain III to closed pores in domain I, and the transition occurring in domain II. None of the existing models capture the overall behavior. However, if we specifically account for the variation of number of grain boundaries with sintering, then the modified EMT model can match the experimental data.

Vincent, C.; Silvain, J. F.; Heintz, J. M.; Chandra, N.

2012-03-01

122

Powder metallurgy T15 tool steel: Part II. Microstructure and properties after heat treatment  

NASA Astrophysics Data System (ADS)

The effect of powder particle size and heat treatment on the micro structure and properties of hot isostatically pressed (hipped) T15 tool steel has been evaluated. Gas-atomized powder was screened into size fractions covering the range of ?44 to 1200 /i-m and hipped at 1130 C or 1195 C. The consolidated powders were austenitized at 1175 C or 1225 C and tempered at 538 C, 552 C, or 565 C to control prior austenite grain size, carbide type, carbide volume fraction, and carbide size distribution. Properties measured were bend strength, C-notch impact toughness, and hot hardness. Prior austenite grain size increases with hot isostatic pressing (hipping) temperature and austenitizing temperature but is independent of the particle size; similarly, the influence of austenitizing temperature on dissolution of MC and M6C is independent of the particle size. In each particle size fraction, the volume fraction and size distribution of MC are independent of the tempering temperature. For M6C, the volume fraction increases and the size distribution is skewed to coarser sizes with increasing tempering temperature. No significant differences in strength and toughness were detected as a function of particle size. Hot hardness is not affected by the particle size. The hot hardness of a powder blend (?1200 ?m) hipped at 1130 C was superior to that of commercial powder metallurgy (PM) T15 tool steel hipped at 1195 C; this is attributed to a finer carbide size in the noncommercial material. It is established that the subcommercial hipping temperature (1130 C) results in significant microstructural refinement; there is an associated small amount of residual porosity, and this controls the mechanical properties.

Kumar, K. S.; Lawley, A.; Koczak, M. J.

1991-11-01

123

Powder metallurgy T15 tool steel: Part I. Characterization of powder and hot isostatically pressed material  

NASA Astrophysics Data System (ADS)

The microstructure and constitution of T15 tool steel processed from gas-atomized powder have been characterized. From the atomized powder, four particle size ranges (?840, 250 to 840, 44 to 100, and ?44 ?m) were consolidated to full density by hot isostatic pressing (hipping) at 1130 C or 1195 C. Both atomized powder and consolidated material were examined by means of optical and electron microscopy, X-ray diffraction, chemical analysis, and micro-hardness. A segregated structure exists in the gas-atomized powder, independent of particle size; MC and M2C carbides are present, primarily at cell boundaries. The matrix of the powders is a mix of martensite and retained austenite. Weight fraction and overall composition of the carbides are insensitive to particle size, but the proportion of MC carbides increases with decreasing particle size. After consolidation, MC, M6C, and M23C6 carbides are present in a ferrite matrix. The carbide size distribution is skewed to larger carbide sizes at the higher consolidation temperature, independent of the prior particle size fraction, but there is no significant change in carbide volume fraction. For a given consolidation temperature, the size distribution of the MC and M6C carbides is broader for the coarser particle size fractions.

Kumar, K. S.; Lawley, A.; Koczak, M. J.

1991-11-01

124

Studies of design parameters in the fabrication of Nb--Al--Ge superconductors by the powder metallurgy infiltration method  

SciTech Connect

Experimental studies have been carried out in which the A15 phase of the Nb-Al-Ge system has been synthesized in the form of thin filaments contained in form rolled wires. A powder metallurgy approach has been used to achieve controlled porosity in compacts of sintered niobium powder. Infiltration with an aluminum-germanium eutectic alloy followed by mechanical deformation has produced small interconnected filaments embedded in the Nb matrix. Diffusion heat treatment for a short time transforms them into the A15 superconducting compound with a size range of 1-5 microns at 1300/sup 0/C and 1-9 microns at 1750/sup 0/C. The superconducting properties T/sub c/ and J/sub c/ were evaluated for samples subjected to different condition of time and temperature. The influence of certain parameters involved in the process has been investigated. The microstructure and microhardness of the Al-Ge eutectic alloy cooled at high and low cooling rates from temperatures between 900-400/sup 0/C have been evaluated. Optical and electron beam metallographic results are presented for the analysis of the different phases and relative compositions. The critical temperature measured inductively is between 16.4/sup 0/K and 18.1/sup 0/K depending on the heat treatment. The critical current density as a function of the applied magnetic field is reported. These data were obtained using a pulsed magnetic field technique that measured J/sub c/ at 4.2/sup 0/K in fields up to 100 kG. J/sub c/ was 8.8 x 10/sup 4/ amp/cm/sup 2/ at 20 kG and 3.6 x 10/sup 4/ amp/cm/sup 2/ at 60 kG for specimens containing approximately 20% A15 phase.

Granda, J.J.

1976-12-01

125

Die compaction of copper powder designed for material parameter identification  

Microsoft Academic Search

This article presents uniaxial compaction experiments of a fine copper powder in a cylindrical die. The compaction process consists of monotonic loading and of loading paths with inserted unloading and reloading cycles. An experimental setup that has been developed for determining the axial and radial stresses during the compaction is described and the calibration of the new device using highly

W. Bier; M. P. Dariel; N. Frage; S. Hartmann; O. Michailov

2007-01-01

126

Starch Consolidation as a New Process for Manufacturing Powder Metallurgy High-Speed Steels  

NASA Astrophysics Data System (ADS)

The development of a new method called starch consolidation, suitable for the production of powder metallurgy (P/M) high-speed steel (HSS) components has been studied. Samples have been consolidated using 1.5, 3.5, and 5vol pct starch and up to 60vol pct powder. The high solid loading was achieved by stabilizing the repulsive forces with a small addition (0.01wt pct) of a dispersant (polyacrylic acid) that resulted in accurate fluidity and consolidation of the prepared slurries. After shaping of the samples, the bending strength of the green bodies was evaluated. Debinding cycles were optimized by comparing carbon and oxygen content in argon, in N2-5H2, and in pure hydrogen. The three atmospheres showed no significant differences in carbon elimination. To determine the influence of H2 in a nitrogen-rich atmosphere during sintering, tests were performed at 1230C in a N2-5H2 and in a nitrogen atmosphere. Pure nitrogen resulted in a microstructure formed by smaller carbides. Heat treatments were performed on the samples with the compositions that gave the best combination of properties. A hardness of 800HV and a bending strength of 1475MPa were obtained.

Romano, P.; Velasco, F. J.; Torralba, J. M.

2007-01-01

127

Characterization and mechanical properties of ultrahigh boron steels produced by powder metallurgy  

SciTech Connect

The present work is part of an investigation into the use of rapid solidification and powder metallurgy techniques to obtain iron-boron alloys with good mechanical properties. Two Fe-B binary alloys and two ultrahigh boron tool steels were gas atomized and consolidated by hot isostatic pressing (HIP) at temperatures ranging from 700 C to 1,100 C to have a fine microstructure. Optimum properties were achieved for the binary alloys at low consolidation temperatures, since the solidification microstructure from the original powders is eliminated and, at the same time, fine microstructures and low porosity are obtained in the alloys. At high temperatures and low strain rates, three of the four alloys exhibited low stress exponents, but only the Fe-2.2 pct B alloy showed tensile elongations higher than 100 pct. At low temperatures, only the Fe-2.2 pct B alloy deformed plastically. This alloy showed values of tensile elongation and ultimate tensile strength that were strongly dependent on testing and consolidation temperatures.

Jimenez, J.A.; Gonzalez-Doncel, G.; Ruano, O.A. [Centro Nacional de Investigaciones Metalurgicas, Madrid (Spain)

1996-07-01

128

Niobium-titanium superconductors produced by powder metallurgy having artificial flux pinning centers  

DOEpatents

Superconductors formed by powder metallurgy have a matrix of niobium-titanium alloy with discrete pinning centers distributed therein which are formed of a compatible metal. The artificial pinning centers in the Nb-Ti matrix are reduced in size by processing steps to sizes on the order of the coherence length, typically in the range of 1 to 10 nm. To produce the superconductor, powders of body centered cubic Nb-Ti alloy and the second phase flux pinning material, such as Nb, are mixed in the desired percentages. The mixture is then isostatically pressed, sintered at a selected temperature and selected time to produce a cohesive structure having desired characteristics without undue chemical reaction, the sintered billet is reduced in size by deformation, such as by swaging, the swaged sample receives heat treatment and recrystallization and additional swaging, if necessary, and is then sheathed in a normal conducting sheath, and the sheathed material is drawn into a wire. The resulting superconducting wire has second phase flux pinning centers distributed therein which provide enhanced J.sub.ct due to the flux pinning effects.

Jablonski, Paul D. (Madison, WI); Larbalestier, David C. (Madison, WI)

1993-01-01

129

Nb/sub 3/Sn(Ti) powder metallurgy processed high field superconductors  

SciTech Connect

Powder metallurgy processed Nb/sub 3/Sn(Ti) superconducting wires were fabricated with Sn x-italic wt. % Ti cores for 0< or =x-italic< or =3, 16 or 22 vol % cores, and a Cu 45 wt. % Nb composite. The processing used swaging, cold hydrostatic extrusions, wire drawing and heat treatments of 750 /sup 0/C for two to four days. Nominal areal reductions of 10/sup 4/ were used. Hydride-dehydride Nb and rotating electrode processed Nb powders gave the same performance. Overall critical current densities J-italic/sub c-italic/ were measured between 4.2 and 1.8 K for applied fields up to 23 T. J-italic/sub c-italic/ increased with increased Ti and/or Sn content. The Nb/sub 3/Sn(Ti) wires using a Sn 3 wt. % Ti, 22 vol % core gave J-italic/sub c-italic/ >10/sup 4/ A/cm/sup 2/ at 20 T and 4.2 K and J-italic/sub c-italic/ = 10/sup 4/ A/cm/sup 2/ at 23 T at 1.8 K. Removal of the precompression of the matrix increased J-italic/sub c-italic/ by about a factor of 2 at 20 T and 4.2 K.

Pourrahimi, S.; Thieme, C.L.H.; Foner, S.; Suenaga, M.

1986-06-30

130

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 (500C to 600C) 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 AMSNE 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 BExternal 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 CFuel 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

131

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

132

Fatigue crack growth behaviour of a gamma-titanium-aluminide alloy prepared by casting and powder metallurgy  

Microsoft Academic Search

The fatigue crack growth behaviour of a Ti48Al2Cr2Nb alloy prepared by two different processing routes, namely casting and powder metallurgy (PM), is examined. The lamellar microstructure of the cast alloy exhibits a higher resistance than the fine equiaxed ? grain microstructure of the PM alloy when tested at R=0.1. Crack closure effects are lower in the PM alloy than in

A.-L. Gloanec; G. Hnaff; D. Bertheau; P. Belaygue; M. Grange

2003-01-01

133

Processing and properties of powder metallurgy NiAl-Cr-Zr-B for use in oxidizing environments  

Microsoft Academic Search

The addition of Cr to B-doped NiAl in small ingots used for alloy development alleviates dynamic embrittlement, as exemplified by low tensile elongation and intergranular fracture, upon testing in air at 600°C. Powder metallurgy (PM) technology is advantageous to properties due to improved microstructure from rapid solidification, and its effectiveness was studied in the up-scale production of four heats of

V. K. Sikka; C. T. Liu; E. A. Loria

1986-01-01

134

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 typesnearly spherical particles of typical size from 30 to 50\\u000a nm,

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

2004-01-01

135

Ni 3 AI intermetallic particles as wear-resistant reinforcement for Al-base composites processed by powder metallurgy  

Microsoft Academic Search

The suitability of Ni3Al intermetallics as reinforcement for Al-base materials for tribological applications has been investigated. For this purpose,\\u000a an Al\\/Ni3Al (5 vol pct) composite was prepared by powder metallurgy and tested in air against steel counterfaces at the load range\\u000a of 45 to 178 N. For comparison, unreinforced Al specimens were processed and tested under the same conditions. Tribological

C. Daz; J. L. Gonzlez-Carrasco; G. Caruana; M. Lieblich

1996-01-01

136

Developing a mathematical model to evaluate wear rate of AA7075\\/SiC p powder metallurgy composites  

Microsoft Academic Search

This paper reports the dry sliding wear behaviour of AA7075 aluminium\\/SiCp composites fabricated by powder metallurgy technique. Five factors, five levels, central composite, rotable design matrix is used to optimize the required number of experiments. The wear test has been conducted in a pin-on-roller wear testing machine, under constant sliding distance of 1km. An attempt has been made to develop

S. Kumar; V. Balasubramanian

2008-01-01

137

Mechanical behavior of powder metallurgy steelExperimental investigation and artificial neural network-based prediction model  

Microsoft Academic Search

Mechanical properties of high-density powder metallurgy (PM) steels have been evaluated using standard tests, and a theoretical\\u000a model using the artificial neural network (ANN) has been developed. Various heat treatments were carried out to study their\\u000a influence on mechanical properties, viz. endurance limit (EL), yield strength (YS), and hardness, and also on the carbon content in PM steel. The material

K. V. Sudhakar; Mohammed E. Haque

2001-01-01

138

Artificial neural network model in surface modification by EDM using tungstencopper powder metallurgy sintered electrodes  

Microsoft Academic Search

Electro-discharge machining (EDM) is a widely accepted nontraditional machining process used mostly for machining materials\\u000a difficult to machine by conventional shearing process. Surface modification by powder metallurgy sintered tools is an uncommon\\u000a aspect of EDM. Of late, it is being explored by many researchers. In the present paper, attempts have been made to model the\\u000a surface modification phenomenon by EDM

Promod Kumar Patowari; Partha Saha; P. K. Mishra

2010-01-01

139

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

140

Static and Dynamic Compaction of CL20 Powders  

Microsoft Academic Search

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

Marcia Cooper; Aaron Brundage; Evan Dudley

2009-01-01

141

STATIC AND DYNAMIC COMPACTION OF CL20 POWDERS  

Microsoft Academic Search

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 0.170.95 km?s. Experiments were conducted in

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

2009-01-01

142

Static and Dynamic Compaction of CL20 Powders  

Microsoft Academic Search

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

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

2009-01-01

143

Heat treatment effects on mechanical behavior of copper-nickel-tin produced via powder metallurgy  

NASA Astrophysics Data System (ADS)

Certain spring applications require a material with a combination of high strength, stiffness, and electrical conductivity. An alloy, Cu-15wt%Ni-8wt%Sn, formed via a powder metallurgy process, is one of several copper-based alloys which can be heat treated/processed to form a metallic nano-structured alloy with good combinations of yield strength and electrical conductivity. For certain heat treatment conditions, this alloy decomposes spinodally from a face centered cubic disordered phase to form tin-rich and tin-lean composition fluctuations that are 10-100nm thick. Additional time at temperature produces ordering of the tin-rich regions. Uniaxial tensile tests have been used to identify the aging conditions with the highest yield strength. The uniaxial tensile and fully-reversed, flexural fatigue properties of the various heat-treated conditions were compared with observed fracture surfaces to characterize the failure mechanisms of the various time and temperature evolved microstructures. The mechanical properties have been correlated with structural information obtained from a variety of different techniques. Optical metallography, transmission electron microscopy, resistivity.

Caris, Joshua Benjamin

144

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

145

Formation of Al3Ti/Mg composite by powder metallurgy of Mg Al Ti system  

NASA Astrophysics Data System (ADS)

An in situ titanium trialuminide (Al3Ti)-particle-reinforced magnesium matrix composite has been successfully fabricated by the powder metallurgy of a Mg-Al-Ti system. The reaction processes and formation mechanism for synthesizing the composite were studied by differential scanning calorimetry (DSC), x-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Al3Ti particles are found to be synthesized in situ in the Mg alloy matrix. During the reaction sintering of the Mg-Al-Ti system, Al3Ti particles are formed through the reaction of liquid Al with as-dissolved Ti around the Ti particles. The formed intermetallic particles accumulate at the original sites of the Ti particles. As sintering time increases, the accumulated intermetallic particles disperse and reach a relatively homogeneous distribution in the matrix. It is found that the reaction process of the Mg-Al-Ti system is almost the same as that of the Al-Ti system. Mg also acts as a catalytic agent and a diluent in the reactions and shifts the reactions of Al and Ti to lower temperatures. An additional amount of Al is required for eliminating residual Ti and solid-solution strengthening of the Mg matrix.

Yang, Zi R.; Wang, Shu Qi; Cui, Xiang H.; Zhao, Yu T.; Gao, Ming J.; Wei, Min X.

2008-07-01

146

Development and Processing of Novel Aluminum Powder Metallurgy Materials for Heat Sink Applications  

NASA Astrophysics Data System (ADS)

The objective of this research was to design aluminum powder metallurgy (PM) alloys and processing strategies that yielded sintered products with thermal properties that rivaled those of the cast and wrought aluminum alloys traditionally employed in heat sink manufacturing. Research has emphasized PM alloys within the Al-Mg-Sn system. In one sub-theme of research, the general processing response of each PM alloy was investigated through a combination of sintering trials, sintered density measurements, and microstructural assessments. In the second, the thermal properties of sintered products were studied in detail. Thermal conductivity was first determined using a calculated approach through discrete measurements of specific heat capacity, thermal diffusivity, and density and subsequently verified using a transient plane source technique on larger specimens. Experimental PM alloys achieved >99 pct theoretical density and exhibited thermal conductivity that ranged from 179 to 225 W/m K. Thermal performance was largely dominated by the amount of magnesium present within the aluminum grains and, in turn, bulk alloy chemistry. Data confirmed that the novel PM alloys were highly competitive with even the most advanced heat sink materials such as wrought 6063 and 6061.

Smith, L. J. B.; Corbin, S. F.; Hexemer, R. L.; Donaldson, I. W.; Bishop, Donald Paul

2013-09-01

147

Preparation and Mechanical Properties of Particulate-Reinforced Powder Metallurgy Titanium Matrix Composites  

NASA Astrophysics Data System (ADS)

This research focuses on the in-situ synthesis of titanium (Ti)-titanium carbide (TiC) composites by powder metallurgy (PM) technology. Newly designed Ti-1.5Fe-2.25Mo-1.2Nd-0.3Al (wt pct) alloy was chosen as the matrix, and the additive was Cr3C2. The microstructure, room/elevated temperature, tensile behavior, and sliding wear behavior of the matrix alloy and the composites are presented and discussed. Microstructural analysis of the composites reveals a uniform dispersion of the TiC reinforcements with near-equiaxed shape in the Ti matrix. Tensile property test results show that the tensile strength increases significantly at both room temperature (RT) and elevated temperature after adding Cr3C2 into matrix alloy. Results of sliding wear resistance examination indicate that the wear properties are improved through the synthesis of TiC reinforcements. High strength of the composites, with Cr3C2 added, is attributed to particle strengthening, grain refining, and solution strengthening of Cr element. Better wear resistance of the composites is attributed to strong interface between particles and Ti matrix and high hardness of the composites. Therefore, Cr3C2 is considered to be a promising additive for processing PM Ti matrix composites.

Liu, B.; Liu, Y.; He, X. Y.; Tang, H. P.; Chen, L. F.; Huang, B. Y.

2007-11-01

148

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

SciTech Connect

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, C.; Sliney, H.E.

1989-01-01

149

Development of textured Ni substrates prepared by powder metallurgy and casting  

NASA Astrophysics Data System (ADS)

We fabricated the textured Ni substrate for YBCO coated conductors and evaluated the effects of processing variables on microstructural evolution and texture transformation. Initial specimens were prepared by two different methods, i.e., powder metallurgy (P/M) and casting. To characterize the role of two preparation methods, the initial specimens of the same size were prepared under the same rolling and annealing conditions. The microstructure and texture were evaluated by orientation distribution function (ODF), electron backscattering diffraction and transmission electron microscopy with selected area diffraction. We observed that the microstructure of the rolled tape varied with preparation methods; the rolled tape prepared by P/M had more deformation bands and stronger ?-fiber texture than that one obtained by casting, resulting in finer microstructure and stronger cube texture after recrystallization. The smaller grains in the former tape were explained by the variation inhibition theory together with in situ TEM result. Texture analysis indicated that the substrate made by P/M had a stronger cube texture and a wider annealing temperature range in which the cube texture became stable, compared to that of the casting-substrate. In addition, abnormal grain growth occurred and consequently formed high angle grain boundary for substrate by casting but not for substrate by P/M.

Lim, Jun Hyung; Kim, Kyu Tae; Joo, Jinho; Kim, Hyoungsub; Jung, Seung-Boo; Jeong, Yeong-Ho; Kim, Chan-Joong

2006-04-01

150

Ultrasonic compacting of zirconium ceramics from ultradispersed powders  

Microsoft Academic Search

A method for compacting ultradisperse powders (UDP) of ZrO2-3% Y2O3 by radially transmitted ultrasonic vibrations (USV) by imposing static pressing pressure is developed. The optimized USV regimes provide compacts from UDP with optimum properties.

O. L. Khasanov; Yu. P. Pokholkov; V. M. Sokolov; . S. Dvilis; A. I. Slosman; S. V. Matrenin

1995-01-01

151

A density-dependent endochronic plasticity for powder compaction processes  

Microsoft Academic Search

This paper is concerned with the numerical modeling of powder cold compaction process using a density-dependent endochronic plasticity model. Endochronic plasticity theory is developed based on a large strain plasticity to describe the nonlinear behavior of powder material. The elastic response is stated in terms of hypoelastic model and endochronic plasticity constitutive equations are stated in unrotated frame of reference.

A. Bakhshiani; A. R. Khoei; M. Mofid

2004-01-01

152

PREPARATION OF METAL POWDER COMPACTS PRIOR TO PRESSING  

DOEpatents

A method of fabricating uranium by a powder metallurgical technique is described. It consists in introducing powdered uranium hydride into a receptacle shaped to coincide with the coatour of the die cavity and heating the hydride so that it decomposes to uranium metal. The metal particles cohere in the shapw of the receptacle and thereafter the prefurmed metal powder is pressed and sintered to obtain a dense compact.

Mansfield, H.

1958-08-26

153

Structure investigations of ferromagnetic Co-Ni-Al alloys obtained by powder metallurgy.  

PubMed

Elemental powders of Co, Ni and Al in the proper amounts to obtain Co(35)Ni(40)Al(25) and Co(40)Ni(35)Al(25) nominal compositions were ball milled in a high-energy mill for 80 h. After 40 h of milling, the formation of a Co (Ni, Al) solid solution with f.c.c. structure was verified by a change of the original lattice parameter and crystallite size. Analytical transmission electron microscopy observations and X-ray diffraction measurements of the final Co (Ni, Al) solid solution showed that the crystallite size scattered from 4 to 8 nm and lattice parameter a = 0.36086 nm. The chemical EDS point analysis of the milled powder particles allowed the calculation of the e/a ratio and revealed a high degree of chemical homogeneity of the powders. Hot pressing in vacuum of the milled powders resulted in obtaining compacts with a density of about 70% of the theoretical one. An additional heat treatment increased the density and induced the martensitic transformation in a parent phase. Selected area diffraction patterns and dark field images obtained from the heat-treated sample revealed small grains around 300 nm in diameter consisting mainly of the ordered gamma phase (gamma'), often appearing as twins, and a small amount of the L1(0) ordered martensite. PMID:20500399

Maziarz, W; Dutkiewicz, J; Lity?ska-Dobrzy?ska, L; Santamarta, R; Cesari, E

2010-03-01

154

Quasi-static compaction studies of a porous pyrotechnic powder  

NASA Astrophysics Data System (ADS)

The compaction and relaxation properties of a live and an inert pyrotechnic powder simulant mixture have been evaluated under quasi-static loading conditions. The pyrotechnic powder consisted of a mixture of potassium perchlorate, magnesium-aluminum alloy, and inert binder. Potassium chloride replaced the potassium perchlorate in the inert mixture. Porous beds of powder were compacted using a double acting piston arrangement, operating at a constant loading rate of 0.11 in/min. Applied and transmitted forces were measured using either 7,500 or 20,000 lbf capacity strain gage load cells. The intragranular stress as a function of percent TMD was determined from the compaction data. The experimental intragranular stress data were further analyzed using a modified Carroll-Holt model to describe the compaction process and to allow extrapolation to a density range not achievable by experiment. The porous bed of pyrotechnic powder was much more rigid than homogeneous crystalline powders such as ammonium perchlorate (AP). Microscopic examination of the compacted material showed only light damage to the crystalline particles with little fracture. Bed relaxation resulted in a 2.8 to 4.5 percent change in bed height after compaction. These data demonstrate the presence of elastic deformation properties in a porous bed of non-viscoelastic material.

Atwood, A. I.; Curran, P. O.; Price, C. F.; Wiknich, J.

1996-05-01

155

Explosive compaction of amorphous ferromagnetic metal powders  

Microsoft Academic Search

The magnetic properties of certain amorphous metals might be better exploited by the electrical industry if these metals, currently available as ribbon, could be consolidated into high density, principally amorphous, bulk shapes. This work attempted to produce such bodies using explosive compaction techniques. Toroidal specimens were successfully produced using a cylindrical explosive compaction technique. The key to this technique was

R. D. Caligiuri; D. R. Curran; P. S. DeCarli

2009-01-01

156

Creep densification of copper powder compact  

Microsoft Academic Search

Densification of metal powder under high temperature processing was investigated. Experimental data were obtained for copper powder under hot isostatic pressing, hot pressing and uniaxial creep compression. Theoretical calculations from the constitutive models by McMeeking and co-workers were compared with the experimental data. The agreements between experimental data and theoretical calculations are reasonably good when hydrostatic stress is dominant, but

M. C. Song; H. G. Kim; K. T. Kim

1996-01-01

157

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.

158

Rapidly solidified powder metallurgy of Al-Ti-Fe-X alloys  

SciTech Connect

Mechanical properties of powder metallurgy (P/M) aluminum alloys have been improved through a rapid solidification (RS) technique. High-strength RS P/M aluminum alloys were recently developed in Al-Ni-(Y or Ce)-(Co, Ti or Zr) systems containing from 89 to 91 at% Al. The alloy systems have a glass-forming ability, resulting in easy attainment of nanocrystalline structure. Recently, the authors have reported that Al{sub 93}Ti{sub 3.5}Fe{sub 3.5}RS P/M alloys exhibited tensile strength of 786 MPa, plastic elongation of 3.2%, high thermal stability up to 600 K, low density of 2.90 gcm{sup {minus}3}, high Young`s modulus of 91 GPa and low coefficient of thermal expansion of 20.2 {times} 10{sup {minus}6} K{sup {minus}1}. The Al-Ti-Fe P/M alloys are expected to be applied as elevated-temperature materials such as Al-Fe-Ce, Al-Fe-Mo, Al-Fe-V-Si and Al-Cr-Zr RS P/M alloys, because the Ti and Fe elements exhibit limited solid solubility and low diffusivity in aluminum. The transition metals of V, Cr, Mo and Zr have low diffusivity in aluminum. The addition of these elements to the Al-Ti-Fe alloys is expected to improve its thermal stability and elevated-temperature strength. The purpose of this paper is to report the synthesis of elevated-temperature Al-Ti-Fe-X (X = V, Cr, Mo and Zr) RS P/M alloys.

Kawamura, Yoshihito; Inoue, Akihisa [Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Takagi, Makoto; Ohta, Hidenobu; Imura, Toru [Aichi Inst. of Tech., Toyota (Japan); Masumoto, Tsuyoshi [Research Inst. for Electric and Magnetic Materials, Sendai (Japan)

1999-04-23

159

The magnetic properties of powdered and compacted microcrystalline permalloy  

NASA Astrophysics Data System (ADS)

The aim of this work is to investigate the magnetic properties of powdered and compacted microcrystalline Ni Fe (81 wt% of Ni) permalloy. It was found by investigating the influence of mechanical milling on the magnetic properties of powder samples prepared by milling of the ribbon that the alloy remains a solid solution with stable structure during the whole milling process. With decreasing particle size the rotation of magnetization vector gradually becomes dominant magnetization process and thus coercivity increases. After compaction of the powder by uniaxial hot pressing the magnetic contact between powder particles is recreated and for resulting bulk the displacement of the domain walls becomes dominant magnetization process with coercivity of 11 A/m (comparable with the coercivity of conventional permalloy).

