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1

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 François Bussière

1998-01-01

2

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

3

Forging of Powder Metallurgy Gears.  

National Technical Information Service (NTIS)

The objective of this program was to produce a very near-net shape spur gear by isothermal forging of a powder metallurgy 4600 grade preform. Die fill and densification on test coupons were complete at a forging temperature of 1650F (900C), pressure of 10...

B. L. Ferguson D. T. Ostberg

1980-01-01

4

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

5

A major advance in powder metallurgy  

NASA Technical Reports Server (NTRS)

Ultramet has developed a process which promises to significantly increase the mechanical properties of powder metallurgy (PM) parts. Current PM technology uses mixed powders of various constituents prior to compaction. The homogeneity and flaw distribution in PM parts depends on the uniformity of mixing and the maintenance of uniformity during compaction. Conventional PM fabrication processes typically result in non-uniform distribution of the matrix, flaw generation due to particle-particle contact when one of the constituents is a brittle material, and grain growth caused by high temperature, long duration compaction processes. Additionally, a significant amount of matrix material is usually necessary to fill voids and create 100 percent dense parts. In Ultramet's process, each individual particle is coated with the matrix material, and compaction is performed by solid state processing. In this program, Ultramet coated 12-micron tungsten particles with approximately 5 wt percent nickel/iron. After compaction, flexure strengths were measured 50 percent higher than those achieved in conventional liquid phase sintered parts (10 wt percent Ni/Fe). Further results and other material combinations are discussed.

Williams, Brian E.; Stiglich, Jacob J., Jr.; Kaplan, Richard B.; Tuffias, Robert H.

1991-01-01

6

Powder metallurgy for the fabrication of bi-axially textured Ni tapes for YBCO coated conductors  

Microsoft Academic Search

Bi-axially textured Ni tapes for YBCO coated conductors were fabricated by forming, sintering, cold rolling and heat treatment of Ni powder compacts. The powder metallurgy process consists of filling of fine Ni powders in a rubber mold, cold isostatical pressing in a water chamber and sintering of the powder compacts. The sintered compacts were cold-rolled and made into tapes with

Dong-Wook Lee; Bong Ki Ji; Jun Hyung Lim; Choong-Hwan Jung; Jinho Joo; Soon-Dong Park; Byung-Hyuk Jun; Gye-Won Hong; Chan-Joong Kim

2003-01-01

7

Ceramic powder compaction.  

National Technical Information Service (NTIS)

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 experime...

S. J. Glass K. G. Ewsuk F. M. Mahoney

1995-01-01

8

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

9

Ceramic Inclusions in Powder Metallurgy Disk Alloys: Characterization and Modeling.  

National Technical Information Service (NTIS)

Powder metallurgy alloys are increasingly used in gas turbine engines, especially in turbine disk applications. Although powder metallurgy materials have many advantages over conventionally cast and wrought alloys (higher strength, higher temperature capa...

P. J. Bonacuse

2001-01-01

10

Powder metallurgy design manual, 2nd edition  

SciTech Connect

This book is the most concise and comprehensive book of its kind on powder metallurgy (P/M) technology for both component design and application. Completely updated from the previous edition, this valuable reference gives an entirely new coverage on metal injection molding (MIM) and powder forging (P/F) with applicable case histories. There is revised information on P/M compared with other technologies, prototyping, and properties and characteristics of alloys, powders and P/M materials. In addition there`s expanded data on sintering including liquid phase processing and hardening.

NONE

1995-12-31

11

Tin core processing of powder metallurgy Cu-Nb-Sn  

SciTech Connect

Powder metallurgy processed Cu-Nb-Sn superconducting wires were fabricated using different internal tin core geometries. Variations of the process included: a single central tin core surrounded by a multifilamentary composite or by a multistrand powder composite, and bundled multistrand compacts, each containing a tin core. External Ta or Nb barriers were also incorporated in the wire. Nominal areal reductions of 10/sup 4/ to 10/sup 6/ were used. Overall critical current densities of 3 X 10/sup 4/ A/cm/sup 2/ at 14 tesla were achieved.

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

1983-05-01

12

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

13

Powder metallurgy technology of NiTi shape memory alloy  

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

14

High Performance Powder Metallurgy Aluminum Alloys: An Overview.  

National Technical Information Service (NTIS)

The historic development of aluminum powder metallurgy dates back to the early 1900s with initial flake powder production and has matured to the present day production of viable aerospace alloys. Primary powder production and processing techniques, such a...

M. J. Koczak M. K. Premkumar

1989-01-01

15

High Performance Powder Metallurgy Aluminum Alloys - an Overview.  

National Technical Information Service (NTIS)

The historic development of aluminum powder metallurgy dates back to the early 1900's with initial flake powder production and has matured to the present day production of viable aerospace alloys. Primary powder production and processing techniques, such ...

M. J. Koczak M. K. Premkumar

1989-01-01

16

Evaluation of powder metallurgy superalloy disk materials  

NASA Technical Reports Server (NTRS)

A program was conducted to develop nickel-base superalloy disk material using prealloyed powder metallurgy techniques. The program included fabrication of test specimens and subscale turbine disks from four different prealloyed powders (NASA-TRW-VIA, AF2-1DA, Mar-M-432 and MERL 80). Based on evaluation of these specimens and disks, two alloys (AF2-1DA and Mar-M-432) were selected for scale-up evaluation. Using fabricating experience gained in the subscale turbine disk effort, test specimens and full scale turbine disks were formed from the selected alloys. These specimens and disks were then subjected to a rigorous test program to evaluate their physical properties and determine their suitability for use in advanced performance turbine engines. A major objective of the program was to develop processes which would yield alloy properties that would be repeatable in producing jet engine disks from the same powder metallurgy alloys. The feasibility of manufacturing full scale gas turbine engine disks by thermomechanical processing of pre-alloyed metal powders was demonstrated. AF2-1DA was shown to possess tensile and creep-rupture properties in excess of those of Astroloy, one of the highest temperature capability disk alloys now in production. It was determined that metallographic evaluation after post-HIP elevated temperature exposure should be used to verify the effectiveness of consolidation of hot isostatically pressed billets.

Evans, D. J.

1975-01-01

17

Scaleup of powder metallurgy processed Nb-Al multifilamentary wire  

SciTech Connect

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 10/sup 5/, 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 heat treatments. All the compacts used tap density powder in a Cu tube and swaging and/or rod rolling and subsequent wire drawing. Both single strand and bundled wires were made. Overall critical current densities, J /SUB c/, of 2 X 10/sup 4/ A/cm/sup 2/ at 14 T and 10/sup 4/ A/cm/sup 2/ at 16 T were achieved for 6 to 8 wt % Al in Nb.

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

1983-05-01

18

Biaxially textured articles formed by powder metallurgy  

DOEpatents

A biaxially textured alloy article comprises Ni powder and at least one powder selected from the group consisting of Cr, W, V, Mo, Cu, Al, Ce, YSZ, Y, Rare Earths, (RE), MgO, CeO.sub.2, and Y.sub.2 O.sub.3 ; compacted and heat treated, then rapidly recrystallized to produce a biaxial texture on the article. In some embodiments the alloy article further comprises electromagnetic or electro-optical devices and possesses superconducting properties.

Goyal, Amit (Knoxville, TN); Williams, Robert K. (Knoxville, TN)

2001-01-01

19

Si Alloys Produced by Powder Metallurgy  

NASA Astrophysics Data System (ADS)

The present paper deals with the properties of bulk nanostructured Al-Fe-V-Si alloys containing 16, 27, and 37 vol.% of Al12(Fe,V)3Si precipitates. The elemental powders were subjected to high-energy ball milling for 60 h followed by hot-pressing in a uniaxial die at 550 °C under 300 MPa. Mechanical properties of consolidated samples were evaluated by hardness, room temperature, and high temperature compression tests and compared with those of rapid solidification-powder metallurgy (RS-PM) counterparts and also those available for conventional and high temperature Al alloys. The results showed that the nanostructured alloy containing Al12(Fe,V)3Si precipitates has good thermal stability at high temperatures. Room temperature compression tests demonstrated that the strength increases and the ductility decreases with increasing the volume percentage of Al12(Fe,V)3Si precipitates. The room temperature yield strength of nanostructured alloys was in the range of 560-758 MPa depending on Al12(Fe,V)3Si content. These values are much higher than those for RS-PM counterparts. In addition, nanostructured Al-Al12(Fe,V)3Si alloys exhibited better strength at elevated temperatures compared with other Al alloys.

Ashrafi, H.; Enayati, M. H.; Emadi, R.

2014-05-01

20

CHARACTERIZATION AND PROPERTIES OF ALUMINUM COMPOSITE MATERIALS PREPARED BY POWDER METALLURGY TECHNIQUES USING CERAMIC SOLID WASTES  

Microsoft Academic Search

This work provides preliminary results of aluminum metal matrix composites (MMCs) reinforced with granulated slag (GS) and electric arc furnace dust (EAFD). The present work concerns the synthesis and properties of Al\\/GS and Al\\/EAFD composites based on powder metallurgy techniques. The hardness and compressive strength of the sintering compacts were determined to compare the mechanical properties of the composite material

L. Ma. Flores-Vélez; J. Chávez; L. Hernández; O. Domínguez

2001-01-01

21

Development of high performance superconductors by powder metallurgy  

SciTech Connect

In summary, powder metallurgy processed materials have a potential for alternative fabrication of a wide variety of novel structures which are not readily feasible with conventional metallurgical technologies. The processes discussed here require highly deformable initial powders with good quality control. We are interested in new and conventional commercial sources of such deformable powders for research and development of some of these novel structures.

Foner, S.

1982-05-01

22

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

23

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 {micro}m,<75 {micro}m, and<45 {micro}m; two different sizes of a hydride-dehydride [HDH]<75 {micro}m and<45 {micro}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, J

2011-05-01

24

CONSTITUTIVE MODELING OF THE DENSIFICATION OF METAL POWDER DURING COMPACTION  

Microsoft Academic Search

Powder metallurgy, or P\\/M, is a process for forming metal parts by compacting and heating metal powders to just below their melting points. Although the process has been existed for more than 100 years, over the past quarter century it has just become widely recognized as a robust process for producing high-quality parts for a variety of important applications. This

YOUSSEF HAMMI; LAURA ARIAS-MEZA; MARK F. HORSTEMEYER

25

Metallurgical examination of powder metallurgy uranium alloy welds  

SciTech Connect

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

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

1986-06-01

26

Yield and compaction behavior of rapidly solidified Al–Si alloy powders  

Microsoft Academic Search

In order to obtain high quality products in powder metallurgy, it is important to control and understand the densification behavior of metal powders. The effect of the characters of powders on the compaction behavior was investigated in this study by using three types of Al–Si powders produced by gas atomization, centrifugal atomization and twin roll-pulverization. The shape of the powders

Hyoung Seop Kim

1998-01-01

27

Influence of Sintering under Nitrogen Atmosphere on Microstructures of Powder Metallurgy Duplex Stainless Steels  

Microsoft Academic Search

Duplex stainless steels (SS) obtained through powder metallurgy (PM) from austenitic AISI 316L and ferritic AISI 430L powders\\u000a were mixed in different amounts to obtain a biphasic structure with an austenite\\/ferrite ratio of 50\\/50, 65\\/35, and 85\\/15.\\u000a Prepared powders were compacted at 750 MPa and sintered in N2-H2 (95 pct–5 pct) at 1250 °C for 1 hour. Some samples sintered in vacuum were taken as

C. García; F. Martin; Y. Blanco; M. P. de Tiedra; M. L. Aparicio

2009-01-01

28

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

Microsoft Academic Search

Titanium matrix syntactic foams have potential for orthopedic applications because of their good biocompatibility, corrosion\\u000a resistance and ability of varying the elastic modulus. This paper studies the fabrication of Ti matrix syntactic foams embedded\\u000a with ceramic microspheres (CMs) by a powder metallurgy method. The percentage of the crushed CMs during compaction was measured\\u000a by the volume measurement and water absorption

Xiaobing Xue; Yuyuan Zhao

2011-01-01

29

A NUMERICAL PROCEDURE FOR MODELING CRACK FORMATION IN POWDER COMPACTION BASED MANUFACTURING PROCESSES  

Microsoft Academic Search

Summary. A numerical model for modelling crack formation during the powder compaction stage of powder metallurgy manufacturing processes is presented. A numerical model, previously developed by the authors, to predict the densification of the powder material during the compaction, is extended to detect the cracks onset during the pressing stage. The main ingredients of the new model are: a) using

J. Oliver; J C. Cante; J A. Hernández

30

Powder-metallurgy superalloy strengthened by a secondary gamma phase.  

NASA Technical Reports Server (NTRS)

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

Kotval, P. S.

1971-01-01

31

Near-Net Shape Powder Metallurgy Rhenium Thruster  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

32

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

33

Dispersion Hardened Titanium Alloys by Powder Metallurgy.  

National Technical Information Service (NTIS)

The characteristics and applications of titanium alloys for structural purposes are discussed. A method of producing dispersion hardened titanium alloys through powder metallurgical techniques is described. An electron beam splatting furnace designed for ...

S. Pattanaik K. G. Gopinathan V. S. Arunachalam

1974-01-01

34

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

35

Microstructure and Aging of Powder-Metallurgy Al Alloys  

NASA Technical Reports Server (NTRS)

Report describes experimental study of thermal responses and aging behaviors of three new aluminum alloys. Alloys produced from rapidly solidified powders and contain 3.20 to 5.15 percent copper, 0.24 to 1.73 percent magnesium, 0.08 to 0.92 percent iron, and smaller amounts of manganese, nickel, titanium, silicon, and zinc. Peak hardness achieved at lower aging temperatures than with standard ingot-metallurgy alloys. Alloys of interest for automobile, aircraft, and aerospace applications.

Blackburn, L. B.

1987-01-01

36

The powder metallurgy processing of refractory metals and alloys  

NASA Astrophysics Data System (ADS)

Molybdenum and tungsten are refractory metals in the elemental form with the largest production volume in the world. The fabrication of these refractory metals, as well as their alloys and intermetallics, using high-temperature powder metallurgy (PM) is reviewed in this article. The primary focus is on the role of traditional high-temperature PM in producing alloys with tailor-made properties. An insight into the bulk production of molybdenum and tungsten alloys with nano-grains is highlighted.

Morales, Ricardo; Aune, Ragnhild E.; Seetharaman, Seshadri; Grinder, Olle

2003-10-01

37

Advanced powder metallurgy aluminum alloys via rapid solidification technology  

NASA Technical Reports Server (NTRS)

Aluminum alloys containing 10 to 11.5 wt. pct. of iron and 1.5 to 3 wt. pct. of chromium using the technique of rapid solidification powder metallurgy were studied. Alloys were prepared as thin ribbons (.002 inch thick) rapidly solidified at uniform rate of 10(6) C/second by the melt spinning process. The melt spun ribbons were pulverized into powders (-60 to 400 mesh) by a rotating hammer mill. The powders were consolidated by hot extrusion at a high reduction ratio of 50:1. The powder extrusion temperature was varied to determine the range of desirable processing conditions necessary to yield useful properties. Powders and consolidated alloys were characterized by SEM and optical metallography. The consolidated alloys were evaluated for (1) thermal stability, (2) tensile properties in the range, room temperature to 450 F, and (3) notch toughness in the range, room temperature to 450 F.

Ray, R.

1984-01-01

38

Device for preparing combinatorial libraries in powder metallurgy.  

PubMed

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

Yang, Shoufeng; Evans, Julian R G

2004-01-01

39

Influence of Sintering under Nitrogen Atmosphere on Microstructures of Powder Metallurgy Duplex Stainless Steels  

NASA Astrophysics Data System (ADS)

Duplex stainless steels (SS) obtained through powder metallurgy (PM) from austenitic AISI 316L and ferritic AISI 430L powders were mixed in different amounts to obtain a biphasic structure with an austenite/ferrite ratio of 50/50, 65/35, and 85/15. Prepared powders were compacted at 750 MPa and sintered in N2-H2 (95 pct-5 pct) at 1250 °C for 1 hour. Some samples sintered in vacuum were taken as references. Optical metallography, X-ray diffraction, and scanning electron microscopy/energy dispersive analysis of X-rays were used for microstructural characterization. Powder metallurgy base materials, AISI 430L and 316L, showed a single lamellar constituent after sintering in nitrogen. A mixed constituent was identified in PM duplex SS sintered in nitrogen and in vacuum. However, coarse and fine lamellar constituents were only present in PM duplex SS sintered in nitrogen. The effects of annealing solution heat treatment (1150 °C) on microstructures were evaluated. Homogeneous structures were obtained for the PM base materials, while for PM duplex SS, annealing dissolved lamellar constituents but mixed constituent were still present.

García, C.; Martin, F.; Blanco, Y.; de Tiedra, M. P.; Aparicio, M. L.

2009-02-01

40

DC Plasma Technology Applied to Powder Metallurgy: an Overview  

NASA Astrophysics Data System (ADS)

DC plasma is a very promising technology for processing different materials, and is becoming especially interesting when low environmental impact and high-performance treatments are needed. Some of the intrinsic characteristics of DC plasma technology, which make it suitable for powder metallurgy (PM) and powder injection molding (PIM) parts production, are low-pressure processing and plasma environment high reactivity. Moreover it can be considered as a highly competitive green technology. In this work, an overview of some of the important DC plasma techniques applied to PM and PIM parts processing is presented. Emphasis is given to the descriptions of the main characteristics and the technique potentials of plasma-assisted nitriding, plasma-assisted thermal debinding, plasma-assisted sintering, and simultaneously plasma-assisted sintering and surface alloying. The aspects presented and discussed in this paper indicate that DC plasma processes are promising and competitive techniques for PM and PIM parts processing.

N. Klein, A.; P. Cardoso, R.; C. Pavanati, H.; Binder, C.; M. Maliska, A.; Hammes, G.; Fusao, D.; Seeber, A.; F. Brunatto, S.; L. R. Muzart, J.

2013-01-01

41

Mesoscale Simulations of Powder Compaction  

NASA Astrophysics Data System (ADS)

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

2009-12-01

42

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

43

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

44

Shock compaction of molybdenum powder  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

45

Powder metallurgy: Solid and liquid phase sintering of copper  

NASA Technical Reports Server (NTRS)

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

Sheldon, Rex; Weiser, Martin W.