Kollr, P.; Olekkov, D.; Fzer, J.; Kov?, J.; Roth, S.; Pola?ski, K.

2007-03-01

160

Densification and compressive strength of in-situ processed Ti\\/TiB composites by powder metallurgy  

Microsoft Academic Search

In the present study, the densification of Ti\\/TiB composites, the growth behavior ofin-situ formed TiB reinforcement, the effects of processing variables such as reactant powder (TiB2, B4C), sintering temperature and time on the microstructures and the mechanical properties ofin-situ processed Ti\\/TiB composites have been investigated. Mixtures of TiB2 or B4C powder with pure titanium powder were compacted and

H. W. Jeong; S. J. Kim; Y. T. Hyun; Y. T. Lee

2002-01-01

161

Effect of coating time on corrosion behavior of electroless nickel-phosphorus coated powder metallurgy iron specimens  

SciTech Connect

Powder metallurgy iron specimens with porosities in the range 0% to 2% were electroless coated with nickel-phosphorus alloy from baths containing sodium hypophosphite (NaH{sub 2}PO{sub 2}{center_dot}H{sub 2}O). The effect of coating time on thickness and phosphorus content of the deposit was analyzed. The free corrosion potentials and corrosion rates of the coated specimens were obtained by the Tafel extrapolation method in 1.0 M hydrochloric acid (HCl) solution. Corrosion rates of the coated specimens after heat treatment also were studied. The observed corrosion characteristics were explained by the mixed-potential theory.

Singh, D.; Balasubramaniam, R.; Dube, R.K. [Indian Inst. of Tech., Kanpur (India). Dept. of Materials and Metallurgical Engineering

1995-08-01

162

Measurement of Electrical Conductivity of Porous Titanium and Ti6Al4V Prepared by the Powder Metallurgy Method  

NASA Astrophysics Data System (ADS)

Porous titanium and Ti6Al4V are produced by the powder metallurgy method. Dependence of the electrical conductivity on the porosity and pore size is investigated and the experimental results are correlative and compared with several earlier models. A newly modified Mori-Tanaka relationship based on the effective field method is proposed, which is successfully applied to describe the dependence of the electrical conductivity of porous titanium and Ti6Al4V on the porosity. The pore size has a minor effect on the electrical conductivity of both samples.

Zhu, Ke; Li, Cheng-Feng; Zhu, Zhen-Gang

2007-01-01

163

Computational modeling of the cold compaction of ceramic powders  

Microsoft Academic Search

A finite-element model of the cold compaction of ceramic powders by uniaxial pressing is developed and validated by comparison\\u000a with experimental data. The mechanical behavior of processing powders is assumed according to the modified Drucker-Prager\\u000a cap model. The frictional effects and the mechanical behavior of tools involved in the process are taken into account. The\\u000a proposed model allows evaluation of

P. Carlone; G. S. Palazzo

2006-01-01

164

Study of Underwater Shock Compaction Device for Compaction of Titanium Diboride Powder  

NASA Astrophysics Data System (ADS)

Shock compaction for powders has been used to study bulk consolidation of powder materials. Shock compaction has the advantage of processing at low temperatures and short duration to limit effects of high temperatures for long times, such as increased grain size and high energy cost. Many methods of shock loading of powders have been employed: direct contact with explosive, explosively driven flyer plates, and flyer plates launched with light gas or propellant gun. Another method, using explosives to create a shockwave in water that is in contact with a powder container, has been used extensively at Kumamoto University. This work presents a study of the development of the underwater shockwave device and investigates the water container geometry for control of parameters for shockwave peak pressure, duration, and distribution through the powder compaction process. Results of simulations for optimization of shock compaction properties are presented along with measurements from input and propagated manganin gauge pressure measurements obtained from underwater shock compaction of titanium diboride. The hardness measurements throughout the bulk of the shock compacted titanium diboride are discussed.

Kennedy, G. B.; Kim, Y. K.; Hokamoto, K.; Itoh, S.

2007-06-01

165

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

166

Process for making titanium, zirconium and hatnium-based metal particles for powder metallurgy  

SciTech Connect

A process to produce passified Group IVb transition metal based metal particles having a controlled particle size distribution is disclosed which produces particles suitable for metallurgy usage without additional particle size reduction. Such particles are also substantially free of halides and are produced at temperatures considerably below that of arc melting temperatures of Group IVb transition metals and alloys based thereon.

Hard, R.A.; Megy, J.A.

1984-09-11

167

A New Multifunctional ? Ti Alloy Produced via Powder Metallurgy for Biomedical Applications  

NASA Astrophysics Data System (ADS)

Recent studies have revealed remarkable properties in ?-Ti alloys, including low elastic modulus, high strength and superelasticity. The unique properties and potentials in engineering and biomedical applications have invoked many physicists, material scientists and metallurgists to study its phenomenon. The requirements of these alloys in biomedical applications restrict the usage of toxic or allergic elements in the alloy design. Only a few alloying elements are suitable for developing non-toxic ? titanium alloys such as Nb, Ta and Zr. In this study a press-and-sinter process was used to consolidate the elemental powder mixture of Ti-Nb-Ta-Zr. Solid state sintering studies were established to investigate the effect of various green densities, sintering temperatures (i.e. 1650 C - 1700 C) and sintering atmosphere (i.e. Argon and Vacuum). PM near net shape process of showed a pathway to obtained a near dense part at sintered density of 97 % with compaction pressure of 707 MPa at 1700C. Majority of the sintered Ti-23Nb-0.7Ta-2Zr (at.%) alloy's structure is ?- austenite (bcc).

Goh, F. C. W.; Hodgson, M. A.; Cao, P.

168

Modern developments in powder metallurgy; Proceedings of the International Powder Metallurgy Conference, Orlando, FL, June 5-10, 1988. Volumes 18, 19, 20, and 21  

Microsoft Academic Search

Topics discussed include hot isostatic pressing, powder forging, metal injection molding, modeling of consolidation processes, liquid-phase sintering, novel P\\/M technology, innovation in tooling, soft magnetic materials, and superconductivity and shielding. Attention is given to the processing and properties of carbides, new tungsten alloys, refractory alloys, tool steels and cutting materials, spray-formed aluminum alloys, copper base and bearing alloys, P\\/M titanium,

P. U. Gummeson; D. A. Gustafson

1988-01-01

169

Mechanism of plastic deformation of powder metallurgy metal matrix composites of CuSn\\/SiC and 6061\\/SiC under compressive stress  

Microsoft Academic Search

Under compressive stress, the plastic deformation mechanism of the powder metallurgy (P\\/M) process metal matrix composite (MMC) varies with the bonding strength of interfaces. The strength of the bonds among the matrix particles, the particle size distribution, and the bonding strength between the matrix particles and the reinforcement dominate the mechanical behaviors of MMC. In this study, simple metal and

Y. C Lin; H. C Li; S. S Liou; M. T Shie

2004-01-01

170

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

171

Effect of boronizing and shot peening in ferrous based FeCuGraphite powder metallurgy material on wear, microstructure and mechanical properties  

Microsoft Academic Search

Ferrous based materials manufactured by powder metallurgy (P\\/M) method are widely used in industry. These materials are very important because they do not require machining, have self-lubricated properties as journal bearing material, find applications in medical industry. In this study, powder metal parts were manufactured from ferrous based FeCuGraphite composites by P\\/M method. Wear and mechanical test samples were manufactured

Selim Sarper Yilmaz; Bekir Sad?k nl; Remzi Varol

2010-01-01

172

Micro structural features and mechanical properties of AlAl 3Ti composite fabricated by in-situ powder metallurgy route  

Microsoft Academic Search

In this paper, an in-situ powder metallurgy technique of fabricating near net shape particulate Al3TiAl composite is developed. Titanium tri-aluminide particles were generated in aluminum matrix by solid state reactive diffusion of homogenous blended pure Ti and Al powders. Effects of titanium particle size, temperature and time of sintering on microstructure and mechanical properties of the composite were studied by

V. Abbasi Chianeh; H. R. Madaah Hosseini; M. Nofar

2009-01-01

173

Analysis of cold compaction densification behaviour of metal powders  

Microsoft Academic Search

Cold compaction behaviour of metal powders was analyzed using Shima, Fleck and Cam-Clay models. The Cam-Clay model reflects a very different plastic deformation mechanism for porous materials when compared with other two models. Brown's triaxial compressive experimental data (loading states: 1:1:1, 1:0.4:0.4, 1:0:0) were employed as the arbiter to these plastic models. It is very clear that only the Cam-Clay

Xue-Kun Sun; Shao-Jie Chen; Jian-Zhong Xu; Li-Dong Zhen; Ki-Tae Kim

1999-01-01

174

Ultrasonic evaluation of elastic parameters of sintered powder compacts  

Microsoft Academic Search

The variation of elastic moduli, M, of sintered powder compacts with porosity, p, has been analysed in terms of an equation M = M0 (1-p)n, where M0 is the elastic modulus of non-porous material and n is a constant. The variation of ultrasonic velocities has also been described in terms of a similar equation derived from the relations given by

A. K. Maitra; K. K. Phani

1994-01-01

175

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

2013-06-01

176

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

177

Production of high-speed steel by the powder metallurgy technique  

Microsoft Academic Search

with regeneration of the alcohol by distillation. With swarf, comminution in attrition or vibratory mills was found to be much more rapid, and resulted in the formation of finer powders. The mean size of carbide inclusions in the particles of powders comminuted under the optimum conditions was 0.8-1.5 p. During comminution, the specific surface of the powders grew, and consequently

S. S. Kiparisov; G. A. Meerson; V. S. Panov; V. I. Tret'yakov; M. M. Smirnova; Ya. K. Manikatov

1975-01-01

178

Characteristics of the pore structures in the compacts of ultrafine zirconia powder  

NASA Astrophysics Data System (ADS)

Compaction behavior of two batches of yttria-stabilized zirconia powders containing different kinds of agglomerates were investigated with the help of pore size distribution measurements for powders and compacts. The pore structure changes during the powder compaction show that the weakest agglomerates obtained with the total dewatering by ethyl alcohol are eliminated in compaction at not higher than 100 MPa and are independent of calcination temperature. Agglomerates in untreated powder with alcohol are strong and cannot be broken at even 500 MPa. Different compaction behaviors of agglomerates are thought to be due to the whole different process taking place during drying and decomposition of the untreated and treated powders.

Shi, J. L.

1991-12-01

179

A new apparatus for non-destructive evaluation of green-state powder metal compacts using the electrical-resistivity method  

NASA Astrophysics Data System (ADS)

This paper presents a new apparatus developed for non-destructive evaluation (NDE) of green-state powder metal compacts. A green-state compact is an intermediate step in the powder metallurgy (PM) manufacturing process, which is produced when a metal powder-lubricant mixture is compacted in a press. This compact is subsequently sintered in a furnace to produce the finished product. Non-destructive material testing is most cost effective in the green state because early flaw detection permits early intervention in the manufacturing cycle and thus avoids scrapping large numbers of parts. Unfortunately, traditional NDE methods have largely been unsuccessful when applied to green-state PM compacts. A new instrumentation approach has been developed, whereby direct currents are injected into the green-state compact and an array of spring-loaded needle contacts records the voltage distributions on the surface. The voltage distribution is processed to identify potentially dangerous surface and sub-surface flaws. This paper presents the custom-designed hardware and software developed for current injection, voltage acquisition, pre-amplification and flaw detection. In addition, the testing algorithm and measurement results are discussed. The success of flaw detection using the apparatus is established by using controlled samples, which are PM compacts with dielectric inclusions inserted.

Bogdanov, Gene; Ludwig, Reinhold; Michalson, William R.

2000-02-01

180

Preparation of aluminium-fly ash particulate composite by powder metallurgy technique  

Microsoft Academic Search

Aluminium-fly ash mixtures containing different weight percentages of fly ash were prepared and compacted at pressures from\\u000a 138414 MPa. The compacts prepared at 414 MPa were sintered in nitrogen atmosphere at 600, 625 and 645C, respectively. The\\u000a time of sintering ranged from 0.56 h. The densification parameter and the green densities of the compacts were determined\\u000a as a function of

R. Q Guo; P. K Rohatgi; D Nath

1997-01-01

181

NiAl powder alloys: II. Compacting of NiAl powders produced by various methods  

NASA Astrophysics Data System (ADS)

The technological properties of granulated NiAl powders produced by gas spraying of melts and NiAl powders produced by calcium hydride reduction (CHR) of mixtures of nickel and aluminum oxides are compared. The possibilities of production of compact workpieces from these powders using hydrostatic pressing, hot pressing, hot isostatic pressing, and hot extrusion are estimated. To improve compressibility, preliminary milling and/or mechanical activation of the powders are proposed. The strength properties of NiAl rods with a diameter of 20 mm extruded from a temperature of 1100C and made from the granulated powders are slightly higher than those made from the CHR powders. At temperatures higher than 800C the properties becomes similar. Transition point t d.b from the ductile to brittle state of samples made from powders sprayed in nitrogen and argon is 100-150C higher than those made from the CHR powders. The difference in the mechanical properties is caused by the structural and chemical microheterogeneity of granules (microingots), which is inherited in the rods after hot deformation and annealing at 1200-1400C and is (0.67-0.88) T m NiAl ( T m is the melting point, K).

Skachkov, O. A.; Povarova, K. B.; Drozdov, A. A.; Morozov, A. E.

2012-05-01

182

Toughness enhancement of powder metallurgy zirconium containing aluminum-lithium alloys through degassing  

Microsoft Academic Search

In a method for producing a consolidated article from a rapidly solidified, zirconium containing aluminum lithium alloy powder, the improvement is described comprising the step of: degassing said powder in a vacuum at a temperature of at least about 450 C, said powder consisting essentially of the formula Al[sub bal]Li[sub a]Cu[sub b]Mg[sub c]Zr[sub d], where a' ranges from about 2.4

J. C. LaSalle; D. Raybould; S. K. Das; E. V. Limoncelli

1993-01-01

183

Powder metallurgy T15 tool steel: Part II. Microstructure and properties after heat treatment  

Microsoft Academic Search

The effect of powder particle size and heat treatment on the micro structure and properties of hot isostatically pressed (``hipped'') T15 tool steel has been evaluated. Gas-atomized powder was screened into size fractions covering the range of <=44 to 1200 \\/i-m and hipped at 1130 C or 1195 C. The consolidated powders were austenitized at 1175 C or 1225 C

K. S. Kumar; A. Lawley; M. J. Koczak

1991-01-01

184

Powder metallurgy T15 tool steel: Part II. Microstructure and properties after heat treatment  

Microsoft Academic Search

The effect of powder particle size and heat treatment on the micro structure and properties of hot isostatically pressed (hipped)\\u000a T15 tool steel has been evaluated. Gas-atomized powder was screened into size fractions covering the range of ?44 to 1200\\u000a \\/i-m and hipped at 1130 C or 1195 C. The consolidated powders were austenitized at 1175 C or 1225 C

K. S. Kumar; A. Lawley; M. J. Koczak

1991-01-01

185

The pre-alloyed powder metallurgy of titanium with boron and carbon additions  

Microsoft Academic Search

Discontinuously reinforced titanium alloys have been produced by gasatomizing Ti-6Al-4V (in weight percent) with additions of boron and\\/or carbon to make a pre-alloyed, in-situ reinforced titanium-alloy powder. The rapid cooling that takes place during atomization results in a fine and uniform dispersion of titanium carbide and titanium boride. The atomized powder can be consolidated using standard titanium powder consolidation methods

C. F. Yolton

2004-01-01

186

Effects of MgO Nano Particles on Microstructural and Mechanical Properties of Aluminum Matrix Composite prepared via Powder Metallurgy Route  

NASA Astrophysics Data System (ADS)

The objective of the present investigation was to evaluate the microstructural and mechanical properties of Al/nano MgO composite prepared via powder metallurgy method. Pure atomized aluminum powder with an average particle size of 1?m and MgO particulate with an average particle size between 60 to 80 nm were used. Composites containing 1.5, 2.5 and 5 percent of volume fraction of MgO were prepared by powder metallurgy method. The specimens were pressed by Cold Isostatic Press machine (CIP), subsequently were sintered at 575, 600 and 625C. After sintering and preparing the samples, mechanical properties were measured. The results of microstructure, compression and hardness tests indicated that addition of MgO particulates to aluminum matrix composites improves the mechanical properties.

Baghchesara, Mohammad Amin; Abdizadeh, Hossein; Baharvandi, Hamid Reza

187

Tungsten and tungsten alloy powder metallurgy. (Latest citations from the Compendex 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

1993-06-01

188

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

189

The pre-alloyed powder metallurgy of titanium with boron and carbon additions  

Microsoft Academic Search

Discontinuously reinforced titanium alloys have been produced by gasatomizing Ti-6Al-4V (in weight percent) with additions\\u000a of boron and\\/or carbon to make a pre-alloyed, in-situ reinforced titanium-alloy powder. The rapid cooling that takes place\\u000a during atomization results in a fine and uniform dispersion of titanium carbide and titanium boride. The atomized powder can\\u000a be consolidated using standard titanium powder consolidation methods

C. F. Yolton

2004-01-01

190

Sintering stress and microstructure in ceramic powder compacts  

SciTech Connect

The behavior of the sintering stress and microstructure during sintering is studied under various thermal and physical conditions. Specifically, the study includes sintering under isothermal or constant heating rate conditions; and altering the starting compact structure by pre-coarsening to increase the particle size, or by compaction to increase the starting density. Loading dilatometry is used to measure the ratio of the densification strain rate to the creep strain rate and the continuous shrinkage history of the systems. The data show that the ratio of the densification to the creep strain rate is remarkably constant within a wide temperature range for densification, from the earliest stages of densification to at least the onset of the final stage. As a consequence, the sintering stress, which is proportional to the strain rate ratio, is nearly independent of sintered density or of temperature. Analysis leads to a simple method for determining the simultaneous densification strain rate over the creep strain rate ratio. A rigorous densification strain rate equation is derived for a model system. The constant sintering stress allows progress on formulating a sintering equation to predict the densification behavior of powder compacts. Analysis of dilatometry data from compacts sintered at various heating rates, and of numerical computations, indicate the need to include separate coarsening processes with different activation energies. The same model is used to describe the differences in pore spacing evolution between pre-coarsened and as-received systems.

Chu, May-Ying (Lawrence Berkeley Lab., CA (USA) California Univ., Berkeley, CA (USA). Dept. of Materials Science and Mineral Engineering)

1990-08-01

191

Compaction Behavior and Mechanical Properties of Uniaxially Pressed Bi-W Composites  

Microsoft Academic Search

Powder metallurgy is a useful route to forming particulate composite materials; however, the densification of hard and soft powder mixtures is usually inhibited by the more refractory phase. The Bi-W powder compacts were uniaxially pressed at room temperature and the compaction behavior and mechanical properties were evaluated. Pressing was performed in incremental steps from ~1 to 540 MPa. After each

L. Peter Martin; Andrea M. Hodge; Geoffrey H. Campbell

2009-01-01

192

Effect of lubricant addition on the powder properties and compacting performance of spray-dried molybdenum powders  

Microsoft Academic Search

Polymeric binders, such as polyvinyl alcohol, are usually added into molybdenum powders so that, after spray drying, large spherical agglomerates with good flow properties can be produced. Since these binders may help to reduce the friction among powders and between powders and the die wall, the necessity of mixing an additional lubricant, such as ethylene bis-stearamide (EBS), to facilitate compaction

H. S Huang; Y. C Lin; K. S Hwang

2002-01-01

193

Mechanical Properties and Microstructure of Argon Atomized Aluminum-Lithium Powder Metallurgy Alloys  

NASA Astrophysics Data System (ADS)

Aluminum-lithium and aluminum-copper-lithium alloy powders were prepared by argon gas atomization. The powders were consolidated by hot pressing and extruded into flat bar. Tensile and impact properties were determined on the extrusions. Transmission electron microscopy was used to examine the extruded microstructures while scanning microscopy was used for the examination of fracture surfaces. The aluminum-lithium alloys showed higher moduli, lower densities, and reduced toughness and elongation compared to conventional aluminum alloys. The loss of toughness was particularly pronounced above 3 pct Li.

Webster, D.; Wald, G.; Cremens, W. S.

1981-08-01

194

Corrosion behaviour of aisi 304l and 316l stainless steels prepared by powder metallurgy in the presence of sulphuric and phosphoric acid  

Microsoft Academic Search

The corrosion rates of AISI 304L and 316L stainless steels prepared by powder metallurgy (P\\\\M) have been studied by continuous electrochemical methods, in different concentrations of inorganic acid solutions (sulphuric and phosphoric) at room temperature (T = 298 K). For comparison purposes, a simultaneous study was carried out on similar composition cast AISI 304L and AISI 316L stainless steels specially

E Otero; A Pardo; M. V Utrilla; E Senz; J. F lvarez

1998-01-01

195

Critical current densities of Jelly-Roll and powder metallurgy NbAl wires as a function of temperature and magnetic field  

Microsoft Academic Search

Critical current densities of multi-filamentary NbAl wire made with the Jelly-Roll process (JR) and mono-core powder metallurgy process (PM) wire were measured as a function of temperature and magnetic field. The temperature dependence of the resistive critical field B{sub c2} was measured in PM wires. There is a significant difference between these resistive B{sub c2} values and the ones determined

C. L. H. Thieme; J. B. Kim; M. Takayasu

1997-01-01

196

Reconstruction of three-dimensional microstructures of TiB phase in a powder metallurgy titanium alloy using montage serial sectioning  

Microsoft Academic Search

Three-dimensional (3D) microstructures of TiB phase in a powder metallurgy Ti6Al4V1.7B alloy processed using two different routes are reconstructed from large-area high-resolution montage serial sections. Visualizations of the 3D microstructures are used to determine the effects of the processing route on the morphology, anisotropy, and spatial distributions of TiB particles.

S. I. Lieberman; A. M. Gokhale; S. Tamirisakandala

2006-01-01

197

Fabrication Metal Objects Using Layer Manufacturing Technology and Powder Metallurgy Science  

Microsoft Academic Search

In order to produce metal objects using Layer Manufacturing Technology, a new fabricating method is introduced by the authors. The layers in the new layer manufacturing process are generated by attracting metal powder to a charged photoreceptor under the influence of an electrostatic field, whereupon they are deposited one by one on a building table. After each deposit operation the

Jim Bakkelund; Roald Karlsen; yvind Bjrke

1997-01-01

198

Turning of advanced Ni based alloys obtained via powder metallurgy route  

Microsoft Academic Search

Nickel based alloys (RR_X) manufactured via powder route are considered the next generation materials that can offer increased efficiency of gas turbine engines. Their chemistry and mechanical properties indicate even lower machinability than the current disc alloys. The paper reports on specifics when rough and finish turning these new Ni based alloys. Tool life, surface finish, workpiece surface integrity and

D. A. Axinte; P. Andrews; W. Li; N. Gindy; P. J. Withers; T. H. C. Childs

2006-01-01

199

Metal Powders (Metall Pulver).  

National Technical Information Service (NTIS)

This book discusses metal powders for powder metallurgy, specific topics include Electrolytic copper powder, Copper alloy powders, Lead powders, tin powders, Partially prealloyed powders, Premixes, Mixed powders to customers' specifications, Quality contr...

1986-01-01

200

Oxidation behavior and mechanism of powder metallurgy Rene95 nickel based superalloy between 800 and 1000 C  

NASA Astrophysics Data System (ADS)

The oxidation behaviors of powder metallurgy (PM) Rene95 Ni-based superalloy in the temperature range of 800-1000 C are investigated in air by virtue of isothermal oxidation testing, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the oxidation kinetics follows a square power law as the time extends at each temperature. The oxidation layers are detected to be composed of Cr 2O 3, TiO 2 and a small amount of NiCr 2O 4. The cross-sectional morphologies indicate that the oxidation layer consists of three parts: Cr-rich oxide layer, Cr and Ti duplex oxide layer, and oxidation affected zone. Theoretical analyses of oxidation kinetics and thicknesses of oxidation layers confirm that the activation energy of oxidation of PM Rene95 superalloy is 165.32 kJ mol -1 and the oxidation process is controlled by diffusions of oxygen, Cr, and Ti. Accordingly, a diffusion-controlled mechanism is suggested to understand the oxidation behaviors of PM Rene95 superalloy at elevated temperatures.

Zheng, Lei; Zhang, Maicang; Dong, Jianxin

2010-10-01

201

Investigations on the growing, cracking and spalling of oxides scales of powder metallurgy Rene95 nickel-based superalloy  

NASA Astrophysics Data System (ADS)

The surface and cross-sectional morphologies of powder metallurgy (PM) Rene95 nickel-based superalloy after 100 h oxidation in the temperature range of 700-1100 C were investigated. It is shown that oxides nucleate first on the surface of the alloy and form an oxides scale. Afterwards, oxides scale endures decohesion, rumpling, cracking and finally spalling owing to the weak cohesive strength of the scale/alloy interface. The XRD and EDS analyses confirmed that the oxides scale of PM Rene95 superalloy is mainly composed by Cr 2O 3 at 800 C and NiCr 2O 4 is the main spinel at 1100 C. The subsequent analysis of internal stress verified that cracking and spalling are caused by growth stress and promoted by thermal stress. On these bases, improvement of the cohesive strength of the scale/alloy interface is considered to be the main way to increase the oxidation resistance of PM Rene95 superalloy.

Zheng, Lei; Zhang, Maicang; Chellali, Reda; Dong, Jianxin

2011-09-01

202

Tungsten and tungsten-alloy powder metallurgy. (Latest citations from the NTIS data base). Published Search  

SciTech Connect

The bibliography contains citations concerning the processing and fabrication of tungsten, tungsten alloys, and tungsten composites. Compacting, pressing, sintering, extruding, and rolling are among the methods described. Infiltration of porous tungsten shapes is included, as well as mechanical properties, thermal properties, and microstructure of end products. Applications include rocket nozzles, nuclear reactor materials, and porous ionizers. (Contains a minimum of 116 citations and includes a subject term index and title list.)

Not Available

1992-10-01

203

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

204

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

205

Fabrication and microstructure of ZrO 2 Ni functional gradient material by powder metallurgy  

Microsoft Academic Search

Functional gradient material (FGM) of the ZrO2-Ni system was developed by a powder metallurgical process, and investigated for its microstructure by means of X-ray diffractometry (XRD), electron probe microanalysis (EPMA), transmission electron microscopy (TEM) and optical microscopy. It was shown that the sintered body of ZrO2-Ni FGM is almost fully densified, and its chemical composition and microstructure have the expected

J. C. Zhu; Z. D. Yin; Z. H. Lai

1996-01-01

206

CuAlNiMn shape memory alloy processed by mechanical alloying and powder metallurgy  

Microsoft Academic Search

The CuAlNiMn shape memory alloy has been fabricated by mechanical alloying and vacuum hot pressing and hot extrusion. SEM and X-ray diffraction analysis have been used to characterize the pre-alloyed powders and the hot extruded sample solution treated at 850C for 10min and then water-quenched. The shape memory recovery of the quenched sample is measured to be 100% as it

Z. Li; Z. Y. Pan; N. Tang; Y. B. Jiang; N. Liu; M. Fang; F. Zheng

2006-01-01

207

A novel approach using powder metallurgy for strengthened RABiTS composite substrates for coated superconductors  

Microsoft Academic Search

We report on the development of mechanically strengthened, highly textured Ni5at.%W\\/Ni12at.%W composite materials prepared by a powder metallurgical approach as promising weakly magnetic substrates for coated superconductors. The key configuration of this composite substrate consists of a thin, sharp cubic textured Ni5at.%W layer on a Ni12at.%W alloy core, thus providing a mechanical reinforcement while decreasing the saturation magnetization of the

Hongli Suo; Yue Zhao; Min Liu; Shuai Ye; Yonghua Zhu; Dong He; Lingji Ma; Yuan Ji; Meiling Zhou

2008-01-01

208

Physical chemistry of the powder metallurgy of beryllium: Chemical characterization of the powder in relation to its granularity  

NASA Astrophysics Data System (ADS)

Combining the systematic quantitative chemical analysis of the light impurities H, C, N, and O, the quantitative thermal desorption of molecular H2O and H2, and X ray diffractometry of various size fractions of a commercial Be powder (SP-65 grade from Brush-Wellman) allowed the precise de-termination of the mean composition and equivalent mean thickness of the surface impurity phases in the passivation-contamination layer on the surface of the particles. The overall surface stoichi-ometry is as follows: 0.2 BeOcrystallized, 0.8 [BeO - 0.59 H2O]amorphous, 0.14 H2Oads The result of the elemental analysis by X-ray photoelectron spectroscopy of the unetched surface of a powder pellet is compared. Analysis of the metallic impurities reveals increased concentrations of Mg, Ca, Ti, and Cr in the finest fraction, presumably due to the liberation of fine particles of intermetallic phases by attrition.

Bracconi, Pierre; Buisson, Laurent; Bonnet, Christian

1996-02-01

209

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

210

Self-passivating bulk tungsten-based alloys manufactured by powder metallurgy  

NASA Astrophysics Data System (ADS)

Self-passivating tungsten-based alloys are expected to provide a major safety advantage compared to pure tungsten, which is at present the main candidate material for the first wall armour of future fusion reactors. WC10Si10 alloys were manufactured by mechanical alloying (MA) in a Planetary mill and subsequent hot isostatic pressing (HIP), achieving densities above 95%. Different MA conditions were studied. After MA under optimized conditions, a core with heterogeneous microstructure was found in larger powder particles, resulting in the presence of some large W grains after HIP. Nevertheless, the obtained microstructure is significantly refined compared to previous work. First MA trials were also performed on the Si-free system WCr12Ti2.5. In this case a very homogeneous structure inside the powder particles was obtained, and a majority ternary metastable bcc phase was found, indicating that almost complete alloying occurred. Therefore, a very fine and homogeneous microstructure can be expected after HIP in future work.

Lpez-Ruiz, P.; Ords, N.; Lindig, S.; Koch, F.; Iturriza, I.; Garca-Rosales, C.

2011-12-01

211

A constitutive model and FE simulation for the sintering process of powder compacts  

Microsoft Academic Search

A model for describing the entire sintering process of powder compacts is presented based on the thermal elasto-viscoplastic theory. The predications of shrinkage and stress changes of WC-6%Co powder compacts during sintering process are simulated using the ABAQUS code. It was found that simulation results for displacements are a good fit of the experimental data. In situ measurement technique and

Michael Gasik; Baosheng Zhang

2000-01-01

212

Microstructural evolution of mullite during the sintering of kaolin powder compacts  

Microsoft Academic Search

Kaolin particles are usually flaky in shape. In the present study, kaolin powder compacts were prepared by applying the die-pressing technique. The kaolin flakes tend to lie down on the plane which is perpendicular to the die-pressing direction. The powder compact thus shows anisotropic shrinkage after firing. A series of phase transformations take place as the kaolin is fired at

C. Y. Chen; G. S. Lan; W. H. Tuan

2000-01-01

213

Effect of adsorbed water on the ultrasonic velocity in alumina powder compacts  

Microsoft Academic Search

The presence of surface adsorbed water has been found to significantly increase the apparent elastic properties of unsintered alumina powder compacts. It is proposed that the increase in the elastic moduli results from the formation of `interparticle bridges' between adjacent particles and, thus, increased effective interparticle contact area. The effects upon the elastic moduli in the unsintered powder compacts were

L. P. Martin; J. C. Poret; A. Danon; M. Rosen

1998-01-01

214

Cold compaction study of Armstrong Process Ti6Al4V powders  

Microsoft Academic Search

The Armstrong Process developed by Cristal US, Inc.\\/International Titanium Powder, is an innovative, low-cost technology for producing Ti and Ti alloy powders in a one-step, continuous process. In this work, Armstrong Ti6Al4V powders were characterized and the cold compaction behavior of the powders were investigated in detail. As-received as well as milled powders were uniaxially die-pressed at designated pressures up

Wei Chen; Yukinori Yamamoto; William H Peter; Sarma B Gorti; Adrian S Sabau; Michael B Clark; Stephen D Nunn; Jim Kiggans; Craig A Blue; J. C. Williams; B. Fuller; K. Akhtar

2011-01-01

215

Effects of compaction pressure and particle shape on the porosity and compression mechanical properties of sintered Ti6Al4V powder compacts for hard tissue implantation.  

PubMed

Sintered Ti6Al4V powder compacts potentially to be used in implant applications were prepared using commercially available spherical and angular powders (100-200 mum) within the porosity range of 34-54%. Cylindrical green powder compacts were cold compacted at various pressures and then sintered at 1200 degrees C for 2 h. The final percent porosity and mean pore sizes were determined as functions of the applied compaction pressure and powder type. The mechanical properties were investigated through compression testing. Results have shown that yield strength of the powder compacts of 40-42% porosity was comparable with that of human cortical bone. As compared with previously investigated Ti powder compacts, Ti6Al4V powder compacts showed higher strength at similar porosity range. Microscopic observations on the failed compact samples revealed that failure occurred primarily by the separation of interparticle bond regions in the planes 45 degrees to the loading axis. PMID:18076095

Gden, Mustafa; Celik, Emrah; Hizal, Alpay; Altindi?, Mustafa; Cetiner, Sinan

2008-05-01

216

Processing and properties of powder metallurgy Ni/sub 3/Al-Cr-Zr-B for use in oxidizing environments  

SciTech Connect

The addition of Cr to B-doped Ni/sub 3/Al in small ingots used for alloy development alleviates dynamic embrittlement, as exemplified by low tensile elongation and intergranular fracture, upon testing in air at 600/sup 0/C. Powder metallurgy (PM) technology is advantageous to properties due to improved microstructure from rapid solidification, and its effectiveness was studied in the up-scale production of four heats of this intermetallic compound with 8 Cr, 0.8 or 1.8 Zr, and 0.02 B (wt %). Sheet derived from a cold-rolling and annealing sequence on extruded product had a satisfactory level of ductility in tensile tests conducted in air within the critical 400 to 800/sup 0/C range. The processing parameters for hot workability of the PM product were established via a number of different strain rate tensils tests in air at temperatures up to 1100/sup 0/C. Superplastic behavior presented the opportunity for fabrication of a forged shape by hot isothermal forging. Preliminary forging of cylinders cut from the extruded bars revealed no peripheral cracking in 60% compression tests at strain rates of 0.1 to 0.5/min at 1100/sup 0/C. Successful isothermal forging of a prototype turbine disk directly from extruded bar stock in a closed die at 1100/sup 0/C and strain rate of 0.5/min was demonstrated, and the microstructure and mechanical properties were at least equal to those of PM sheet and bar products. 12 figs., 5 tabs.

Sikka, V.K.; Liu, C.T.; Loria, E.A.

1986-10-01

217

The effect of heat treatment on explosively compacted (Y?Ba?K?Cu?O) superconductive powders  

Microsoft Academic Search

A ceramic powder mixture corresponding to the stoichiometric ratio of YBa1.95K0.05Cu3Oy superconducting ceramic with 10% w\\/w Ag was heat treated at 950C for 3 h in flowing oxygen. The resultant superconducting powder was consolidated in a silver tube by the explosive compaction technique (pre-heat treated ceramic). The same fabrication technique, i.e. explosive compaction, was employed to the initial stoichiometric powder

A. G. Mamalis; I. Kotsis; G. Pantazopoulos; M. Enisz; A. Szalay; D. E. Manolakos

1997-01-01

218

Study of compaction and ejection of hydrided-dehydrided titanium powder  

Microsoft Academic Search

Three similar varieties of pure Ti hydride-dehydried (HDH) powders were tested for the understanding of the variables that\\u000a have an influence on the compaction process of Ti powders. The study shows that small differences in the characteristics of\\u000a the powders lead to very different behaviours in the compaction stage. Compressibility curves, friction with the die walls\\u000a and ejection forces are

P. G. Esteban; Y. Thomas; E. Baril; E. M. Ruiz-Navas; E. Gordo

2011-01-01

219

Observation of particle behavior in copper powder compact during pulsed electric discharge  

Microsoft Academic Search

The behavior of spherical copper powder particles of uniform size (average diameter: 550 ?m) in a powder compact was observed under an optical microscope during a single-pulse electric discharge of 500 ms duration. The morphologies of necks formed between powder particles were observed under a scanning electron microscope, and their diameters were measured. The results obtained are summarized as follows:

O. Yanagisawa; H. Kuramoto; K. Matsugi; M. Komatsu

2003-01-01

220

In situ formation of titanium carbide in titanium powder compacts by gassolid reaction  

Microsoft Academic Search

Porous titanium compacts of fine and coarse sponge titanium powders were reacted with methane gas to produce TiTiC in situ composites. The kinetics of titanium carbide formation during the reaction were studied in relation to powder size, reaction temperature and time, and methane flow rate. The titanium carbide was initially formed as a layer around each titanium powder and the

Y.-J. Kim; H. Chung; S.-J. L. Kang

2001-01-01

221

Thermally stimulated current spectra of binder resin powders for copiers: Correction for thermal shrinkage of the sample powder compactions  

NASA Astrophysics Data System (ADS)

Thermally stimulated current (TSC) spectra observed under open- circuit condition for styrene- acrylic binder resin powder compactions for toners are corrected for their thermal shrinkage during TSC observation. For this binder resin, extrinsic current from motion of powder compactions with charges due to their thermal shrinkage was found to be much more effective than the sensitivity coefficient of a TSC measuring apparatus used. Particle size dependence of charge retention power of the resin powders was also examined by using this correction method and found that it decreased with decreasing their particle size.

Ikezakt, K.; Murata, Y.

2008-12-01

222

Acoustic harmonic generation measurement applications: Detection of tight cracks in powder metallurgy compacts  

Microsoft Academic Search

Standard linear ultrasonic testing techniques have long been employed for locating and characterizing relatively open cracks in a wide variety of materials, from metallic alloys and ceramics to composites. In all these materials, the detection of open cracks easily accomplished because the void between the two crack surfaces provides sufficient acoustic impedance mismatch to reflect the incident energy. Closed or

D. J. Barnard; J. C. Foley

2000-01-01

223

Characterization techniques to validate models of density variations in pressed powder compacts.  

National Technical Information Service (NTIS)

Techniques for characterizing density gradients generated during typical powder compaction processes are reviewed and several are evaluated. The techniques reviewed are ultrasonic velocity measurements, laser ultrasonic velocity measurements, x-ray radiog...

T. Garino M. Mahoney M. Readey K. Ewsuk J. Gieske

1995-01-01

224

Cold compaction study of Armstrong Process Ti-6Al-4V powders  

SciTech Connect

This work investigates the cold compaction behavior of Ti-6Al-4V powders produced by Armstrong Process . As-received as well as milled powders were characterized and these powders were uniaxially die-pressed at designated pressures up to 690 MPa to form disk samples with different aspect ratios. Samples with high aspect ratio exhibited non-uniform density along the pressing axis and the density distribution is in consistent with the result predicted by finite element analysis. The linear regression analysis on the experimental density data can be used to predict density of compacts with different aspect ratios. In the studied pressure range, an empirical powder compaction equation represents the green density pressure relationship very well for both the as-received and 1-hr milled Armstrong Ti-6Al-4V powders.

Chen, Wei [ORNL; Yamamoto, Yukinori [ORNL; Peter, William H [ORNL; Gorti, Sarma B [ORNL; Sabau, Adrian S [ORNL; Clark, Michael B [ORNL; Nunn, Stephen D [ORNL; Kiggans, Jim [ORNL; Blue, Craig A [ORNL; Fuller, Brian [International Titanium Powder; Akhtar, Kamal [International Titanium Powder

2011-01-01

225

Full strength compacts by extrusion of glassy metal powder at the supercooled liquid state  

Microsoft Academic Search

We report the production of full strength compacts of metallic glass by warm extrusion of powders at the supercooled liquid state just above the glass transition temperature. The alloy used was Zr65Al10Ni10Cu15 (at. %) which has the lowest viscosity among Zr-based metallic glasses with large supercooled liquid region. The tensile strength and Youngs modulus of the glassy powder compacts were

Yoshihito Kawamura; Hidemi Kato; Akihisa Inoue; Tsuyoshi Masumoto

1995-01-01

226

Compacting Corrundum Powder Composites and Carbide Phases with a Chemically Activated Surface  

Microsoft Academic Search

Addition of aluminum alcoholates and trioctylaluminum to the aluminum oxide-titanium (silicon) carbide system in the blend preparation stage favors a more compact microstructure of the resulting composite material. Highly dispersed thermolysis products react with titanium and silicon carbides to give oxycarbide phases that stimulate compacting of composites of corundum powder with the carbides.

Yu. I. Ryabkov; T. L. Lekanova; P. A. Sitnikov; T. M. Sporsheva; Yu. S. Matveev; A. V. Kuchin

2002-01-01

227

Dynamic powder compaction of rapidly solidified Path A alloy with increased carbon and titanium content  

SciTech Connect

The objective of this study is to show the potential of the dynamic powder compaction technique to consolidate rapidly solidified Path A alloys and to develop microstructures with improved irradiation performance in the fusion environment. Samples of rapidly solidified and dynamically compacted Path A alloy with increased carbon and titanium content have been included in alloy development irradiation experiments.

Megusar, J.; Imeson, D.; Vander Sande, J.B.; Grant, N.J.

1982-01-01

228

A design of ultrasonic compaction tools for metal powder magnetic core of motors  

Microsoft Academic Search

This report presents the metal powder compaction using ultrasonic vibration for the fabrication of a three-dimensionally-shaped magnetic core. First, we describe a design of ultrasonic compaction tools using FEM. Side wall of the sample was ultrasonically excited by a radial vibration of the die, while the upper and lower punches are driven by longitudinal vibrations. Second, we present the results

Shinichi Kikuchi; Daisuke Koyama; Kentaro Nakamura

2008-01-01

229

Effect of ceramic ball inclusion on densification of metal powder compact  

Microsoft Academic Search

The effect of a ceramic ball inclusion on densification behavior of a metal powder compact was investigated under cold isostatic pressing, pressureless sintering and hot isostatic pressing. Several constitutive models in the literature were implemented into a finite element program (ABAQUS) to analyse densification behaviors of metal powder with a ceramic ball inclusion under cold isostatic pressing, pressureless sintering and

K. T. Kim

2000-01-01

230

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

Microsoft Academic Search

In this paper, we present a modified density-dependent Drucker-Prager Cap (DPC) model to simulate the compaction behaviour of pharmaceutical powders. In particular, a nonlinear elasticity law is proposed to describe the observed nonlinear unloading behaviour following compaction. To extract the material parameters for the modified DPC model, a novel experimental calibration procedure is used, based on uniaxial single-ended compaction tests

L. H. Han; J. A. Elliott; A. C. Bentham; A. Mills; G. E. Amidon; B. C. Hancock

2008-01-01

231

Laser-Based Ultrasonic Tomographic Imaging of Powder Metal Compacts  

NASA Astrophysics Data System (ADS)

A new laser excitation system is used to obtain the cross-sectional tomographic images of density gradients of power metal compacts in the P/M industry. An equiangular fan data collection pattern is exploited for image reconstruction of cylindrical compacts. This new system makes the data collection process non-contact, makes real-time monitoring possible, and also increases the full resolution area of the reconstructed images up to the outer edge of the compacts.

Bian, H.; Shi, Y.; Rose, J. L.

2004-02-01

232

Laser-Based Ultrasonic Tomographic Imaging of Powder Metal Compacts  

Microsoft Academic Search

A new laser excitation system is used to obtain the cross-sectional tomographic images of density gradients of power metal compacts in the P\\/M industry. An equiangular fan data collection pattern is exploited for image reconstruction of cylindrical compacts. This new system makes the data collection process non-contact, makes real-time monitoring possible, and also increases the full resolution area of the

H. Bian; Y. Shi; J. L. Rose

2004-01-01

233

Compression testing of a sintered Ti6Al4V powder compact for biomedical applications  

SciTech Connect

In this study, the compression deformation behavior of a Ti6Al4V powder compact, prepared by the sintering of cold compacted atomized spherical particles (100-200 {mu}m) and containing 36-38% porosity, was investigated at quasi-static (1.6x10{sup -3}-1.6x10{sup -1} s{sup -1}) and high strain rates (300 and 900 s{sup -1}) using, respectively, conventional mechanical testing and Split Hopkinson Pressure Bar techniques. Microscopic studies of as-received powder and sintered powder compact showed that sintering at high temperature (1200 deg. C) and subsequent slow rate of cooling in the furnace changed the microstructure of powder from the acicular alpha ({alpha}) to the Widmanstaetten ({alpha}+{beta}) microstructure. In compression testing, at both quasi-static and high strain rates, the compact failed via shear bands formed along the diagonal axis, 45 deg. to the loading direction. Increasing the strain rate was found to increase both the flow stress and compressive strength of the compact but it did not affect the critical strain for shear localization. Microscopic analyses of failed samples and deformed but not failed samples of the compact further showed that fracture occurred in a ductile (dimpled) mode consisting of void initiation and growth in {alpha} phase and/or at the {alpha}/{beta} interface and macrocracking by void coalescence in the interparticle bond region.

Guden, M. [Department of Mechanical Engineering, Izmir Institute of Technology, Gulbahce Koyu, Urla, Izmir (Turkey); Center for Materials Research, Izmir Institute of Technology, Gulbahce Koyu, Urla, Izmir (Turkey); E-mail: mustafaguden@iyte.edu.tr; Celik, E. [Materials Science and Engineering Program, Izmir Institute of Technology, Gulbahce Koyu, Urla, Izmir (Turkey); Akar, E. [Department of Mechanical Engineering, Izmir Institute of Technology, Gulbahce Koyu, Urla, Izmir (Turkey); Cetiner, S. [Hipokrat A.S., 407/6 Sok., No:10, Pinarbasi, Izmir (Turkey)

2005-05-15

234

Critical current densities of Jelly-Roll and powder metallurgy Nb{sub 3}Al wires as a function of temperature and magnetic field  

SciTech Connect

Critical current densities of multi-filamentary Nb{sub 3}Al wire made with the Jelly-Roll process (JR) and mono-core powder metallurgy process (PM) wire were measured as a function of temperature and magnetic field. The temperature dependence of the resistive critical field B{sub c2} was measured in PM wires. There is a significant difference between these resistive B{sub c2} values and the ones determined by Kramer plots. The field dependence of the critical current depends on the manufacturing method. In general, it follows a relationship that falls between pure Kramer and one where the pinning force is inversely proportional with B{sup 2}. In contrast with Nb{sub 3}Sn no maximum in the bulk pinning force is observed down to 3 T (0.15MxB{sub c2}).

Thieme, C.L.H.; Kim, J.B. [Francis Bitter National Magnet Lab., Cambridge, MA (United States); Takayasu, M. [Massachusetts Institute of Technology, Cambridge, MA (United States)] [and others

1997-06-01

235

Nanostructured bulk MnBi magnets fabricated by hot compaction of cryomilled powders  

NASA Astrophysics Data System (ADS)

Cryomilling was employed for Mn50+xBi50-x (x = 0,5) alloys to synthesize nanocrystalline powders with particle size of 400-500 nm without much increase of the unwanted secondary Bi phase. At room temperature, the cryomilled powders showed large coercivity (Hc) values of 18.5 kOe and 20.7 kOe for Mn50Bi50 and Mn55Bi45, respectively. Cryomilled powders were hot compacted to form a bulk nanostructured MnBi magnet. The Mn50Bi50 hot compacted magnet exhibits Hc of 12.9 kOe with remanence value of 26 emu g-1 at room temperature. The microstructure of hot compacted magnet illustrates uniform grains with an average size of 40 nm. Furthermore, the magnet shows a large positive temperature coefficient of Hc which reaches a value of more than 30 kOe above 450 K.

Rama Rao, N. V.; Gabay, A. M.; Li, W. F.; Hadjipanayis, G. C.

2013-07-01

236

Nondestructive evaluation of elastic parameters of sintered iron powder compacts  

Microsoft Academic Search

A systematic study of the variation of elastic moduli and Poisson's ratio of sintered iron compacts of porosity (up to 21.6%) has been carried out by measuring longitudinal and shear ultrasonic velocities. The variation of these parameters with porosity is compared with predictions of elasticity and scattering theories. Further, a linear relationship was observed between the elastic moduli and the

J. P. Panakkal; H. Willems; W. Arnold

1990-01-01

237

Vibratory-Compaction Tests on Graphite Powders for Neutron Shielding.  

National Technical Information Service (NTIS)

Mistures of three size ranges of graphite powders have been vibratory packed to densities as high as 1.40 gm/cm exp 3 , which is 87.5 percent of the design density for the graphte segment of the FMIT test cell shield. Ultrasonic resonance vibration of the...

W. C. Morgan

1982-01-01

238

Equipment for investigation of cryogenic compaction of nanosize silicon nitride powders  

SciTech Connect

This paper describes a system for studies of time-dependent compaction of nanosize silicon nitride powders under various atmospheres at 77 to 1000 K. The system incorporates a screw-driven press (10 ton capacity) with a piston-cylinder type die and can produce cylindrical powder compacts, 3 mm dia and about 1 mm thick, using pressures up to 3 GPa. The system is computer-controlled and permits accurate measurements of the sample volume, and, after appropriate calibration, can determine the rate and degree of densification of the compacting powder as pressure is applied. Frictional forces between the piston and the die are measured during the compaction process. For calibration of the system, powders with known volume-change accompanied by phase transition under pressure were studied, and good agreement with published results was demonstrated. Several Si{sub 3}N{sub 4} samples have been compacted and sintered at 1300 to 1600{degrees}C. Max random packing density of 64% has been obtained using liquid nitrogen lubricant at pressure less than 2.5 GPa. Both green samples and samples sintered at temperatures to 1500{degrees}C were transparent.

Chen, Wei; Piermarini, G.J.; Dapkunas, S.J.; Malghan, S.G. [National Inst. of Standards and Technology (MSEL), Gaithersburg, MD (United States). Ceramics Div.; Pechenik, A. [Air Force Office of Scientific Research, Washington, DC (United States); Danforth, S. [Rutgers--the State Univ., Newark, NJ (United States)

1992-12-31

239

Real-Time Ultrasonic Nondestructive Evaluation of Green State Ceramic Powders during Compaction  

Microsoft Academic Search

A real-time ultrasonic technique for the nondestructive evaluation of ceramic powders during compaction has been demonstrated. Initial results indicate that this technique can detect the presence of hard agglomerates in a spray-dried alumina powder. The proposed sensor could be employed by industry to spot flawed parts prior to removing them from the die, and to provide on-line criteria for control

Martin P. Jones; Gerald V. Blessing

1986-01-01

240

Effects of marble powder and slag on the properties of self compacting mortars  

Microsoft Academic Search

In this study, binary and ternary use of marble powder (MP) and ground granulated blast furnace slag (GGBFS) have been investigated\\u000a in the production of self compacting mortars (SCMs). The marble powder was obtained as an industrial by-product during sawing,\\u000a shaping, and polishing of marble. A total of 19 SCM mixtures were proportioned having a constant water-binder ratio of 0.40

Erhan Gneyisi; Mehmet Geso?lu; Erdo?an zbay

2009-01-01

241

Compaction Behavior and Mechanical Properties of Uniaxially Pressed Bi-W Composites  

Microsoft Academic Search

Powder metallurgy is a useful route to forming particulate composite materials; however, the densification of hard and soft\\u000a powder mixtures is usually inhibited by the more refractory phase. The Bi-W powder compacts were uniaxially pressed at room\\u000a temperature and the compaction behavior and mechanical properties were evaluated. Pressing was performed in incremental steps\\u000a from ~1 to 540MPa. After each step,

L. Peter Martin; Andrea M. Hodge; Geoffrey H. Campbell

2009-01-01

242

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

1994-04-01

243

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

244

Explosive compaction of amorphous ferromagnetic metal powders. Final report  

Microsoft Academic Search

The significant and useful magnetic properties of certain amorphous metals might be better exploited by the electrical industry if these amorphous metals, currently available as ribbon, could be consolidated into high density, principally amorphous, bulk shapes. This work attempted to produce such bodies using explosive compaction techniques. Toroidal specimens, 4.43 cm (1.75 in.) outside diameter, 2.5 cm (1.0 in.) inside

Caligiuri

1983-01-01

245

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.

Jonsn, P.; Hggblad, H.-A.?.

2007-05-01

246

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

247

Vibratory compaction tests on graphite powders for neutron shielding  

Microsoft Academic Search

Mistures of three size ranges of graphite powders have been vibratory packed to densities as high as 1.40 gm\\/cm, which is 87.5 percent of the design density for the graphte segment of the FMIT test cell shield. Ultrasonic resonance vibration of the particles was determined to be an impractical method for achieving the required density. Possible options for fabricating the

1982-01-01

248

Continuum-based FEM modeling of ceramic powder compaction using a cap-plasticity constitutive model  

SciTech Connect

Common ceramic component manufacturing typically involves the processing of the raw materials in powder form. Granulated powder is formed into a green body of the desired size and shape by consolidation, often by simply pressing nominally dry powder. Ceramic powders are commonly pressed in steel dies or rubber bags with the aim of producing a near-net-shape green body for subsequent sintering. Density gradients in these compacts, introduced during the pressing operation, are often severe enough to cause distortions in the shape of the part during sintering due to nonuniform shrinkage. In such cases, green machining or diamond grinding operations may be needed to obtain the desired final shape and size part. In severe cases, nonuniform shrinkage may even cause fracture in the parts during sintering. Likewise, density gradients can result in green bodies that break during ejection from the die or that are too fragile to be handled during subsequent processing. Empirical relationships currently exist to describe powder compaction but provide little understanding of how to control die design or compaction parameters to minimize density gradients thereby forcing the designer to use expensive and time consuming trial and error procedures. For this reason, interest has grown in developing computational tools to address this problem (Aydin et al., 1996 and Coube, 1998). The goal of the present work was to develop a general continuum-based finite element model for ceramic powder compaction that can be used to aid and guide the design and pressing of ceramic powders. Such a model can be used to improve both part and die/bag pressing design, resulting in more efficient and cost effective ways to make better parts.

ARGUELLO JR.,JOSE G.; FOSSUM,ARLO F.; ZEUCH,DAVID H.; EWSUK,KEVIN G.

2000-01-25

249

A new method for estimation of elastic properties of sintered iron powder compacts from ultrasonic longitudinal velocity  

Microsoft Academic Search

A new methodology has been proposed for estimation of elastic moduli of iron powder compacts solely based on longitudinal ultrasonic velocity. New correlations have been semianalytically derived between the elastic moduli and the longitudinal ultrasonic velocity. The moduli estimated on the basis of the suggested methodology agreed reasonably well with data reported for iron powder compacts in the literature. The

Kalyan K. Phani; Dipayan Sanyal

2008-01-01

250

Fabrication of Al7wt%Si0.4wt%Mg\\/SiC nanocomposite powders and bulk nanocomposites by high energy ball milling and powder metallurgy  

Microsoft Academic Search

By using high energy ball milling of a mixture of powders, SiC nanometer sized particle included Al7wt%Si0.4wt%Mg composite powder can be obtained. The effect of milling on the AlSi eutectic reaction of the matrix was studied and it was found that the eutectic reaction occurred during milling. High energy ball milling increased the sintering rate of the composite powder due

K. D. Woo; D. L. Zhang

2004-01-01

251

Liquid precursor infiltration processing of powder compacts. 2: Fracture toughness and strength  

SciTech Connect

Si{sub 3}N{sub 4} powder compacts were infiltrated with liquid precursors which produce either Zr(Y)O{sub 2} (3 mol% Y{sub 2}O{sub 3}) solid solution or amorphous Si{sub 3}N{sub 4} after pyrolysis at relative low temperatures and without shrinkage. Results show that cracks which occur within a thin, surface layer of the precursor during pyrolysis can extend into the powder compact. As suggested by theory, this cracking phenomenon could be avoided either by making the powder compact stronger before infiltration or by removing the thin precursor layer before pyrolysis. The mechanical properties of these materials were studied as a function of residual porosity. It was observed that crack extension occurred within the second phase produced by infiltration and pyrolysis. The second phase appeared to govern the critical stress intensity factor (K{sub c}) of the material. K{sub c} was found to be a linear function of the change in residual, relative porosity divided by the initial, relative porosity in the powder compact. Reasonable flexural strengths ({approx} 300 MPa) could be achieved despite considerable residual porosity.