1993-01-01

46

N18, powder metallurgy superalloy for disks: Development and applications  

SciTech Connect

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

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

1993-08-01

47

Mesoscale simulations of powder compaction  

NASA Astrophysics Data System (ADS)

Mesoscale 3D simulations of metal and ceramic powder compaction in shock waves have been performed with an Eulerian hydrocode GEODYN. The approach was validated by simulating shock compaction of porous well-characterized ductile metal using Steinberg material model. Results of the simulations with handbook values for parameters of solid 2024 aluminum have good agreement with experimental compaction curves and wave profiles. Brittle ceramic materials are not so well studied as metals, so material model for ceramic (tungsten carbide) has been fitted to shock compression experiments of non-porous samples and further calibrated to experimental match compaction curves. Direct simulations of gas gun experiments with ceramic powder have been performed and showed good agreement with experimental data. Numerical shock wave profile has same character and thickness as measured with VISAR. Numerical results show evidence of hard-to-explain reshock states above the single-shock Hugoniot line, which have also been observed in the experiments. We found that to receive good quantitative agreement with experiment it is essential to perform 3D simulations, since 2D results tend to underpredict stress levels for high-porosity powders regardless of material properties. We developed a process to extract macroscale information for the simulation which can be directly used in calibration of continuum model for heterogeneous media.

Lomov, Ilya; Antoun, Tarabay; Liu, Benjamin

2009-06-01

48

Nb-A1 powder metallurgy processed multifilamentary wire  

SciTech Connect

Powder metallurgy processed Nb-Al wire with overall critical current densities, J /SUB c/ , at 4.2K up to 10/sup 4/A/cm/sup 2/ at 19T has been investigated in more detail. Kramer plots and directly measured H /SUB c2/ values of samples with different heat treatments show an increase in H /SUB c2/ at 4.2K up to 24.5T. Test coils, using long lengths of wire, and tested in fields up to 15T, show J /SUB c/ values equal to those of short samples. Multiple strand hydrostatic small scale extrusions were made. A number of third element additions including B, Mg, Co, Cr and Ni in fine powder form were incorporated in the P/M processing but these did not improve J /SUB c/ . ac losses were measured and used to determine J /SUB c/ at low fields. The high field ac losses are lower than that for any in Situ or powder processed Nb/sub 3/Sn wires.

Thieme, C.L.H.; Foner, S.; Pourrahimi, S.; Schwartz, B.B.

1985-03-01

49

Method for forming biaxially textured articles by powder metallurgy  

DOEpatents

A method of preparing a biaxially textured alloy article comprises the steps of preparing a mixture comprising Ni powder and at least one powder selected from the group consisting of Cr, W, V, Mo, Cu, Al, Ce, YSZ, Y, Rare Earths, (RE), MgO, CeO.sub.2, and Y.sub.2 O.sub.3 ; compacting the mixture, followed by heat treating and rapidly recrystallizing to produce a biaxial texture on the article. In some embodiments the alloy article further comprises electromagnetic or electro-optical devices and possesses superconducting properties.

Goyal, Amit (Knoxville, TN); Williams, Robert K. (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN)

2002-01-01

50

Initial Evaluation of Advanced Powder Metallurgy Magnesium Alloys for Dynamic Applications.  

National Technical Information Service (NTIS)

The U.S. Army Research Laboratory (ARL) is interested in assessing the performance of different magnesium alloys. The ARL and the Joining and Welding Research Institute (JWRI) conducted a joint effort to develop and evaluate advanced powder metallurgy mag...

K. Kondoh T. Jones

2009-01-01

51

The Casting and Powder-Metallurgy Forming of Precipitation-Hardenable Stainless Steels.  

National Technical Information Service (NTIS)

The state of the art of making shapes of precipitation-hardenable stainless steels by methods other than machining from wrought materials is reviewed. The methods reviewed are casting and powder metallurgy. Of these methods, only casting is extensively pr...

J. G. Kura V. D. Barth H. O. McIntire

1966-01-01

52

Gas Entrapment and Evolution in Aluminium Alloys Produced by Powder Metallurgy.  

National Technical Information Service (NTIS)

Part of a comprehensive research program involving different aspects of degassing of powder metallurgy (PM) aluminum alloys is presented. Some fundamentals concerning gas entrapment and evolution such as the relationship between surface composition and ch...

J. L. Estradahaen

1990-01-01

53

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

National Technical Information Service (NTIS)

In the absence of extrinsic surface damage, the fatigue life of metals is often dictated by the distribution of intrinsic defects. In powder metallurgy (PM) alloys, relatively large defects occur rarely enough that a typical characterization with a limite...

P. J. Bonacuse P. T. Kantzos R. Barrie J. Telesman L. J. Ghosn T. P. Gabb

2004-01-01

54

Dynamic Compaction of Metal and Ceramic Powders.  

National Technical Information Service (NTIS)

The state of the art and the technological potential for the dynamic consolidation of metal and ceramic powders were assessed. Fundamental consideration of dynamic consolidation, consolidation phenomena during dynamic compaction, dynamic compaction and co...

V. D. Linse O. R. Bergmann C. F. Cline J. D. Mote H. Palmour

1983-01-01

55

Taguchi analysis of surface modification technique using W-Cu powder metallurgy sintered tools in EDM and characterization of the deposited layer  

Microsoft Academic Search

The present study describes an experimental research on surface modification during electrical discharge machining (EDM) by\\u000a depositing a hard layer over the work surface of C-40 grade plain carbon steel using specially prepared powder metallurgy\\u000a compact tools. The investigated process parameters were composition, compaction pressure, sintering temperature, pulse on-time,\\u000a peak–current setting, and duty factor. Measurements of deposited layer thickness, mass

Promod K. Patowari; Partha Saha; Prasanta K. Mishra

2011-01-01

56

Corrosion inhibition of powder metallurgy Mg by fluoride treatments.  

PubMed

Pure Mg has been proposed as a potential degradable biomaterial to avoid both the disadvantages of non-degradable internal fixation implants and the use of alloying elements that may be toxic. However, it shows excessively high corrosion rate and insufficient yield strength. The effects of reinforcing Mg by a powder metallurgy (PM) route and the application of biocompatible corrosion inhibitors (immersion in 0.1 and 1M KF solution treatments, 0.1M FST and 1M FST, respectively) were analyzed in order to improve Mg mechanical and corrosion resistance, respectively. Open circuit potential measurements, polarization techniques (PT), scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS) were performed to evaluate its corrosion behavior. SECM showed that the local current of attacked areas decreased during the F(-) treatments. The corrosion inhibitory action of 0.1M FST and 1M FST in phosphate buffered solution was assessed by PT and EIS. Under the experimental conditions assayed, 0.1M FST revealed better performance. X-ray photoelectron spectroscopy, energy dispersive X-ray and X-ray diffraction analyses of Mg(PM) with 0.1M FST showed the presence of KMgF(3) crystals on the surface while a MgF(2) film was detected for 1M FST. After fluoride inhibition treatments, promising results were observed for Mg(PM) as degradable metallic biomaterial due to its higher yield strength and lower initial corrosion rate than untreated Mg, as well as a progressive loss of the protective characteristics of the F(-)-containing film which ensures the gradual degradation process. PMID:19913114

Pereda, M D; Alonso, C; Burgos-Asperilla, L; del Valle, J A; Ruano, O A; Perez, P; Fernández Lorenzo de Mele, M A

2010-05-01

57

Mechanics of Powder Plastic Powder Compacts.  

National Technical Information Service (NTIS)

Colloidal Isopressing is a new method for the shaping of ceramic components from powder suspensions in a rapid and effective manner. Colloidal Isopressing starts with a slurry containing a relatively low volume fraction of powder, where the particles weak...

F. F. Lange

2001-01-01

58

The stress-corrosion cracking behavior of high-strength aluminum powder metallurgy alloys  

Microsoft Academic Search

The susceptibility to stress-corrosion cracking (SCC) of rapidly solidified (RS) aluminum powder metallurgy (P\\/M) alloys 7090\\u000a and 7091, mechanically alloyed aluminum P\\/M alloy IN* 9052, and ingot metallurgy (I\\/M) alloys of similar compositions was\\u000a compared using bolt-loaded double cantilever beam specimens. In addition, the effects of aging, grain size, grain boundary\\u000a segregation, pre-exposure embrittlement, and loading mode on the SCC

J. R. Pickens; L. Christodoulou

1987-01-01

59

Electrosintering of iron powder compacts  

NASA Astrophysics Data System (ADS)

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

Fahmy, Yusef; Conrad, Hans

2001-03-01

60

Development of coarse grain structures in a powder metallurgy nickel base superalloy N18  

Microsoft Academic Search

N18 is a new nickel base superalloy produced by powder metallurgy and specifically designed for high temperature turbine disk applications. The goal of the present work is to understand the conditions under which very large grains can grow in PM nickel base superalloy N18 and to identify the mechanisms responsible for this growth. Abnormal grain growth, defined as the growth

M. Soucail; M. Marty; H. Octor

1996-01-01

61

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

NASA Technical Reports Server (NTRS)

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

Harf, Fredric H.

1989-01-01

62

Shape memory alloys for MEMS components made by powder metallurgy processes  

Microsoft Academic Search

The paper presents some research results in the field of NiTi shape memory alloys made through powder metallurgy techniques. These techniques allow the obtaining of materials with savings of energy and time due to use of NiTi heat formation for the material synthesis. Ni-Ti, Ni-Ti-Fe and Ni-Ti-Cu alloys were performed by self propagation high temperature synthesis, starting from elemental powders.

M. Lucaci; R. L. Orban; V. Tsakiris; D. Cirstea

2008-01-01

63

Crack prevention in shock compaction of powders  

SciTech Connect

The occurrence of macro-cracks in compacts fabricated by shock compaction of powders is a severe problem preventing this consolidation technique from commercial applications. In this paper the sources of important failure types that typically occur in the cylindrical configuration i.e. radial, transverse, and spiral cracks and the Mach stem are described. Subsequently, solutions for their prevention are given supported by experimental results and/or computer simulations. Some conflicting requirements for obtaining bonded crack-free compacts are discussed.

Carton, E. P. [TNO Prins Maurits Laboratory, P.O. Box 45, 2280 AA, Rijswijk (Netherlands); Delft University of Technology, Laboratory for Applied Inorganic Chemistry, P.O. Box 5045, 2600 Georgia, Delft (Netherlands); Stuivinga, M.; Verbeek, H. J. [TNO Prins Maurits Laboratory, P.O. Box 45, 2280 AA, Rijswijk (Netherlands)

1998-07-10

64

Investigation of machinability of iron based metal matrix composite (MMC) powder metallurgy parts  

NASA Astrophysics Data System (ADS)

One of the advantages of powder metallurgy technology is that we may produce the final geometry of the required part saving considerable time and cost. However there are several applications that require parts need additional machining for example when the product contains threads, cross bore or slots. In these cases cutting of the hard and porous material may causes difficulties in manufacturing. The aim of the introduced research is the experimental investigation of the machinability of the iron based MMC powder metallurgy parts, determining the favourable composition of the powder and advantageous process parameters regarding the properties of the machinability. The research try to answer to the challenge of the poorly defined expression: machinability, and after defining the features and methods of the evaluation we develop advises for the proper technology parameters.

Szalay, Tibor; Czampa, Miklós; Markos, Sándor; Farkas, Balázs

2012-09-01

65

Conventional Powder Metallurgy Process and Characterization of Porous Titanium for Biomedical Applications  

NASA Astrophysics Data System (ADS)

Commercially pure titanium (c.p. Ti) is one of the best metallic biomaterials for bone tissue replacement. However, one of its main drawbacks, which compromises the service reliability of the implants, is the stress-shielding phenomenon (Young's modulus mismatch with respect to that one of the bone). Several previous works attempted to solve this problem. One alternative to solve that problem has been the development of biocomposites implants and, more recently, the fabrication of titanium porous implants. In this work, porous samples of c.p. Ti grade 4 were obtained using conventional powder metallurgy technique. The influence of the processing parameters (compacting pressure and sintering temperature) on the microstructure features (size, type, morphology, and percentage of porosity), as well as on the mechanical properties (compressive yield strength, and conventional and dynamic Young's modulus) were investigated. The results indicated that there is an increment in density, roundness of pores, and mean free path between them as compacting pressure and/or sintering temperature is increased. The Young's modulus (conventional and dynamic) and yield strength showed the same behavior. Better stiffness results, in the central part of cylindrical samples, were obtained for a uniaxial compression of 38.5 MPa using a sintering temperature of 1273 K and 1373 K (1000 °C and 1100 °C). An evaluation of porosity and Young's modulus along a cylindrical sample divided in three parts showed that is possible to obtain a titanium sample with graded porosity that could be used to design implants. This approach opens a new alternative to solve the bone resorption problems associated with the stress-shielding phenomenon.

Torres, Y.; Pavón, J. J.; Nieto, I.; Rodríguez, J. A.

2011-08-01

66

High field performance of superconducting magnets using powder metallurgy processed Cu-Nb-Sn and Nb-Al  

SciTech Connect

Small superconducting magnets were fabricated with powder metallurgy processed Nb-Al wire and with powder metallurgy processed multistrand Cu-Nb--Sn wire with 19 tin cores. Tests in a background field of up to 15 T showed that short sample characteristics were achieved for three coils. Upper limits of resistivity were established for both powder metallurgy processed wires. The reacted wires in the magnets gave upper limits of resistivity at 10 T of less than 1.4 x 10/sup -14/ ..cap omega.. cm for the Nb/sub 3/Sn wire, and less than 9 x 10/sup -13/ ..cap omega.. cm for the Nb-Al wire.

Zaleski, A.J.; Foner, S.

1984-06-01

67

Net-Shape HIP Powder Metallurgy Components for Rocket Engines.  

National Technical Information Service (NTIS)

True net shape consolidation of powder metal (PM) by hot isostatic pressing (HIP) provides opportunities for many cost, performance and life benefits over conventional fabrication processes for large rocket engine structures. Various forms of selectively ...

C. Bampton W. Goodin T. VanDaam G. Creeger S. James

2005-01-01

68

Porous mandrels provide uniform deformation in hydrostatic powder metallurgy  

NASA Technical Reports Server (NTRS)

Porous copper mandrels prevent uneven deformation of beryllium machining blanks. The beryllium powder is arranged around these mandrels and hot isostatically pressed to form the blanks. The mandrels are then removed by leaching.

Gripshover, P. J.; Hanes, H. D.

1967-01-01

69

Densification of powder compacts by vibration  

Microsoft Academic Search

Various packing methods such as vibration, shaking, etc., in addition to normal gravitational settling, can be often used\\u000a to density powder compacts. Many issues relevant to this matter are of great importance in advanced ceramic powder processing.\\u000a In the present work, the relaxation of structure due to vibration is addressed by using a computer experimental model based\\u000a on Monte Carlo

Hern Kim; Moo-Sil Pyun

1995-01-01

70

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

Microsoft Academic Search

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

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

2008-01-01

71

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

Microsoft Academic Search

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

Yoshihito Kawamura; Akihisa Inoue; Makoto Takagi; Hidenobu Ohta; Toru Imura; Tsuyoshi Masumoto

1999-01-01

72

Microstructural effects on the dry wear resistance of powder metallurgy Al–Si alloys  

Microsoft Academic Search

Wear resistance of a new powder metallurgy (P\\/M) Al–Si alloy was studied at two successive development stages, with marked microstructural differences. Wear tests were conducted by a pin-on-disk tribometer, without lubricant, at different loads. Microstructural observations of the alloy at the first stage of development revealed the existence of a porous superficial layer, that directly affects the mechanical and wear

D. Casellas; A. Beltran; J. M. Prado; A. Larson; A. Romero

2004-01-01

73

The mechanical properties of Fe-Co heterogeneous alloys fabricated by powder metallurgy techniques  

Microsoft Academic Search

Fe-Co heterogeneous alloys fabricated by powder metallurgy techniques were hot rolled, cold rolled and then heat treated. These processes produced a type of fibre-reinforced composite which consisted of fibrous Fe and Fe-Co phases. The tensile strength of the alloys depended on the composition and degree of order of the Fe-Co phase. The rule of mixtures was applicable, provided that the

Morihiko Nakamura; Kazuo Tsuya

1977-01-01

74

2014 and 6061 aluminium alloy-based powder metallurgy composites containing silicon carbide particles\\/fibres  

Microsoft Academic Search

The present investigation covers the processing and mechanical properties of 2014 and 6061 Al alloy-based power metallurgy composites containing up to 8 vol% of SiC in either particle or continuous fibre form. For consolidation of the green compacts, liquid phase sintering under vaccum at 635°C was adopted. The addition of reinforcement imparted improved densification such that particulate composites were better

C. Srinivasa Rao; G. S. Upadhyaya

1995-01-01

75

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

76

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

77

On the cold compaction of powders  

Microsoft Academic Search

Constitutive models are developed for stage I cold compaction of powders under general loading. Densification is assumed to occur by plastic deformation at the isolated contacts between particles. The shape of the yield surface is found to be sensitive to the cohesive strength between particles and to be less sensitive to the degree of inter-particle friction. An internal state variable

N. A. Fleck

1995-01-01

78

Processing of Cr 2Nb precursor through powder metallurgy route  

Microsoft Academic Search

Mechanical milling (MM) has been adopted to develop Cr2Nb intermetallic precursor, required for the processing of Cu–Cr–Nb alloy. Process parameters have been optimized through particle characterisation of powders produced by different milling time and conditions. It has been observed that particle morphology and size change with milling time. A milling time of 15h, followed by annealing at 1400°C has been

G. P. Khanra; Abhay K. Jha; S. Girikumar; K. Thomas Tharian; Suresh Kumar

2010-01-01

79

Net-Shape HIP Powder Metallurgy Components for Rocket Engines  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

80

Army P/M research and development overview. Final report. [P/M (powder metallurgy)  

SciTech Connect

The Army uses of powder metallurgy (P/M) extend from the conventional press and sinter to the more exotic processes of liquid phase sintering of tungsten heavy alloys (WHA) and powder injection molding (PIM). Many of the more advanced high performance applications require extensive research and development (R and D) prior to fielding of the application. Examples arc the intense research into WHA in the last ten years. This research has led to great understanding of these heavy alloys and application into some kinetic energy systems. The Navy has taken great advantage of WHA by employing them iii the phalanx close-in weapon system (CIWS). The Army intends that research will lead to an alloy or composite of tungsten that, when used as a long rod penetrator, will perform as well as, or better than, current depleted uranium (DU) penetrators. This will allow possible replacement of the controversial DU. Powder injection molding of WHA is an area receiving attention because of the potential for producing small and medium caliber projectiles. The drawbacks at this time include the need to develop an alloy that does not require post sinter cold working to develop the strength required for these demanding applications. Other possible problems include producing slender long rod projectiles with desired product straightness. In addition to the work on tungsten alloys, a discussion is underway of other powder metallurgy R and D and is under active investigation within the Army. These topics include aluminum and titanium alloys, intermetallics, and ultrahigh strength steels for structural and propulsion applications, as well as nonequilibrium P/M produced structures.... Powder metallurgy, Tungsten alloys, Aluminum alloys, Titanium alloys, Intermetallic.

Dowding, R.J.; Wells, M.G.; Crowson, A.

1993-05-01

81

Temperature evolution during compaction of pharmaceutical powders.  

PubMed

A numerical approach to the prediction of temperature evolution in tablet compaction is presented here. It is based on a coupled thermomechanical finite element analysis and a calibrated Drucker-Prager Cap model. This approach is capable of predicting transient temperatures during compaction, which cannot be assessed by experimental techniques due to inherent test limitations. Model predictions are validated with infrared (IR) temperature measurements of the top tablet surface after ejection and match well with experiments. The dependence of temperature fields on speed and degree of compaction are naturally captured. The estimated transient temperatures are maximum at the end of compaction at the center of the tablet and close to the die wall next to the powder/die interface. PMID:17969108

Zavaliangos, Antonios; Galen, Steve; Cunningham, John; Winstead, Denita

2008-08-01

82

High-strength powder metallurgy aluminum alloys in glass-forming Al-Ni-Ce-(Ti or Zr) systems  

SciTech Connect

Powder metallurgy (P/M) aluminum alloys with high mechanical strengths have been developed by taking advantage of rapid solidification (RS). The improved strengths result from structural modifications such as reduction of segregation, refinement of grain size and increase in solid solubility limit which mainly depend on the amount of undercooling of melt. To produce crystalline alloys with a refined structure, few approaches are considered: the crystallization of an amorphous alloy, the control of cooling rate from melt and the selection of optimum composition for glass-forming alloys. However, these methods are generally attended with a disadvantage for embrittlement. Recently, it has been found that Al-based amorphous alloys exhibiting high tensile strength and good bending ductility form by liquid quenching in the Al-Ln-TM (Ln: lanthanide metal, TM: transition metal) system. Furthermore, the consolidation of the amorphous alloy powders to a bulk amorphous alloy has also been achieved by warm extrusion. The first aim of this paper is to examine the effect of alloy composition on the strength and ductility of crystalline compacts produced by extrusion of rapidly solidified powders in the Al-Ni-Ce-TM(TM:Ti, Mn, Fe, Co, Cu, Zr) systems where an amorphous phase is formed by melt spinning. The second is to investigate whether or not the structural refinement by using glass-forming alloys is useful to develop high-strength P/M aluminum alloys.

Kawamura, Y.; Inoue, A.; Sasamori, K.; Masumoto, T. (Tohoku Univ., Sendai (Japan))

1993-07-15

83

A densification model for mixed metal powder under cold compaction  

Microsoft Academic Search

Densification behavior of mixed copper and tool steel powder under cold compaction was investigated. By mixing the yield functions proposed by Fleck et al. and by Gurson for pure powder in terms of volume fractions of Cu powder and the fraction of contact, a new mixed yield function was employed for densification of powder composites under cold compaction. The constitutive

K. T Kim; J. H Cho

2001-01-01

84

Dose and Dose Risk Caused by Natural Phenomena - Proposed Powder Metallurgy Core Manufacturing Facility  

SciTech Connect

The offsite radiological effects from high velocity straight winds, tornadoes, and earthquakes have been estimated for a proposed facility for manufacturing enriched uranium fuel cores by powder metallurgy. Projected doses range up to 30 mrem/event to the maximum offsite individual for high winds and up to 85 mrem/event for very severe earthquakes. Even under conservative assumptions on meteorological conditions, the maximum offsite dose would be about 20 per cent of the DOE limit for accidents involving enriched uranium storage facilities. The total dose risk is low and is dominated by the risk from earthquakes. This report discusses this test.

Holmes, W.G.

2001-08-16

85

Porosity effect on the electrical conductivity of sintered powder compacts  

Microsoft Academic Search

A new equation for calculating the electrical conductivity of sintered powder compacts is proposed. In this equation, the\\u000a effective resistivity of porous compacts is a function of the fully dense material conductivity, the porosity of the compact\\u000a and the tap porosity of the starting powder. The new equation is applicable to powder sintered compacts from zero porosity\\u000a to tap porosity.

J. M. Montes; F. G. Cuevas; J. Cintas

2008-01-01

86

Submicron multifilamentary high performance Nb/sub 3/Sn produced by powder metallurgy processing of large powders  

SciTech Connect

Powder metallurgy processed submicron multifilamentary Nb/sub 3/Sn superconducting wires were fabricated starting with 250--500-..mu..m-diam powders. A multiple strand bundling procedure was used to simulate large scale production with actual areal reductions greater than 10/sup 6/ to achieve submicron fibers. Both external tin and tin core processing were successful. Typical Cu-36 wt.% Nb-Sn materials gave overall critical current densities of 8 x 10/sup 4/ A/cm/sup 2/ at 12 T, 3 x 10/sup 4/ A/cm/sup 2/ at 14 T, and 6 x 10/sup 3/ A/cm/sup 2/ at 16 T. These results demonstrate that particle size and billet size can be scaled from earlier laboratory scale to large scale fabrication to produce high performance materials.

Otubo, J.; Pourrahimi, S.; Zhang, H.; Thieme, C.L.H.; Foner, S.

1983-03-01

87

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

NASA Technical Reports Server (NTRS)

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

Kent, W. B.

1977-01-01

88

Metallographic preparation of pressed and sintered powder-metallurgy material (tungsten, niobium, lead, and copper)  

SciTech Connect

An object of this invention is to provide a metallographic preparation procedure for obtaining a flat and scratch-free surface of a representative sample of a pressed and sintered powder-metallurgy material. A further object of this invention is to provide a metallographic preparation procedure for obtaining a flat and scratch-free surface of a representative sample of a pressed and sintered powder-metallurgy material comprised of a composite of the refractory metals tungsten and columbium and the soft metals lead and copper. The representative samples of Table I contain hard and soft constituents. The hard constituents are refractory metals of tungsten and niobium, and the soft constituents are soft metals of copper and lead. All samples were selected and cut from parent material and encapsulated in epoxy resin prior to polishing, Stage A. The encapsulation enabled the sample to be held during grinding and polishing for the metallographic preparation technique disclosed by the additional Stages B-E and steps outlined below.

Goodwin, E.L.

1987-03-28

89

Applied mechanics modeling of granulated ceramic powder compaction  

Microsoft Academic Search

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

F. M. Mahoney; M. J. Readey

1995-01-01

90

The viscoplastic compaction of composite powders  

NASA Astrophysics Data System (ADS)

A model for the densification of spherical powders is developed for the early stages of cold and hot compaction under general loading. General viscoplastic properties are adopted which reduce to strain hardening plasticity at ambient temperature and to power law creep at elevated temperature. A large strain analysis is carried out to determine the macroscopic compaction behaviour, based on the affine motion of particles with viscoplastic dissipation occurring at the contacts between particles. Random packing is assumed and the model includes the increase in the number of contacts per particle with densification. A general prescription is given for computing the macroscopic stress as a function of strain rate and accumulated strain. Detailed results are presented for yield surfaces and creep dissipation surfaces after isostatic and closed die compaction. A scalar constraint factor is derived for a random mixture of two populations of particles with different sizes and strengths. The predictions include the limiting case of deformable spheres reinforced with rigid spheres of different size.

Storåkers, B.; Fleck, N. A.; McMeeking, R. M.

1999-02-01

91

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

Microsoft Academic Search

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

Sofiane Terzi; Raphael Couturier; Laure Guétaz; Bernard Viguier

2008-01-01

92

High-strength powder metallurgy aluminum alloys in glass-forming Al-Ni-Ce-(Ti or Zr) systems  

Microsoft Academic Search

Powder metallurgy (P\\/M) aluminum alloys with high mechanical strengths have been developed by taking advantage of rapid solidification (RS). The improved strengths result from structural modifications such as reduction of segregation, refinement of grain size and increase in solid solubility limit which mainly depend on the amount of undercooling of melt. To produce crystalline alloys with a refined structure, few

Y. Kawamura; A. Inoue; K. Sasamori; T. Masumoto

1993-01-01

93

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 310±0.5 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

94

Particles into 410L Stainless Steel by a Powder Metallurgy Route  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

95

Machinability of Green Powder Metallurgy Components: Part I. Characterization of the Influence of Tool Wear  

NASA Astrophysics Data System (ADS)

The green machining process is an interesting approach for solving the mediocre machining behavior of high-performance powder metallurgy (PM) steels. This process appears as a promising method for extending tool life and reducing machining costs. Recent improvements in binder/lubricant technologies have led to high green strength systems that enable green machining. So far, tool wear has been considered negligible when characterizing the machinability of green PM specimens. This inaccurate assumption may lead to the selection of suboptimum cutting conditions. The first part of this study involves the optimization of the machining parameters to minimize the effects of tool wear on the machinability in turning of green PM components. The second part of our work compares the sintered mechanical properties of components machined in green state with other machined after sintering.

Robert-Perron, Etienne; Blais, Carl; Pelletier, Sylvain; Thomas, Yannig

2007-06-01

96

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

97

Abnormal magnetic behaviour of powder metallurgy austenitic stainless steels sintered in nitrogen  

NASA Astrophysics Data System (ADS)

The magnetic response of AISI 304L and AISI 316L obtained through powder metallurgy and sintered in nitrogen were studied. AISI 304L sintered in nitrogen showed a ferromagnetic behaviour in as-sintered state while AISI 316L was paramagnetic. After solution annealing both were paramagnetic. Magnetic behaviour was analysed by using a vibrating sample magnetometer, a magnetic ferritscope and magnetic etching. A microstructural characterization was performed by means of optical metallography, X-ray diffraction, scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDS). Some samples when needed were submitted to aged heat treatments at 675 and 875 °C for 90 min, 4, 6, 8 or 48 h. The main microstructural feature found was the presence of a lamellar constituent formed by nitride precipitates and an interlamellar matrix of austenite and/or ferrite. The abnormal magnetic response was explained based on this.

García, C.; Martin, F.; Blanco, Y.

2009-10-01

98

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

NASA Astrophysics Data System (ADS)

A ferritic stainless steel has been manufactured through the powder metallurgy (P/M) route: uniaxial pressing and sintering. The sintering process was carried out in vacuum, at 1215 °C for 30 min. After sintering, materials showed nearly 90% of density. A complete metallographic study was carried out using optical microscopy and scanning electron microscopy (SEM). Wear behavior was evaluated using a “pin on disk” test according to ASTM Standard G99. Eight test conditions were studied, varying the load (5 and 10 N), the speed (0.1 and 0.4 m/s), and the counter-material (chromium steel and a martensitic stainless steel). The sliding distance was 400 m, and tests were carried out on polished materials, with less than 30% of relative humidity. Moreover, wear tracks were observed by SEM in order to understand the wear processes involved, which depend mainly on the counter-material.

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

2001-08-01

99

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

100

Application of Powder Technology to Military Hardware.  

National Technical Information Service (NTIS)

A short description of powder metallurgy and its possible application to the manufacture of military hardware is discussed. The first part deals with the experimental aspects of producing compacts from powders. The basic processes of material preparation ...

J. P. Drolet

1972-01-01

101

Novelties in physics of explosive welding and powder compaction  

Microsoft Academic Search

Widely known technologies of explosive (X) welding and explosive (X) powder compaction are based on applications of porous composite solid or liquid explosives. Recent results on dynamics of X-welding and X-powder compaction are presented and discussed in this paper in the conceptual context of an orderly oscillating detonation wave (DW), a synergetic phenomenon observed in detonation of all classes of

I. Plaksin; J. Campos; J. Ribeiro; R. Mendes; J. Direito; D. Braga; R. Pruemmer

2003-01-01

102

Power-law creep model for densification of powder compacts  

Microsoft Academic Search

Densification behaviour of powder compacts by power-law creep during pressure-assisted compaction at an elevated temperature was investigated. A constitutive model was proposed for the densification behavior of powder compacts under a power-law creep situation based on the plastic deformation theory for porous materials which satisfies the uniaxial stress condition. The proposed power-law creep model is compared with Shima and Oyane’s

Hyoung Seop Kim; Dong Nyung Lee

1999-01-01

103

Discrete element analysis of powder processing: Fill and compaction  

Microsoft Academic Search

The production of various ceramic components is often achieved by processing powder into the desired shape and dimensions. The process includes filling a die with powder, which then is compacted. Even today, most parameters are adjusted by trial-and-error. The quality of the product is associated with its density homogeneity. This is a function of powder properties, die geometry, filling method

Consuelo Margarita Kong

2000-01-01

104

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 1230°C 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

105

Powder metallurgy processed Nb/sub 3/Sn employing extrusion and varying Nb content  

SciTech Connect

Extension of powder metallurgy (P/M) processing of Cu-Nb-Sn is described for small scale industrial uniaxial extrusion (R less than or equal to 10/sup 4/) and for small scale hydrostatic extrusions for areal reductions R = 2000. Successful 2.5 cm o.d. uniaxial P/M processed extrusions at 950 and 250 /SUP o/ F were obtained. Model cold hydrostatic extrusions of single tin core and multitin core wire are described. The effect of Nb content for Cu-x wt% Nb, where 36 less than or equal to x less than or equal to 60 was examined. Increased overall critical current densities, J /SUB c/ , were obtained with increased Nb content up to 50 wt% Nb. For proper comparisons, values of J /SUB cm/ (where the prestress is removed), are given for several compositions. Improvement in J /SUB c/ for T less than or equal to 4.2K is also presented. Incorporation of Ti in Nb/sub 3/Sn by means of Sn-Ti core processing results in further increases in J /SUB c/ . The low R and large initial powder sizes result in relatively thick Nb fibers which are not completely reacted. The present extrusion P/M processed wires demonstrate several practical approaches for development of high performance materials. Optimization should yield high values of J /SUB c/ at 20 tesla.

Pourrahimi, S.; Foner, S.; Schwartz, B.B.; Thieme, C.L.H.

1985-03-01

106

Improved high field performance of Nb-Al powder metallurgy processed superconducting wires  

SciTech Connect

Improved overall critical current densities J/sub c/'s were achieved with powder metallurgy processed Nb-A1 which combined reduced powder sizes and increased nominal areal reductions R. Increased J/sub c/ values were obtained for a variety of different heat treatments. For a Nb-8 wt. % A1 wire with R = 3.4 x 10/sup 5/ a very short treatment at 1100 /sup 0/C followed by a 750 /sup 0/C treatment gave (at 4.2 K)J/sub c/>10/sup 4/ A/cm/sup 2/ at 19 T; a 900 /sup 0/C treatment followed by a 750 /sup 0/C treatment gave J/sub c/ = 10/sup 4/ A/cm/sup 2/ at 18 T and, at 2 K, J/sub c/ was greater than 10/sup 4/ A/cm/sup 2/ at 20 T; and a treatment of 800 /sup 0/C for 8 h gave (at 4.2 K)J/sub c/ = 10/sup 4/ A/cm/sup 2/ at 17.5 T.

Thieme, C.L.H.; Pourrahimi, S.; Schwartz, B.B.; Foner, S.

1984-01-15

107

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

108

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

109

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

110

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

SciTech Connect

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

Sean M. McDeavitt

2011-04-29

111

Methodology for modeling viscoelastic, uniaxial, and roller compacted pharmaceutical powders  

Microsoft Academic Search

Roller compaction is a pharmaceutical unit operation typically scaled-up and controlled through trial and error to produce compacted powders with specific qualities. The goal of this research was to develop a methodology to predict final roller compact properties based on raw material properties and process conditions for use in scale-up and control. Uniaxial compacts were created with an Instron\\/Sintech universal

Anna Rose Alsman Hayes

2008-01-01

112

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. Díaz; J. L. González-Carrasco; G. Caruana; M. Lieblich

1996-01-01

113

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

Microsoft Academic Search

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

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

2008-01-01

114

Compactability and sinterability of spherical ceramic model powder.  

National Technical Information Service (NTIS)

The ultimate research objectives of the current research program are to examine the compacting characteristics and to examine the sintering characteristics of ceramic model powders having a spherical particle shape. In particular, the current first-year r...

K. Cho H. S. Yu C. W. Ann Kwun H. G. Kim

1994-01-01

115

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

SciTech Connect

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

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

1997-12-01

116

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

117

Dwell Notch Low Cycle Fatigue Behavior of a Powder Metallurgy Nickel Disk Alloy  

NASA Technical Reports Server (NTRS)

A study was conducted to determine the processes which govern dwell notch low cycle fatigue (NLCF) behavior of a powder metallurgy (P/M) ME3 disk superalloy. The emphasis was placed on the environmentally driven mechanisms which may embrittle the highly stressed notch surface regions and reduce NLCF life. In conjunction with the environmentally driven notch surface degradation processes, the visco-plastic driven mechanisms which can significantly change the notch root stresses were also considered. Dwell notch low cycle fatigue testing was performed in air and vacuum on a ME3 P/M disk alloy specimens heat treated using either a fast or a slow cooling rate from the solutioning treatment. It was shown that dwells at the minimum stress typically produced a greater life debit than the dwells applied at the maximum stress, especially for the slow cooled heat treatment. Two different environmentally driven failure mechanisms were identified as the root cause of early crack initiation in the min dwell tests. Both of these failure mechanisms produced mostly a transgranular crack initiation failure mode and yet still resulted in low NLCF fatigue lives. The lack of stress relaxation during the min dwell tests produced higher notch root stresses which caused early crack initiation and premature failure when combined with the environmentally driven surface degradation mechanisms. The importance of environmental degradation mechanisms was further highlighted by vacuum dwell NLCF tests which resulted in considerably longer NLCF lives, especially for the min dwell tests.

Telesman, J.; Gabb, T. P.; Yamada, Y.; Ghosn, L. J.; Jayaraman, N.