Tu, W.C.; Lange, F.F. [Univ. of California, Santa Barbara, CA (United States)

1995-12-01

252

Characterization techniques to validate models of density variations in pressed powder compacts  

Microsoft Academic Search

Techniques for characterizing density gradients generated during typical powder compaction processes are reviewed and several are evaluated. The techniques reviewed are ultrasonic velocity measurements, laser ultrasonic velocity measurements, x-ray radiography, autoradiography, computer tomography (CT), magnetic resonance imaging (MRI), and simple image analysis of polished cross-sections. Experimental results are reported for all of these techniques except autoradiography, CT and MRI. The

Terry Garino; Mike Mahoney; Mike Readey; Kevin Ewsuk; John Gieske; Gerry Stoker; Shermann Min

1995-01-01

253

Wear behaviour of organic asbestos based and bronze based powder metal brake linings  

Microsoft Academic Search

Bronze based brake linings, were produced by powder metallurgy technique and their wear behaviour was investigated and compared to that of asbestos ones. Bronze powders were compacted under 350, 500 and 600 MPa pressures and sintered at 810 C in ammonia atmosphere for 75 min. For the same friction distance, it was determined that temperature increase in the bronze based

Adem Kurt; Mustafa Boz

2005-01-01

254

Compaction of Ceramic Microspheres, Spherical Molybdenum Powder and Other Materials to 3 GPa  

SciTech Connect

Pressure-volume relationships were measured at room temperature for eight granular materials and one specimen of epoxy foam. The granular materials included hollow ceramic microspheres, spherical molybdenum powder, Ottawa sand, aluminum, copper, titanium and silicon carbide powders and glassy carbon spheres. Measurements were made to 0.9 GPa in a liquid medium press for all of the granular materials and to 3 GPa in a solid medium press for the ceramic microspheres and molybdenum powder. A single specimen of epoxy foam was compressed to 30 MPa in the liquid medium press. Bulk moduli were calculated as a function of pressure for the ceramic microspheres, the molybdenum powder and three other granular materials. The energy expended in compacting the granular materials was determined by numerically integrating pressure-volume curves. More energy was expended per unit volume in compacting the molybdenum powder to 1 GPa than for the other materials, but compaction of the ceramic microspheres required more energy per gram due to their very low initial density. The merge pressure, the pressure at which all porosity is removed, was estimated for each material by plotting porosity against pressure on a semi-log plot. The pressure-volume curves were then extrapolated to the predicted merge pressures and numerically integrated to estimate the energy required to reach full density for each material. The results suggest that the glassy carbon spheres and the ceramic microspheres would require more energy than the other materials to attain full density.

Carlson, S R; Bonner, B P; Ryerson, F J; Hart, M M

2006-01-27

255

SANS study of microstructural inhomogeneities on Al nano-powder compacts  

NASA Astrophysics Data System (ADS)

The nano-crystalline materials have excellent mechanical and electrical properties compared to conventional materials. These advantages mainly come from their nano-sized grain structure. Usually the nano-crystalline materials are fabricated using nano powder. The optimum consolidation process is essential to obtain a fully densified structure. The quantitative characterization of remaining pores is important to study the consolidation process. SANS is the best technique to characterize the nano sized inhomogeneities in bulk samples. Al nano powder was synthesized by pulsed wire evaporation (PWE) method and the nano-powder compacts were fabricated by magnetic pulse compaction (MPC) method. The Aluminum oxide was observed by transmission electron microscopy (TEM) at the surface of Al nano powder. The small angle neutron scattering experiments were performed both at the instrument V4 in HMI and at the SANS facility in Korea Atomic Energy Research Institute (KAERI). The SANS data measured in KAERI were compared with the SANS data measured in HMI. The scattering intensity at high Q region increases with decreasing relative density, while the intensity at low Q region increases with increasing relative density in the Al nano powder compacts. The scattering intensity depends on the content of residual pores and Al oxide particles. The volume fraction of Al oxide particle increases with relative density due to the fragmentation of Al oxide layer. The extra scattering at low Q region results from the presence of Al oxide particles.

Han, Young Soo; Seong, Baek Seok; Lee, Chang Hee; Lee, Geun Hee; Rhee, Chang Kyu; Kim, Whung Whoe; Wiedenmann, A.

2004-07-01

256

Tungsten and tungsten alloy powder metallurgy. (Latest citations from the EI Cmpendex*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 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1997-03-01

257

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 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1995-11-01

258

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 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1998-03-01

259

Decoupling of paramagnetic and ferrimagnetic AMS development during the experimental chemical compaction of illite shale powder  

NASA Astrophysics Data System (ADS)

Inclination shallowing of detrital remanent magnetization in sedimentary strata has solely been constrained for the mechanical processes associated with mud deposition and shallow compaction of clay-rich sediment, even though a significant part of mud diagenesis involves chemical compaction. Here we report, for the first time, on the laboratory simulation of magnetic assemblage development in a chemically compacting illite shale powder of natural origin. The experimental procedure comprised three compaction stages that, when combined, simulate the diagenesis and low-grade metamorphism of illite mud. First, the full extent of load-sensitive mechanical compaction is simulated by room temperature dry axial compression. Subsequently, temperature controlled chemical compaction is initiated by exposing the sample in two stages to amphibolite or granulite facies conditions (temperature is 490 to 750C and confining pressure is 170 or 300 MPa) both in the absence (confining pressure only) and presence of a deformation stress field (axial compression or confined torsion). Thermodynamic equilibrium in the last two compaction stages was not reached, but illite and mica dehydroxylation initiated, thus providing a wet environment. Magnetic properties were characterized by magnetic susceptibility and its anisotropy (AMS) in both high- and low-applied field. Acquisition of isothermal remanent magnetization (IRM), stepwise three-component thermal de-magnetization of IRM and first-order reversal curves were used to characterize the remanence-bearing minerals. During the chemical compaction experiments ferrimagnetic iron-sulphides formed after reduction of magnetite and detrital pyrite in a low sulphur fugacity environment. The degree of low-field AMS is unaffected by porosity reduction from 15 to 1 per cent, regardless of operating conditions and compaction history. High-field paramagnetic AMS increases with compaction for all employed stress regimes and conditions, and is attributed to illite transformation to iron-bearing mica. AMS of authigenic iron-sulphide minerals remained constant during compaction indicating an independence of ferrimagnetic fabric development to chemical compaction in illite shale powder. The decoupling of paramagnetic and ferrimagnetic AMS development during chemical compaction of pelite contrasts with findings from mechanical compaction studies.

Bruijn, Rolf H. C.; Almqvist, Bjarne S. G.; Hirt, Ann M.; Benson, Philip M.

2013-03-01

260

Effects of thermocapillary forces during welding of 316L-type wrought, cast and powder metallurgy austenitic stainless steels  

Microsoft Academic Search

The Large Hadron Collider (LHC) is now under construction at the European Organisation for Nuclear Research (CERN). This 27km long accelerator requires 1248 superconducting dipole magnets operating at 1.9K. The cold mass of the dipole magnets is closed by a shrinking cylinder and two end covers at both extremities of the cylinder. The end covers are welded, cast or powder

S. Sgobba; T. Daniellou

2003-01-01

261

A comparative study of roll compaction of free-flowing and cohesive pharmaceutical powders.  

PubMed

Roll compaction is widely adopted as a dry granulation method in the pharmaceutical industry. The roll compaction behaviour of feed powders is primarily governed by two parameters: the maximum pressure and the nip angle. Although the maximum pressure can be measured directly using pressure sensors fitted in the rolls, it is not a trivial task to determine the nip angle, which is a measure of the size of the compaction zone and hence the degree of compression. Thus a robust approach based upon the calculation of the pressure gradient, which can be obtained directly from experiments using an instrumented roll compactor, was developed. It has been shown that the resulting nip angles are comparable to those obtained using the methods reported in literature. Nevertheless, the proposed approach has distinctive advantages including (1) it is based on the intrinsic features of slip and no-slip interactions between the powder and roll surface and (2) it is not necessary to carry out wall friction measurements that involve plates that may not be representative of the roll compactor in terms of the surface topography and surface energy. The method was evaluated by investigating the effect of roll speed for two pharmaceutical excipients with distinctive material properties: microcrystalline cellulose (MCC) and di-calcium phosphate dihydrate (DCPD). It was found that the maximum pressure and nip angle for DCPD, which is a cohesive powder, decrease sharply with increasing roll speed whereas they are essentially independent of roll speed for MCC, which is an easy flowing powder. The roll compaction behaviour of MCC-DCPD mixtures with various compositions was also investigated in order to evaluate the effect of flowability. It was found that the nip angle and maximum pressure generally increased with improved flowability of the feed powders. PMID:22402475

Yu, Shen; Gururajan, Bindhu; Reynolds, Gavin; Roberts, Ron; Adams, Michael J; Wu, Chuan-Yu

2012-02-28

262

Heat-Treatment Effects on the Microstructure and Tensile Properties of Powder Metallurgy Ti-6Al-4V Alloys Modified with Boron  

NASA Astrophysics Data System (ADS)

The Ti-6Al-4V (Ti-64) alloys modified with two levels of boron (1B and 1.7B (wt pct)) representing hypoeutectic and hypereutectic compositions, produced via a prealloyed powder metallurgy approach, were subjected to various standard heat treatments of Ti-64 to study the microstructural evolution and its influence on tensile properties. Boron-modified Ti-64 (Ti-64B) alloys exhibited differences in microstructural response to heat treatment compared to that of Ti-64 due to variations in constituent phase fractions and the influence of TiB on the beta-to-alpha phase transformation kinetics. The tensile elastic modulus of Ti-64B alloys increased nearly linearly with the boron content (or TiB volume fraction) and the increase could be satisfactorily predicted with an isostrain rule of mixtures (ROMs) and the Halpin-Tsai model. The Ti-64-1B possessed a good combination of tensile strength (1200 to1370 MPa) and ductility (10 to 13 pct), while Ti-64-1.7B exhibited high strength (1300 to 1695 MPa) and modest ductility (2 to 3.5 pct). Coarse primary TiB particles present in Ti-64-1.7B were found to initiate premature failure. Strength modeling revealed that load sharing by the micron-sized TiB whiskers provides the major contribution for the increase in yield strength.

McEldowney, Dale J.; Tamirisakandala, Seshacharyulu; Miracle, Daniel B.

2010-04-01

263

Effect of inclusion size on the high cycle fatigue strength and failure mode of a high V alloyed powder metallurgy tool steel  

NASA Astrophysics Data System (ADS)

The fatigue strength of a high V alloyed powder metallurgy tool steel with two different inclusion size levels, tempered at different temperatures, was investigated by a series of high cycle fatigue tests. It was shown that brittle inclusions with large sizes above 30 ?m prompted the occurrence of subsurface crack initiation and the reduction in fatigue strength. The fracture toughness and the stress amplitude both exerted a significant influence on the fish-eye size. A larger fish-eye area would form in the sample with a higher fracture toughness subjected to a lower stress amplitude. The stress intensity factor of the inclusion was found to lie above a typical value of the threshold stress intensity factor of 4 MPam1/2. The fracture toughness of the sample with a hardness above HRC 56 could be estimated by the mean value of the stress intensity factor of the fish-eye. According to fractographic evaluation, the critical inclusion size can be calculated by linear fracture mechanics.

Yao, Jun; Qu, Xuan-hui; He, Xin-bo; Zhang, Lin

2012-07-01

264

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

265

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

266

High strain rate deformation microstructures of stainless steel 316L by cold spraying and explosive powder compaction  

Microsoft Academic Search

Cold spraying is a new coating technique in which dense, tightly bonded coatings form only due to the high kinetic energy\\u000a of impinging particles of the spray powder. These particles are still in the solid state during impact. Explosive powder compaction\\u000a is a technique where powder is consolidated by a shock wave. In the shock front the powder is deformed

C. Borchers; T. Schmidt; F. Grtner; H. Kreye

2008-01-01

267

Analysis of NSWC Quasi-Static Compaction Data for Porous Beds of Ball Powder, Melamine, and Teflon, Using Structural Compaction Model.  

National Technical Information Service (NTIS)

A structural compaction model is used to correlate NSWC quasi-static compaction data on porous beds of six (6) different materials, i.e., four (4) ball powders, melamine, and Teflon. Initial densities of the porous beds ranged from 44 percent solid theore...

A. M. Weston E. L. Lee

1983-01-01

268

Densification dynamics of copper and iron powder billets in hot shock compaction: Simulation and analysis  

Microsoft Academic Search

The paper presents the results from computer simulation and analysis of experimental data on the densification of copper and\\u000a iron powder billets during hot shock compaction. It is established for the first time that the shear viscosity of the porous\\u000a material matrix shows a stronger dependence on the initial impact velocity than the billet temperature does. The estimated\\u000a activation energy

M. S. Kovalchenko; L. F. Ochkas

2008-01-01

269

Sintering anisotropy in slip-cast SiC-whisker\\/Si3N4-powder compacts  

Microsoft Academic Search

Sintering anisotropy in slip-cast SiC-whisker\\/Si3N4-powder compacts was studied at 1750C in 0.1 MPa N2 or at 1825C in 1.0 MPa N2. It was shown that whiskers oriented parallel to the mould surface and nearly 1.5-dimensionally along the slip flow direction when the whisker content was 10 wt%. Linear shrinkage was largest perpendicular to the mould surface and smallest perpendicular to

Mamoru Mitomo; Shin-Ichi Saito; Toshitsugu Matsuda; Takao Yonezawa

1993-01-01

270

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

Microsoft Academic Search

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

Tachai Luangvaranunt; Thotsaphon Threrujirapapong; Sawai Danchaivijit; Katsuyoshi Kondoh

2007-01-01

271

Manufacture strengthening of corundum-zirconium ceramic in ultrasonic compacting of ultradisperse powders  

Microsoft Academic Search

The effect of ultrasonic compacting (USC) of ultradisperse oxide powders of the ZrO2-Al2O3 system on sintering of the ceramic was analyzed. It was shown that USC increases the density of pressed samples to 55% of\\u000a the theoretical density of the ceramic. The sintering temperature of the corundum-zirconium ceramic was reduced by 200300C\\u000a with the USC method. The ceramic obtained had

Yu. M. Annenkov; N. N. Aparov; V. M. Sokolov; T. S. Fragul'yan; S. V. Matrenin

1994-01-01

272

Manufacture strengthening of corundum-zirconium ceramic in ultrasonic compacting of ultradisperse powders  

Microsoft Academic Search

The effect of ultrasonic compacting (USC) of ultradisperse oxide powders of the ZrO-AlO system on sintering of the ceramic was analyzed. It was shown that USC increases the density of pressed samples to 55% of the theoretical density of the ceramic. The sintering temperature of the corundum-zirconium ceramic was reduced by 200-300°C with the USC method. The ceramic obtained had

Yu. M. Annenkov; N. N. Aparov; V. M. Sokolov

1995-01-01

273

A new approach for estimation of Poissons ratio of porous powder compacts  

Microsoft Academic Search

A new correlation between Poissons ratio (?) and ultrasonic longitudinal wave velocity (V\\u000a L) has been established and the resulting correlation has been shown to agree well with experimental data on ? versus V\\u000a L for a variety of porous powder compacts. Further, it has been demonstrated that ultrasonic longitudinal wave velocity can\\u000a be used to estimate the elastic properties

Kalyan Kumar Phani; Dipayan Sanyal

2007-01-01

274

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.  

National Technical Information Service (NTIS)

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 forg...

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

1985-01-01

275

Micro-scale simulation of dynamic compaction of oxide and metal powder mixture  

NASA Astrophysics Data System (ADS)

Many features of the dynamic compaction of powders are potentially favorable for use in processing high T(sub c) oxide superconductors. Conventional sintering methods tend to produce unwanted impurities, voids, and oxygen-deficient grain boundaries and have, thus, failed to form bulk oxide superconductors with high critical current. One proposed approach for a dynamic process is to compress a mixture of high purity single crystallite particles and fine silver particles. Computer modeling of dynamic compaction has thus far been limited to bulk simulation of the process by continuum mechanics codes. Results of compaction experiments are not reliably predicted with such techniques because the micro-scale dynamics of powder compaction are only modeled by phenomenological approximation. A micro-scale simulation technique was developed and applied to computer models similar to those of molecular dynamics, which were originally designed to simulate the flow behavior of inelastic, frictional particles. In this method, the oxide grain is represented by a nearly elastic sphere while an individual silver grain is modeled by an aggregate of effective inelastic-frictional particles bound by a prescribed interparticle force. The first 2-D simulation results for a simple configuration (a single aggregate silver grain crushed between two nearly elastic ceramic spheres) are compared with the continuum calculations for the same configuration. This micro-scale simulation technique can be extended to study an assembly of dissimilar grains in 3-D space.

Kamegai, M.; Walton, Otis R.; Taylor, A. G.

1989-10-01

276

Microstructures, Mechanical Properties, and Shape Memory Characteristics of Powder Metallurgy Ti51Ni49 Modified with Boron  

NASA Astrophysics Data System (ADS)

Ti51Ni49 compacts consolidated with persistent liquid-phase sintering usually contain Ti2Ni networks at the grain boundaries, which cause adverse effects on mechanical properties. With 0.5 and 1.0 at pct B additions, fine TiB forms during heating and sintering and acts as a nucleation site for Ti2Ni to precipitate within the grain during cooling. The resultant uniform distribution of TiB and Ti2Ni impedes grain growth and prevents the formation of continuous Ti2Ni precipitates at grain boundaries. As a result, a significant increase in tensile elongation, and not a decrease, as in most as-cast titanium alloys, is obtained because of these changes. The tensile strength also increases, without deterioration of the shape memory characteristics. The tensile strength and elongation are close to those of wrought TiNi alloys.

Yen, Fu-Cheng; Hwang, Kuen-Shyang

2012-02-01

277

Structure and magnetic properties of Fe-Nb-B amorphous/nanocrystalline alloys produced by compaction of mechanically alloyed powders  

NASA Astrophysics Data System (ADS)

Mechanical alloying of Fe75Nb10B15 and Fe85Nb5B10 systems has been performed from an initial mixture of elemental powders. A bcc supersaturated solid solution is developed during milling for both alloys. However, Fe75Nb10B15 alloy also develops an amorphous phase, which amount increases with milling time. Milled powder samples were compacted at 7.7 GPa at different temperatures. Scanning electron microscopy images show that the presence of amorphous phase enhances the quality of compaction. Compaction at 823 K preserves both microstructure and magnetic properties of as-milled powders in both alloys. Compaction at 973 K affects mainly the crystalline fraction of the alloy with 10 at. % Nb. Compaction at 1273 K yields the formation of bcc Nb and fcc Fe23B6 phases, which magnetically harden the material.

Ipus, J. J.; Blzquez, J. S.; Franco, V.; Conde, A.; Krasnowski, M.; Kulik, T.; Lozano-Prez, S.

2010-04-01

278

Analysis of NSWC quasi-static compaction data for porous beds of ball powder, melamine, and Teflon, using structural compaction model  

SciTech Connect

A structural compaction model is used to correlate NSWC quasi-static compaction data on porous beds of six (6) different materials, i.e., four (4) ball powders, melamine, and Teflon. Initial densities of the porous beds ranged from 44 percent solid theoretical maximum density (TMD) to 70 percent TMD. Maximum compacted densities were about 90 percent TMD except for Teflon which was compacted to approximately 98 percent TMD. Pressures calculated by the model, plotted as a function of percent TMD, agree well with the NSWC data.

Weston, A.M.; Lee, E.L.

1983-04-06

279

?TCP ceramic doped with dicalcium silicate for bone regeneration applications prepared by powder metallurgy method: in vitro and in vivo studies.  

PubMed

This study reports on the in vitro and in vivo behavior of ?-tricalcium phosphate (?TCP) and also ?TCP doped with either 1.5 or 3.0 wt % of dicalcium silicate (C2 S). The ceramics were successfully prepared by powder metallurgy method combined with homogenization and heat treatment procedures. All materials were composed of a single-phase, ?TCP in the case of a pure material, or solid solution of C2 S in ?TCP for the doped ?TCP, which were stable at room temperature. The ceramics were tested for bioactivity in simulated body fluid, cell culture medium containing adult mesenchymal stem cells of human origin, and in animals. Analytical scanning electron microscopy combined with chemical elemental analysis was used and Fourier transform infrared and conventional histology methods. The in vivo behavior of the ceramics matched the in vitro results, independently of the C2 S content in ?TCP. Carbonated hydroxyapatite (CHA) layer was formed on the surface and within the inner parts of the specimens in all cases. A fully mineralized new bone growing in direct contact with the implants was found under the in vivo conditions. The bioactivity and biocompatibility of the implants increased with the C2 S content in ?TCP. The C2 S doped ceramics also favoured a phase transformation of ?TCP into CHA, important for full implant integration during the natural bone healing processes. ?TCP ceramic doped with 3.0 wt % C2 S showed the best bioactive in vitro and in vivo properties of all the compositions and hence could be of interest in specific applications for bone restorative purposes. PMID:23225787

Velasquez, Pablo; Luklinska, Zofia B; Meseguer-Olmo, Luis; Mate-Sanchez de Val, Jose E; Delgado-Ruiz, Rafael A; Calvo-Guirado, Jose L; Ramirez-Fernandez, Ma P; de Aza, Piedad N

2012-12-05

280

Tungsten and tungsten alloy powder metallurgy: Powder production and applications excluding lamps. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search  

SciTech Connect

The bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys, including applications of these materials. The hydrogen reduction of tungsten compounds together with alloying element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. Tungsten halogen lamps are examined in a separate bibliography. (Contains a minimum of 115 citations and includes a subject term index and title list.)

NONE

1995-02-01

281

Tungsten and tungsten alloy powder metallurgy: Powder production and applications excluding lamps. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search  

SciTech Connect

The bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys, including applications of these materials. The hydrogen reduction of tungsten compounds together with alloying element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. Tungsten halogen lamps are examined in a separate bibliography.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1997-01-01

282

Tungsten and tungsten alloy powder metallurgy: Powder production and applications excluding lamps. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search  

SciTech Connect

The bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys, including applications of these materials. The hydrogen reduction of tungsten compounds together with alloying element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. Tungsten halogen lamps are examined in a separate bibliography.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1995-12-01

283

Tungsten and tungsten alloy powder metallurgy: Powder production and applications excluding lamps. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search  

SciTech Connect

The bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys, including applications of these materials. The hydrogen reduction of tungsten compounds together with alloying element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. (Contains a minimum of 109 citations and includes a subject term index and title list.)

Not Available

1994-04-01

284

Effect of degree of methoxylation and particle size on compression properties and compactibility of pectin powders.  

PubMed

This study examines the effect of the degree of methoxylation (DM) and particle size on compression properties and compactibility of pectin powders. A powder classification system based on sequential handling of compression parameters was applied. A single size fraction (90-125 ?m) of pectin powders with DM values ranging from 5-72% was studied. For DM 25%, the effect of different particle size fractions (180-250, 125-180, 90-125, 63-90, 45-63, <45 ?m) were investigated. Compression parameters were derived based on time-resolved force-displacement data using Heckel, Kawakita and Shapiro equations. Volume-specific surface area was estimated for powders and tablets. Tablet tensile strength was determined. It was found that all pectin powders displayed low degrees of particle rearrangement and relatively low degrees of fragmentation (class IIA materials). Pectin particles were found to be relatively soft, with a tendency towards softer particles for pectins of higher DM. The overall variation in fragmentation and deformation behavior was limited. Both DM and initial particle size affected the tensile strength of pectin tablets. The difference in surface hydrophobicity caused by the DM was suggested as being responsible for the variation in the mechanical strengths. The study shows that pectin grades with DM ? 40% are potential direct compression excipients. PMID:21142830

Salbu, Linda; Bauer-Brandl, Annette; Alderborn, Gran; Tho, Ingunn

2010-12-13

285

Characterization techniques to validate models of density variations in pressed powder compacts  

SciTech Connect

Techniques for characterizing density gradients generated during typical powder compaction processes are reviewed and several are evaluated. The techniques reviewed are ultrasonic velocity measurements, laser ultrasonic velocity measurements, x-ray radiography, autoradiography, computer tomography (CT), magnetic resonance imaging (MRI), and simple image analysis of polished cross-sections. Experimental results are reported for all of these techniques except autoradiography, CT and MRI. The test specimens examined were right circular cylinders of a high length/diameter ratio (to ensure significant density variation) pressed from commercial spray-dried alumina powders. Although the density gradients could be detected with all four techniques, ultrasonic velocity measurements gave the best contour map of gradients and is therefore most suitable for model validation. On the other hand, it was concluded that x-ray radiography is preferable in situations where cost and/or number of samples are more important that high resolution.

Garino, T.; Mahoney, M.; Readey, M.; Ewsuk, K.; Gieske, J.; Stoker, G. [Sandia National Labs., Albuquerque, NM (United States); Min, S. [Sandia National Labs., Livermore, CA (United States)

1995-07-01

286

Characterization techniques to validate models of density variations in pressed powder compacts  

NASA Astrophysics Data System (ADS)

Techniques for characterizing density gradients generated during typical powder compaction processes are reviewed and several are evaluated. The techniques reviewed are ultrasonic velocity measurements, laser ultrasonic velocity measurements, x-ray radiography, autoradiography, computer tomography (CT), magnetic resonance imaging (MRI), and simple image analysis of polished cross-sections. Experimental results are reported for all of these techniques except autoradiography, CT and MRI. The test specimens examined were right circular cylinders of a high length/diameter ratio (to ensure significant density variation) pressed from commercial spray-dried alumina powders. Although the density gradients could be detected with all four techniques, ultrasonic velocity measurements gave the best contour map of gradients and is therefore most suitable for model validation. On the other hand, it was concluded that x-ray radiography is preferable in situations where cost and/or number of samples are more important that high resolution.

Garino, Terry; Mahoney, Mike; Readey, Mike; Ewsuk, Kevin; Gieske, John; Stoker, Gerry; Min, Shermann

287

Minimum Amount of Binder Removal Required during Solvent Debinding of Powder-Injection-Molded Compacts  

NASA Astrophysics Data System (ADS)

Unsatisfactory dimensional control, distortion, and defects are frequently observed in powder-injection-molded parts, particularly after the solvent and thermal-debinding processing steps. One of the reasons is that the amount of soluble binder removed during the first step, solvent debinding, is not great enough to form interconnected pores throughout the compact, particularly in the core region. Thus, blistering, cracking, and bubbles can form easily during the subsequent thermal debinding. To determine the minimum debinding fraction required for solvent debinding, at which point interconnected pore channels are formed at the center, modeling of the distribution of the remaining soluble binder in the compact was established. The actual distribution, which was obtained by measuring the binder content layer by layer with the soxhelt extraction method, is in good agreement with the model. The modeling, bubble test, and fluorescence dye-penetration analysis show that, regardless of the compact thickness, the minimum bulk debinding fraction needed is consistently approximately 59 pct, yielding a local debinding fraction of 37 pct and a porosity of 8.5 pct at the center. This porosity is close to the value at which pores in a sintered compact transform from open to closed at the beginning of the final stage of sintering.

Fan, Yang-Liang; Hwang, Kuen-Shyang; Wu, Shiau-Han; Liau, Yau-Ching

2009-04-01

288

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

289

Continuum-Based FEM Modeling of Ceramic Powder Compaction Using a Cap-Plasticity Constitutive Model  

SciTech Connect

Software has been developed and extended to allow finite element (FE) modeling of ceramic powder compaction using a cap-plasticity constitutive model. The underlying, general-purpose FE software can be used to model even the most complex three-dimensional (3D) geometries envisioned. Additionally, specialized software has been developed within this framework to address a general subclass of axisymmetric compacts that are common in industry. The expertise required to build the input deck, run the FE code, and post-process the results for this subclass of compacts is embedded within the specialized software. The user simply responds to a series of prompts, evaluates the quality of the FE mesh that is generated, and analyzes the graphical results that are produced. The specialized software allows users with little or no FE expertise to benefit from the tremendous power and insight that FE analysis can bring to the design cycle. The more general underlying software provides complete flexibility to model more complicated geometries and processes of interest to ceramic component manufacturers but requires significantly more user interaction and expertise.