2012-01-01

118

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

119

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

120

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

121

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

122

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

123

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

124

Microwave Heating, Isothermal Sintering, and Mechanical Properties of Powder Metallurgy Titanium and Titanium Alloys  

NASA Astrophysics Data System (ADS)

This article presents a detailed assessment of microwave (MW) heating, isothermal sintering, and the resulting tensile properties of commercially pure Ti (CP-Ti), Ti-6Al-4V, and Ti-10V-2Fe-3Al (wt pct), by comparison with those fabricated by conventional vacuum sintering. The potential of MW sintering for titanium fabrication is evaluated accordingly. Pure MW radiation is capable of heating titanium powder to ?1573 K (1300 °C), but the heating response is erratic and difficult to reproduce. In contrast, the use of SiC MW susceptors ensures rapid, consistent, and controllable MW heating of titanium powder. MW sintering can consolidate CP-Ti and Ti alloys compacted from -100 mesh hydride-dehydride (HDH) Ti powder to ~95.0 pct theoretical density (TD) at 1573 K (1300 °C), but no accelerated isothermal sintering has been observed over conventional practice. Significant interstitial contamination occurred from the Al2O3-SiC insulation-susceptor package, despite the high vacuum used (?4.0 × 10-3 Pa). This leads to erratic mechanical properties including poor tensile ductility. The use of Ti sponge as impurity (O, N, C, and Si) absorbers can effectively eliminate this problem and ensure good-to-excellent tensile properties for MW-sintered CP-Ti, Ti-10V-2Fe-3Al, and Ti-6Al-4V. The mechanisms behind various observations are discussed. The prime benefit of MW sintering of Ti powder is rapid heating. MW sintering of Ti powder is suitable for the fabrication of small titanium parts or titanium preforms for subsequent thermomechanical processing.

Luo, S. D.; Guan, C. L.; Yang, Y. F.; Schaffer, G. B.; Qian, M.

2013-04-01

125

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

SciTech Connect

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

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

2008-02-15

126

Hot Isostatic Pressing of Ceramic Powder Compacts.  

National Technical Information Service (NTIS)

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

J. K. McCoy R. R. Wills

1984-01-01

127

Compaction Studies of Palladium/Aluminum Powders.  

National Technical Information Service (NTIS)

A compaction study has been performed comparing predicted and experimentally determined density gradients in palladium/aluminum mixtures of differing weight fractions. A modified constitutive equation for porous media was used to predict the density gradi...

O. L. Burchett M. R. Birnbaum C. T. Oien

1978-01-01

128

Magnetoresistance of Chromium Dioxide Powder Compacts  

Microsoft Academic Search

Cold-pressed powders of the half-metallic ferromagnet CrO2 are dielectric granular metals. Hysteretic magnetoresistance with maxima at the coercive field arises from interparticle contacts. Dilution with insulating antiferromagnetic Cr2O3 powder reduces the conductivity by 3 orders of magnitude, but enhances the magnetoresistance ratio which reaches 50% at 5K. The negative magnetoresistance is due to tunneling between contiguous ferromagnetic particles along a

J. M. D. Coey; A. E. Berkowitz; Ll. Balcells; F. F. Putris; A. Barry

1998-01-01

129

Magnetoresistance of Chromium Dioxide Powder Compacts  

NASA Astrophysics Data System (ADS)

Cold-pressed powders of the half-metallic ferromagnet CrO2 are dielectric granular metals. Hysteretic magnetoresistance with maxima at the coercive field arises from interparticle contacts. Dilution with insulating antiferromagnetic Cr2O3 powder reduces the conductivity by 3 orders of magnitude, but enhances the magnetoresistance ratio which reaches 50% at 5K. The negative magnetoresistance is due to tunneling between contiguous ferromagnetic particles along a critical path with a spin-dependent Coulomb gap.

Coey, J. M. D.; Berkowitz, A. E.; Balcells, Ll.; Putris, F. F.; Barry, A.

1998-04-01

130

Dynamic Compaction Modeling of Porous Silica Powder  

Microsoft Academic Search

A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized a linear Us-Up Hugoniot. The compaction events were

John P. Borg; Larry Schwalbe; John Cogar; D. J. Chapman; K. Tsembelis; Aaron Ward; Andrew Lloyd

2006-01-01

131

Controlled powder morphology experiments in megabar 304 stainless steel compaction  

SciTech Connect

Experiments with controlled morphology including shape, size, and size distribution were made on 304L stainless steel powders. These experiments involved not only the powder variables but pressure variables of 0.08 to 1.0 Mbar. Also included are measured container strain on the material ranging from 1.5% to 26%. Using a new strain controllable design it was possible to seperate and control, independently, strain and pressure. Results indicate that powder morphology, size distribution, packing density are among the pertinent parameters in predicting compaction of these powders.

Staudhammer, K.P.; Johnson, K.A.

1985-01-01

132

Novelties in physics of explosive welding and powder compaction  

NASA Astrophysics Data System (ADS)

Widely known technologies of explosive (X) welding and explosive (X) powder compaction are based on applications of porous composite solid or liquid explosives. Recent results on dynamics of X-welding and X-powder compaction are presented and discussed in this paper in the conceptual context of an orderly oscillating detonation wave (DW), a synergetic phenomenon observed in detonation of all classes of composite energetic materials, that was discovered in LEDAP in last eight years. Regular instabilities that are induced by oscillating DW, are transmitted through the interface of the impacted materials, causing the local instability and fluctuations in both processes, formation of the interfacial waves (X-welding mechanism) and in an initial phase of powder compaction. Application of high resolution optical probes (spatial resolution 250 ?m, temporal resolution 1 ns, 96 independent channels) allowed the simultaneous registration of the oscillating DW in the X-charge and transmission of oscillations, through the flyer plate, up to the welding zone. Similar measurements have been made in experiments with X-compaction of tungsten powder providing the continuos registration of shock wave velocity inside the compacted powder, its geometrical shape, their instabilities and irregularities.

Plaksin, I.; Campos, J.; Ribeiro, J.; Mendes, R.; Direito, J.; Braga, D.; Pruemmer, R.

2003-09-01

133

Dynamic Compaction Modeling of Porous Silica Powder  

NASA Astrophysics Data System (ADS)

A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized a linear Us-Up Hugoniot. The compaction events were modeled with CTH, a 3D Eulerian hydrocode developed at Sandia National Laboratory. Simulated pressures at two test locations are presented and compared with measurements.

Borg, John P.; Schwalbe, Larry; Cogar, John; Chapman, D. J.; Tsembelis, K.; Ward, Aaron; Lloyd, Andrew

2006-07-01

134

Influence of Thermal Aging on the Microstructure and Mechanical Behavior of Dual Phase Precipitation Hardened Powder Metallurgy Stainless Steels  

NASA Astrophysics Data System (ADS)

Increasing demand for high strength powder metallurgy (PM) steels has resulted in the development of dual phase PM steels. In this work, the effects of thermal aging on the microstructure and mechanical behavior of dual phase precipitation hardened powder metallurgy (PM) stainless steels of varying ferrite-martensite content were examined. Quantitative analyses of the inherent porosity and phase fractions were conducted on the steels and no significant differences were noted with respect to aging temperature. Tensile strength, yield strength, and elongation to fracture all increased with increasing aging temperature reaching maxima at 538°C in most cases. Increased strength and decreased ductility were observed in steels of higher martensite content. Nanoindentation of the individual microconstituents was employed to obtain a fundamental understanding of the strengthening contributions. Both the ferrite and martensite hardness values increased with aging temperature and exhibited similar maxima to the bulk tensile properties. Due to the complex non-uniform stresses and strains associated with conventional nanoindentation, micropillar compression has become an attractive method to probe local mechanical behavior while limiting strain gradients and contributions from surrounding features. In this study, micropillars of ferrite and martensite were fabricated by focused ion beam (FIB) milling of dual phase precipitation hardened powder metallurgy (PM) stainless steels. Compression testing was conducted using a nanoindenter equipped with a flat punch indenter. The stress-strain curves of the individual microconstituents were calculated from the load-displacement curves less the extraneous displacements of the system. Using a rule of mixtures approach in conjunction with porosity corrections, the mechanical properties of ferrite and martensite were combined for comparison to tensile tests of the bulk material, and reasonable agreement was found for the ultimate tensile strength. Micropillar compression experiments of both as sintered and thermally aged material allowed for investigation of the effect of thermal aging.

Stewart, Jennifer

135

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

NASA Technical Reports Server (NTRS)

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

Walder, A.; Hivert, A.

1982-01-01

136

Computational modeling of 3D powder compaction processes  

Microsoft Academic Search

In this paper, the 3D numerical simulation of powder compaction processes is presented using a double-surface plasticity theory. A cone-cap plasticity model based on a combination of a convex yield surface consisting of a failure envelope and a hardening cap is developed for nonlinear behavior of powder materials in the concept of the generalized plasticity formulation. The constitutive elasto-plastic matrix

A. R. Khoei; A. R. Azami; S. Azizi

2007-01-01

137

Homogenization of compacted blends of nickel and tungsten powders  

Microsoft Academic Search

The diffusional homogenization of compacted blends of elemental Ni and W powders was studied using quantitative metallography and X-ray compositional line broadening. Homogenization treatments were carried out in the temperature range from 1156 to 1271°C (in the region of the Ni-W phase diagram where only the terminal solid solutions exist). The mean compositions of the compacts studied ranged from 0.06

R. A. Tanzilli; R. W. Heckel

1975-01-01

138

Homogenization of compacted blends of nickel and tungsten powders  

Microsoft Academic Search

The diffusional homogenization of compacted blends of elemental Ni and W powders was studied using quantitative metallography\\u000a and X-ray compositional line broadening. Homogenization treatments were carried out in the temperature range from 1156 to\\u000a 1271°C (in the region of the Ni-W phase diagram where only the terminal solid solutions exist). The mean compositions of the\\u000a compacts studied ranged from 0.06

R. A. Tanzilli; R. W. Heckel

1975-01-01

139

Preparation of Cu and Fly Ash Composite by Powder Metallurgy Technique  

NASA Astrophysics Data System (ADS)

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

Chew, P. Y.; Zahi, S.; You, A. H.; Lim, P. S.; Ng, M. C.

2011-03-01

140

Gamma prime precipitation modeling and strength responses in powder metallurgy superalloys  

NASA Astrophysics Data System (ADS)

Precipitation-hardened nickel-based superalloys have been widely used as high temperature structural materials in gas turbine engine applications for more than 50 years. Powder metallurgy (P/M) technology was introduced as an innovative manufacturing process to overcome severe segregation and poor workability of alloys with high alloying contents. The excellent mechanical properties of P/M superalloys also depend upon the characteristic microstructures, including grain size and size distribution of gamma' precipitates. Heat treatment is the most critical processing step that has ultimate influences on the microstructure, and hence, on the mechanical properties of the materials. The main objective of this research was to study the gamma ' precipitation kinetics in various cooling circumstances and also study the strength response to the cooling history in two model alloys, Rne88DT and U720LI. The research is summarized below: (1) An experimental method was developed to allow accurate simulation and control of any desired cooling profile. Two novel cooling methods were introduced: continuous cooling and interrupt cooling. Isothermal aging was also carried out. (2) The growth and coarsening kinetics of the cooling gamma' precipitates were experimentally studied under different cooling and aging conditions, and the empirical equations were established. It was found that the cooling gamma' precipitate versus the cooling rate follows a power law. The gamma' precipitate size versus aging time obeys the LSW cube law for coarsening. (3) The strengthening of the material responses to the cooling rate and the decreasing temperature during cooling was investigated in both alloys. The tensile strength increases with the cooling rate. In addition, the non-monotonic response of strength versus interrupt temperature is of great interest. (4) An energy-driven model integrated with the classic growth and coarsen theories was successfully embedded in a computer program developed to simulate the cooling gamma ' precipitation based on the first principle of thermodynamics. The combination of the thermodynamic and the kinetic approaches provided a more practical method to determine the critical nucleation energy. (5) The simulation results proved the gamma' burst theory and the existence of the multi-stage burst of gamma' precipitates, which shows good agreement with the experimental data in a variety of aspects.

Mao, Jian

141

Synthesis and Characterization of CrCuFeMnMo0.5Ti Multicomponent Alloy Bulks by Powder Metallurgy  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

142

Characterization of uniaxial compaction in spray dried ceramic powders  

Microsoft Academic Search

A model spray dried alumina powder system was studied with systematically varied binder content (2, 3, 4 and 5 wt%) and binder glass transition temperature (Tg). The Tg of the poly(vinyl alcohol) binder was adjusted between -32°C and +35°C by equilibration at five relative humidities. Compaction curves were constructed and dimensional changes on ejection were measured for all twenty compositions

Robert David Carneim

2000-01-01

143

Mechanical properties of porous titanium compacts prepared by powder sintering  

Microsoft Academic Search

Porous Ti compacts for biomedical applications are successfully fabricated in the porosity range from 5.0 to 37.1 vol% by controlling sintering conditions and Ti powder sizes. Young’s modulus and bending strength at the porosity of around 30 vol% are found to be similar to those of human cortical bone.

Ik-Hyun Oh; Naoyuki Nomura; Naoya Masahashi; Shuji Hanada

2003-01-01

144

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

145

Initial Assessment of the Effects of Nonmetallic Inclusions on Fatigue Life of Powder-Metallurgy-Processed Udimet(TM) 720  

NASA Technical Reports Server (NTRS)

The fatigue lives of modern powder metallurgy (PM) disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary due to the different steps of materials/component processing and machining. One of these variables, the presence of nonmetallic inclusions, has been shown to significantly degrade low-cycle fatigue (LCF) life. Nonmetallic inclusions are inherent defects in powder alloys that are a by-product of powder-processing techniques. Contamination of the powder can occur in the melt, during powder atomization, or during any of the various handling processes through consolidation. In modern nickel disk powder processing facilities, the levels of inclusion contamination have been reduced to less than 1 part per million by weight. Despite the efforts of manufacturers to ensure the cleanliness of their powder production processes, the presence of inclusions remains a source of great concern for the designer. the objective of this study was to investigate the effects on fatigue life of these inclusions. Since natural inclusions occur so infrequently, elevated levels of inclusions were carefully introduced in a nickel-based disk superalloy, Udimet 720 (registered trademark of Special Metals Corporation), produced using PM processing. Multiple strain-controlled fatigue tests were then performed on this material at 650 C. Analyses were performed to compare the LCF lives and failure initiation sites as functions of inclusion content and fatigue conditions. A large majority of the failures in specimens with introduced inclusions occurred at cracks initiating from inclusions at the specimen surface. The inclusions could reduce fatigue life by up to 100 times. These effects were found to be dependent on strain range and strain ratio. Tests at lower strain ranges and higher strain ratios produced larger effects of inclusions on life.

Gabb, T. P.; Telesman, J.; Kantzos, P. T.; Bonacuse, P. J.; Barrie, R. L.

2002-01-01

146

Effect of powder compaction variables on the performance of a pyrotechnic igniter  

Microsoft Academic Search

The compaction of the pyrotechnic powder against a bridgewire in an igniter is very critical to performance. The density of the compact at the bridgewire interface can be effected by the powder characteristics, environment, surface finish and configuration of the compact holder and the loading process. Some of these parameters have been evaluated and the effect determined on the bridgewire-powder

A. C. Munger; N. J. Seubert; J. R. Brinkman

1978-01-01

147

Compact, Non-Pneumatic Rock-Powder Samplers  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

148

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

149

The roles of rare earth dispersoids and process route on the low cycle fatigue behavior of a rapidly solidified powder metallurgy titanium alloy  

SciTech Connect

Low cycle fatigue tests were conducted at 482C (900F) on forgings and extrusions of a rapidly solidified powder metallurgy titanium base alloy with and without rare earth additions. The variables studied were process temperature and heat treatment. Rare earth dispersions reduced fatigue life, and fracture surfaces indicated internal fatigue crack initiation at rare earth particles.

Gigliotti, M.F.X. (General Electric Corp. Research and Development, Schenectady, NY (United States)); Woodfield, A.P. (General Electric Aircraft Engines, Evendale, OH (United States))

1993-08-01

150

Using Microwave-Assisted Powder Metallurgy Route and Nano-size Reinforcements to Develop High-Strength Solder Composites  

NASA Astrophysics Data System (ADS)

In the present study, Sn-0.7Cu and Sn-3.5Ag lead-free solders used in the electronics packaging industry were reinforced with different volume percentages of nano-size alumina and tin oxide particulates, respectively, to synthesize two new sets of nanocomposites. These composites were developed using microwave-assisted powder metallurgy route followed by extrusion. The effects of addition of particulates on the physical, microstructural, and mechanical properties of the nanocomposites were investigated. Mechanical properties (microhardness, 0.2% YS, and UTS) for both composite systems increase with the presence of particulates. The best tensile strength was realized for composite solders reinforced with 1.5 vol.% alumina and 0.7 vol.% tin oxide particulates, which far exceeds the strength of eutectic Sn-Pb solder. The morphology of pores was observed to be one of the most dominating factors affecting the strength of materials.

Nai, S. M. L.; Kuma, J. V. M.; Alam, M. E.; Zhong, X. L.; Babaghorbani, P.; Gupta, M.

2010-04-01

151

Incorporation of Y2O3 Particles into 410L Stainless Steel by a Powder Metallurgy Route  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

152

Calculation of a constitutive potential for isostatic powder compaction  

Microsoft Academic Search

A macroscopic constitutive potential has been developed for the deformation of a powder compact of cylindrical particles during pressure sintering. The derivation is based on finite-element simulations of the densification process that proceeds under the synergistic action of power-law creep deformation in the particles, evolution of the nonlinearly developing contact area between the particles, and interparticle and pore free-surface diffusional

S. J. Subramanian; P. Sofronis

2002-01-01

153

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

154

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

155

Processing and microstructure of powder metallurgy Al-Fe-Ni alloys  

Microsoft Academic Search

Prealloyed rapidly solidified Al-Fe-Ni alloy powder with dispersoid volume fractions of 0.19, 0.25, and 0.32 FeNiAl9 was produced by air atomization. The powder was degassed, canned, and consolidated to full density by vacuum hot pressing\\u000a and extrusion or by direct extrusion. Microstructures in the alloy powder and consolidated material were characterized by\\u000a means of optical, scanning (SEM), and transmission electron

M. K. Premkumar; A. Lawley; M. J. Koczak

1992-01-01

156

Processing and microstructure of powder metallurgy Al-Fe-Ni alloys  

Microsoft Academic Search

Prealloyed rapidly solidified Al-Fe-Ni alloy powder with dispersoid volume fractions of 0.19, 0.25, and 0.32 FeNiAl9 was produced by air atomization. The powder was degassed, canned, and consolidated to full density by vacuum hot pressing and extrusion or by direct extrusion. Microstructures in the alloy powder and consolidated material were characterized by means of optical, scanning (SEM), and transmission electron

M. K. Premkumar; A. Lawley; M. J. Koczak

1992-01-01

157

Development of powder metallurgy technique for synthesis of U 3Si 2 dispersoid  

NASA Astrophysics Data System (ADS)

The Indian research reactor APSARA, which uses HEU based UAl 3 fuel dispersed in aluminium matrix, is to undergo core conversion to LEU based U 3Si 2 dispersoid in aluminium matrix fuel. Work has been initiated at BARC, to prepare uranium silicide (U 3Si 2) compound using powder processing route in place of vacuum induction melting or arc melting route. This paper describes the preparation flow-sheet of the U 3Si 2 dispersoid by an innovative powder processing route with uranium metal powder and silicon powder as starting materials.