ARGUELLO JR.,JOSE G.; FOSSUM,ARLO F.; ZEUCH,DAVID H.; EWSUK,KEVIN G.

2000-05-01

290

High strain rate deformation microstructures of stainless steel 316L by cold spraying and explosive powder compaction  

NASA Astrophysics Data System (ADS)

Cold spraying is a new coating technique in which dense, tightly bonded coatings form only due to the high kinetic energy of impinging particles of the spray powder. These particles are still in the solid state during impact. Explosive powder compaction is a technique where powder is consolidated by a shock wave. In the shock front the powder is deformed under high strain rates, which under suitable conditions results in high-strength bonding of the particles. Thus, the microstructural features obtained by both techniques should be similar. This study correlates the microstructure of cold-sprayed 316L austenitic steel coatings in comparison to the microstructure of 316L samples obtained by explosive compaction. The results provide insight into the prevailing local deformation mechanisms, as well as into the physical background of observed phase transformations.

Borchers, C.; Schmidt, T.; Grtner, F.; Kreye, H.

2008-03-01

291

Effect of isothermal forging on microstructure and fatigue behavior of blended elemental Ti6Al4V powder compacts  

Microsoft Academic Search

The effect of isothermal hot forging (IHF) on microstructure, pore closure, and tensile and fatigue properties of Ti-6A1-4V\\u000a blended elemental cold pressed and sintered powder compacts was investigated. Two types of sponge fines were used: (a) high\\u000a chloride produced by the Hunter sodium reduction process (HP) and (b) low chloride produced by the electrolytic process (EP).\\u000a The as-sintered HP compacts

I. Weiss; D. Eylon; M. W. Toaz; F. H. Froes

1986-01-01

292

Effect of isothermal forging on microstructure and fatigue behavior of blended elemental Ti6Al4V powder compacts  

Microsoft Academic Search

The effect of isothermal hot forging (IHF) on microstructure, pore closure, and tensile and fatigue properties of Ti-6A1-4V blended elemental cold pressed and sintered powder compacts was investigated. Two types of sponge fines were used: (a) high chloride produced by the Hunter sodium reduction process (HP) and (b) low chloride produced by the electrolytic process (EP). The as-sintered HP compacts

I. Weiss; D. Eylon; M. W. Toaz; F. H. Froes

1986-01-01

293

Small-angle neutron scattering investigations on sintering behavior in the powder compacts of ceria (CeO 2)  

Microsoft Academic Search

Nano-crystalline ceria powders have been synthesized by gel combustion process. The effect of sintering temperature on the pore morphology of the powder compacts has been investigated by small-angle neutron scattering (SANS) in the accessible scattering wave vector q range of 0.0030.17nm?1 of a double crystal based instrument. The scattering profiles do not follow normal q?4 power law at higher q-values.

Vinila Bedekar; A. K. Patra; D. Sen; S. Mazumder; A. K. Tyagi

2008-01-01

294

Compaction of spray-dried ceramic powders: An experimental study of the factors that control green density  

SciTech Connect

The pressure-compaction response of a spray-dried, 94% alumina powder containing several percent of a polymeric binder was investigated as a function of die diameter and compact aspect ratio. The results show that the die fill density decreases markedly with decreasing die diameter and aspect ratio, while the final green density (at 120 MPa) decreases only slightly under the same conditions. These results suggest that the ratio of the initial compact dimensions to the size of the granules may be much more important than previously considered.

Readey, M.J.; Mahoney, F.M. [Sandia National Labs., Albuquerque, NM (United States). Glass and Electronic Ceramics

1995-11-01

295

Ultrasonic characterization of density and elastic properties in Bi-2212 powder compacts  

NASA Astrophysics Data System (ADS)

This paper addresses the development and application of advanced sensing based on emerging nondestructive evaluation techniques, such as ultrasound, resonant frequency, x-ray, etc., for characterizing product quality at various stages of high temperature superconducting (HTS) conductor manufacturing. These techniques provide valuable information on the relationships between process variables and product properties, and enable new/emerging manufacturing process optimization. Such techniques are being explored for the characterization of critical product parameters at various stages of Bi-2212 powde-intube process. In addition, these techniques, when implemented in real-time, promise significant benefits for sensing and process control of HTS conductor processing. Specifically, this paper discusses the development of ultrasonic techniques for characterizing density and elastic properties in Bi-2212 powder compacts. Ultrasonic longitudinal and shear wave velocities in these materials were measured at 2.25 MHz. Ultrasonic velocity is a strong function of density (hence porosity) and provides a potential means of measurement of this quantity. Also presented are ultrasonic measurement of elastic properties of Bi-2212 compacts.

Parthasarathi, S.; Aesoph, M. D.; Yuan, D.-W.; Jo, J.; Kajuch, J.

1994-11-01

296

Explosive compaction of clad graphite powders and obtaining of coatings on their base.  

SciTech Connect

In order to consolidate graphite based powders and in order to obtain coatings with density values near to the theoretical ones clad graphite powders of the C{sub graphite} - Ni (C, - Ni) compositions were explosively compacted under different loading conditions. Theoretical calculations revealed that for assessing the stressdeformed state of C, - Ni compositions and computing the normal and tangent stress components (when VD < C{sub longitudinal} V{sub D} < C{sub transversal})it is recommended to apply the dynamic problem's solution model while the pressure impulse P = f (x) is being uniformly spread with constant rate along the boundary of a semi-infinite elastic body. The results of our experiments showed that it is possible to obtain high dense coatings from C{sub g} - Ni compositions bonded by an inteimediate layer to the substrate material. The structure and properties of the coatings depends on the intensity of the shock loading and temperature. The effect of the shock loading conditions (temperature, loading intensity) on the structure, properties and structure/properties relationships for the C{sub g} -Ni coatings are discussed.

Peikrishvili, A. B. (Akaki B.); Japaridze, L. A. (Levan A.); Marquis, F. D. S. (Fernand D. S.); Staudhammer, Karl P.; Chikhradze, N. M. (Nikoloz M.); Gobejishvili, T. G. (Tamaz G.); Bantzuri, E. G. (Eka G.)

2001-01-01

297

EXPLOSIVE COMPACTION OF CLAD GRAPHITE POWDERS AND OBTAINING OF COATINGS ON THEIR BASE  

SciTech Connect

In order to consolidate graphite based powders and in order to obtain coatings with density values near to the theoretical ones clad graphite powders of the C{sub graphite} - Ni (C{sub g} - Ni) compositions were explosively compacted under different loading conditions. Theoretical calculations revealed that for assessing the stress-deformed state of C{sub g} - Ni compositions and computing the normal and tangent stress components (when V{sub D} < C{sub longitudinal} and V{sub D} < C{sub transversal}) it is recommended to apply the dynamic problem's solution model while the pressure impulse P = f(x) is being uniformly spread with constant rate along the boundary of a semi-infinite elastic body. The results of our experiments showed that it is possible to obtain high dense coatings from C{sub g}-Ni compositions bonded by an intermediate layer to the substrate material. The structure and properties of the coatings depends on the intensity of the shock loading and temperature. The effect of the shock loading conditions (temperature, loading intensity) on the structure, properties and structure/properties relationships for the C{sub g} - Ni coatings are discussed.

A. B. PEIKRISHIVILI; ET AL

2000-11-01

298

Hydride-dehydride conversion of solid Ti6Al4V to powder form  

SciTech Connect

An investigation is described in which the aim was to produce through the hydride-dehydride process a titanium alloy powder from Ti6Al4V alloy in a compact form (cast rods or electrode chips) and from oxidized Ti6Al4V REP powder. The possibilities and efficiency of obtaining Ti6Al4V powders for use in powder metallurgy applications were examined. The conditions of a reversible hydride-dehydride process were determined by X-ray and scanning electron microscopy characterization of the powders.

Mitkov, M.; Bozic, D. [Vinca Inst. of Nuclear Sciences, Belgrade (Yugoslavia). Materials Science Lab.

1996-08-01

299

Aspects of the metallurgy of uranium and constructional metals  

Microsoft Academic Search

On the basis of foreign material presented at the Second International Conference on the Peaceful Uses of Atomic Energy (Geneva, 1958), we examine aspects of uranium production (reductive melting, casting, pressure treatment, and powder metallurgy); zirconium metallurgy (new data on the technological scheme, the nature of sponge and the dimensions of ingots); the production of the new constructional metals, niobium

G. A. Meerson

1960-01-01

300

Numerical simulation of solid-state sintering of metal powder compact dominated by grain boundary diffusion  

NASA Astrophysics Data System (ADS)

The research effort is oriented towards the modeling of metal powder sintering to accurately predict the densification and distortion of a sintered part, which is mainly due to the differential shrinkage of a green compact. This research focuses on the study of the simulation of the sintering process that is dominated by grain boundary diffusion, which is recognized as one of the dominating sintering mechanisms. Specifically, a viscoelasticity model that accounts for the microstructural grain growth has been developed to simulate the thermal induced creep deformation in sintering. Sintering stress is treated as an equivalent hydrostatic pressure that links the microscale evolution to the macroscale deformation. To support that linkage, a grain boundary counting procedure has been modified to quantify the grain size distribution. The material resistance of viscous flow is included in the model as a thermally activated process using an Arrhenius-type temperature relation to represent the apparent viscosity. The finite element method is used to implement the simulation. Results of the compaction simulation such as shape change, residual stress and density distribution data are transferred into the sintering simulation as initial conditions. Since no extra heat source is generated during sintering, the thermal analysis is independent of the creep analysis so that an uncoupled heat transfer analysis yields time-dependent temperature fields that are used to drive the sintering simulation. The simulation is performed in ABAQUS, and an in-house FEM code (SinSolver) is used as a supporting tool and verification. Stainless steel 316L is chosen in this research due to its wide range of industrial applications and representative sintering mechanisms. Comparison and analysis on the simulation versus the dilatometry experiments of shrinkage are consistently close and improve the understanding of when and how the sintering mechanisms act in a sintering cycle.

Zhang, Rui

301

Experimental studies and modeling of the roller compaction of pharmaceutical powders  

NASA Astrophysics Data System (ADS)

During roller compaction in the pharmaceutical industry, mixtures of active and inert powders are fed via a screw to counter-rotating rolls, drawn into the nip and compacted under hydrostatic and shear stresses. Experimental studies were conducted using microcrystalline cellulose on a roller compactor that measured feed force, surface roll pressure and shear stress. The following observations were made: densification correlated with maximum roll pressure; increasing feed force increased roll gap; and significant variation in roll pressure and shear stress exists in the transverse and rolling directions. A slab model highlighted the importance of roll friction, feed stress and entry angle on pre-densification in the feed zone. 2-D and 3-D explicit finite element models with adaptive meshing and arbitrary Eulerian-Lagrangian capabilities were developed. A Drucker-Prager/cap model was calibrated using diametrical and simple compression and die compaction tests. The roll friction was estimated using a die instrumented to measure radial stress. The effects of roll friction, feed stress, roll gap to diameter and entry angle on roll force, torque, profiles of roll pressure and roll shear stress, nip angle, neutral angle, and relative density were evaluated. The results indicated increasing entry angle, decreasing roll gap to diameter, increasing feed stress and/or increasing roll friction lead to higher maximum roll surface pressure and attendant relative density at the exit. The results may be explained by the nip angle and amount of pre-densification. Simulations with pressure-dependent frictional coefficients indicated significant difference in densification. Oscillating feed stress conditions revealed periodic variations in roll pressures and relative densities. Variations in the through-the-thickness were significant in the slip region and diminished in the nip region. The 3-D model predicted lower roll pressure and densities near the edges due to side seal friction. In addition, variable inflow of material along the roll width was related to variation in roll pressure. Overall, the model predictions followed experimental trends. Microcrystalline cellulose experienced higher expansion on release than predicted---related to its non-linear elastic behavior. Various combinations of boundary conditions and geometrical parameters resulted in similar roll pressure profiles and densification thus accurate experimental inputs are essential for model verification.

Cunningham, John C.

302

Effect of Powder Type and Compaction Pressure on the Density, Hardness and Oxidation Resistance of Sintered and Steam-treated Steels  

NASA Astrophysics Data System (ADS)

Two types of Hoganas iron powderssponge (NC), and highly compressible (SC) were investigated. These specimens were compacted with a pressure of 300, 400, 500, 600, and 700 MPa, before sintering in a production belt-type furnace. Steam treatment of the specimens was at 570 C for 30 min. The sintered density and as-sintered hardness increase with increasing compaction pressure, and are significantly influenced by the powder structural characteristics. During steam treatment the type of powder and compaction pressure have an important influence on the extent of pore closure and weight gain. The maximum hardness was obtained for the components compacted at a pressure of 500 MPa for both groups of iron powders. Surface pore closure and oxidation resistance of the steam-treated components are improved with increasing compaction pressure.

Wang, Wen-Fung

2007-10-01

303

Microstructures and Mechanical Properties of Ultrafine Grained Ti-47Al-2Cr (at %) Alloy Produced Using Powder Compact Forging  

NASA Astrophysics Data System (ADS)

Development of innovative techniques to produce gamma TiAl based alloys, with good mechanical properties, while still maintaining ultra fine grain size can be rewarding, but also is a great challenge. In the present study study a Ti-47Al-2Cr (at %) alloy has been synthesized by directly forging green powder compacts of a Ti/Al/Cr composite powder produced by high energy mechanical milling of a mixture of elemental Ti, Al, Cr powders. It has been found that the density of the bulk consolidated alloy sample after forging decreases from 95% of the theoretical density in the central region to 84% in the periphery region. The microstructure of the bulk alloy consisted of several Ti rich regions, which was expected to be mainly due to initial powder condition. The room temperature tensile strength of the samples produced from this process was found to be in the range of 115 - 130 MPa. The roles of canning and green powder compact density in determining the forged sample porosity level and distribution are discussed.

Nadakuduru, Vijay N.; Zhang, Deliang; Cao, Peng; Gabbittas, Brian

304

The effect of density anisotropy on the yielding and flow behavior of partially consolidated powder compacts  

SciTech Connect

The effect of density anisotropy on the flow behavior of partially consolidated powder compacts of an alpha-two titanium aluminide alloy (Ti-24Al-11Nb) was established by conducting hot compression tests on samples made by hot die pressing or hot isostatic pressing (hipping). For the former consolidation method, in which anisotropic density distributions were developed, the upset tests were conducted both parallel and perpendicular to the die pressing direction. The flow stress results from these experiments, as well as those from the tests on the hipped material, were interpreted in terms of calculations of the stress intensification factor ({phi}). When the stress intensification factors were plotted as a function of areal relative density, rather than volumetric relative density, a unique dependence of {phi} on density was obtained. This dependence showed a smooth transition from a behavior measured by others for the early stages of densification to a behavior theoretically predicted for the latter stages of densification, in which isolated pores are closed.

Dutton, R.E.; Semiatin, S.L. [Air Force Research Lab., Wright Patterson AFB, OH (United States). Materials and Manufacturing Directorate

1998-05-01

305

Effects of ultrasonic vibrations on the porosity and hardness of compacts in the pressing of hard-alloy powder mixtures  

Microsoft Academic Search

1.A study was made of the effectiveness of ultrasonic vibration in the pressing of powder mixtures employed in the manufacture of drill bits.2.Experimental data have been obtained on the variation of porosity and hardness with pressure in ultrasonic pressing.3.It was established that pressing with ultrasonic vibrations decreases the porosity of compacts in the as-pressed state on an average by 1012%

L. G. Kostin; L. T. Buchek; N. N. Sumaneev; M. E. Grenader; V. A. Starkov

1975-01-01

306

Acoustic studies of the effect of SiC particle reinforcement on the compaction of alumina powder  

Microsoft Academic Search

A number of acoustic techniques namely, ultrasonic (US), acousto-ultrasonic (AU) and acoustic emission (AE), were employed to study the effect of reinforcement in the form of SiC particles on the compaction of spray-dried alumina powder. The US and AU techniques were shown to be capable of monitoring the processes occurring during loading and unloading, whereas AE could be used, in

T. Kathrina; R. D. Rawlings

1997-01-01

307

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

308

Innovations in titanium powder processing  

NASA Astrophysics Data System (ADS)

One way of reducing the cost of titanium components is to use near-net shape powder-metallurgy techniques. This article describes a number of new approaches to producing components using the powder-metallurgy method for the aerospace, industrial, and consumer marketplaces.

Moxson, Vladimir; Senkov, O. N.; Froes, F. H.

2000-05-01

309

Effect of process control agent on the porous structure and mechanical properties of a biomedical Ti-Sn-Nb alloy produced by powder metallurgy.  

PubMed

The influence of different amounts and types of process control agent (PCA), i.e., stearic acid and ethylene bis-stearamide, on the porous structure and mechanical properties of a biomedical Ti-16Sn-4Nb (wt.%) alloy was investigated. Alloy synthesis was performed on elemental metal powders using high-energy ball milling for 5h. Results indicated that varying the PCA content during ball milling led to a drastic change in morphology and particle-size distribution of the ball-milled powders. Porous titanium alloy samples sintered from the powders ball milled with the addition of various amounts of PCA also revealed different pore morphology and porosity. The Vickers hardness of the sintered titanium alloy samples exhibited a considerable increase with increasing PCA content. Moreover, the addition of larger amounts of PCA in the powder mixture resulted in a significant increase in the elastic modulus and peak stress for the sintered porous titanium alloy samples under compression. It should also be mentioned that the addition of PCA introduced contamination (mainly carbon and oxygen) into the sintered porous product. PMID:19815096

Nouri, A; Hodgson, P D; Wen, C E

2009-10-06

310

Development of cube texture in pure Ni, NiW and NiMo alloys prepared by the powder metallurgy route  

Microsoft Academic Search

Development of textures after heavy cold rolling (?95%) and annealing were studied in powder metallurgically prepared pure Ni, Ni5at.%W and Ni5at.%Mo alloys. It has been found that W and Mo additions to Ni are beneficial for the development of sharp cube texture, although W has a much more pronounced effect than Mo.

P. P. Bhattacharjee; R. K. Ray; A. Upadhyaya

2005-01-01

311

Compaction Dynamique de Poudres Metalliques Par Choc Laser (Dynamic Sintering of Metallic Powders by Laser Shock).  

National Technical Information Service (NTIS)

Experimental sintering of metallic powders is carried out using a 0.53 micrometer laser beam of 2 (10 to the 9th power) W/sq cm, with 25 ns pulses focused over 2 mm diameter. The experimental target is aluminum powder presintered statically at 60 percent ...

P. Darquey J. Romain M. Hallouin F. Cottet

1988-01-01

312

Wear-resistant coatings produced by shock-wave compaction of powders  

NASA Astrophysics Data System (ADS)

Wear-resistant metal-matrix composite coatings with a thickness of 1.5 mm were fabricated on low-alloy steel substrates by explosively generated shock waves. Starting materials were equivolume mixtures of WC or Cr3C2 powder mixed with either titanium or cobalt powder as a binder phase. Three different planar geometries were used, with powder layer thicknesses varying from 1 to 3 mm. Microstructural examination showed that fully dense, crack-free coatings could be produced with a uniform distribution of the carbides within the metallic binder phase. Shear strengths in excess of 40 MPa were measured for coatings composed of equivolume powder mixtures of (Cr3C2 + Ti) and (WC + Ti). The weight loss of a coating produced from an equivolume (WC + Co) powder mixture measured from a two-body abrasive wear test was significantly lower than that measured for a wear-resistant tool steel used as a reference material.

Kiiski, A. A.; Ruuskanen, P. R.; Rubin, J. B.

1996-08-01

313

Shock compaction of rapidly solidified nickel based Mo--Al--W alloy powders with pressure up to 1. 2 mbar  

SciTech Connect

The alloy described in this paper is a high strength nickel alloy containing 10 wt% Mo, 6.8 wt% Al, and 6 wt% W. It cannot be easily prepared by conventional casting methods without gross segregation occurring in the form of massive dendrites. Gas atomization to form fine powders reduces the dendrite size and therefore, the segregation. The spacing of the secondary dendrite arm has been used to estimate the cooling rate of this powder. The experimental investigation of shock compaction is based in part on mach stem lens formation work. One of the fortuitous aspects of the cylindrical explosion design is its suitability as a screening tool with its very high success rate of recovery. Use of the radial implosion design has allowed for the determination of optimum pressures required for consolidation of RSR Ni--10Mo--6.8Al--6W alloy powders as a function of initial packing density. These sets of experiments are in line with previous work on other shock consolidated powders showed that an increase of initial density decreased the melt zone, and only required a slight increase in the pressure to consolidate. 4 refs., 8 figs.

Staudhammer, K.P.

1988-01-01

314

Exploration for shallow compaction-induced gas accumulations in sandstones of the Fort Union Formation, Powder River Basin, Wyoming  

SciTech Connect

Commercial quantities of gas have been produced from shallow sandstone reservoirs of the Tongue River Member of the Fort Union Formation (Paleocene) in the Wyoming portion of the Powder River Basin. The two largest accumulations discovered to date, Oedekoven and Chan pools, were drilled on prospects which invoked differential compaction as a mechanism for gas entrapment and prospect delineation. Coal-sourced bacterial gas may have accumulated in localized structural highs early in the burial history of lenticular sand bodies and associated sediments. Structural relief is due to the compaction contrast between sand and stratigraphically equivalent fine-grained sediments. A shallow gas play targeting sandstones as potential reservoirs was initiated in the Recluse area in response as sources for bacterial gas, and the presence of lenticular sandstones that may have promoted the development of compaction structures early in the burial process, to which early-formed bacterial gas migrated. Prospects were ranked based on a number of geologic elements related to compaction-induced trap development. Drilling of the Oedekoven prospect, which possessed all prospect elements, led to the discovery and development of the Oedekoven Fort Union gas pool, which has produced nearly 2 BCF of gas from a depth of 340 ft. Production figures from the Oedekoven and Chan pools demonstrate the commercial gas potential of Fort Union sandstone reservoirs in the Powder River Basin. The shallow depths of the reservoirs, coupled with low drilling and completion costs, an abundance of subsurface control with which to delineate prospects, and an existing network of gas-gathering systems, make them attractive primary targets in shallow exploration efforts as well as secondary objectives in deeper drilling programs.

Oldham, D.W. [West Virginia Univ., Morgantown, WV (United States)

1997-01-01

315

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

2011-04-05

316

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

317

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

318

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.

Verhoeven, John D. (Ames, IA); Spitzig, William A. (Ames, IA); Gibson, Edwin D. (Ames, IA); Anderson, Iver E. (Ames, IA)

1991-08-27

319

Powder compaction characteristics and tube dimensions in PIT fabrication of Ag\\/BPSCCO superconducting tapes  

Microsoft Academic Search

Density variations of the superconductor core during the powder-in-tube (PIT) fabrication of Ag\\/BPSCCO monolayer tapes have been studied. The PIT procedure involved steps such as filling the tubes with precursor powder, rich in 2212 phase, with packing densities in the range 20 - 55% of theoretical density, groove rolling, flat rolling and finally a four-stage repeated rolling - annealing cycle.

M. S. Sarma; U. Syamaprasad; P. S. Mukherjee; P. Guruswamy; K. G. K. Warrier; A. D. Damodaran

1997-01-01

320

Fabrication of fully dense nanostructured MnBi magnet by hot compaction of cryo-milled powders  

NASA Astrophysics Data System (ADS)

Recently, rare-earth-free permanent magnets (REFPMs) have attracted much attention globally owing to rare-earth metal crisis and high cost. Among the REFPMs, MnBi is a potential candidate due to its unusual large magnetocrystalline anisotropy (K 10^7 erg/cc) and positive temperature of coefficient of coercivity. In this work, we report for the first time a novel processing method that combines the cryo-milling with hot compaction to produce fully dense bulk nanostructured MnBi magnet. The effect of cryo-milling on particle size, phase formation, and magnetic properties of MnBi has been studied in detail. Also, the microstructural and magnetic properties of bulk nanostructured MnBi magnet were investigated. Adoption of cryo-milling results in nanocrystalline powders with particle size of 400-500 nm. Large coercivity (Hc) values of 18.5 kOe, and 12.9 kOe were obtained in cryo-milled powders and hot compacted magnet respectively. The MnBi magnet shows a large positive temperature coefficient of Hc and the Hc reaches a value of more than 30 kOe above 450 K.

Hadjipanayis, George; Ramarao Neelam, Venkata; Gabay, Alex; Li, Wang

2013-03-01

321

Piezochromic Phenomena of Nanometer Voids Formed by Mono-Dispersed Nanometer Powders Compacting Process  

PubMed Central

Piezochromism describes a tendency of certain materials changing colors when they are subjected to various pressure levels. It occurs particularly in some polymers or inorganic materials, such as in palladium complexes. However, piezochromism is generally believed to work at high pressure range of 0.110 GPa. This research work focused on unique piezochromism responses of the nanometer voids formed by the 520 nm inorganic ISOH nanometer powders. It was discovered that microstructures of the nanometer voids could change color at very low pressures of only 0.0020.01 GPa; its sensitivity to pressure was increased by tens of times. It is believed that the uniform microstructures of nanometer powders contributed to the material's high sensitivity of piezochromic phenomena. One factor which quantum optical change caused by nanometer voids affected the quantum confinement effect; another is surface Plasmon Resonance of great difference dielectric property between conductive ITO powder and insulation hydroxide.

Su, Lihong; Wan, Caixia; Zhou, Jianren; Wang, Yiguang; Wang, Liang; Ai, Yanling; Zhao, Xu

2013-01-01

322

Structure and properties of FeNiSiB and CoFeNiSiB alloys obtained by explosive compaction of amorphous powders  

Microsoft Academic Search

Hard (up to 16 GPa) amorphous-crystalline compacts of cobalt-based alloys and iron-based alloys are made by explosive compaction\\u000a from powders at pressures of 12 and 15 GPa. Their magnetic properties correspond to the amorphous-crystalline state. X-ray\\u000a investigations reveal pronounced segregation of the alloying elements as a result of plastic deformation due to the blast\\u000a wave. The cobalt-based alloy is more

N. M. Mordovets; V. I. Kovtun; V. Ya. Kurovskii; A. P. Rachek; Yu. V. Mil'man; O. A. Panasyuk; V. G. Strat'ev

1999-01-01

323

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.

324

Metallurgy and properties of plasma spray formed materials  

SciTech Connect

Understanding the fundamental metallurgy of vacuum plasma spray formed materials is the key to enhancing and developing full material properties. Investigations have shown that the microstructure of plasma sprayed materials must evolve from a powder splat morphology to a recrystallized grain structure to assure high strength and ductility. A fully, or near fully, dense material that exhibits a powder splat morphology will perform as a brittle material compared to a recrystallized grain structure for the same amount of porosity. Metallurgy and material properties of nickel, iron, and copper base alloys will be presented and correlated to microstructure.

Mckechnie, T.N.; Liaw, Y.K.; Zimmerman, F.R.; Poorman, R.M.

1992-01-01

325

STATIC VS CYCLIC WORK HARDENING BEHAVIOUR OF GAS ATOMIZED TiAl ALLOY POWDER COMPACTS  

Microsoft Academic Search

Pre-alloyed powders of composition Ti49Al47Cr2Nb2 produced by inert gas atomization and consolidated by Hot Isostatic Pressing (HIP) have been investigated in terms of microstructure\\/static-versus-cyclic property relationships. A large variety of microstructures, typically from the fully lamellar microstructure to the near-? equiaxed microstructure, have been tailored using different heat treatments. Room-temperature tensile properties and in particular the work hardening rate during

O. BERTEAUX; M. THOMAS; G. HENAFF; M. JOUIAD

326

Quantitative analysis of packed and compacted granular systems by x-ray microtomography  

NASA Astrophysics Data System (ADS)

The packing and compaction of powders are general processes in pharmaceutical, food, ceramic and powder metallurgy industries. Understanding how particles pack in a confined space and how powders behave during compaction is crucial for producing high quality products. This paper outlines a new technique, based on modern desktop X-ray tomography and image processing, to quantitatively investigate the packing of particles in the process of powder compaction and provide great insights on how powder densify during powder compaction, which relate in terms of materials properties and processing conditions to tablet manufacture by compaction. A variety of powder systems were considered, which include glass, sugar, NaCl, with a typical particle size of 200-300 ?m and binary mixtures of NaCl-Glass Spheres. The results are new and have been validated by SEM observation and numerical simulations using discrete element methods (DEM). The research demonstrates that XMT technique has the potential in further investigating of pharmaceutical processing and even verifying other physical models on complex packing.

Fu, Xiaowei; Milroy, Georgina E.; Dutt, Meenakshi; Bentham, A. Craig; Hancock, Bruno C.; Elliott, James A.

2005-04-01

327

Powdered Metal Sintering of Jet Vanes.  

National Technical Information Service (NTIS)

This report presents the successful efforts to use powdered metallurgy techniques in manufacturing jet vanes from sintered and copper infiltrated tungsten. Isostatic pressing of the powdered tungsten to net shape imparts sufficient hardening to allow hand...

M. J. Ripley-Lotee S. M. O'Neil

1982-01-01

328

Neutron powder diffraction of small-volume samples at high pressure using compact opposed-anvil cells and focused beam  

NASA Astrophysics Data System (ADS)

Neutron powder diffraction techniques of small-volume samples at high pressure using compact opposed-anvil cells were developed at J-PARC pulsed neutron source. For this purpose we apply a few types of super-hard materials as opposed anvils with culet diameters between 3 to 5 mm. Generated pressures with these anvils were up to 9 GPa for 2 to 4 mm3 and up to 14 GPa for 0.7 mm3 sample volumes, which not only depends on the anvil geometry and material but even more depends on the metallic gasket geometry and material. A representative anvil geometry with 4 mm in culet diameter, along with TiZr "null alloy" metallic gasket containing varying sample volumes, were then applied to time-of-flight neutron powder diffraction experiments, where methane hydrate of 4 mm3 volume and lead of 0.7 mm3 volume were separately measured and their signal-to-background ratios were evaluated. A neutron-focusing optics was used to concentrate the neutron beam into these small-volume samples to increase the intensity of diffraction. Although spurious diffraction peaks from the anvils were prominent, more than seven diffraction peaks are clearly observed from both of the samples. In spite of the smaller sample capacity than previous standard high-pressure apparatus for neutron, it is concluded that the opposed-anvil cells will become alternative apparatuses for neutron scattering at strong pulsed neutron sources where sufficient neutron intensity was granted.

Okuchi, T.; Sasaki, S.; Ohno, Y.; Abe, J.; Arima, H.; Osakabe, T.; Hattori, T.; Sano-Furukawa, A.; Komatsu, K.; Kagi, H.; Utsumi, W.; Harjo, S.; Ito, T.; Aizawa, K.

2012-07-01

329

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

330

Developments in Die Pressing Strategies for Low-Cost Titanium Powders  

SciTech Connect

Recent developments in the production of low-cost titanium powders have rejuvenated interest in manufacturing titanium powder metallurgy components by direct press and sinter techniques. However excessive friction typically observed during titanium powder pressing operations leads to numerous problems ranging from non-homogeneous green densities of the compacted powder to excessive part ejection forces and reduced die life due to wear and galling. An instrumented double-acting die press was developed to both investigate the mechanics of titanium powder pressing (particularly for the new low-cost powder morphologies) and to screen potential lubricants that could reduce frictional effects. As will be discussed, the instrument was used to determine friction coefficients and to evaluate a number of candidate lubricants. These results were then used to optimize the lubricant system to reduce die-wall stresses and improve part density uniformity.

Hovanski, Yuri; Weil, K. Scott; Lavender, Curt A.

2009-05-01

331

Metallurgy Beyond Iron  

Microsoft Academic Search

Metallurgy is one of the oldest sciences. Its history can be traced back to 6000 BCE with the discovery of Gold, and each new discovery - Copper, Silver, Lead, Tin, Iron and Mercury - marked the beginning of a new era of civilization. Currently there are 86 known metals, but until the end of the 17th century, only 12 of

Isabella Gallino; Ralf Busch

2009-01-01

332

Extractive Metallurgy of Beryllium  

Microsoft Academic Search

A comprehensive review of the extractive metallurgy of beryllium is presented. Due to the strategic importance and element of secrecy surrounding the metal, any open literature on beryllium is rather limited. However, this review has been made to cover all important aspects of beryllium extraction technology namely, resources of the metal; processing of ores; reduction of fluoride and oxide to

C. K. GUPTA; S. SAHA

2002-01-01

333

Extractive Metallurgy of Beryllium  

Microsoft Academic Search

A comprehensive review of the extractive metallurgy of beryllium is presented. Due to the strategic importance and element of secrecy surrounding the metal, any open literature on beryllium is rather limited. However, this review has been made to cover all important aspects of beryllium extraction technology namely, resources of the metal; processing of ores; reduction of fluoride and oxide to

C. K. GUPTA; S. SAHA

2001-01-01

334

Tungsten and tungsten-alloy powder metallurgy: Powder production and applications-excluding lamps. November 1971-July 1989 (Citations from the US Patent data base). Report for November 1971-July 1989  

SciTech Connect

This bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys including various applications of these materials. The hydrogen reduction of tungsten compounds together with alloying-element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of various cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. Tungsten halogen lamps are examined in a separate bibliography. (Contains 60 citations fully indexed and including a title list.)

Not Available

1989-10-01

335

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

336

Effect of particle- and specimen-level transport on product state in compacted-powder combustion synthesis and thermal debinding of polymers from molded powders  

NASA Astrophysics Data System (ADS)

The existence of large gradients within particles and fast temporal variations in the temperature and species concentration prevents the use of asymptotic approximations for the closure of the volume-averaged, specimen-level formulations. In this case a solution of the particle-level transport problem is needed to complement the specimen-level volume-averaged equations. Here, the use of combined specimen-level and particle-level models for transport in reactive porous media is demonstrated with two examples. For the gasless compacted-powder combustion synthesis, a three-scale model is developed. The specimen-level model is based on the volume-averaged equations for species and temperature. Local thermal equilibrium is assumed and the macroscopic mass diffusion and convection fluxes are neglected. The particle-level model accounts for the interparticle diffusion (i.e., the liquid migration from liquid-rich to liquid-lean regions) and the intraparticle diffusion (i.e., the species mass diffusion within the product layer formed at the surface of the high melting temperature component). It is found that the interparticle diffusion controls the extent of conversion to the final product, the maximum temperature, and to a smaller degree the propagation velocity. The intraparticle diffusion controls the propagation velocity and to a smaller degree the maximum temperature. The initial stages of thermal degradation of EVA from molded specimens is modeled using volume-averaged equations for the species and empirical models for the kinetics of the thermal degradation, the vapor-liquid equilibrium, and the diffusion coefficient of acetic acid in the molten polymer. It is assumed that a bubble forms when the partial pressure of acetic acid exceeds the external ambient pressure. It is found that the removal of acetic acid is characterized by two regimes, a pre-charge dominated regime and a generation dominated regime. For the development of an optimum debinding schedule, the heating rate is modulated to avoid bubbling, while the concentration and temperature follow the bubble-point line for the mixture. The results show a strong dependence on the presence of a pre-charge. It is shown that isolation of the pre-charge effect by using temporary lower heating rates results in an optimum schedule for which the process time is reduced by over 70% when compared to a constant heating rate schedule.

Oliveira, Amir Antonio Martins

337

Integration approach of the Couette inverse problem of powder type self-compacting concrete in a wide-gap concentric cylinder rheometer  

Microsoft Academic Search

For powder type self-compacting concrete (SCC) mixes, commonly used in Belgium, a shear thickening (HerschelBulkley) flow behaviour of the fresh mixes is quite often observed.A longstanding problem in rheometry is the so-called Couette inverse problem, where one tries to derive the flow curve ?(??) from the torque measurements T(N) in a (wide-gap) concentric cylinder (Couette) rheometer, with T the torque

G. Heirman; L. Vandewalle; D. Van Gemert; . Wallevik

2008-01-01

338

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 400600 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 ironnickel 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

339

Compaction Behavior and Mechanical Properties of Uniaxially Pressed Bi-W Composites  

NASA Astrophysics Data System (ADS)

Powder metallurgy is a useful route to forming particulate composite materials; however, the densification of hard and soft powder mixtures is usually inhibited by the more refractory phase. The Bi-W powder compacts were uniaxially pressed at room temperature and the compaction behavior and mechanical properties were evaluated. Pressing was performed in incremental steps from ~1 to 540 MPa. After each step, the pressure was relieved and the thickness and sound-wave transit time were measured in situ (in the die), in order to determine the density and sound-wave velocity in the compact. The data show that the unreinforced Bi powder compacts to ~98 pct density at 540 MPa. The W reinforcement inhibits the densification process, resulting in increased levels of residual porosity. The compaction behavior was evaluated using a modified Heckel equation, while the porosity dependence of the ultrasonically determined elastic modulus was described by a site percolation approach. Postcompaction sound-wave velocity and Vickers hardness measurements show <5 pct anisotropy between the axial (pressing) and radial directions. The mechanical characterization illustrates the competing effects of the W reinforcement and the associated residual porosity.

Peter Martin, L.; Hodge, Andrea M.; Campbell, Geoffrey H.

2009-09-01

340

Metallurgy Beyond Iron  

NASA Astrophysics Data System (ADS)

Metallurgy is one of the oldest sciences. Its history can be traced back to 6000 BCE with the discovery of Gold, and each new discovery - Copper, Silver, Lead, Tin, Iron and Mercury - marked the beginning of a new era of civilization. Currently there are 86 known metals, but until the end of the 17th century, only 12 of these were known. Steel (Fe-C alloy) was discovered in the 11th century BCE; however, it took until 1709 CE before we mastered the smelting of pig-iron by using coke instead of charcoal and started the industrial revolution. The metallurgy of nowadays is mainly about discovering better materials with superior properties to fulfil the increasing demand of the global market. Promising are the Glassy Metals or Bulk Metallic Glasses (BMGs) - discovered at first in the late 50s at the California Institute of Technology - which are several times stronger than the best industrial steels and 10-times springier. The unusual structure that lacks crystalline grains makes BMGs so promising. They have a liquid-like structure that means they melt at lower temperatures, can be moulded nearly as easily as plastics, and can be shaped into features just 10 nm across. The best BMG formers are based on Zr, Pd, Pt, Ca, Au and, recently discovered, also Fe. They have typically three to five components with large atomic size mismatch and a composition close to a deep eutectic. Packing in such liquids is very dense, with a low content of free volume, resulting in viscosities that are several orders of magnitude higher than in pure metal melts.

Gallino, Isabella; Busch, Ralf

2009-08-01

341

Ignition of Titanium Powder Layers by Electrostatic Discharge  

Microsoft Academic Search

Titanium powder heating and ignition by an electrostatic discharge (ESD) or spark was investigated. The effect of powder layer thickness and morphology was determined. Ti powder was chosen for these experiments because it is commonly found in energetic formulations, used for materials preparation by self-propagating high-temperature synthesis, and is extensively used in powder metallurgy. Two Ti powders were used: spherical

Ervin Beloni; Edward L. Dreizin

2011-01-01

342

Advanced NDE Techniques for Powder Metal Components.  

National Technical Information Service (NTIS)

Nondestructive evaluation encompasses numerous technologies that assess materials and determine important properties. This paper demonstrates the applicability of several of these technologies to the field of powder metallurgy. The usual application of no...

P. Martin J. Haskins G. Thomas K. Dolan

2003-01-01

343

An estimate of the macroscopic yield surfaces of powder compacts using the kinematic approach of the yield design theory  

Microsoft Academic Search

The 3D compaction of a square array of spherical particles of uniform size is studied using the kinematic approach of the yield\\u000a design theory. The densification is assumed to occur by plastic deformation at the mutual zone contacts between grains where\\u000a the dissipation is localized. The compaction response of the array of spherical particles is considered in term of representative

Anouar BENABBES; Luc DORMIEUX; Larbi SIAD

2008-01-01

344

Performance Study of compact wood powder material processing for improved impact characteristics aiming at substitute for plastics  

Microsoft Academic Search

Recently, a plastic-like material has been obtained by compression of wood powder only under an appropriate temperature and pressure conditions. It is considered that this change in a surface texture like transformation comes from auto-condensation of wood components. The static bending strength of the wood powder material (WPM) at 23C is roughly the same as that of plastics such as

T. Miki; K. Takeuchi; H. Sugimoto; K. Kanayama

2007-01-01

345

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

346

Quasi-static compaction of porous propellant beds. I. Modeling ball powder experiments with deformed spheres in a regular lattice  

Microsoft Academic Search

A simple but physically-based model describing compaction of granular energetic materials is presented for the case where the grains deform plastically. The model assumes an ideal porous bed consisting of initially uniform spherical particles arranged in a cubic lattice. As the bed is loaded, the spheres are flattened at each contact; particle volume is conserved by allowing the radius of

S. J. Jacobs; H. W. Sandusky; W. L. Elban

1996-01-01

347

The extractive metallurgy of gold  

NASA Astrophysics Data System (ADS)

Mssbauer spectroscopy has been successfully used in investigation of the gold compounds present in ores and the gold species which occur during the process metallurgy of this metal. This paper is a survey of the basic recovery methods and techniques used in extractive metallurgy of gold. Process fundamentals on mineral processing, ore leaching, zinc dust cementation, adsorption on activated carbon, electrowinning and refining are examined. The recovery of gold as a by-product of the copper industry is also described. Alternative processing methods are indicated in order to shed light on new interesting research topics where Mssbauer spectroscopy could be applied.

Kongolo, K.; Mwema, M. D.

1998-12-01

348

Shock compaction of rapidly solidified nickel based Mo--Al--W alloy powders with pressure up to 1. 2 mbar  

Microsoft Academic Search

The alloy described in this paper is a high strength nickel alloy containing 10 wt% Mo, 6.8 wt% Al, and 6 wt% W. It cannot be easily prepared by conventional casting methods without gross segregation occurring in the form of massive dendrites. Gas atomization to form fine powders reduces the dendrite size and therefore, the segregation. The spacing of the

Staudhammer

1988-01-01

349

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

350

A comparison between two powder compaction parameters of plasticity: the effective medium A parameter and the Heckel 1/K parameter.  

PubMed

The purpose of the research was to introduce a procedure to derive a powder compression parameter (EM A) representing particle yield stress using an effective medium equation and to compare the EM A parameter with the Heckel compression parameter (1/K). 16 pharmaceutical powders, including drugs and excipients, were compressed in a materials testing instrument and powder compression profiles were derived using the EM and Heckel equations. The compression profiles thus obtained could be sub-divided into regions among which one region was approximately linear and from this region, the compression parameters EM A and 1/K were calculated. A linear relationship between the EM A parameter and the 1/K parameter was obtained with a strong correlation. The slope of the plot was close to 1 (0.84) and the intercept of the plot was small in comparison to the range of parameter values obtained. The relationship between the theoretical EM A parameter and the 1/K parameter supports the interpretation of the empirical Heckel parameter as being a measure of yield stress. It is concluded that the combination of Heckel and EM equations represents a suitable procedure to derive a value of particle plasticity from powder compression data. PMID:23810817

Mahmoodi, Foad; Klevan, Ingvild; Nordstrm, Josefina; Alderborn, Gran; Frenning, Gran

2013-06-26

351

Microstructure studies of dynamically compacted material  

Microsoft Academic Search

Dynamic compaction has been used successfully to compact aluminum and titanium powder. A light gas (helium) gun was used for these studies. Fine oxide powders were added to the metal powders to identify the interparticle boundaries in the compacted material. The as-compacted and heat treated microstructures, particularly the interparticle boundary region, were examined by TEM and optical microscopy. These results

D. J. Miller; D. G. Konitzer; H. L. Fraser

2008-01-01

352

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

353

Physical causes and mechanisms of the formation of boundary regions in the two-dimensional explosive compaction of powdered materials  

Microsoft Academic Search

2, Test Materials. The experiments were conducted on powdered titanium, nickel, cop- per, titanium nickelide (TiNi), and tin bronze. The bronze particles had a form close to spherical, while the other particles were irregularly shaped. Dispersity ranged from 20-50 to 400-630 #m. The initial density of the PM was 30-63% of the density in the monolithic state. The barrier assemblies

N. A. Kostyukov

1991-01-01

354

Resistive and magnetoresistive properties of compacted CrO2 powders with different types of intergranular dielectric layers  

NASA Astrophysics Data System (ADS)

Resistive, magnetoresistive and magnetic properties of four types of pressed CrO2 powders synthesized from chromic anhydride by the hydrothermal method were investigated. The new synthesis method allowed controlling the thickness of dielectric shells. The powders consisted of rounded particles (~120 nm in dia.) or acicular crystals (~22.9 nm in dia. and 302 nm in length). The particles were covered with a surface dielectric shell of different thickness and type (e.g. ?-CrOOH oxyhydroxide or chromium oxide Cr2O3). The influence of the properties and the thickness of intergranular dielectric layers as well as the shape of CrO2 particles on the tunneling resistance and magnetoresistance (MR) of the pressed powders was studied. It was found that at low temperatures all the investigated samples displayed a nonmetallic temperature dependence of resistance and a giant negative MR. The maximal values of MR at T ~ 5 K were found to be approx. 37% in relatively low magnetic fields (0.5 T). The MR decreased rapidly with increasing temperature (down to approx. 1% in 1 T at T ~ 200 K). At low temperatures the powders with acicular particles exhibited a new type of MR hysteresis and nonmonotonous dependence of MR with increasing magnetic field. A nonmonotonous temperature dependence Hp(T), where Hp is the field in which the resistance is maximal, mismatch between the values of Hp and coercive force Hc, and the anisotropy of MR as a function of mutual orientation of transport current and magnetic field were observed.

Dalakova, N. V.; Belevtsev, B. I.; Beliayev, E. Yu.; Bludov, A. N.; Pashchenko, V. N.; Osmolovsky, M. G.; Osmolovskaya, O. M.

2012-12-01

355

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

356

Welding Metallurgy and Weldability of Stainless Steels  

Microsoft Academic Search

Welding Metallurgy and Weldability of Stainless Steels, the first book in over twenty years to address welding metallurgy and weldability issues associated with stainless steel, offers the most up-to-date and comprehensive treatment of these topics currently available. The authors emphasize fundamental metallurgical principles governing microstructure evolution and property development of stainless steels, including martensistic, ferric, austenitic, duplex, and precipitation hardening

John C. Lippold; Damian J. Kotecki

2005-01-01

357

METHOD OF FORMING ELONGATED COMPACTS  

DOEpatents

A powder compacting procedure and apparatus which produces elongated compacts of Be is described. The powdered metal is placed in a thin metal tube which is chemically compatible to lubricant, powder, atmosphere, and die material and will undergo a high degree of plastic deformation and have intermediate hardness. The tube is capped and placed in the die, and punches are applied to the ends. During the compacting stroke the powder seizes the tube and a thickening and shortening of the tube occurs. The tube is easily removed from the die, split, and peeled from the compact. (T.R.H.)

Larson, H.F.

1959-05-01

358

Sintering of sponge and hydride-dehydride titanium powders  

Microsoft Academic Search

The sintering behavior of compacts produced from sponge and hydride-dehydride (HDH) Ti powders was examined. Compacts were vacuum sintered at 1200 or 1300 deg C for 30, 60, 120, 240, 480 or 960 minutes. The porosity decreased with sintering time and\\/or temperature in compacts produced from the HDH powders. Compacts produced from these powders could be sintered to essentially full

David E. Alman; Stephen J. Gerdemann

2004-01-01

359

Sinterability of titanium powder  

Microsoft Academic Search

The sintering process of compacts from dispersed titanium powders (as well as from metal powders with easily reducible oxides) is accomplished in two stages a nonsteady stage with a high densification rate and a steady stage, whose rate is determined by volume diffusion. The low values of energy of activation for densification in the first stage of sintering may

D. S. Arensburger

1970-01-01

360

Sintering titanium powders  

SciTech Connect

Recently, there has been renewed interest in low-cost titanium. Near-net-shape powder metallurgy offers the potential of manufacturing titanium articles without costly and difficult forming and machining operations; hence, processing methods such as conventional press-and-sinter, powder forging and powder injection molding are of interest. The sintering behavior of a variety of commercial and experimental titanium powders was studied. Commercial powders were acquired that were produced different routes: (i) sponge fines from the primary titanium processing; (ii) via the hydride-dehydride process; and (iii) gas atomization. The influence of vacuum sintering time (0.5 to 32 hrs) and temperature (1200, 1275 or 1350C) on the microstructure (porosity present) of cold pressed powders was studied. The results are discussed in terms of the difference in powder characteristics, with the aim of identify the characteristics required for full density via press-and-sinter processing. Near-net-shape tensile bars were consolidated via cold pressed and sintered. After sintering, a sub-set of the tensile bars was hot-isostatic pressed (HIPed). The microstructure and properties of the bars were compared in the sintered and HIPed conditions.

Gerdemann, Stephen J.; Alman, David E.

2005-09-01

361

Methods of increasing the erosion resistance of powder metallurgy steel  

SciTech Connect

The authors comparatively assess the effects of a variety of surface hardening methods--including carburizing, boriding, chromizing, and carbochromizing, as well as the flame, plasma arc, and detonation spraying of nickel and molybdenum coatings--on the wear, corrosion resistance, and pore structure of steel 45, and outline testing procedures used to arrive at their results.

Kulu, P.A.

1987-09-01

362

Geometric reasoning for manufacturability evaluation--application to powder metallurgy  

Microsoft Academic Search

A new approach to perform geometric reasoning for manufacturability evaluation is developed using three-dimensional objects that are based on a process-dependent geometric model. It is demonstrated that by incorporating the limitations of the process directly in the geometric representation scheme, the task of manufacturability evaluation becomes straightforward and can be performed without either feature extraction or designing with features. The

Thomas E. Dissinger; Edward B. Magrab

1996-01-01

363

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

364

Better metallurgy for process equipment  

SciTech Connect

Metallurgy choices have expanded significantly for process equipment and pumps used for handling difficult corrosive fluids. If they have been specifying the austenitic AISI types 316, 316L, 317, 317L or the newer first generation alloy 329 in their pumps, there is a strong message in recent literature. Based on tests and experience there are better, often less costly alternatives. In the case of CD[sub 4]MCu, N08020 and 904L, there are lower-cost material alternatives for many applications. For SA S31254 and SA N08367, there are some less aggressive can be substituted. These alternatives are the new second generation duplex steels. The lower cost of the duplex alloys is a result of the reduced nickel content, which is about half that of the standard austenitics. Also, their carbon content is low; the same as 316L and 317L for most alloys, including S31803. The second generation duplex alloys offer significant value improvement in a vast majority of applications over the common austenitics and ferritics. Further, their improved resistance to corrosion and improved physical properties relative to the expensive. and in many cases proprietary, highly corrosion-resistant, super-ferritics and super-austenitics, means that they can and should be considered as an alternative for applications where those materials are now overqualified. Strength, toughness and wide corrosion resistance are all-important properties and considerations for process pump materials. Combine these with competitive cost and there is an opportunity that must be investigated.

Rayner, R.E.

1994-01-01

365

Thermal characteristics of Fe powders with micro-and nano-sized particles  

Microsoft Academic Search

This paper investigates characteristics of heat transfer in Fe micrometer and nanometer powders. The understanding for thermal properties of the powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. Nanosized particles possess characteristic physical and chemical properties different from those of bulk materials due to the confinement

C. Y. Ho; Y. H. Tsai

2011-01-01

366

Welding Metallurgy and Weldability of Stainless Steels  

NASA Astrophysics Data System (ADS)

Welding Metallurgy and Weldability of Stainless Steels, the first book in over twenty years to address welding metallurgy and weldability issues associated with stainless steel, offers the most up-to-date and comprehensive treatment of these topics currently available. The authors emphasize fundamental metallurgical principles governing microstructure evolution and property development of stainless steels, including martensistic, ferric, austenitic, duplex, and precipitation hardening grades. They present a logical and well-organized look at the history, evolution, and primary uses of each stainless steel, including detailed descriptions of the associated weldability issues.

Lippold, John C.; Kotecki, Damian J.

2005-03-01

367

Estimation of constitutive parameters for powder pressing by inverse modelling  

Microsoft Academic Search

Powder metallurgy processes are used in many material technologies for manufacturing of a wide range of industrial parts.\\u000a Products such as components for cars, cemented carbides and high-speed steels for mechanical cutting, magnets and soft magnetic\\u000a materials, bearings and refractory metals are made from powder. These parts are manufactured by powder die pressing followed\\u000a by sintering of the resulting green

B. Wikman; G. Bergman; M. Oldenburg; H.-. Hggblad

2006-01-01

368

Fatigue-crack propagation in aluminum-lithium alloys processed by power and ingot metallurgy  

Microsoft Academic Search

Fatigue-crack propagation behavior in powder-metallurgy (P\\/M) aluminum-lithium alloys, namely, mechanically-alloyed (MA) Al-4.0Mg-1.5Li-1.1C-0.80 (Inco 905-XL) and rapid-solidification-processed (RSP) Al-2.6Li-1.0Cu-0.5Mg-0.5Zr (Allied 644-B) extrusions, has been studied, and results compared with data on an equivalent ingot-metallurgy (I\\/M) Al-Li alloy, 2090-T81 plate. Fatigue-crack growth resistance of the RSP Al-Li alloy is found to be comparable to the I\\/M Al-Li alloy; in contrast, crack velocities

K. T. Venkateswara Rao; R. O. Ritchie; N. J. Kim; P. P. Pizzo

1990-01-01

369

Plasma Technology in Extractive and Process Metallurgy  

Microsoft Academic Search

Thermal plasma technology may be useful for a broad range of applications in extractive and process metallurgy. Plasma technology is being used in the melting\\/remelting and refining of metals\\/alloys and scrap. Plasma technology may also be potentially useful in the benericiation of complex ores, treatment of wastes, reduction of oxides, the generation of value added products, and the recovery of

PATRICK R. TAYLOR; SHAHID A. PIRZADA

1993-01-01

370

EDM surface: Topography, chemistry, and metallurgy.  

National Technical Information Service (NTIS)

The surface created by the electric discharge machining (EDM) process is of special interest because it has been shown to have a negative effect on the fatigue properties of many alloys. An understanding of the surface metallurgy and chemistry is importan...

J. E. Fuller

1991-01-01

371

Processing and Characterization of Cu-Al-Ni Shape Memory Alloy Strips Prepared from Prealloyed Powder by Hot Densification Rolling of Powder Preforms  

NASA Astrophysics Data System (ADS)

The present work deals with the preparation of near-full density Cu-Al-Ni shape memory alloy (SMA) strips from argon-atomized prealloyed powder via a powder metallurgy (PM) route comprising cold die compaction to prepare powder preforms, sintering, and hot densification rolling of unsheathed sintered powder preforms under protective atmosphere at 1273 K (1000 C). It has been shown that argon-atomized spherical Cu-Al-Ni SMA powder consisted of very fine equiaxed grains and no appreciable grain growth occurred during sintering at 1273 K (1000 C). It also has been shown that no appreciable densification occurred during sintering, and densification was primarily achieved by hot rolling. The densification behavior of the sintered powder preforms during hot rolling was discussed. The hot-rolled Cu-Al-Ni strips were heat-treated at 1223 K (950 C) for 60 minutes and water quenched. The heat-treated strips consisted of equiaxed grains with average size approximately 90 ?m. The heat-treated Cu-Al-Ni SMA strips consisted of self-accommodated ?1' martensite primarily, and showed smooth ?1 Rightarrow ?1' transformation behavior coupled with a very low hysteresis (?25 K (25 C)). The heat-treated strips exhibited an extremely good combination of mechanical properties with fracture strength of 530 MPa and 12.3 pct fracture strain. The mode of fracture in the finished strip was primarily void-coalescence-type ductile together with some brittle transgranular type. The shape memory tests showed almost 100 pct one-way shape recovery after 100 bending-unconstrained heating cycles at 4 pct applied prestrain, exhibiting good stability of Cu-Al-Ni strips under thermomechanical actuation cycling. The two-way shape memory strain was found approximately 0.45 pct after 15 training cycles at 4 pct training strain.