Sinha, V. P.; Mishra, G. P.; Pal, S.; Khan, K. B.; Hegde, P. V.; Prasad, G. J.

2008-12-01

158

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 625°C. 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

159

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 1100°C and made from the granulated powders are slightly higher than those made from the CHR powders. At temperatures higher than 800°C 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 100-150°C 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 1200-1400°C 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

160

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

161

Compaction behavior of Al6061 powder in the semi-solid state  

Microsoft Academic Search

Semi-solid powder processing involves compaction of metallic alloy powders in temperature ranges when both solid and liquid phases coexist. However, modeling of such process has been very scarce. In this study, compaction behavior of Al6061 powder in the presence of liquid phase was investigated. The relationship between compaction pressure and relative density of powder in the semi-solid state was modeled

Yufeng Wu; Gap-Yong Kim

2011-01-01

162

A REVIEW OF NONDESTRUCTIVE TESTING METHODS AND THEIR APPLICABILITY TO POWDER METALLURGY PROCESSING  

Microsoft Academic Search

The problem of forming defects in green parts during compaction and ejec tion has become more prevalent as parts producers have started to use higher compaction pressures in an effort to achieve high density, high performance P\\/M steels. In this review, several nondestructive inspection methods are evaluat ed, with the aim of identifying those, which are practical for detecting defects

R. C. O'Brien; W. B. James

163

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

164

Effects of carbon and hafnium concentrations in wrought powder-metallurgy superalloys based on nasa 2b-11 alloy  

Microsoft Academic Search

A candidate alloy for advanced-temperature turbine engine disks and four modifications of that alloy with various C and Hf concentrations were produced as cross-rolled disks from prealloyed powder that was hot isostatically compacted. The mechanical properties, microstructures, and phase relations of the alloys are discussed in terms of their C and Hf concentrations. A low-C and high-Hf modification of IIB-11

Miner; R. V. Jr

1976-01-01

165

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

166

Effect of SiC NanoParticles Content and Mg Addition on the Characteristics of Al\\/SiC Composite Powders Produced via In Situ Powder Metallurgy (IPM) Method  

Microsoft Academic Search

In the present study, the effect of the nano-sized SiC particles loading and Mg addition on the characteristics of Al\\/SiC composite powders produced via a relatively new method called “in situ powder metallurgy (IPM)” was investigated. Specified amounts of SiC particles (within a size range of 250–600 µm) together with SiC nano-particles (average size of 60 nm) were preheated and added to

Mohammad Moazami-Goudarzi; Farshad Akhlaghi

2012-01-01

167

Mechanical Properties of Mg2Si/Mg Composites via Powder Metallurgy Process  

NASA Astrophysics Data System (ADS)

The mechanical properties of the Mg2Si/Mg composites solid-state synthesized from the mixed Mg-Si powders have been investigated. The macro-hardness (HRE) and the tensile strength of the composites increase with increasing the Si content and decreasing the Si size. The particle size of the synthesized Mg2Si depends on the initial Si size; the mechanical properties of the Mg2Si/Mg composite are remarkably improved by using fine Si particles or by decreasing the grain size of Mg matrix grains when the powder mixture was prepared via bulk mechanical alloying process.

Muramatsu, Hiroshi; Kondoh, Katsuyoshi; Yuasa, Eiji; Aizawa, Tatsuhiko

168

Microstructural refinement and mechanical properties improvement of elemental powder metallurgy processed Ti46.6Al1.4Mn2Mo alloy by carbon addition  

Microsoft Academic Search

Strengthening of a gamma TiAl alloy was sought by a chemical modification of the composition with carbon. Up to 0.6 at. pct of carbon was added to the Ti-46.6Al-1.4Mn-2Mo alloy processed by elemental powder metallurgy. Carbon addition resulted in considerable microstructural changes such as refinement, by a factor of about 2, of the lamellar microstructure and carbide precipitation. The cause

H. S. Park; S. K. Hwang; C. M. Lee; Y. C. Yoo; S. W. Nam; N. J. Kim

2001-01-01

169

Influence of Thermal Aging on the Microstructure and Mechanical Behavior of Dual-Phase, Precipitation-Hardened, Powder Metallurgy Stainless Steels  

Microsoft Academic Search

The effects of thermal aging on the microstructure and mechanical behavior of dual-phase, precipitation-hardened, powder metallurgy\\u000a (PM) stainless steels of varying ferrite–martensite content were examined. Quantitative analyses of the inherent porosity\\u000a and phase fractions were conducted on the steels, and no significant differences were noted with respect to aging temperature.\\u000a Tensile strength, yield strength, and elongation to fracture all increased

J. L. Stewart; J. J. Williams; N. Chawla

170

Brief description of working conditions in contemporary technological operations in the powder-metallurgy industry  

Microsoft Academic Search

in the preparation of the molten metal in a mixer, in the pulverization (spraying) of the liquid metal, in drying, and in preparing the raw powder material for annealing the concentrations of iron oxide dust reach tens of milligrams per cubic meter. The carbon monoxide content in the work zone at the electric-arc furnaces amounts to 250 and that of

I. T. Brakhnova

1991-01-01

171

Processing and Properties of 18Ni Maraging Steel by Powder Metallurgy.  

National Technical Information Service (NTIS)

Using 18Ni Mar 300 powder processed by the rotating electrode process, rods were extruded under varying temperatures and ram speeds. It is observed that control of both variables allows structure control and increases the Charpy V-notch toughness from 7 t...

E. P. Abrahamson

1973-01-01

172

Ni3AI intermetallic particles as wear-resistant reinforcement for Al-base composites processed by powder metallurgy  

NASA Astrophysics Data System (ADS)

The suitability of Ni3Al intermetallics as reinforcement for Al-base materials for tribological applications has been investigated. For this purpose, an Al/Ni3Al (5 vol pct) composite was prepared by powder metallurgy and tested in air against steel counterfaces at the load range of 45 to 178 N. For comparison, unreinforced Al specimens were processed and tested under the same conditions. Tribological behavior was evaluated by microstructural examination of wear-affected zones and weightloss measurements of specimens and counterfaces. It was found that a significant amount of Fe-rich oxide particles become incorporated into the Al matrix during wear, forming a cracked tribolayer. The wear behavior of Al/Ni3l composite as a function of the applied load was not accurately reflected by the weight loss of worn specimens. Results highlight the role of Ni3Al particles as loadbearing elements due to their excellent bonding to the Al matrix, their interfaces withstanding the wear stresses even at the highest applied load. Moreover, Ni3Al particles limited the incorporation of wear debris to the Al matrix and reduced wear damage occasioned to the steel counterfaces compared to that of pure aluminum specimens.

Díaz, C.; González-Carrasco, J. L.; Caruana, G.; Lieblich, M.

1996-10-01

173

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

174

Thermomechanical response of a powder metallurgy Ti-6Al-4V alloy modified with 2.9 Pct Boron  

NASA Astrophysics Data System (ADS)

The thermomechanical response of Ti-6A1-4V modified with 2.9 pct B produced by a blended powder metallurgy route was studied with isothermal constant strain-rate hot compression tests in the temperature range 850°C to 1200°C and strain rate range 10-3 to 10s-1. Detailed analyses of the flow stress data were conducted to identify various microstructural deformation and damage mechanisms during hot working by applying available materials modeling techniques. In the ?+? phase field, cavitation at the matrix/TiB interfaces and TiB particle fracture occurs at low strain rates (<10-1 s-1), while adiabatic shear banding also occurs at high strain rates. At low strain rates, the ? phase deforms superplastically due to the stabilization of a fine grain size by the TiB particles. Grain boundary and matrix/TiB interface sliding with simultaneous diffusional accommodation are observed to contribute to the ? superplasticity. The deformation behavior at high strain rates in the ?-phase field is similar to that of the ?+? phase field, with microstructural manifestations of extensive cavitation at the matrix/TiB interfaces and TiB particle fracture.

Bhat, Radhakrishna B.; Tamirisakandala, Seshacharyulu; Miracle, Daniel B.; Ravi, Vilupanur A.

2005-03-01

175

Kinetic Analysis of Solid-State Formation of Mg2Si by Powder Metallurgy Process  

NASA Astrophysics Data System (ADS)

The synthesis kinetics of Mg2Si intermetallic compounds (IMC) from the elemental mixture of Mg-Si powders was studied by using differential thermal analysis (DTA). The exothermic peaks were at 818 K, which indicated the synthesis reaction of 2Mg+Si ? Mg2Si. The synthesis kinetics of Mg2Si was evaluated by the Ozawa method and KAS method. The activation energy of Mg2Si was calculated as 376.0 kJ/mol by using the data from DTA curves. The bulky materials of Mg-Mg2Si composite were prepared through solid-state reaction by using SPS consolidation process. From the results of XRD and SEM-EDS analysis, it was known that Mg and Si powders never react completely at low temperatures of 813 K and 833 K, and the suitable temperature of solid-state synthesis by SPS should be about 853 K.

Sun, Bin; Li, Shufeng; Imai, Hisashi; Umeda, Junko; Kondoh, Katsuyoshi

176

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

NASA Technical Reports Server (NTRS)

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

Calhoun, C. D.

1971-01-01

177

Powder metallurgy magnesium composite with magnesium silicide in using rice husk silica particles  

Microsoft Academic Search

By using the solid-state reaction of rice husk silica particles with magnesium powder, P\\/M magnesium based composites dispersed with the magnesium silicide (Mg2Si) and magnesium oxide (MgO) were fabricated. High-purity silica particles were originated from rice husks, one of the major agricultural wastes, via the citric acid leaching treatment and combustion in air. The effects of the silica particle characteristics

Junko Umeda; Katsuyoshi Kondoh; Masashi Kawakami; Hisashi Imai

2009-01-01

178

Influence of texture on the mechanical properties of commercially pure magnesium prepared by powder metallurgy  

Microsoft Academic Search

In the present work the influence of texture on the mechanical properties up to 500 °C of commercially pure magnesium prepared\\u000a by PM was determined. Extrusion of magnesium powders was carried out between 250 and 450 °C. All extruded materials exhibited\\u000a an intense fibre texture with the basal planes parallel to the extrusion direction whose intensity increased in line with\\u000a the

P. Pérez; G. Garcés; P. Adeva

2007-01-01

179

Development of powder metallurgy technique for synthesis of U 3Si 2 dispersoid  

Microsoft Academic Search

The Indian research reactor APSARA, which uses HEU based UAl3 fuel dispersed in aluminium matrix, is to undergo core conversion to LEU based U3Si2 dispersoid in aluminium matrix fuel. Work has been initiated at BARC, to prepare uranium silicide (U3Si2) compound using powder processing route in place of vacuum induction melting or arc melting route. This paper describes the preparation

V. P. Sinha; G. P. Mishra; S. Pal; K. B. Khan; P. V. Hegde; G. J. Prasad

2008-01-01

180

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

181

A compact high-resolution X-ray powder diffractometer  

PubMed Central

A new powder diffractometer operating in transmission mode is described. It can work as a rapid very compact instrument or as a high-resolution instrument, and the sample preparation is simplified. The incident beam optics create pure Cu K?1 radiation, giving rise to peak widths of ?0.1° in 2? in compact form with a sample-to-detector minimum radius of 55?mm, reducing to peak widths of <0.05° in high-resolution mode by increasing the detector radius to 240?mm. The resolution of the diffractometer is shown to be governed by a complex mixture of angular divergence, sample size, diffraction effects and the dimensions of the detector pixels. The data can be collected instantaneously, which combined with trivial sample preparation and no sample alignment, makes it a suitable method for very rapid phase identification. As the detector is moved further from the sample, the angular step from the pixel dimension is reduced and the resolution improves significantly for very detailed studies, including structure determination and analysis of the microstructure. The advantage of this geometry is that the resolution of the diffractometer can be calculated precisely and the instrumental artefacts can be analysed easily without a sample present. The performance is demonstrated with LaB6 and paracetamol, and a critical appraisal of the uncertainties in the measurements is presented. The instantaneous data collection offers possibilities in dynamic experiments.

Fewster, Paul F.; Trout, David R. D.

2013-01-01

182

Densification and crystallization of glass powder compacts during constant heating rate sintering  

Microsoft Academic Search

Heating microscopy was used to study the interaction between the processes of densification and crystallization of glass powder compacts under constant heating rate sintering conditions without the application of external loads. For barium magnesium aluminosilicate (BMAS) glass powder compacts sintered between 800–1100 °C, it has been shown that the relative rates of crystallization and densification can be controlled by changing

A. R. Boccaccini; W. Stumpfe; D. M. R. Taplin; C. B. Ponton

1996-01-01

183

On the influence from punch geometry on the stress distribution at powder compaction  

Microsoft Academic Search

A numerical analysis, using the finite element method, of the mechanical behavior at powder compaction at higher densities was performed. In this investigation the material behavior is modeled using an advanced macroscopic constitutive description initially presented by Brandt and Nilsson [1]. This material model, like many other models describing powder compaction at higher densities, includes a large number of constitutive

Daniel C. Andersson; Per-Lennart Larsson; Alessandro Cadario; Per Lindskog

2010-01-01

184

Oxidation and the Effects of High Temperature Exposures on Notched Fatigue Life of an Advanced Powder Metallurgy Disk Superalloy  

NASA Technical Reports Server (NTRS)

Oxidation and the effects of high temperature exposures on notched fatigue life were considered for a powder metallurgy processed supersolvus heat-treated ME3 disk superalloy. The isothermal static oxidation response at 704 C, 760 C, and 815 C was consistent with other chromia forming nickel-based superalloys: a TiO2-Cr2O3 external oxide formed with a branched Al2O3 internal subscale that extended into a recrystallized - dissolution layer. These surface changes can potentially impact disk durability, making layer growth rates important. Growth of the external scales and dissolution layers followed a cubic rate law, while Al2O3 subscales followed a parabolic rate law. Cr- rich M23C6 carbides at the grain boundaries dissolved to help sustain Cr2O3 growth to depths about 12 times thicker than the scale. The effect of prior exposures was examined through notched low cycle fatigue tests performed to failure in air at 704 C. Prior exposures led to pronounced debits of up to 99 % in fatigue life, where fatigue life decreased inversely with exposure time. Exposures that produced roughly equivalent 1 m thick external scales at the various isotherms showed statistically equivalent fatigue lives, establishing that surface damage drives fatigue debit, not exposure temperature. Fractographic evaluation indicated the failure mode for the pre-exposed specimens involved surface crack initiations that shifted with exposure from predominately single intergranular initiations with transgranular propagation to multi-initiations from the cracked external oxide with intergranular propagation. Weakened grain boundaries at the surface resulting from the M23C6 carbide dissolution are partially responsible for the intergranular cracking. Removing the scale and subscale while leaving a layer where M23C6 carbides were dissolved did not lead to a significant fatigue life improvement, however, also removing the M23C6 carbide dissolution layer led to nearly full recovery of life, with a transgranular initiation typical to that observed in unexposed specimens.

Sudbrack, Chantal K.; Draper, Susan L.; Gorman, Timothy T.; Telesman, Jack; Gab, Timothy P.; Hull, David R.

2012-01-01

185

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

NASA Technical Reports Server (NTRS)

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

Ray, Ranjan; Jha, Sunil C.

1987-01-01

186

Analysis of tablet compaction. I. Characterization of mechanical behavior of powder and powder/tooling friction.  

PubMed

In this first of two articles on the modeling of tablet compaction, the experimental inputs related to the constitutive model of the powder and the powder/tooling friction are determined. The continuum-based analysis of tableting makes use of an elasto-plastic model, which incorporates the elements of yield, plastic flow potential, and hardening, to describe the mechanical behavior of microcrystalline cellulose over the range of densities experienced during tableting. Specifically, a modified Drucker-Prager/cap plasticity model, which includes material parameters such as cohesion, internal friction, and hydrostatic yield pressure that evolve with the internal state variable relative density, was applied. Linear elasticity is assumed with the elastic parameters, Young's modulus, and Poisson's ratio dependent on the relative density. The calibration techniques were developed based on a series of simple mechanical tests including diametrical compression, simple compression, and die compaction using an instrumented die. The friction behavior is measured using an instrumented die and the experimental data are analyzed using the method of differential slices. The constitutive model and frictional properties are essential experimental inputs to the finite element-based model described in the companion article. PMID:15236452

Cunningham, J C; Sinka, I C; Zavaliangos, A

2004-08-01

187

Powder compaction, sintering, and rolling of ultra high molecular weight polyethylene and its composites  

Microsoft Academic Search

The applicability of powder compaction and sintering techniques to the processing of ultra high molecular weight polyethylene (UHMWPE) powder is demonstrated. With proper processing procedure and type of UHMWPE powder, the mechanical properties obtained are nearly equivalent to those obtained by conventional melt processes. The properties were optimized by selection of a sintering temperature just above the melting point and

K. S. Han; J. F. Wallace; R. W. Truss; P. H. Geil

1981-01-01

188

A study on the Cap model for metal and ceramic powder under cold compaction  

Microsoft Academic Search

Densification behavior of various metal and ceramic powder was investigated under cold compaction. The Cap model was proposed by using the parameters involved in the yield function for sintered metal powder and volumetric strain evolution under cold isostatic pressing. The material parameters for ceramic powder were obtained from experimental data under triaxial compression. The Cap model was implemented into a

S. C. Lee; K. T. Kim

2007-01-01

189

Linear shrinkage of metal powder compacts during sintering  

Microsoft Academic Search

The influence exerted by various factors (particle size, particle size distribution, ultrafine powder addition, sintering temperature, etc.) on the linear shrinkage ratio during sintering was examined. Electrolytic, atomized, and ultrafine copper powders, as well as electrolytic iron powder, were used.

H. H. Hausner; O. V. Roman

1965-01-01

190

Microstructural refinement and mechanical properties improvement of elemental powder metallurgy processed Ti46.6Al1.4Mn2Mo alloy by carbon addition  

Microsoft Academic Search

Strengthening of a gamma TiAl alloy was sought by a chemical modification of the composition with carbon. Up to 0.6 at. pct\\u000a of carbon was added to the Ti-46.6Al-1.4Mn-2Mo alloy processed by elemental powder metallurgy. Carbon addition resulted in\\u000a considerable microstructural changes such as refinement, by a factor of about 2, of the lamellar microstructure and carbide\\u000a precipitation. The cause

H. S. Park; S. K. Hwang; C. M. Lee; Y. C. Yoo; S. W. Nam; N. J. Kim

2001-01-01

191

Thermal conductivity of NiAl powder compacts for reaction synthesis  

Microsoft Academic Search

Thermal conductivity of 3Ni–1Al elemental powder compacts was measured using a laser-flash method as a function of temperature, compact density and heat treatment. Temperature dependence of thermal conductivity of the compacts is similar to that of pure Ni and Al metals. Heat treatment has a significant effect on the thermal conductivity of the compacts as particles are joined together to

Seiji Miura; Yoshihiro Terada; Tomoo Suzuki; C. T Liu; Yoshinao Mishima

2000-01-01

192

Effect of compact density on phase transition kinetics from anatase phase to rutile phase during sintering of ultrafine titania powder compacts  

Microsoft Academic Search

The effect of compact density on the phase transition from anatase phase to rutile phase during sintering of ultrafine TiO2 powder compacts has been investigated. The compact densities are varied using different compaction pressures. The shrinkage behaviors of compacts are monitored in situ at the condition of uniform heating rate by dilatometric measurement and subsequently related to the phase transition

Jae-Pyoung Ahn; Jong-Ku Park; Gyeungho Kim

1998-01-01

193

A discrete finite element modelling and measurements for powder compaction  

NASA Astrophysics Data System (ADS)

An experimental investigation into friction between powder and a target surface together with numerical modelling of compaction and friction processes at a micro-scale are presented in this paper. The experimental work explores friction mechanisms by using an extended sliding plate apparatus operating at low load while sliding over a long distance. Tests were conducted for copper and 316 steel with variation in loads, surface finish and its orientation. The behaviours of the static and dynamic friction were identified highlighting the important influence of particle size, particle shape, material response and surface topography. The results also highlighted that under light loading the friction coefficient remains at a level lower than that derived from experiments on equipment having a wider dynamic range and this is attributed to the enhanced sensitivity of the measurement equipment. The results also suggest that friction variation with sliding distance is a consequence of damage, rather than presentation of an uncontaminated target sliding surface. The complete experimental cycle was modelled numerically using a combined discrete and finite element scheme enabling exploration of mechanisms that are defined at the particle level. Using compaction as the starting point, a number of simulation factors and process parameters were investigated. Comparisons were made with previously published work, showing reasonable agreement and the simulations were then used to explore the process response to the range of particle scale factors. Models comprising regular packing of round particles exhibited stiff response with high initial density. Models with random packing were explored and were found to reflect trends that are more closely aligned with experimental observation, including rearrangement, followed by compaction under a regime of elastic then plastic deformation. Numerical modelling of the compaction stage was extended to account for the shearing stage of the extended sliding plate experiment. This allowed micro-scale simulations of the friction mechanisms seen within the experimental programme. The frictional response with similar stress level in the normal direction as reported for the experiment was first emulated and explored and qualitative agreement was achieved showing a similar pattern. The factors identified from the experiments were investigated on smooth and rough surfaces highlighting each effect. It was confirmed that the rough surface clearly leads to higher friction coefficient since it accounts for both plain friction and topographical effects and the average stress distribution increased against the restraining die wall when the rough surface was introduced for the model with round regular packing of particles. Random packed models again showed a better reflection of the experimental conditions. A wider distribution of stress was observed because of the further rearrangements. Interlocking was observed for the models with irregularly shaped particles on a rough surface, which led to an increase in normal stress on the top punch. This would lead to dilation in the case where a punch was force level controlled as for the experiment.

Choi, J. L.; Gethin, D. T.

2009-04-01

194

Modeling of large deformation frictional contact in powder compaction processes  

Microsoft Academic Search

In this paper, the computational aspects of large deformation frictional contact are presented in powder forming processes. The influence of powder–tool friction on the mechanical properties of the final product is investigated in pressing metal powders. A general formulation of continuum model is developed for frictional contact and the computational algorithm is presented for analyzing the phenomena. It is particularly

A. R. Khoei; Sh. Keshavarz; A. R. Khaloo

2008-01-01

195

Effect of Agglomerates in Zr02 Powder Compacts on Microstructural Development.  

National Technical Information Service (NTIS)

Ultrafine zirconia powders were prepared by a coprecipitation and spray-drying method. Agglomerates may be fragmented or present in green bodies after compaction. The effect of agglomerates on sintering and microstructural development was studied and it w...

J. L. Shi J. H. Gao Z. X. Lin D. S. Yan

1994-01-01

196

Optimal design of powder compaction processes via genetic algorithm technique  

Microsoft Academic Search

In this paper, an optimal design is performed for powder die-pressing process based on the genetic algorithm approach. It includes the shape optimization of powder component, the optimal design of punch movements, and the friction optimization of powder–tool interface. The genetic algorithm is employed to perform an optimal design based on a fixed-length vector of design variables. The technique is

A. R. Khoei; Sh. Keshavarz; S. O. R. Biabanaki

2010-01-01

197

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

198

TiNi synthesis from elemental powder components  

Microsoft Academic Search

Commercially, the shape memory alloy TiNi is produced by either vacuum induction melting or by vacuum arc remelting of the pure metal ingots. Powder metallurgy techniques provide an alternative fabrication route but problems arise achieving chemical homogeneity. In this study TiNi compacts were cold pressed from the blended elemental powders and sintered in vacuum for varying times at temperatures from

Janet C. Hey; A. Peter Jardine

1994-01-01

199

Compacting and sintering agglomerated ultradispersed ZrO 2 powders  

Microsoft Academic Search

Method of Investigation. We used powders of composition ZrO 2 + 3%Y203 (molar parts), obtained by the coprecipitation process, using mineral salts of Zr and Y. The density of the powders was measured by the gas (helium) pycnometric method, for which we used the SY-3 apparatus made by the Quantachrom Company (USA). The density of the moldings was determined by

A. V. Galakhov; I. V. Vyazov; V. Ya. Shevchenko

1989-01-01

200

Sintering behavior of bi-modal powder compacts  

Microsoft Academic Search

Time dependent sintering of a compact consisting of two regions which sinter at different rates is analyzed. The analysis combines densification with deviatoric creep, since creep serves to relax the stress concentration produced by incompatible densification. The structure of the bi-modal compact is assumed to consist of a sphere of one type of material embedded in a matrix of the

R. Raj; R. K. Bordia

1984-01-01

201

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

202

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

203

Influence of Thermal Aging on the Microstructure and Mechanical Behavior of Dual-Phase, Precipitation-Hardened, Powder Metallurgy Stainless Steels  

NASA Astrophysics Data System (ADS)

The effects of thermal aging on the microstructure and mechanical behavior of dual-phase, precipitation-hardened, powder metallurgy (PM) stainless steels of varying ferrite-martensite content were examined. Quantitative analyses of the inherent porosity and phase fractions were conducted on the steels, and no significant differences were noted with respect to aging temperature. Tensile strength, yield strength, and elongation to fracture all increased with increasing aging temperature reaching maxima at 811 K (538 °C) in most cases. Increased strength and decreased ductility were observed in steels of higher martensite content. Nanoindentation of the individual microconstituents was employed to obtain a fundamental understanding of the strengthening contributions. Both the ferrite and martensite nanohardness values increased with aging temperature and exhibited similar maxima to the bulk tensile properties.

Stewart, J. L.; Williams, J. J.; Chawla, N.

2012-01-01

204

Cold Compaction of Copper Powders Under Mechanical Vibration and Uniaxial Compression  

NASA Astrophysics Data System (ADS)

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

An, Xizhong; Xing, Zhitao; Jia, Chengchang

2014-04-01

205

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

SciTech Connect

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

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

2000-05-10

206

Strength and electrical conductivity of deformation-processed Cu15 Vol Pct Fe alloys produced by powder metallurgy techniques  

Microsoft Academic Search

Powder metallurgical techniques have been employed to prepare the precursor billets in the preparation of Cu-15 vol pct Fe alloys by deformation processing. It has been demonstrated that by (1) using high-purity gas-atomized Cu powders blended with commercial high-purity Fe powders and (2) controlling the time\\/temperature processing conditions within specific limits, it is possible to produce Cu-Fe deformation-processed alloys with

G. A. Jerman; I. E. Anderson; J. D. Verhoeven

1993-01-01

207

Effect of Magnetic Fields on Explosive Welding of Metals and Explosive Compaction of Powders  

NASA Astrophysics Data System (ADS)

Explosive welding and explosive compaction of powders are new technologies for producing composite materials, which have been actively studied in recent decades. Considerable experience has been accumulated in producing composite materials with new physical properties, and these materials have been widely used in industry. At the same time, these technologies have certain limitations for high-temperature materials. The present research into the influence of magnetic fields on the explosive welding of metals and the explosive compaction of powders seeks to extend the possibilities of the indicated technologies. The results of the first experiments have shown that the use of magnetic fields holds promise for extending the possibilities of material welding and powder compaction.

Shvetsov, G. A.; Mali, V. I.; Bashkatov, Yu. L.; Anisimov, A. G.; Matrosov, A. D.; Teslenko, T. S.

2005-07-01

208

Mechanical properties of partially dense alumina produced from powder compacts  

Microsoft Academic Search

The elastic modulus (E), the critical strain energy release rate (G[sub c]), and the flexural strength ([sigma]) have been determined for two partially dense alumina bodies produced from the same powder but with different initial densities. The mechanical properties were measured for specimens fabricated at four different relative densities. The measured elastic modulus, critical strain energy release rate, and a

David C. C. Lam; Fred F. Lange; Anthony G. Evans

1994-01-01

209

Comparison of various plasticity models for metal powder compaction processes  

Microsoft Academic Search

The computer-based process simulation of powder metal (PM) components requires suitable material model to describe the deformation behavior in order to examine the effects of parametric variation. Over the years, several plasticity models with various yield function coefficients have been proposed (Eq. (2)), but the qualitative performance are, hitherto, unavailable in open literature, to the best of author's knowledge. In

K. Biswas

2005-01-01

210

Creep and densification during sintering of glass powder compacts  

Microsoft Academic Search

The simultaneous creep and densification of glass power compacts was studied as a function of low applied uniaxial stress, temperature, and particle size. The creep rate can be expressed as the sum of the contribution from the applied stress that varies linearly with stress, and a contribution due to anisotropic densification that varies linearly with the densification rate. For a

MOHAMED N. RAHAMAN; LUTGARD C. DE JONGHE; GEORGE W. SCHERER; RICHARD J. BROOK

1987-01-01

211

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

212

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 Güneyisi; Mehmet Geso?lu; Erdo?an Özbay

2009-01-01

213

Dynamic compaction of copper powder: 2D numerical simulation and experimental results  

Microsoft Academic Search

A method for plate-impact dynamic compaction of copper powder has been developped. The optimization of the experimental set-up (impedance adjustments, tensile wave traps, relative thickness of impactor and target,…) is presented.2D axisymetrical numerical simulations have been performed with a Lagrangian finite element code. Geometrical characteristics of the experimental set-up as well as the dynamic response of the powder (Reaugh equation

T. Thomas; P. Bensussan; P. Chartagnac; Y. Bienvenu

1991-01-01

214

Physical properties of a nickel-base alloy prepared by isostatic pressing and sintering of the powdered metal.  

PubMed

The physical and mechanical properties of samples of a nickel-base alloy fabricated by powder metallurgy were determined. The particle sizes of the powders used to make the samples varied from -80/ +200 mesh to -325 mesh. The compaction pressure varied from 138 to 414 MN/m2 and the sintering temperature varied from 1150 to 1250 degrees C. The shrinkage during processing, the porosity, tensile strength, yield strength, elongation, and elastic modulus were used to characterize the samples. The strength of the samples generally increased with decreasing particle size of the powder and increasing compaction pressure and sintering temperatures. The porosity and strength, therefore, could be varied over a wide range by controlling the various parameters. The properties of the samples prepared by powder metallurgy were compared with those of the cast alloy and compact bone. Conditions can be selected that will yield equivalent or better properties by powder metallurgy than by casting. PMID:1066448

Fuys, R A; Craig, R G; Asger, K

1976-04-01

215

Dynamic Compaction Modeling Comparison for Porous Silica Powder  

NASA Astrophysics Data System (ADS)

A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized porous material models, P-lambda and P-alpha, in conjunction with a linear Us-up Hugoniot. Two hydrocodes were used to simulate the compaction event: CTH and KO. CTH is a three-dimensional Eulerian hydrocode developed at Sandia National Laboratory and KO is a one-dimensional Lagrangian hydrocode developed at Lawrence Livermore National Laboratory. A comparison of the advantages and disadvantages, along with a discussion of the salient features, of the two models are presented.

Borg, John; Schwalbe, Larry; Chapman, D. J.; Lloyd, Andrew; Ward, Aaron

2005-07-01

216

Dynamic Compaction Modeling Comparison for Porous Silica Powder  

Microsoft Academic Search

A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized porous material models, P-lambda and P-alpha, in conjunction

John Borg; Larry Schwalbe; D. J. Chapman; Andrew Lloyd; Aaron Ward

2005-01-01

217

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

218

Phase composition, microstructure, and mechanical properties of porous Ti-Nb-Zr alloys prepared by a two-step foaming powder metallurgy method.  

PubMed

Porous Ti-Nb-Zr alloys with different porosities from 6.06 to 62.8% are prepared by a two-step foaming powder metallurgy method using TiH2, Nb, and Zr powders together with 0 to 50wt% of NH4HCO3. The effects of the amounts of Nb and Zr as well as the sintering temperature (1473 to 1673K) on their phase composition, porosity, morphology, and mechanical characteristics are investigated. By controlling the porosity, Nb and Zr concentrations as well as the sintering temperature, porous Ti-Nb-Zr alloys with different mechanical properties can be obtained, for example, the hardness between 290 and 63HV, the compressive strength between 1530.5 and 73.4MPa, and the elastic modulus between 10.8 and 1.2GPa. The mechanical properties of the sintered porous Ti-Nb-Zr alloys can be tailored to match different requirements for the human bones and are thus potentially useful in the hard tissue implants. PMID:24556322

Rao, X; Chu, C L; Zheng, Y Y

2014-06-01

219

Strength and electrical conductivity of deformation-processed Cu15 Vol Pct Fe alloys produced by powder metallurgy techniques  

Microsoft Academic Search

Powder metallurgical techniques have been employed to prepare the precursor billets in the preparation of Cu-15 vol pct Fe\\u000a alloys by deformation processing. It has been demonstrated that by (1) using high-purity gas-atomized Cu powders blended with\\u000a commercial high-purity Fe powders and (2) controlling the time\\/temperature processing conditions within specific limits, it\\u000a is possible to produce Cu-Fe deformation-processed alloys with

G. A. Jerman; I. E. Anderson; J. D. Verhoeven

1993-01-01

220

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

NASA Astrophysics Data System (ADS)

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

Çavdar, U?ur; Atik, Enver

2014-05-01

221

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

NASA Astrophysics Data System (ADS)

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

Çavdar, U?ur; Atik, Enver

2014-06-01

222

Powder Metallurgy of Particle-Reinforced Aluminium Matrix Composites (AMC) by Means of High-Energy Ball Milling  

Microsoft Academic Search

\\u000a This paper deals with the production of aluminium matrix composites through high-energy milling, hot isostatic pressing and\\u000a extrusion. Spherical powder of the aluminium alloy AA2017 (grain fraction > 100 ?m) was used as matrix material. SiC and Al2O3 powders of submicron and micron grain size (< 2 ?m) where chosen as reinforcement particles with contents between 5 and 15 vol.%\\u000a respectively. The high-energy

Daisy Nestler; Steve Siebeck; Harry Podlesak; Swetlana Wagner; Matthias Hockauf; Bernhard Wielage

223

A study on the sensitivity of Drucker–Prager Cap model parameters during the decompression phase of powder compaction simulations  

Microsoft Academic Search

The compaction of pharmaceutical powders can be simulated using phenomenological elasto-plastic continuum models adopted from soil mechanics. These models are typically implemented in finite element codes and have been used recently to investigate the macroscopic property distributions in powders during compaction.The present study demonstrates the importance of obtaining accurate yield surface parameters for use in such models. A commercial finite

Tuhin Sinha; Jennifer S. Curtis; Bruno C. Hancock; Carl Wassgren

2010-01-01

224

Oxidation resistance of powder compacts of the Nb–Si–Cr system and Nb 3Si 5Al 2 matrix compacts prepared by spark plasma sintering  

Microsoft Academic Search

Powder compacts with several different compositions of the Nb–Si–Cr system and Nb3Al2Si5 matrix compacts with a composition of Nb–47Si–20Al (at.%) were prepared by spark plasma sintering. The microstructure, oxidation behavior and mechanical and physical properties of each compact were investigated. Adding more than 10 at.% Cr to NbSi2 compacts greatly improved their poor oxidation resistance at 1023 K. However, the

T Murakami; S Sasaki; K Ichikawa; A Kitahara

2001-01-01

225

Densification and crystallisation behaviour of barium magnesium aluminosilicate glass powder compacts  

Microsoft Academic Search

The densification and crystallisation of barium magnesium aluminosilicate (BMAS) glass powder has been investigated. The aim of the study was to draw conclusions of value for the optimisation of the processing parameters for BMAS matrix ceramic composites. Pressureless sintering and hot-pressing techniques were investigated. The pressureless densification behaviour of cold-uniaxially pressed compacts was determined at isothermal and constant heating rate

K. Lambrinou; O. van der Biest; A. R. Boccaccini; D. M. R. Taplin

1996-01-01

226

Anisotropic shrinkage of barium-magnesium aluminosilicate glass powder compacts during sintering  