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

2011-10-01

372

Sintering of sponge and hydride-dehydride titanium powders  

SciTech Connect

The sintering behavior of compacts produced from sponge and hydride-dehydride (HDH) Ti powders was examined. Compacts were vacuum sintered at 1200 or 1300 deg C for 30, 60, 120, 240, 480 or 960 minutes. The porosity decreased with sintering time and/or temperature in compacts produced from the HDH powders. Compacts produced from these powders could be sintered to essentially full density. However, the sintering condition did not influence the amount of porosity present in compacts produced from the sponge powders. These samples could only be sintered to a density of 97% theoretical. The sintering behavior was attributed to the chemical impurities in the powders.

Alman, David E.; Gerdemann, Stephen J.

2004-04-01

373

Effect of a rigid component (tungsten alloy) on the process of formation of mixtures based on copper powder and the properties of heterogeneous unsintered compacts  

Microsoft Academic Search

We have analyzed the process of structure formation during pressing of copper-tungsten composites. We have established the\\u000a effect of the amount of the rigid phase (tungsten alloy) in the mix on the pattern of structure formation and the properties\\u000a (Youngs modulus and bending strength) of unsintered articles made from heterogeneous powder material based on copper. We\\u000a have experimentally established that

T. A. Epifantseva; Yu. N. Podrezov; D. G. Verbilo; V. G. Kayuk; I. D. Martyukhin; G. G. Serdyuk

2005-01-01

374

X-ray photoelectron spectroscopy (XPS) investigation of the surface film on magnesium powders.  

PubMed

Magnesium (Mg) and its alloys are attractive for use in automotive and aerospace applications because of their low density and good mechanical properties. However, difficulty in forming magnesium and the limited number of available commercial alloys limit their use. Powder metallurgy may be a suitable solution for forming near-net-shape parts. However, sintering pure magnesium presents difficulties due to surface film that forms on the magnesium powder particles. The present work investigates the composition of the surface film that forms on the surface of pure magnesium powders exposed to atmospheric conditions and on pure magnesium powders after compaction under uniaxial pressing at a pressure of 500 MPa and sintering under argon at 600 C for 40 minutes. Initially, focused ion beam microscopy was utilized to determine the thickness of the surface layer of the magnesium powder and found it to be ~10 nm. The X-ray photoelectron analysis of the green magnesium sample prior to sintering confirmed the presence of MgO, MgCO(3)3H(2)O, and Mg(OH)(2) in the surface layer of the powder with a core of pure magnesium. The outer portion of the surface layer was found to contain MgCO(3)3H(2)O and Mg(OH)(2), while the inner portion of the layer is primarily MgO. After sintering, the MgCO(3)3H(2)O was found to be almost completely absent, and the amount of Mg(OH)(2) was also decreased significantly. This is postulated to occur by decomposition of the compounds to MgO and gases during the high temperature of sintering. An increase in the MgO content after sintering supports this theory. PMID:22524956

Burke, Paul J; Bayindir, Zeynel; Kipouros, Georges J

2012-05-01

375

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

376

Damping Performance and Mechanism of High Strength Aluminum Alloy Prepared by Rapidly Solidified\\/power Metallurgy Process  

Microsoft Academic Search

The investigation of damping property, microstructure and damping mechanism of High Strength Aluminum Alloy (HSAA) prepared by rapid solidified\\/powder metallurgy (RS\\/PM) process were conducted by means of Dynamic Mechanical Thermal Analyzer (DMTA) and Transmission Electron Microscopy (TEM) in the paper. The damping capacity (Q-1) of the HSAA was (0.5~3.1)10-2 in the temperature range of 20~250C, reaching to the level of

Junchen Yao; Haitao Zhao; Liming Yu; Yue Ma; Yan Li; Huibin Xu

2006-01-01

377

The EDM surface: Topography, chemistry, and metallurgy  

SciTech Connect

The surface created by the electric discharge machining (EDM) process is of special interest because it has been shown to have a negative effect on the fatigue properties of many alloys. An understanding of the surface metallurgy and chemistry is important in predicting those alloys which are most susceptible to failure. Remedial actions, including thickness minimization, alteration, or removal of the surface layer are addressed.

Fuller, J.E.

1991-01-01

378

Thermal analysis and evolution of shape loss phenomena during polymer burnout in powder metal processing  

NASA Astrophysics Data System (ADS)

Powder metallurgy technology involves manufacturing of net shape or near net shape components starting from metal powders. Polymers are used to provide lubrication during shaping and handling strength to the shaped component. After shaping, the polymers are removed from the shaped components by providing thermal energy to burnout the polymers. Polymer burnout is one of the most critical step in powder metal processing. Improper design of the polymer burnout cycle will result in formation of defects, shape loss, or carbon contamination of the components. The effect of metal particles on polymer burnout and shape loss were addressed in the present research. The study addressing the effect of metal powders on polymer burnout was based on the hypothesis that metal powders act to catalyze polymer burnout. Thermogravimetric analysis (TGA) on pure polymer, ethylene vinyl acetate (EVA), and on admixed powders of 316L stainless steel and 1 wt. % EVA were carried out to verify the hypothesis. The effect of metal powders additions was studied by monitoring the onset temperature for polymer degradation and the temperature at which maximum rate of weight loss occurred from the TGA data. The catalytic behavior of the powders was verified by varying the particle size and shape of the 316L stainless powder. The addition of metal particles lowered the polymer burnout temperatures. The onset temperature for burnout was found to be sensitive to the surface area of the metal particle as well as the polymer distribution. Powders with low surface area and uniform distribution of polymer showed a lower burnout temperature. The evolution of shape loss during polymer burnout was based on the hypothesis that shape loss occurs during the softening of the polymer and depends on the sequence of chemical bonding in the polymer during burnout. In situ observation of shape loss was carried out on thin beams compacted from admixed powders of 316L stainless steel and 1 wt. % ethylene vinyl acetate (EVA). The results showed that shape loss primarily occurs by viscous creep during the softening of the polymer. At the onset of burnout of EVA, a recovery in shape loss was observed. The recovery occurred primarily during the first stage burnout of EVA and was attributed to the formation of polyethylene co-polyacetylene which forms with a carbon double bond. The in situ strength was also found to increase during the formation of polyethylene co-polyacetylene. No recovery of shape loss was observed during burnout of polymers (polyethylene and polypropylene) which convert to yield hydrocarbons without forming carbon double bonds. (Abstract shortened by UMI.)

Enneti, Ravi Kumar

379

Light attrition of uranium dioxide powder  

Microsoft Academic Search

Sinterable uranium dioxide powders prepared through the ammonium diuranate route are prone to agglomeration causing difficulty in compaction and sintering. UO2 powder after light (short duration and low ball to charge ratio) attrition has been found to require lower compaction pressures and resulted in higher yields after sintering and finish grinding. Details of an in-house-built attritor are given. Experimental results

Palanki Balakrishna; B Narasimha Murty; D. V Ratnam; M Anuradha; C Ganguly

2003-01-01

380

Mound powder loader, Mod 1  

SciTech Connect

At the investigation of Sandia Albuquerque, a semiautomatic powder loader was designed and fabricated for pyrotechnics devices. The basic functions of the system were to load a precise, measured amount of powder into a charge holder and to compact the mixture to a specified density. This report documents the history, rationale, design, and performance of the Mod 1 loader.

Gress, A.V. Jr.

1985-08-21

381

Effect of electrical resistivity on core losses in soft magnetic iron powder materials  

Microsoft Academic Search

Iron powder should be electrically insulated with a dielectric to reduce eddy current losses in components fabricated by powder metallurgy intended for AC soft magnetic applications. However, most of the dielectrics act as distributed air gaps and reduce the apparent permeability of the material. To obtain materials with good magnetic properties, the dielectric amount should then be kept as low

L. P. Lefebvre; S. Pelletier; C. Glinas

1997-01-01

382

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. Kerdi

2009-01-01

383

Characterizing titanium powder: morphology, flow and segregation  

NASA Astrophysics Data System (ADS)

Powder metallurgy manufacturing with titanium could achieve near-net shape for parts with high strength-to-weight ratio. However, pure titanium (Ti) powders have large aspect ratios that prevent smooth flow. Features of Ti powder were examined experimentally to understand its limited flowability. The surface morphology was measured using a SEM for both raw powder as well as those made ``uniform'' via milling. The poly-disperse mixture had particle sizes between 45--700 ?m, of which a significant concentration were <45?m, which results in a very steep and unsteady angle of repose when the powder was placed in a rotating tumbler. The flat surface and steady flow typical of macroscopic particles is not present, but instead has slumping motion as material piles up and collapses intermittently. Spectral analysis indicates that increasing Froude number causes the slumping behavior to move to higher frequencies, but spread over a larger range. Size segregation causes porous streaks to form at the periphery of the tumbler where the angular separation of the streaks decreases with increasing Froude number. The overall conclusion is that more narrow ranges of particle size are necessary to yield usable titanium in powder metallurgy manufacturing.

Pohlman, Nicholas A.; Roberts, John A.; Gonser, Matthew

2011-11-01

384

PREPARATION OF COMPACTS MADE FROM URANIUM AND BERYLLIUM BY SINTERING  

DOEpatents

A powder metallurgical method for making high-density compacts of uranium and beryllium is reported. Powdered UBe/sub 9/ and powdered Be are blended, compacted, and then sintered by rapidly heating to a temperature of approximately 1220 to 1280 deg C in an inert atmosphere.

Angier, R.P.

1961-04-11

385

Powder Die Fill Study for Powder Metallurgy Applications Using New Experimental Approaches  

Microsoft Academic Search

p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Times; color: #2d2d2d} span.s1 {color: #4c4c4c} span.s2 {font: 11.0px Helvetica}\\u000ap.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Times} span.s1 {font: 11.0px Helvetica} span.s2 {font: 10.0px Verdana} span.Apple-tab-span {white-space:pre}\\u000aThe aim of this research is to enhance performance and durability of the final PM component by improving spatial density homogeneity at die

Dhanashree Aole

2010-01-01

386

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.

387

Pipeline Failure: The Roles Played by Corrosion, Flow and Metallurgy  

Microsoft Academic Search

Carbon dioxide corrosion has been widely studied in the field and laboratory. It is recognized that flow regime and metallurgy are important factors that influence in -situ corrosion rates but there are relatively few documented case studies that are able to separate the individual contributions of corrosion, flow regime and metallurgy on the observed corrosion damage. This paper deals with

Nathan Barrett; Dominic Paisley; Owen Wilson

1999-01-01

388

THE PHYSICAL METALLURGY OF PRECIPITATION-HARDENABLE STAINLESS STEELS  

Microsoft Academic Search

The present knowledge on the physical metallurgy of precipitation-; hardenable stainless steels is presented. The alloys discussed include the ; martensitic types (Stainless W and 17-4 PH), the semiaustenitic types (177 PH, PH ; 15-7 Mo, AM 350, and AM 355), and the austenitic types (A-286 and HNM). The ; areas of metallurgy common to most or all of these

D. C. Ludwigson; A. M. Hall

1959-01-01

389

Advanced NDE Technologies for Powder Metal Components  

SciTech Connect

Nondestructive evaluation encompasses numerous technologies that assess materials and determine important properties. This paper demonstrates the applicability of several of these technologies to the field of powder metallurgy. The usual application of nondestructive evaluation is to detect and quantify defects in fully sintered product. But probably its most appealing role is to sense problems earlier in the manufacturing process to avoid making defects at all. Also nondestructive evaluation can be incorporated into the manufacturing processes to monitor important parameters and control the processes to produce defect free product. Nondestructive evaluation can characterize powders, evaluate components in the green state, monitor the sintering process, and inspect the final component.

Martin, P; Haskins, J; Thomas, G; Dolan, K

2003-05-01

390

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

391

Shock compaction of Fe-Nd-B  

Microsoft Academic Search

Shock compaction was performed using the 6.5-m-long two-stage light gas gun facility at LLNL on powders of Fe74Nd20B6, 1020 ?m in size which were prepared using conventional powder metallurgical techniques. The behavior of Fe-Nd-B powders and Fe-Nd-B powders blended with 10 vol. % Al was examined. X-ray-diffraction experiments detected no discernable difference in phase distribution or crystallinity when shock pressures

Mahesh Chandramouli; Gareth Thomas; W. J. Nellis

1993-01-01

392

Characterization, Processing, and Consolidation of Nanoscale Tungsten Powder.  

National Technical Information Service (NTIS)

Nanoscale tungsten powder was consolidated by the Plasma Pressure Compaction (P2C) method. The starting powder was first characterized to determine particle size, morphology, and presence of chemical impurities. The characterization data led to efforts to...

B. R. Klotz E. M. Klier F. R. Kellogg K. C. Cho R. J. Dowding

2009-01-01

393

Broadband electromagnetic wave absorbers prepared by grading magnetic powder density  

NASA Astrophysics Data System (ADS)

Resin compacts including iron-based magnetic powders were prepared using a centrifugal molding technique. Energy dispersive x-ray analyses demonstrated the formation of a concentration gradient of the magnetic powder in the resin compacts. The resultant concentration-graded resin compacts exhibited better broadband electromagnetic wave absorption than the homogeneous resin compacts prepared as a reference. This absorption ability was further enhanced by attaching a urethane foam plate to the absorber surface.

Itoh, Masahiro; Terada, Masao; Shogano, Fumiyoshi; Machida, Ken-Ichi

2010-09-01

394

Magnetic inductor based on nanosize amorphous metal powder  

Microsoft Academic Search

Amorphous metal powders with sizes from 2050nm were prepared by the borohydride reaction of metal salts. The as-processed powders were observed to form chains of different lengths. Magnetic cores were fabricated from the powders compacted with epoxy resin. Following compaction, the powders remained in chains oriented randomly throughout the cores. The resultant magnetic behavior is such that the cores BH

Ryusuke Hasegawa; V. H. Hammond; J. M. OReilly

2007-01-01

395

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

396

Influence of particle-size composition of brass powder on the properties of hot-pressed parts  

Microsoft Academic Search

At present brass powders have found wide use for the production of parts for electrical, machine building, and instrument building purposes. They are characterized by high electrical and thermal conductivity, corrosion resistance, and capacity for the application of galvanic coatings. The use of powder metallurgy methods makes it possible to significantly reduce the labor requirement for the production of parts

I. D. Radomysel'skii; G. E. Mazharova; G. A. Baglyuk; S. P. Chernysheva; S. N. Voleinik

1984-01-01

397

Dynamic compaction of aluminum nanocrystals  

SciTech Connect

The authors investigated shock-compaction behavior of nanocrystalline aluminum (n-Al) powder with an average particle size of about 50--70 nm. The starting powders were analyzed using various analytical tools, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The initial Al particles were found to be coated naturally by a uniform, thin ({approximately}5 nm) near-stoichiometric, amorphous oxide layer. Shock compaction was carried out at 2--3 GPa (20--30 kbars) to obtain high-density disks. The microstructure of samples prior to and after consolidation were both examined. Despite substantial deformation during dynamic compaction, the surface oxide remained intact at the pressures employed and prevented a metallurgical bond between the nano-sized particles. Theoretical simulations of the dynamic compaction of n-Al were also carried out using an Eulerian hydrocode. The results were in good agreement with experimental observations.

Nieh, T.G.; Luo, P.; Nellis, W.; Lesuer, D. [Lawrence Livermore National Lab., CA (United States); Benson, D. [Univ. of California, San Diego, La Jolla, CA (United States). Dept. of Applied Mechanics and Engineering Sciences

1996-09-01

398

Dynamic compaction of aluminum nanocrystals  

Microsoft Academic Search

We investigated shock-compaction behavior of nanocrystalline aluminum (n-Al) powder with an average particle size of about 5070 nm. The starting powders were analyzed using various analytical tools, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The initial Al particles were found to be coated naturally by a uniform, thin (? 5

T. G. Nieh; P. Luo; W. Nellis; D. Lesuer; D. Benson

1996-01-01

399

Dissemination and Assimilation of Material Presented in Journals on Metallurgy.  

National Technical Information Service (NTIS)

The study focuses on the production, dissemination, and assimilation of material published in the major journals on metallurgy. Selection of journals began with those most frequently mentioned by the 1967 AIME meeting-presentation authors as journals to w...

1970-01-01

400

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

401

Fatigue-crack propagation in aluminum-lithium alloys processed by power and ingot metallurgy  

SciTech Connect

Fatigue-crack propagation behavior in powder-metallurgy (P/M) aluminum-lithium alloys, namely, mechanically-alloyed (MA) Al-4.0Mg-1.5Li-1.1C-0.80{sub 2} (Inco 905-XL) and rapid-solidification-processed (RSP) Al-2.6Li-1.0Cu-0.5Mg-0.5Zr (Allied 644-B) extrusions, has been studied, and results compared with data on an equivalent ingot-metallurgy (I/M) Al-Li alloy, 2090-T81 plate. Fatigue-crack growth resistance of the RSP Al-Li alloy is found to be comparable to the I/M Al-Li alloy; in contrast, crack velocities in MA 905-XL extrusions are nearly three orders of magnitude faster. Growth-rate response in both P/M Al-Li alloys, however, is high anisotropic. Results are interpreted in terms of the microstructural influence of strengthening mechanism, slip mode, grain morphology and texture on the development of crack-tip shielding from crack-path deflection and crack closure. 14 refs., 7 figs., 2 tabs.

Venkateswara Rao, K.T.; Ritchie, R.O. (Lawrence Berkeley Lab., CA (United States)); Kim, N.J. (Pohang Inst. of Science and Technology (Korea, Republic of)); Pizzo, P.P. (San Jose State Univ., CA (United States))

1990-04-01

402

Stress analysis of lead-free solders with under bump metallurgy in a wafer level chip scale package  

Microsoft Academic Search

The wafer level chip scale assembly (WLCSP) has increasingly become popular due to its compact, wafer scale assembly. In a WLCSP assembly, the under bump metallurgy (UBM) connecting the solder joints and the chip is crucial for the assembly reliability. This study focuses on a WLCSP with 96.5Sn3.5Ag\\/95.5Sn3.8Ag0.7Cu solder joints and Ti\\/Cu\\/Ni UBM on a 2layer microvia build-up electric board.

S. C. Tseng; R. S. Chen; C. C. Lio

2006-01-01

403

Characteristics of PMN-PT Powder Prepared by Partial Oxalate Process Route  

Microsoft Academic Search

Powder compaction and sintering characteristics of the PMN-PT powder prepared by the partial oxalate route have been studied. The PMN-PT powder achieved 60% of theoretical density during compaction by pressing at 100 MPa. The powder compacts were sintered to > 99% TD at 1270C for 2 hours. Microstructure of the sintered ceramic showed an average grain size of 6.1 ?

E. M. JAYASINGH; R. SOORAJ; K. PRABHAKARAN; C. DURGAPRASAD; S. C. SHARMA

2009-01-01

404

Effects of chromium addition on the metallurgy and P/M processing response of Alumix 431D  

NASA Astrophysics Data System (ADS)

The ever growing industry of Powder Metallurgy (P/M) is developing to include new alloys and improve those currently available. This project relates to the optimization of a commercially available Al-Zn-Mg-Cu based alloy (Alumix 431D). This alloy is the P/M equivalent of the wrought 7075 alloy, and yields some of the top performance found in any available aluminum alloy. Optimization of the alloy has been conducted with a focus on sintering conditions; in particular the effect of sintering temperature and post-sintering cooling. Five sintering temperatures were investigated and the optimal temperature was found to be 605C. Cr was added in trace amounts as per literature recommendations in an attempt to improve corrosion resistance. Both the Cr-free and Cr-containing alloys were then assessed for post-sinter cooling effects. The Alumix 431D w/Cr compacted and sintered to a higher density which further resulted in improved hardness over the Cr-free counterpart. The cooling profile was modified to include an increasingly larger post-sinter furnace-cooling section, before gas quenching. Seven quenching temperatures were chosen to investigate ranging from the sintering temperature (605C) down to 480C. This furnace cooling allowed the alloy-rich liquid phase to dwell for an extended time at elevated temperature and thereby diffuse into the matrix grains increasing the alloy content. This was confirmed through EPMA and correlated with an increase in mechanical properties. For both alloys peak hardness was produced by specimens cooled to 520C before quenching. Tensile strength also increased by as much as 12% when furnace cooled to 540C. The heat treatment parameters were determined to yield an optimal T6 temper. Specimens of both alloys processed under all conditions were then subjected to this heat treatment and further characterized. Many of the improvements offered by furnace cooling that were obvious in the T1 'as-sintered' product, became less pronounced after heat treatment. Corrosion resistance was also studied and compared to the wrought 7075 equivalent. For 'as-sintered' P/M components the Tafel extrapolation was less effective in accurately determining corrosion rate due to the effect of porosity on surface area. To remedy this, samples were hot worked to near full density (>99.5% theoretical), heat treated and tested. The hot worked P/M samples performed up to 2x better than the wrought 7075 with respect to corrosion current densities.

Mosher, Michael Patrick

405

Atomic force microscopy study of silica nanopowder compacts  

Microsoft Academic Search

Nanometer silica powders compacted at different pressures have been studied by atomic force microscopy (AFM). Local elastic moduli measurements made on the powder compacts yield values smaller than that of bulk silica. Loading force-distance curves measured show break points at some critical pressures. AFM images obtained at constant contact forces above and below the critical force at which a break

Steven Harrington; Da-Ming Zhu; A. Thirunavukkarasu; Anil. Misra

1999-01-01

406

Analysis of some initial sintering parameters of real oxide powders  

Microsoft Academic Search

Results of studies are presented on correlation of the shrinkage of UO\\/; sub 2\\/ and AlO compacts at initial sintering stages with mea n ; particle size of the starting powders, particle packing, and pore structure. The ; results obtained during the initial sintering stage of agglomerated UO ; powder compacts, indicate a dependence of shrinkage on the mean particle

Vlajic

1973-01-01

407

Quality control of press-powders for engineering ceramics  

Microsoft Academic Search

The present paper deals with a study of the methods and means of evaluation of the macrostructure of granules, compactibility of press-powders, porosity, and green strength of the compacted products. The techniques developed successfully went through laboratory and industrial testing. The properties of press-powders depend on the properties of individual granules, which are aggregates of dispersed particles with binders, lubricants,

A. A. Polyakov

1982-01-01

408

Shock consolidation of powders: theory and experiment  

Microsoft Academic Search

A recently proposed model of shock consolidation of powders quantitatively predicts regimes of input energy and shock duration required to produce well-bonded compacts. A growing data base from shock experiments in which the shock wave and powder parameters of importance are controlled allows evaluation of the model. Rapidly solidified crystalline AISI 9310, and microcrystalline Markomet 3.11, as well as amorphous

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

1984-01-01

409

Dry ultrasonic compaction of (Ba,Sr)TiO3 nanopowder for ceramics production  

Microsoft Academic Search

The method of dry ultrasonic compaction was applied to press sol-gel ultrafine powder of (Ba,Sr)TiO3. Green compacts and sintered ceramics densities were compared depending on the powder compaction conditions (compaction pressure P, ultrasound power W). The grain size of sintered ceramics was analysed in dependence on the compaction conditions and sintering regimes (sintering temperature, holding time, heating rate). It was

Suk-Ryong Hahn; O. L. Khasanov; Yu. P. Pokholkov; V. M. Sokolov; E. S. Dvilis; Myung-Soo Han

2000-01-01

410

A study on an atomized Al-Fe-Mo-Zr powder to be processed for high temperature applications  

Microsoft Academic Search

The performance of a powder metallurgy material in processing and service depends very much upon the initial characteristics of the atomized powder. An investigation on the characterization of an Al-8.5Fe-2Mo-1Zr alloy powder, to be further processed for high temperature applications, has, therefore, been carried out. Analyses have been performed of its composition, morphology, size and microstructure by means of chemical

J. Zhou; J. Duszczyk; B. M. Korevaar

1991-01-01

411

Ceramic compaction models: Useful design tools or simple trend indicators?  

SciTech Connect

It is well-known that dry pressing of ceramic powders leads to density gradients in a ceramic compact resulting in non-uniform shrinkage during densification. This necessitates diamond grinding to final dimensions which, in addition to being an extra processing step, greatly increases the manufacturing cost of ceramic components. To develop methods to control and thus mitigate density variations in compacted powders, it has been an objective of researchers to better understand the mechanics of the compaction process and the underlying material and tooling effects on the formation of density gradients. This paper presents a review of models existing in the literature related to the compaction behavior of ceramic powders. In particular, this paper focuses on several well-known compaction models that predict pressure and density variations in powder compacts.

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

1995-08-01

412

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

Federal Register 2010, 2011, 2012, 2013

...NUCLEAR REGULATORY...Committee on Reactor Safeguards...Phenomena and Materials, Metallurgy and Reactor Fuels; Notice...Phenomena and Materials, Metallurgy and Reactor Fuels will...degradation (TCD) issue, how TCD...

2013-02-05

413

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

Microsoft Academic Search

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

Paul Galon Allison

2009-01-01

414

Fabrication and Properties of Powder Metallurgically Manufactured Aluminum Products and Composites.  

National Technical Information Service (NTIS)

Various processes for the hot extrusion of powder metallurgy aluminum alloys (corresponding to types P/M 2014 and P/M 7090) with or without silicon carbide particulate or whisker reinforcement were studied. The microstructure of the alloys was characteriz...

A. Jokinen A. Mahiout K. Rahka S. Hannula

1990-01-01

415

U Sub 3 O sub 8 Powder from Uranyl-Loaded Cation Exchange Resin.  

National Technical Information Service (NTIS)

Large batches of U sub 3 O sub 8 , suitable for powder metallurgy fabrication of Al-U sub 3 O sub 8 cores for reactor fuel tubes, have been produced by deep-bed calcination of granular uranyl-loaded macroporous sulfonate cation exchange resin at 900 to 95...

W. C. Mosley

1985-01-01

416

Explosive consolidation of titanium-nickel shape-memory alloy from pure titanium powder and pure nickel powder  

Microsoft Academic Search

Increasing numbers of applications of shapememory alloys have been developed and the alloys that are most successfully used among the many kinds of shape-memory alloys are TiNi alloys. TiNi alloys have excellent mechanical properties and shape-memory effect. However, its high cost resulting from complicated melting and machining procedures has limited its application. By contrast, powder metallurgy is a method for

T. C. Li; Y. B. Qui; J. T. Liu; F. T. Wang; M. Zhu; D. Z. Yang

1992-01-01

417

Effect of plasma activated sintering (PAS) parameters on densification of copper powder  

Microsoft Academic Search

Copper (Cu) powder compacts were sintered by plasma activated sintering (PAS), and the effects of PAS parameters on the densification process of these compacts were investigated. A larger direct current caused a higher rate of temperature increase and therefore a higher densification rate of the Cu powder compact. Under a constant electric current, however, higher mechanical pressure resulted in a

S. W Wang; L. D Chen; Y. S Kang; M Niino; T Hirai

2000-01-01

418

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

419

Effect of shock duration on the dynamic consolidation of powders. [AISI 9310  

Microsoft Academic Search

A recent advanced model for the shock consolidation of powders predicts, for a powder given distension, the regimes of shock pressure and shock duration expected to yield fully densified compacts of near optimum strength. The model is evaluated in terms of UTS measurements in compacts of rapidly solidified powders of AISI 9310 alloy, shocked to initial shock pressures between 3.6

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

1983-01-01

420

Comparative analysis of alumina-zirconium powders compressibility with different dispersibility  

Microsoft Academic Search

In the given work analysis of alumina-zirconium powders compressibility with different dispersibility and also influence of plasticizer under ultrasonic compacting, single axis pressing were carried out. It was demonstrated, porosity of specimens, which were produced of superdispersed powders, is higher than porosity of specimens, which were produced by single axis and ultrasonic compacting, its ride powder agglomeration.

U. M. Annenkov; A. S. Ivaschutenko; A. A. Kondratyuk

2005-01-01

421

UO powder from uranyl-loaded cation exchange resin  

Microsoft Academic Search

UO powder has been produced from uranyl-loaded cation exchange resin with density, particle size distribution, and grain size suitable for powder metallurgy fabrication of reactor fuel tubes with Al-UO cores. Macroporous sulfonate resin in granular form is used in the process. Resin conversion techniques that were evaluated include batch, rotary, and fluidized bed calcination. 2 refs., 16 figs.