Microsoft Academic Search

The shrinkage behaviour of barium-magnesium aluminosilicate glass powder compacts has been measured at isothermal conditions using a heating microscope. The samples showed a varying shrinkage anisotropy during densification at a temperature of 930 °C. This behaviour could not be explained solely on the basis of the pore\\/solid interface orientation during sintering. The experimental values for the shrinkage behaviour are in

A. R. Boccaccini; P. A. Trusty; D. M. R. Taplin

1995-01-01

227

Thermal debinding processing of 316L stainless steel powder injection molding compacts  

Microsoft Academic Search

The process of thermal debinding of injection molded water atomized 316L stainless steel powder compacts was studied in a vacuum and hydrogen atmosphere using a mercury porosimetry and the thermogravimetric analysis method. The vacuum debinding rate was investigated under the conditions of different binder compositions and temperature-increase rates, especially at the low temperature stage. The process of thermal debinding in

Yimin Li; Shaojun Liu; Xuanhui Qu; Baiyun Huang

2003-01-01

228

Sintering Crystalline Solids. II. Experimental Test of Diffusion Models in Powder Compacts  

Microsoft Academic Search

During sintering in alumina powder compacts, the density has been found to increase linearly with the logarithm of time, and the grain size increases with the one-third power of time. Incorporation of the time dependence of grain size increase into latestage bulk diffusion sintering models (from Part I) [R. L. Coble, J. Appl. Phys. 32, 787 (1961)] leads to corrected

R. L. Coble

1961-01-01

229

Pore size distributions calculated from 3-D images of DEM-simulated powder compacts  

Microsoft Academic Search

Numerical methods for determining pore size distributions from 3-D digitized microstructures of plastically compacted powders are presented. The microstructures are generated by simulations using the discrete element method (DEM). Two types of pore size distribution are considered: first, a “chamber” pore size distribution similar to the pore size distribution measured by quantitative metallography, second, a “throat” pore size distribution that

S. M Sweeney; C. L Martin

2003-01-01

230

High-temperature strength of compacted sub-micrometer aluminium powder  

Microsoft Academic Search

Aluminium powders with a mean particle size of around 1?m were compacted by cold isostatic pressing (CIP) and additional forging. The specimens are characterized by hot compression tests, dilatometry and metallography. A 3D interconnected structure of alumina films <5nm in thickness is observed by transmission electron microscopy and field emission gun scanning electron microscopy; it is associated with the natural

C. Poletti; M. Balog; F. Simancik; H. P. Degischer

2010-01-01

231

Elastoplastic finite element model development and validation for low pressure uniaxial compaction of dry cohesive powders  

Microsoft Academic Search

A basic elastoplastic model (modified Cam-clay) was applied to wheat flour, a dry cohesive powder. Five constitutive parameters for the modified Cam-clay model have been previously determined for wheat flour using triaxial tests. To apply the elastoplastic constitutive model, a test cylinder was built that uniaxially compacted the wheat flour under constant axial displacement. Hoop and vertical strains in the

M. A. Tripodi; V. M. Puri; H. B. Manbeck; G. L. Messing

1995-01-01

232

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

233

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.

234

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

Microsoft Academic Search

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

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

2011-01-01

235

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 750°C 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

236

Consolidation processing parameters and alternative processing methods for powder metallurgy Al-Cu-Mg-X-X alloys  

NASA Technical Reports Server (NTRS)

The effects of varying the vacuum degassing parameters on the microstructure and properties of Al-4Cu-1Mg-X-X (X-X = 1.5Li-0.2Zr or 1.5Fe-0.75Ce) alloys processed from either prealloyed (PA) or mechanically alloyed (M) powder, and consolidated by either using sealed aluminum containers or containerless vacuum hot pressing were studied. The consolidated billets were hot extruded to evaluate microstructure and properties. The MA Li-containing alloy did not include Zr, and the MA Fe- and Ce-containing alloy was made from both elemental and partially prealloyed powder. The alloys were vacuum degassed both above and below the solution heat treatment temperature. While vacuum degassing lowered the hydrogen content of these alloys, the range over which the vacuum degassing parameters were varied was not large enough to cause significant changes in degassing efficiency, and the observed variations in the mechanical properties of the heat treated alloys were attributed to varying contributions to strengthening by the sub-structure and the dispersoids. Mechanical alloying increased the strength over that of alloys of similar composition made from PA powder. The inferior properties in the transverse orientation, especially in the Li-containing alloys, suggested deficiencies in degassing. Among all of the alloys processed for this study, the Fe- and Ce-containing alloys made from MA powder possessed better combinations of strength and toughness.

Sankaran, K. K.

1987-01-01

237

Processing and Characterization of Cu-Al-Ni Shape Memory Alloy Strips Prepared from Elemental Powders via a Novel Powder Metallurgy Route  

Microsoft Academic Search

In the present work, Cu-Al-Ni shape memory alloy strips were prepared successfully from premixed elemental Cu, Al, and Ni\\u000a powders in the ratio 82:14:4 (wt pct) by a novel processing route consisting of preparing powder preforms, sintering, and\\u000a unsheathed hot rolling of the sintered preforms. Subsequently, the hot rolled strips were homogenized. The as-rolled strips\\u000a consisted of two phases—? and ??.

Mohit Sharma; Sanjay Kumar Vajpai; Ravindra Kumar Dube

2010-01-01

238

Processing and Characterization of Cu-Al-Ni Shape Memory Alloy Strips Prepared from Elemental Powders via a Novel Powder Metallurgy Route  

Microsoft Academic Search

In the present work, Cu-Al-Ni shape memory alloy strips were prepared successfully from premixed elemental Cu, Al, and Ni powders in the ratio 82:14:4 (wt pct) by a novel processing route consisting of preparing powder preforms, sintering, and unsheathed hot rolling of the sintered preforms. Subsequently, the hot rolled strips were homogenized. The as-rolled strips consisted of two phases--- alpha

Mohit Sharma; Sanjay Kumar Vajpai; Ravindra Kumar Dube

2010-01-01

239

Modelling of the mechanical behaviour of two pure PTFE powders during their compaction at room temperature  

NASA Astrophysics Data System (ADS)

Since PolyTetraFluoroEthylene (PTFE) is not melt processible because of its very high melt viscosity, parts made of this material are generally manufactured by cold compaction of powder material followed by sintering of the green compact. The aim of this study is to identify 3-D constitutive equations suitable for the finite element analysis of PTFE powder compaction. To exhibit the influence of their geometrical aspect on their mechanical behaviour, two pure PTFE resins were tested, viz. a free flowing pelletized resin and a granular fine cut resin. To study the behaviour of these powders during their compaction along different loading paths, a novel triaxial device has been designed and installed on a six-actuator triaxial testing machine. The results obtained for hydrostatic loading were favourably compared with results obtained by isostatic pressing. Various complex loading paths were also investigated. Full 3D elasto-viscoplastic non-associated constitutive equations, viz. a non-linear Drucker-Prager/cap type model, could be identified.

Frédy, Carole; Canto, Rodrigo B.; Schmitt, Nicolas; Roux, Stéphane; Billardon, René

2013-06-01

240

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

SciTech Connect

The suitability of Ni{sub 3}Al intermetallics as reinforcement for Al-base materials for tribological applications has been investigated. For this purpose, an Al/Ni{sub 3}Al (5 vol pct) composite was prepared by powder metallurgy and tested in air against steel counterfaces at the load range of 45 to 178 N. For comparison, unreinforced Al specimens were processed and tested under the same conditions. Tribological behavior was evaluated by microstructural examination of wear-affected zones and weight-loss measurements of specimens and counterfaces. It was found that a significant amount of Fe-rich oxide particles become incorporated into the Al matrix during wear, forming a cracked tribolayer. The wear behavior of Al/Ni{sub 3}Al composite as a function of the applied load was not accurately reflected by the weight loss of worn specimens. Results highlight the role of Ni{sub 3}Al particles as load-bearing elements due to their excellent bonding to the Al matrix, their interfaces withstanding the wear stresses even at the highest applied load. Moreover, Ni{sub 3}Al particles limited the incorporation of wear debris to the Al matrix and reduced wear damage occasioned to the steel counterfaces compared to that of pure aluminum specimens.

Diaz, C.; Gonzalez-Carrasco, J.L.; Caruana, G.; Lieblich, M. [Centro Nacional de Investigaciones Metalurgicas, Madrid (Spain)

1996-10-01

241

The fluid surface shape and capillary phenomena under lowered gravity or weightlessness with application to space materials science (powder metallurgy technology: impregnation, liquid-phase sintering; welding, brazing)  

NASA Astrophysics Data System (ADS)

Some capillary phenomena, shapes of surfaces and menisci of liquids, wetting processes under lowered or zero value of Earth gravitation acceleration (weightlessness) are studied. Theoretically, on the basis of computer integration of classic capillarity equations using previously created programs and varying acceleration g values, and experimentally, modelling weightlessness on the Earth (using small volumes, namely drops of a liquid under lowered gravitation action, or creating interphase boundaries between nonmiscible liquids of equal density), the shape of liquid phases surface (for molten metals) are studied in most typical systems: a drop on a solid surface and liquid meniscus in a cylindrical channel. The experiments concerning to wetting contact angles dependence on gravitation discussed today were carried out (independence of wetting contact angle on value and direction of gravitation vector action is shown). The wetting contact angles in model systems are specially measured also at zero gravitational pressure, which is of basic importance for the theory of capillarity. The results are used in technology of materials brazing, powder metallurgy, in manufacturing of heat pipes porous capillary structures with an eye to implementation of these technologies in space environments (microgravitation).

Naidich, Yu. V.; Gab, I. I.; Evdokimov, V. A.; Kurkova, D. I.; Stetsyuk, T. V.; Grigorenko, N. F.; Chemigovtsev, E. P.; Zhuraviev, V. S.; Krasovsky, V. P.

242

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 MPa·m1/2. 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

243

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

244

The equal channel angular pressing of magnesium and magnesium alloy powders  

NASA Astrophysics Data System (ADS)

Applications for magnesium powders have generally been restricted to the area of pyrotechnology, but with improved safety measures and novel processing technologies there are now more opportunities opening up for magnesium powder metallurgy components. Conventional powder metallurgy involving liquid phase sintering may not be a viable option, however, due to the high reactivity of molten magnesium in air. Solid-state consolidation processes are therefore desirable, with direct powder extrusion and equal channel angular pressing (ECAP) offering real alternatives to the conventional press/sinter routes. With this move toward purely solid-state metallurgy come opportunities for alternative alloy design strategies, potentially leading to microstructures not readily achieved through traditional casting routes. This paper will discuss the suitability of the ECAP route for magnesium powder compaction and explore the novel alloying strategies that become available with the success of these solid-state powder metallurgical processes.

Moss, M.; Lapovok, R.; Bettles, C. J.

2007-08-01

245

Ferrous Metallurgy.  

National Technical Information Service (NTIS)

The article reviews the performance of the ferrous metallurgy industry in 1972. Areas of non-fulfillment of plans and other shortcomings are noted. The program for opening up new metallurgical capacities during 1971 and 1972 was not fulfilled. Last year t...

1973-01-01

246

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

247

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. Gärtner; H. Kreye

2008-01-01

248

Modeling the reaction synthesis of shock-densified titanium-silicon powder mixture compacts  

Microsoft Academic Search

The reaction behavior of shock-consolidated Ti-Si powder mixture compacts, densified at 5 to 7 GPa pressure, was investigated\\u000a to determine conditions required for solid-state reaction synthesis leading to the formation of dense Ti5Si3 intermetallic compounds with fine-grained microstructure. It was observed that at temperatures greater than 1000 C, the\\u000a heat released following reaction initiation in the solid state exceeds the

S. A. Namjoshi; N. N. Thadhani

2000-01-01

249

An Investigation into some Mechanical and Metallurgical Properties of Stainless Steel Reinforced Aluminium Alloy Powder Compacts  

Microsoft Academic Search

An experimental investigation into uniaxial tension and transverse bending of thin rectangular sheets made of stainless steel\\u000a wire mesh and microcable reinforced sintered 6061 aluminium alloy powder compacts was made in order to determine some of their\\u000a mechanical and metallurgical properties. Theoretical predictions based on the rule of mixtures were made for the ultimate\\u000a tensile strength and for the Youngs

N. R. Chitkara; A. Vagionitis

2001-01-01

250

Shock-wave compacting of a Fe-Ni-Al powder mixture and its study  

Microsoft Academic Search

The results are presented which concern measurements of X-ray diffraction spectra, microstructure, temperature dependences\\u000a of the real part of the complex magnetic susceptibility, the elastic modulus, and internal friction of an Fe65Ni23Al12 powder mixture obtained by shock-wave compacting. A series of anomalies of the magnetic and elastic properties have been\\u000a found. It has been assumed that the observed features of

F. Kh. Akopov; V. M. Gabuniya; G. I. Mamniashvili; G. S. Martkoplishvili; G. Sh. Oniashvili; A. V. Peikrishvili; N. M. Chikhradze; I. V. Chkhartishvili

2006-01-01

251

Weak hydrogen bonding interactions influence slip system activity and compaction behavior of pharmaceutical powders.  

PubMed

Markedly different mechanical behavior of powders of polymorphs, cocrystals, hydrate/anhydrate pairs, or structurally similar molecules has been attributed to the presence of active slip planes system in their crystal structures. Presence of slip planes in the crystal lattice allows easier slip under the applied compaction pressure. This allows greater plastic deformation of the powder and results into increased interparticulate bonding area and greater tensile strength of the compacts. Thus, based on this crystallographic feature, tableting performance of the active pharmaceutical ingredients can be predicted. Recently, we encountered a case where larger numbers of C?H···O type interactions across the proposed slip planes hinder the slip and thus resist plastic deformation of the powder under the applied compaction pressure. Hence, attention must be given to these types of interactions while identifying slip planes by visualization method. Generally, slip planes are visualized as flat layers often strengthened by a two-dimensional hydrogen-bonding network within the layers or planes. No hydrogen bonding should exist between these layers to consider them as slip planes. Moreover, one should also check the presence of C?H···O type interactions across these planes. Mercury software provides an option for visualization of these weak hydrogen bonding interactions. Hence, caution must be exercised while selecting appropriate solid form based on this crystallographic feature. PMID:24136007

Khomane, Kailas S; Bansal, Arvind K

2013-12-01

252

A hypoelasto-plastic finite strain simulation of powder compaction processes with density-dependent endochronic model  

Microsoft Academic Search

In this paper, a new approach is developed based on an endochronic density-dependent plasticity model for describing the isothermal deformation behavior of metal powder at low homologous temperature. As large deformations are observed in powder compaction processes, the endochronic constitutive model is presented based on large strain plasticity and an integration scheme is established for the rate constitutive equations. Endochronic

A. R. Khoei; A. Bakhshiani

2004-01-01

253

Effect of iron particle size on the diffusion bonding of Fe–5%Cu powder compact to wrought carbon steels  

Microsoft Academic Search

In the present work, diffusion bonding of Fe–5%Cu powder compact to wrought carbon steels was studied. Effects of iron particle size and carbon content of the solid component on the bond strength, which is the maximum shear stress required to obtain separation at the interface, were investigated. Atomized iron powders with the mean particle size of 36, 56, 90, 106,

M. G. Fillabi; A. Simchi; A. H. Kokabi

2008-01-01

254

The effect of limestone powder, fly ash and silica fume on the properties of self-compacting repair mortars  

Microsoft Academic Search

Self-compacting repair mortars (SCRM) are preferred for the rehabil- itation and repair of reinforced concrete structures especially at narrow mould sys- tems. Self compactability and stability are susceptible to ternary effects of chemical and mineral admixture type and their content. In this study, the effect of limestone powder (LP) on the properties of SCRM has been compared with other mineral

255

3D computational modeling of powder compaction processes using a three-invariant hardening cap plasticity model  

Microsoft Academic Search

In this paper, a three-invariant cap plasticity is developed for description of powder behavior under cold compaction process. The constitutive elasto-plastic matrix and its components are derived as the nonlinear functions of powder relative density. Different aspects of 2D and 3D cap plasticity models are illustrated and the procedure for determination of powder parameters is described. It is shown how

A. R. Azami; A. R. Khoei

2006-01-01

256

The effect of wall friction in the compaction of pharmaceutical tablets with curved faces: a validation study of the Drucker–Prager Cap model  

Microsoft Academic Search

The compaction of porous materials can be modelled using micromechanical or phenomenological approaches. The micromechanical models are developed for either dense random packings or near fully dense ductile materials. Phenomenological models have been developed to describe the response of the material over a range of relative densities encountered in powder metallurgy, ceramics or composites industries. Pharmaceutical powders are particular in

I. C Sinka; J. C Cunningham; A Zavaliangos

2003-01-01

257

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

258

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

259

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

260

Dynamic compaction of powders by an oblique detonation wave in the cylindrical configuration  

SciTech Connect

A new method has been applied to dynamically compact ceramic powders in the cylindrical configuration. In this method, a converging oblique detonation is used instead of the sliding detonation used in the standard method. The oblique detonation is generated by a configuration using two explosive layers. X-ray flash photographs have been made that show the detonation and shock fronts in both the standard and new configuration. In the present article, the shock wave and particle velocities in the B{sub 4}C powder have been calculated using the shock and detonation angles obtained from the photographs in combination with the measured detonation velocity. In the two-layer configuration, the pressure applied to the powder was increased by a factor of 3.5 compared to the one-layer configuration, in agreement with calculations. The working principle of the two-layer configuration is discussed and compared with a computer simulation of the process. {copyright} {ital 1997 American Institute of Physics.}

Carton, E.P. [TNO-Prins Maurits Laboratory, Post Office Box 45, 2280 AA, Rijswijk (The Netherlands)] [TNO-Prins Maurits Laboratory, Post Office Box 45, 2280 AA, Rijswijk (The Netherlands); [Laboratory for Applied Inorganic Chemistry, Delft University of Technology, Post Office Box 5045, 2600 GA, Delft (The Netherlands); Verbeek, H.J.; Stuivinga, M. [TNO-Prins Maurits Laboratory, Post Office Box 45, 2280 AA, Rijswijk (The Netherlands)] [TNO-Prins Maurits Laboratory, Post Office Box 45, 2280 AA, Rijswijk (The Netherlands); Schoonman, J. [Laboratory for Applied Inorganic Chemistry, Delft University of Technology, Post Office Box 5045, 2600 GA, Delft (The Netherlands)] [Laboratory for Applied Inorganic Chemistry, Delft University of Technology, Post Office Box 5045, 2600 GA, Delft (The Netherlands)

1997-04-01

261

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

262

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.; Gärtner, F.; Kreye, H.