1985-01-01

422

Processing and microstructural characterization of Al-Cu alloys produced from rapidly solidified powders  

Microsoft Academic Search

This paper concerns the processing of Al-Cu alloys via a novel powder-metallurgy route. The specific technique used for powder processing involves the rapid solidification of coarse,\\u000a molten droplets following impulse atomization. This produces a fine, homogeneous, dendritic microstructure within the alloy\\u000a granules. Following consolidation via hot pressing, the microstructure consists mostly of an Al matrix with fine CuAl2 particles and

K. T. Conlon; E. Maire; D. S. Wilkinson; H. Henein

2000-01-01

423

Mystery Powders  

NSDL National Science Digital Library

In this activity on page 2 of the PDF, learners conduct chemical tests on certain powders used in cooking. After completing the tests, learners try to figure out the identity of a mystery powder. Learners record their observations on a chart. Note: you will need an adult helper for this activity.

Society, American C.

2000-01-01

424

METHOD OF PRODUCING SHAPED BODIES FROM POWDERED METALS  

DOEpatents

A method is given for enclosing a body of uranium in a sheath of compacted beryllium or zirconium powder and comprises enveloping the body with uncompacted powder and pressing at a temperature above the beta - gamma transition point of uranium, thereby causing the uranium to flow and isotropically compress the powder.

Blainey, A.

1960-05-31

425

Compact Storage  

USGS Multimedia Gallery

After a detailed inventory is completed and published on the web, processed materials are stored in compact shelving in the Field Records Collection. Collections are organized by scientist and project....

2009-04-09

426

The mysterious world of plutonium metallurgy: Past and future  

Microsoft Academic Search

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

S. S. Hecker; E. F. Hammel

1998-01-01

427

Metallurgy and Properties of Thoria-Strengthened Nickel.  

National Technical Information Service (NTIS)

The memorandum deals with the metallurgy and properties of thoria-strengthened nickel, a material which shows promise as a structural metal for use in the temperature of 1900 to 2400 F where the present nickel- and cobalt-base superalloys lose most of the...

L. P. Rice

1965-01-01

428

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

429

Process for synthesizing compounds from elemental powders  

DOEpatents

A process for synthesizing intermetallic compounds from elemental powders. The elemental powders are initially combined in ratio a 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.

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

1990-01-01

430

Process for synthesizing compounds from elemental powders  

DOEpatents

A process for synthesizing intermetallic compounds from elemental powders. The elemental powders are initially combined in ratio a 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.

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

1990-12-31

431

Electrically conductive ceramic powders  

NASA Astrophysics Data System (ADS)

Electrically conductive ceramic powders were investigated in this project. There are three ways to produce those materials. The first is doping alkali metal into the titanium dioxides in an inert or reducing atmosphere. The second is reducing un-doped titanium dioxide, forming a non-stoichiometric composition in a hydrogen atmosphere. The third is to coat a conductive layer, reduced titanium dioxide, on an insulating core such as alumina. Highly conductive powders have been produced by all these processes. The conductivity of powder compacts ranged between 10-2 and 10 S/cm. A novel doping process was developed. All samples were doped by a solid-vapor reaction instead of a solid state reaction. Titanium dioxide was doped with alkali metals such as Na or Li in this study. The alkali metal atom contributes an electron to the host material (TiO2), which then creates Ti 3+ ion. The conductivity was enhanced by creating the donor level due to the presence of these Ti3+ ions. The conductivity of those alkali doped titanium oxides was dependent on the doping level and charge mobility. Non-stoichiometric titanium oxides were produced by reduction of titanium dioxide in a hydrogen atmosphere at 800C to 1000C for 2 to 6 hours. The reduced titanium oxides showed better stability with respect to conductivity at ambient condition when compared with the Na or Li doped samples. Conductive coatings were prepared by coating titanium precursors on insulating core materials like SiO2, Al2O3 or mica. The titania coating was made by hydrolysis of titanyl sulfate (TiOSO 4) followed by a reduction procedure to form reduced titanium oxide. The reduced titanium oxides are highly conductive. A uniform coating of titanium oxides on alumina cores was successfully produced. The conductivity of coated powder composites was a function of coating quantity and hydrolysis reaction temperature. The conductivity of the powder as a function of structure, composition, temperature, frequency and moisture was studied. Three classifications of structure were identified for alkali-doped titanium oxides: (1) Pure titanium dioxide phase with alkali ions located in interstitial positions. (2) The titanium bronze phases. (3) Alkali-doped titanium oxides. Highly conductive powders were obtained in the first and second classifications with conductivity of 10-2 to 10 S/cm. Materials in the third classification had poor conductivity below 10-3 S/cm. The conductivity of a powder was determined mainly by the grain conductivity and the grain contact conductivity. The present results of impedance spectroscopy suggested that the grain contact resistance was a major factor of the electrical resistance of the samples. The aging effect at different moisture conditions was also caused by an increase of the contact resistance. Both sodium-doped and reduced titanium oxides showed re-oxidation at elevated temperature (above 140C) in air, which is most probably caused by oxidizing the Ti3+ ions under those conditions. Lithium doped titanium oxides did not show this re-oxidation at temperatures up to 200C. Theoretical models were applied to describe the effects of porosity, contact configuration and grain surface on conductivity of powder compacts. Percolation theory was used in the present study to demonstrate the effect of mixtures of conductive and non-conductive powders, which is one of applications for conductive ceramic powders when they are used as filler materials in paper, paints or plastics.

Lu, Yanxia

1999-11-01

432

Processing of Terfenol-D alloy based magnetostrictive composites by dynamic compaction  

Microsoft Academic Search

Composites of Terfenol-D with metal binders were produced by explosive compaction. Compacts produced from powders prepared this way had a soft phase and intimate contact and bonding between particles are achieved. Ms\\/volume follows the expected trend based on the separate Ms\\/volume values of the constituents added. Magnetostriction of compacts made from mixture of Cu coated terfenol-D powder and Cu powder

Sivaraman Guruswamy; Michael R. Loveless; Nakorn Srisukhumbowornchai; Michael K. McCarter; Joseph P. Teter

2000-01-01

433

Powder Particulars  

NSDL National Science Digital Library

In this introductory activity and demonstration, learners are introduced to the concept that different substances react chemically in characteristic ways. First learners compare the way baking soda and baking powder react with vinegar. Then they see dramatic color changes when red cabbage indicator is added to cream of tartar and laundry detergent. From this, learners are ready to identify unknown powders based on their reactive properties.

Kessler, James H.; Galvan, Patricia M.

2007-01-01

434

Study of Underwater Shock Compaction Device for Compaction of Titanium Diboride  

NASA Astrophysics Data System (ADS)

Shock compaction for powders has been used to study bulk consolidation of powder materials. Shock compaction has the advantage of processing at low temperatures and short duration to limit effects of high temperatures for long times, such as increased grain size and high energy cost. Many methods of shock loading of powders have been employed: direct contact with explosive, explosively driven flyer plates, and flyer plates launched with light gas or propellant gun. Another method, using explosives to create a shockwave in water that is then contact with a powder container, has been used extensively at Kumamoto University. This work presents a study of the development of the underwater shockwave device and investigates the water container geometry for control of parameters for shockwave peak pressure, duration, and distribution through the powder compaction process. Results of simulations for optimization of shock compaction properties are presented along with measurements from manganin gauge pressure measurements obtained from underwater shock compaction of titanium diboride. The goal of this work is to develop a better understanding of the entire compaction process to utilize the in-situ data to modify numerical simulations to predict performance.

Kennedy, G. B.; Kim, Y. K.; Hokamoto, K.; Itoh, S.

2007-12-01

435

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

Microsoft Academic Search

Abstract 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 modification method by EDM with powder suspended

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

436

Characterization of prealloyed copper powders treated in high energy ball mill  

Microsoft Academic Search

The inert gas atomised prealloyed copper powders containing 3.5 wt.% Al were milled up to 20 h in the planetary ball mill in order to oxidize aluminium in situ with oxygen from the air. In the next procedure compacts from milled powder were synthesized by hot-pressing in argon atmosphere. Compacts from as-received Cu-3.5 wt.% Al powder and electrolytic copper powder

Viseslava. Rajkovic; Dusan Bozic; Milan T. Jovanovic

2006-01-01

437

Pressure sintering of powder materials  

Microsoft Academic Search

Rheological models for pressure sintering of powder materials are described. The rheological models of deformable bodies and\\u000a the associated dynamic deformation theory for porous bodies based on the energy conservation law enable a quantitative description\\u000a of their densification under impulse and static hot pressing as well as hot forging using crank presses. The simulation of\\u000a compaction of porous metals shows

M. S. Kovalchenko

2011-01-01

438

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

439

The calculation of the shock velocity particle velocity relationship for a copper powder by direct numerical simulation  

Microsoft Academic Search

The dynamic compaction of ceramics, oxide superconductors, and superhard materials is an active area of research world-wide. The current knowledge about shock processes in materials is based primarily on phenomenological modeling. In order to optimize the dynamic powder compaction process, a detailed understanding of the micromechanical behavior of the powder during the compaction process is necessary. As a first step,

David J. Benson

1995-01-01

440

Shock consolidation of powders: theory and experiment  

SciTech Connect

A recently proposed model of shock consolidation of powders quantitatively predicts regimes of input energy and shock duration required to produce well-bonded compacts. A growing data base from shock experiments in which the shock wave and powder parameters of importance are controlled allows evaluation of the model. Rapidly solidified crystalline AISI 9310, and microcrystalline Markomet 3.11, as well as amorphous Markomet 1064 and crystalline Mo powders, have been consolidated by shocks up to 2 ..mu..s duration. The formation of amorphous layers on Marko 3.11 particle surfaces indicates that surface melting and rapid solidification occurred. Decreasing amounts of amorphous structure are retained in Marko 3.11 and 1064 powder compacts with increasing shock energies. Significant improvement in Mo particle bonding is achieved by reducing surface oxides prior to shock consolidation.

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

1984-01-01

441

Early West African Metallurgies: New Data and Old Orthodoxy  

Microsoft Academic Search

The debate on West African metallurgies cannot be properly understood without reference to the colonial template that featured\\u000a Africa as the receiving partner in all crucial social, economic, and technological development. The interesting debate that\\u000a took place in West Africa during the Colonial Period was more meta-theoretical than factual. These conflicting glosses, despite\\u000a their lack of empirical foundations, have constrained

Augustin F. C. Holl

2009-01-01

442

Welding metallurgy and weldability of high strength aluminum alloys  

Microsoft Academic Search

A literature survey was conducted to gather the information available on the welding metallurgy of high strength aluminum alloys, and its effect on their weldability. The report focuses on fusion welding of high strength aluminum alloys. Both conventional high strength aluminum alloys and newer products, e.g., PM aluminum alloys, Al-Li alloys and Al-matrix composites, are included. The survey covers a

Kou

1986-01-01

443

A New Approach on Diffusion Welding of FeCuC and FeZnC Powder Metal Parts  

Microsoft Academic Search

Cylindrical parts made from pre-strengthened FeCuC and FeZnC powders, fabricated under 1000MPa-cold press, were welded in a vacuum furnace at different temperatures by diffusion welding. A novel approach was used where powder metallurgy parts were sintered together with diffusion welding with no extra pressure applied during the welding process. Chemical composition, cold press pressure, and sintering time (consequently welding time)

Y. Babayev; F. Kahraman; S. Karadeniz

2010-01-01

444

Characterizing and modeling organic binder burnout from green ceramic compacts.  

National Technical Information Service (NTIS)

New characterization and computational techniques have been developed to evaluate and simulate binder burnout from pressed powder compacts. Using engineering data and a control volume finite element method (CVFEM) thermal model, a nominally one dimensiona...

K. G. Ewsuk J. Cesarano R. J. Cochran B. F. Blackwell D. R. Adkins

1995-01-01

445

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

Microsoft Academic Search

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

Zhongqi Cui; Wang Zhong; Qingbin Wei

1994-01-01

446

Study of Fatigue Crack Propagation in Powder Metallurgy Hot Isotatically Pressed Nickel-Base Alloy.  

National Technical Information Service (NTIS)

L.C. Astroloy contains a complex distribution of rounded cuboidal gamma prime precipitates (0.1 micrometers edge dimension), cooling gamma prime(0.01 micrometers dia) and prior particle boundary particles of MC, ZrO2, alpha-Al2O3 and M3B2; the majority of...

R. W. Hertzberg

1986-01-01

447

Self-passivating bulk tungsten-based alloys manufactured by powder metallurgy  

Microsoft Academic Search

Self-passivating tungsten-based alloys are expected to provide a major safety advantage compared to pure tungsten, which is at present the main candidate material for the first wall armour of future fusion reactors. WC10Si10 alloys were manufactured by mechanical alloying (MA) in a Planetary mill and subsequent hot isostatic pressing (HIP), achieving densities above 95%. Different MA conditions were studied. After

P Lpez-Ruiz; N Ords; S Lindig; F Koch; I Iturriza; C Garca-Rosales

2011-01-01

448

Opportunities for Conversion of Powertrain Components from Malleable\\/Ductile Cast Irons to Powder Metallurgy  

Microsoft Academic Search

Malleable and ductile cast irons are used extensively in gearing and high strength applications within automotive power train applications. Advantages of malleable and ductile cast irons are low material cost with mechanical properties that meet or exceed the requirements of the intended application(s). One disadvantage of the malleable cast iron is the extensive heat treating required to obtain the proper

Francis Hanejko; Arthur Rawlings; Robert Causton

449

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

450

SiC particle cracking in powder metallurgy processed aluminum matrix composite materials  

Microsoft Academic Search

Particle cracking is one of the key elements in the fracture process of particulate-reinforced metal-matrix composite (MMC)\\u000a materials. The present study quantitatively examined the amount of new surface area created by particle cracking and the number\\u000a fraction of cracked particles in a series of SiC-reinforced aluminum-matrix composite materials. These composite materials\\u000a were fabricated by liquid-phase sintering and contained 9 vol

B. Wang; G. M. Janowski; B. R. Patterson

1995-01-01

451

Characterization of Properties of Cryogenically Treated AlSiC 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

452

Fatigue failure probability in a powder metallurgy Ni-base superalloy  

Microsoft Academic Search

A probabilistic model of fatigue failure of PM superalloy is presented which takes into account the size, shape and location of the defects which initiate fatigue cracks. The fatigue failure probability is linked with the growth rate of cracks initiated from inclusions, which is described using fracture mechanics. The risk of fatigue failure from surface, sub-surface and internal particles is

J. Grison; L. Remy

1997-01-01

453

Interfacial design of Cu\\/SiC composites prepared by powder metallurgy for heat sink applications  

Microsoft Academic Search

In order to dissipate the heat generated in electronic packages, suitable materials must be developed as heat spreaders or heat sinks. Metal matrix composites (MMCs) offer the possibility to tailor the properties of a metal (Cu) by adding an appropriate reinforcement phase (SiC) to meet the demands for high thermal conductivities in thermal management applications. Copper\\/SiC composites have been produced

Th. Schubert; A. Brendel; K. Schmid; Th. Koeck; ?. Ciupi?ski; W. Zieli?ski; T. Weigrber; B. Kieback

2007-01-01

454

Oxidation Behavior at 900C of Austenitic, Ferritic, and Duplex Stainless Steels Manufactured by Powder Metallurgy  

Microsoft Academic Search

This study examines the resistance to cyclic oxidation at 900C of two commercial P\\/M stainless steelsone austenitic (AISI 316L), the other ferritic (AISI 434L)and of three duplex stainless steels of different compositions. The test results show that the porosity of these materials leads to notable differences between their high-temperature oxidation behavior and that of conventional stainless steels of similar composition.

A. Bautista; F. Velasco; M. Campos; M. E. Rabanal; J. M. Torralba

2003-01-01

455

A neural network approach for solution of the inverse problem for selection of powder metallurgy materials  

Microsoft Academic Search

This paper describes research that has been conducted into artificial intelligence techniques for solving the inverse problem, for assisting with materials selection. The term inverse problem refers to the task of employing process output information (i.e. the required mechanical or physical properties of the final material), in order to recommend suitable input settings for the process concerned. For example, for

L. N. Smith; R. M. German; M. L. Smith

2002-01-01

456

Application of powder metallurgy techniques for the development of non-toxic ammunition. Final CRADA report  

SciTech Connect

The purpose of the Cooperative Research and Development Agreement (CRADA) between Martin Marietta Energy Systems, Inc., and Delta Frangible Ammunition (DFA), was to identify and evaluate composite materials for the development of small arms ammunition. Currently available small arms ammunition utilizes lead as the major component of the projectile. The introduction of lead into the environment by these projectiles when they are expended is a rapidly increasing environmental problem. At certain levels, lead is a toxic metal to the environment and a continual health and safety concern for firearm users as well as those who must conduct lead recovery operations from the environment. DFA is a leading supplier of high-density mixtures, which will be used to replace lead-based ammunition in specific applications. Current non-lead ammunition has several limitations that prevent it from replacing lead-based ammunition in many applications (such as applications that require ballistics, weapon recoil, and weapon function identical to that of lead-based ammunition). The purpose of the CRADA was to perform the research and development to identify cost-effective materials to be used in small arms ammunition that eventually will be used in commercially viable, environmentally conscious, non-lead, frangible and/or non-frangible, ammunition.

Lowden, R. [Lockheed Martin Energy Systems, Inc., Oak Ridge, TN (United States); Kelly, R. [Delta Defense, Inc., Arlington, VA (United States)

1997-05-30

457

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

458

Demonstration of Shear Localization in Ultrafine Grained Tungsten Alloys via Powder Metallurgy Processing Route.  

National Technical Information Service (NTIS)

Mechanical properties and deformation characteristics are very closely linked to the underlying microstructure of a material. As the grain size of a metal is pushed to ultrafine (<1000 nm) and nano (<100 nm) length-scales, there is often a fundamental shi...

A. Dwivedi B. Butler D. Casem E. Klier M. Gallagher

2012-01-01

459

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

460

Sintering and microstructural development of ceria-gadolinia dispersed powders  

Microsoft Academic Search

Well-dispersed ceria-gadolinia oxide powders were obtained from thoroughly isopropanol-washed coprecipitated oxalates, followed by calcination at 800 C. The characteristics of the calcined powders and the microstructure of the green compacts were found to be of great importance in the sintering behaviour. Those green bodies in which some agglomerate survived after compaction reached a lower final density, while those having soft

P. Durn; C. Moure; J. R. Jurado

1994-01-01

461

Dynamic Magnetic Compaction for Near Net Shape Forming of Advanced Material Products.  

National Technical Information Service (NTIS)

During the SBIR Phase II study, we have applied Dynamic Magnetic Compaction (DMC) technology for compacting the steel powders to high densities of 7.6 gms/cc. The conventional die pressing will yield densities of 7.2 gms/cc in steel powders. Auto market, ...

B. Chelluri

1997-01-01

462

Determination of dry compaction parameters of ceramic nanopowder and influence of ultrasound action on them  

Microsoft Academic Search

The conditions of ceramic nanopowder compaction essentially influence the quality and properties of sintered ceramics. Methods for determination of important parameters of nanopowder dry compaction with regard to powder body elastic properties are presented for the following parameters: powder body elastic modulus and sound velocity; Poisson ratio; coefficients of internal friction, wall friction, lateral pressure; elastic aftereffect in height and

O. L. Khasanov; E. S. Dvilis; Yu. P. Pomhoikov; V. M. Sokolov

2000-01-01

463

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

464

RAPID COMMUNICATION: Ultrasonic wave propagation in SAP compacts  

Microsoft Academic Search

Sound velocity measurement have been made on sintered aluminium powder (SAP) compacts in the density range 1400-2400 kg m-3. The sound velocity, and hence the acoustic impedance, is noticeably reduced in the lower-density compacts suggesting they may have some application as quarter-wave acoustic couplers.

J. M. Brettell

1990-01-01

465

SONIC AND ULTRASONIC COMPACTION OF UO  

Microsoft Academic Search

Two methods for packing nonsintered ceramic fuels by applied vibration ; are described. Vibrationally compacted UO is produced with frequencies in ; the sonic range and yr-eld densities of 89 to 94% of the theoretical density ; depending on the diameter of the cladding material. Characteristics of the ; powder and cladding, frequencies and accelerations, particle size distribution, ; and

J. Servais; Cl. Descamps

1961-01-01

466

Wet powder seal for gas containment  

DOEpatents

A gas seal is formed by a compact layer of an insoluble powder and liquid filling the fine interstices of that layer. The smaller the particle size of the selected powder, such as sand or talc, the finer will be the interstices or capillary spaces in the layer and the greater will be the resulting sealing capacity, i.e., the gas pressure differential which the wet powder layer can withstand. Such wet powder seal is useful in constructing underground gas reservoirs or storage cavities for nuclear wastes as well as stopping leaks in gas mains buried under ground or situated under water. The sealing capacity of the wet powder seal can be augmented by the hydrostatic head of a liquid body established over the seal.

Stang, Louis G. (Sayville, NY)

1982-01-01

467

Wet powder seal for gas containment  

DOEpatents

A gas seal is formed by a compact layer of an insoluble powder and liquid filling the fine interstices of that layer. The smaller the particle size of the selected powder, such as sand or talc, the finer will be the interstices or capillary spaces in the layer and the greater will be the resulting sealing capacity, i.e., the gas pressure differential which the wet powder layer can withstand. Such wet powder seal is useful in constructing underground gas reservoirs or storage cavities for nuclear wastes as well as stopping leaks in gas mains buried under ground or situated under water. The sealing capacity of the wet powder seal can be augmented by the hydrostatic head of a liquid body established over the seal.

Stang, L.G.

1979-08-29

468

Experience of Improving Standards and Methods for Studying the Properties of Metal Powders and Sintered Articles  

Microsoft Academic Search

Reasons are considered for improving standards in the following methods for testing powder materials: tensile, transverse bending, gas and liquid permeability, and determination of powder compact dimensions after compaction pressure removal and during sintering. Calculated data for representative specimen dimensions (cross section and thickness) for these and other test methods for sintered articles (materials) prepared from mono- and polyfraction iron

Yurii G. Bezymyannyi

2003-01-01

469

Shock consolidation of rapidly solidified type 304 stainless steel powders  

Microsoft Academic Search

Shock compaction of dissolved gas (DGA) and centrifugal atomized (CA) Type 304 SS powders have been assessed using explosive techniques. The goal of the study is to produce full dense crack free monoliths for structure\\/property correlations, retaining the unique microstructural features afforded by RSP. Peak shock pressures range from 5 to 30 GPa, and fully dense compacts have been produced

J. E. Flinn; G. E. Korth; R. A. Graham; R. C. Green; L. H. Schoenlein

2008-01-01

470

Effect of porosty on thermal conductivity of powder metal materials  

Microsoft Academic Search

In this study, the effect porosity on thermal conductivity of powder metal materials have been investigated. Metal powders produced from Hoganas ASC 100.29 which have been compacted in 245, 290, 368 MPa pressures and sintered at 900, 1025, 1150 C temperatures. As-received samples had various porosity. Thermal conductivity of these materials was measured and it was observed that thermal conductivity

Adem Kurt; Hakan Ates

2007-01-01

471

Air gas dynamic spraying of powder mixtures: Theory and application  

NASA Astrophysics Data System (ADS)

The radial injection gas dynamic spray (RIGDS) technology of powder coatings deposition was considered for this work. A coating was created by injecting powders with variable compositions into a supersonic air jet and depositing powder on the substrate. This study describes the preliminary analysis of an air gas dynamic spray method realized by a portable RIGDS apparatus with a radial injection of powder. Attention was given to shock compaction processes during the coating structure formation and examples of powder mixtures utilization in RIGDS. It was shown that the operational parameters of supersonic powder-gas jet have a significant influence on the coating's microstructure, thus defining the high performance of the coating. Compaction and bonding of particles were analyzed.

Maev, R. Gr.; Leshchynsky, V.

2006-06-01

472

A comparison of the sintering of various titanium powders  

SciTech Connect

Recently, there has been renewed interest in low-cost titanium. Near-net-shape powder metallurgy offers the potential of manufacturing titanium articles without costly and difficult forming and machining operations; hence, processing methods such as conventional press- and-sinter, powder forging and powder injection molding are of interest. The sintering behavior of a variety of commercial and experimental titanium powders was studied. Commercial powders were acquired that were produced different routes: (i) sponge fines from the primary titanium processing; (ii) via the hydride-dehydride process; and (iii) gas atomization. The influence of vacuum sintering time (0.5 to 32 hrs) and temperature (1200, 1275 or 1350C) on the microstructure (porosity present) of cold pressed powders was studied. The results are discussed in terms of the difference in powder characteristics; with the aim of identify the characteristics required for full density via press-and-sinter processing. Near-net-shape tensile bars were consolidated via cold pressed and sintered. After sintering, a sub-set of the tensile bars was hot-isostatic pressed (HIPed). The microstructure and properties of the bars were compared in the sintered and HIPed conditions.

Gerdemann, Stephen J.; Alman, David E.

2005-02-01

473

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

474

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

475

Welding metallurgy and weldability of high strength aluminum alloys  

SciTech Connect

A literature survey was conducted to gather the information available on the welding metallurgy of high strength aluminum alloys, and its effect on their weldability. The report focuses on fusion welding of high strength aluminum alloys. Both conventional high strength aluminum alloys and newer products, e.g., PM aluminum alloys, Al-Li alloys and Al-matrix composites, are included. The survey covers a wide spectrum of publications, ranging from those using traditional equipment of study to those using more modern analytical instruments, such as electron microscopy and high speed computers. Recommendations of subjects for further research programs are presented. 84 references.

Kou, S.

1986-12-01

476

Mach stem characterization in Mbar designs using RSR powder  

SciTech Connect

Suitable selection of powders can be used as a modeling device for complicated experimental designs. The powder melt zone is clearly defined and the RSR-834 powder is reasonably well behaved. This experiment was with only one composition, size and distribution. However, it is believed that other morphologies, composition, and size distributions could result in a more complete modeling of the compaction process that would enable heuristic calculations of the combined effects of adiabatic temperature rise and entropic heating (strain/deformation).

Staudhammer, K.P.; Johnson, K.A.

1985-01-01

477

Change in Iron Powder Properties with Treatment in Rolls  

Microsoft Academic Search

Conditioned iron powders are prepared by carbothermal reduction of Blue Dust (India) ore concentrate followed by compaction treatment in rolling mill and a decarburizing anneal. The properties of powder prepared by grinding in a vibration and rolling mill are determined. The method makes it possible to control the bulk density of the powder from 1.75 to 2.75 g\\/cm3. Determination of

O. A. Katrus; Alexander K. Radchenko; Dmitrii N. Fedorov; Boris I. Bondarenko; Alexei M. Svyatenko; Eugenii P. Pokotilo

2005-01-01

478

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

479

UO powder from uranyl-loaded cation exchange resin  

Microsoft Academic Search

Production-size batches of UO, suitable for powder metallurgy fabrication of Al-UO cores for reactor fuel tubes, have been produced by deep-bed calcination of granular uranyl-loaded macroporous sulfonate cation exchange resin at 900° to 950°C in air. Deep-bed calcination is the backup process for the reference process of rotary calcination and sintering. These processes are to be used for recycling uranium

1986-01-01

480

UO powder from uranyl-loaded cation exchange resin  

Microsoft Academic Search

Large batches of UO, suitable for powder metallurgy fabrication of Al-UO cores for reactor fuel tubes, have been produced by deep-bed calcination of granular uranyl-loaded macroporous sulfonate cation exchange resin at 900 to 950°C in air. Deep-bed calcination is the backup process for the reference process of rotary calcination and sintering. These processes are to be used for recycling uranium,

1985-01-01

481

Stable cube texture in an advanced Ni alloy composite substrate prepared by powder metallurgic method  

Microsoft Academic Search

Thin, reinforced and biaxially textured Ni5W\\/Ni12W\\/Ni5W composite substrate for coated conductor applications has been fabricated by traditional powder metallurgy method using the sparking plasma sintering (SPS) technology, followed by cold rolling and annealing. In-situ EBSD strain-stress analysis shows that the yield stress (delta0.2) can reach 240MPa. The high quality of