2008-03-01

263

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

264

The effect of limestone powder, fly ash and silica fume on the properties of self-compacting repair mortars  

Microsoft Academic Search

Self-compacting repair mortars (SCRM) are preferred for the rehabilitation and repair of reinforced concrete structures especially\\u000a at narrow mould systems. Self compactability and stability are susceptible to ternary effects of chemical and mineral admixture\\u000a type and their content. In this study, the effect of limestone powder (LP) on the properties of SCRM has been compared with\\u000a other mineral additives (silica

Selçuk Türkel; Yi?it Altunta?

2009-01-01

265

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

Microsoft Academic Search

The present work deals with the preparation of near-full density Cu-Al-Ni shape memory alloy (SMA) strips from argon-atomized\\u000a prealloyed powder via a powder metallurgy (PM) route comprising cold die compaction to prepare powder preforms, sintering, and hot densification\\u000a rolling of unsheathed sintered powder preforms under protective atmosphere at 1273 K (1000 °C). It has been shown that argon-atomized\\u000a spherical Cu-Al-Ni SMA powder

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

266

Syntheses of full-density nanocrystalline titanium nitride compacts by plasma-activated sintering of mechanically reacted powder  

NASA Astrophysics Data System (ADS)

Nearly equiatomic nanocrystalline titanium nitride (Ti56N44) powder with an average grain size of 5 nm has been synthesized by ball milling elemental Ti powder under nitrogen gas flow at room temperature. During the first stage of reactive ball milling (RBM) (time <3.6 ks), the metallic Ti powder tends to agglomerate to form powder particles with a larger diameter. At the second stage (3.6 to 22.0 ks), the agglomerated particles of Ti fragment to form smaller particles. These smaller particles that have new or fresh surfaces begin to react with the milling atmosphere (nitrogen) during the third stage of milling (22 to 86 ks) to form TiN powder coexisting with unreacted Ti powder. Toward the end of milling (86 to 173 ks), a single phase of nanocrystalline TiN (NaCl structure) is obtained. The powder of this end-product has a spherical-like morphology with an average particle size of about 0.4 ?m diameter. A sintering procedure using plasma activation has been employed to consolidate the powder particles at several stages of the RBM. The as-milled and as-consolidated powders have been characterized as a function of the RBM time by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical metallography, and chemical analyses. Density measurements of the consolidated samples show that after 86 to 173 ks of the RBM time, the compacted samples are essentially fully dense (above 96 pct of the theoretical density for TiN). The results also show that the consolidated TiN compacts still maintain their unique nanocrystalline properties with an average grain size of about 65 nm. The hardness and some mechanical properties of the consolidated TiN compacts have been determined as a function of the RBM time.

Sherif El-Eskandarany, M.; Omori, M.; Hirai, T.; Konno, T. J.; Sumiyama, K.; Suzuki, K.

1998-07-01

267

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

268

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

269

The genetic algorithm approach for shape optimization of powder compaction processes considering contact friction and cap plasticity models  

Microsoft Academic Search

Purpose – The purpose of this paper is to present a shape optimization technique for powder forming processes based on the genetic algorithm approach. The genetic algorithm is employed to optimize the geometry of component based on a fixed-length vector of design variables representing the changes in nodal coordinates. The technique is used to obtain the desired optimal compacted component

A. R. Khoei; Sh. Keshavarz; A. R. Khaloo

2010-01-01

270

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

271

Effect of isothermal forging on microstructure and fatigue behavior of blended elemental Ti-6Al-4V powder compacts  

NASA Astrophysics Data System (ADS)

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 were 99 pct dense while the EP compacts were only 92 pct dense. All sintered preforms were isothermally hot forged below the beta transus temperature and reached almost full density. The microstructure of the HP forged compacts consisted of fine equiaxed alpha, while the EP forged compacts exhibited a coarse lenticular alpha structure after 30 pct reduction and a partially recrystallized structure after 68 pct reduction. It was found that EP compacts forged to a 30 pct reduction exhibited a low fatigue limit of 172 MPa (25 ksi), since the lenticular alpha morphology and the residual porosity resulted in premature fatigue crack initiation. On the other hand, a higher fatigue strength of 485 MPa (70 ksi) was obtained for EP compacts forged to a 78 pct reduction due to the mixed equiaxed/lenticular alpha morphology as well as removal of stress concentration features such as interparticle pore interfaces.

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

1986-03-01

272

Compaction of TiH sub 1. 65 /KClO sub 4 pyrotechnic powder during confined burn  

SciTech Connect

The burning behavior of titanium subhydride potassium perchlorate (TiH{sub 1.65}/KClO{sub 4}) is currently under investigation. The research is presently aimed at studying the dynamic compaction of the material as a confined cylindrical charge of the pyrotechnic burns. Flash radiography equipment, optical fibers, and piezoelectric pressure transducers are used to study this phenomenon. The length to diameter ratio of the test charge is thirty and it is pressed in increments, which have a length to diameter ratio of one, into a cylindrical fixture consisting of an epoxy liner in a stainless steel housing. The housing has a series of radial holes to allow optical monitoring, through the transparent liner, of the ignition-front. Lead disks, placed between increments of powder, serve as x-ray tracers. Three 300 kilovolt x-ray heads are pulsed during each experiment, providing information regarding the state of compaction of the powder at three different times during the burn. Fiber optics are used to monitor the location of the ignition front. Pressure transducers monitor the pressure history inside the closed bomb. Tests have been performed with the powder at different initial densities and the data indicate that a significant amount of compaction occurs as the charge burns. 7 refs., 6 figs.

Hingorani-Norenberg, S.L. (Sandia National Labs., Albuquerque, NM (USA)); Razani, A.; Shahinpoor, M. (New Mexico Univ., Albuquerque, NM (USA). Dept. of Mechanical Engineering)

1990-01-01

273

Components of the core losses under low frequency magnetic field of the bulk Ni-Fe compacted powder material  

NASA Astrophysics Data System (ADS)

Permalloy is the name of nickel-iron alloys, which after heat treatment have an initial permeability much larger than that one of pure iron and are produced usually in the form of thin sheet. Therefore it is logical to attempt to prepare such material in more "bulk" form, for example in the form of a cylinder or a ring, which would be more convenient for some industrial applications. The aim of this work was to investigate the influence of the powder size on ac and dc magnetic properties of the bulk samples prepared by a hot compaction of the powder. By analysis of the contributions of the hysteresis losses, the eddy current losses and the anomalous losses to the core losses we obtained that the fraction of all contributions strongly depends on the particle size of the powder used for preparation of the bulk material.

Olekšáková, Denisa; Füzer, Ján; Kollár, Peter; Roth, S.

2013-05-01

274

Sintering behaviour improvement of a low Cr–Mo prealloyed powder steel through Mn additions and others liquid phase promoters  

Microsoft Academic Search

Although its good hardenability, chromium has being avoided in powder metallurgy (PM) steels because of its high oxygen affinity and difficulties in sintering. For this purpose, a prealloyed iron powder Fe–3Cr–0.5Mo Astaloy CrM® grade, with different carbon content and some alloying elements additions have been studied. Mixtures were uniaxially compacted at 700MPa. Sintering process was carried out at 1120° in

M Campos; D Sanchez; J. M Torralba

2003-01-01

275

Magnetic cosserat continuum theory to simulate behavior of magnetic powder during compaction in applied magnetic field  

Microsoft Academic Search

Numerical method based on the Cosserat continuum theory is proposed for simulating behavior of a magnetic powder in an applied\\u000a magnetic field. The Maxwell stress is induced in the magnetic powder. During powder forming process in the magnetic field,\\u000a the magnetic particles are thus rotated and transferred by both mechanical and magnetic interaction. To simulate such powder\\u000a behavior, we formulate

Hidetoshi Kotera; Muneo Sawada; Susumu Shima

1998-01-01

276

Use of Cation Exchange Resins for Production of UâOâ Suitable for the Al-UâOâ Powder Metallurgy Process  

Microsoft Academic Search

This report describes the production of UâOâ 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.

2001-01-01

277

Compaction behavior of rapidly solidified Al-Si-Fe-Cr alloy powders  

Microsoft Academic Search

Recently, the powder forging process of rapidly solidified Al alloys was investigated in order to develop an inexpensive alternative process to produce high strength parts with complex shapes. It has been shown that the mechanical properties of powder-forged parts are as good as those produced by extrusion. In this study, the consolidation behaviors of rapidly solidified Al-Si-Fe-Cr alloy powders with

Hyoung Seop Kin; Sun Jae Kim; Hong Ro Lee; Chang Whan Won; seong Seock Cho; Byung Sun Chun

1997-01-01

278

Equal channel angular extrusion compaction of semi-amorphous Al 85Ni 10Y 2.5La 2.5 alloy powder  

Microsoft Academic Search

Al85Ni10Y2.5La2.5 alloy powder produced by gas atomization was compacted using equal channel angular extrusion (ECAE). The powder particle size was below 40 ?m (?325 mesh grade), the powder was partially (?60%) amorphous and it contained intermetallic phases. Differential scanning calorimetry showed that crystallization of the amorphous phase starts at about 220°C by precipitation of Al-based f.c.c. particles and continues at

O. N Senkov; D. B Miracle; J. M Scott; S. V Senkova

2004-01-01

279

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

Microsoft Academic Search

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

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

2006-01-01

280

The powder flow and compact mechanical properties of sucrose and three high-intensity sweeteners used in chewable tablets.  

PubMed

The physical, flow, and mechanical properties of four common pharmaceutical sweeteners were measured to assess their relative manufacturability in solid dosage formulations. Sucrose, acesulfame potassium (Sunett), saccharin sodium, and aspartame were evaluated to determine significant differences in particle shape, size distribution, and true density. Powder flow and cohesivity as well as compact mechanical properties such as ductility, elasticity, and tensile strength were measured and found to be noticeably different. Among these sweeteners, sucrose and acesulfame potassium demonstrated excellent flowability and marginal mechanical property performance relative to over 100 commonly used pharmaceutical excipients evaluated in the authors' laboratory. Saccharin sodium and aspartame demonstrated poor flowability and superior compact strength relative to sucrose and acesulfame, despite their noticeably higher brittleness. These data suggest that careful selection of an appropriate sweetener is warranted in obtaining desirable process and tableting robustness, particularly if sweetener loading is high. Detailed descriptions of each material property and recommendations for sweetener selection in formulation development are included. PMID:12711177

Mullarney, Matthew P; Hancock, Bruno C; Carlson, Glenn T; Ladipo, Dauda D; Langdon, Beth A

2003-05-12

281

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

282

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

283

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

284

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

285

Use of limestone powder during incorporation of Pb-containing cathode ray tube waste in self-compacting concrete.  

PubMed

For several decades, cathode ray tubes (CRTs) were the primary display component of televisions and computers. The CRT glass envelope contains sufficient levels of lead oxide (PbO) to be considered hazardous, and there is a need for effective methods of permanently encapsulating this material during waste disposal. We examined the effect of adding limestone powder (LS) on the fresh and cured properties of self-compacting concrete (SCC) mixtures containing waste CRT glass. The SCC mixtures were prepared using Type 1 Portland cement at a constant cement content of 600 kg/m(3) and a water-to-cement ratio (w/c) of 0.38. CRT glass waste cullet was blended with river sand in proportions of 20 or 40% by weight. To suppress potential viscosity effects limestone powder was added at levels of 5, 10, or 15% by weight. The slump flow time, slump flow diameter, V-funnel flow time, Marsh cone flow time, and setting time of the fresh concrete were tested, as well as the compressive strength and ultrasonic pulse velocity of the hardened concrete. Addition of limestone powder improved the fresh and hardened properties. Pb leaching levels from the cured concrete were within US EPA allowable limits. PMID:23892134

Sua-iam, Gritsada; Makul, Natt

2013-10-15

286

Piezochromic phenomena of nanometer voids formed by mono-dispersed nanometer powders compacting process.  

PubMed

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 0.1-10 GPa. This research work focused on unique piezochromism responses of the nanometer voids formed by the 5-20 nm inorganic ISOH nanometer powders. It was discovered that microstructures of the nanometer voids could change color at very low pressures of only 0.002-0.01 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. PMID:24115999

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

2013-01-01

287

Powder processing for the fabrication of SiâNâ ceramics. 1: Influence of spray-dried granule strength on pore size distribution in green compacts  

Microsoft Academic Search

The effect of spray-dried granule strength on the microstructure of green compacts obtained by isostatic pressing was quantitatively analyzed. The fracture strength of single granules of SiâNâ powder made with ultrafine AlâOâ and YâOâ powders was measured directly by diametral compression. It was found that fracture strength increased notably with the increasing relative density of the granule and the decreasing

Hidehiro Kamiya; Kenji Isomura; Genji Jimbo; Tsubaki Jun-ichiro

1995-01-01

288

Metallurgy and properties of plasma spray formed materials  

NASA Technical Reports Server (NTRS)

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

289

SANS study of microstructural inhomogeneities on Al nano-powder compacts  

Microsoft Academic Search

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

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

2004-01-01

290

ON THERMAL CONDUCTIVITY OF POROUS MATERIALS: COMPACTED COLD-PRESSED ZINC OXIDE AND CHARCOAL POWDERS  

Microsoft Academic Search

A semi-absolute steady-state method is applied to measure the thermal conductivity of powder material, manufactured in the form of small discs having different porosities, within the technically possible porosity range (50–70%). The results show that heat-transfer through porous materials depends on the porosity and on other factors. These results are represented by a family of curves, which tend to converge

M. I. ISMAIL; I. I. SHERIF; A. S. A. AMMAR; S. A. EL-MESSIH

1984-01-01

291

Titanium Sheet Production from Commercial Powder.  

National Technical Information Service (NTIS)

Powder metallurgy titanium sheet was produced from hydride dehydride (HDH) powder using a diverse industrial supply chain. Three different processing routes were developed and production protocols were established in each route to provide options for manu...

D. Harper T. R. Muth W. Chen W. H. Peter Y. Yamamoto

2013-01-01

292

Effect of the variation in the ambient moisture on the compaction behavior of powder undergoing roller-compaction and on the characteristics of tablets produced from the post-milled granules.  

PubMed

Effect of variation in the ambient moisture levels on the compaction behavior of a 10% acetaminophen (APAP) powder blend in microcrystalline cellulose (MCC) powder was studied by comparing the physical and mechanical properties of ribbons prepared by roller compaction with those of simulated ribbons, i.e., tablets prepared under uni-axial compression. Relative density, moisture content, tensile strength, and Young's modulus were used as key compact properties for comparison. Moisture was found to facilitate the particle rearrangement of both, the APAP and the MCC particles, as well as the deformation of the MCC particles. The tensile strength of the simulated ribbons also showed an increase with increasing moisture content. An interesting observation was that the tensile strength of the roller compacted samples first increased and then decreased with increasing moisture content. Variation in the ambient moisture during roller compaction was also found to influence the characteristics of tablets produced from the granules obtained post-milling the ribbons. A method to study this influence is also reported. PMID:16136545

Gupta, Abhay; Peck, Garnet E; Miller, Ronald W; Morris, Kenneth R

2005-10-01

293

Syntheses of full-density nanocrystalline titanium nitride compacts by plasma-activated sintering of mechanically reacted powder  

Microsoft Academic Search

Nearly equiatomic nanocrystalline titanium nitride (Ti56N44) powder with an average grain size of 5 nm has been synthesized by ball milling elemental Ti powder under nitrogen gas flow\\u000a at room temperature. During the first stage of reactive ball milling (RBM) (time <3.6 ks), the metallic Ti powder tends to\\u000a agglomerate to form powder particles with a larger diameter. At the

M. Sherif El-Eskandarany; M. Omori; T. Hirai; T. J. Konno; K. Sumiyama; K. Suzuki

1998-01-01

294

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

295

Properties of an atomized iron powder  

Microsoft Academic Search

ction Association by atomization of molten EP-612 steel with water under a pressure of 40 atm gauge [2] and two reduced iron powders - Brovary Powder Metallurgy Factory PZh4M2 powder and Hoeganaes NC 100.24 powder, in addition, a similar study was made of specially prepared atomized powders having particle-size distributions corresponding to those of PZh4M2 and NC 100.24 powders. By

A. E. Kushchevskii; A. T. Pekarik; O. S. Nichiporenko; A. B. Medvedovskii

1978-01-01

296

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

297

Agglomeration of a model food powder: Effect of maltodextrin and gum Arabic dispersions on flow behavior and compacted mass  

Microsoft Academic Search

The process of agglomeration of particulate foods was studied by employing corn starch as a model system. The effect of different liquid binders (maltodextrin and gum Arabic) to the extent of 1–5% was used to study the changes in the characteristics of the powder. Rheological behavior of powder was quantified in terms of textural indices like maximum force, and energy

Sudeep Ghosal; T. N. Indira; Suvendu Bhattacharya

2010-01-01

298

Numerical Modeling of the Compaction of Powder Articles of Complex Shape in Rigid Dies: Effect of Pressing Method on Density Distribution. 1. Mechanical Model of Powder Densification  

Microsoft Academic Search

A theory of plasticity of a porous body was formulated taking into account the specifics of powder behavior under pressing. The proposed model of the material under compression is one-parameter with all functions depending on the current density. In order to determine the parameters of the model, use was made of the equilibrium density attained during the compression of an

Mikhail B. Shtern; Oleg V. Mikhailov

2002-01-01

299

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

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

300

Modeling the uniaxial compaction of pharmaceutical powders using the mechanical properties of single crystals. I: Ductile materials.  

PubMed

A model is presented which uses the Vickers microindentation hardness of ductile crystals such as sodium chloride to predict the uniaxial compaction behavior of compacts. A general approach first developed in the materials science field to predict the densification of particulate matter under hydrostatic loading was followed. However, modifications to account for the effects of particle geometry and the closed-die loading conditions were considered. Using the standard microindentation hardness value of sodium chloride, the model predicted the densification behavior of this material at a punch displacement rate of 1 mm/min. Densification at higher compaction rates was predicted by considering the effect of deformation kinetics on the hardness. Secondary factors which affect compaction, such as particle size effects and die-wall friction, are also briefly discussed. PMID:2324963

Duncan-Hewitt, W C; Weatherly, G C

1990-02-01

301

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 23°C is roughly the same as that of plastics such as

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

2007-01-01

302

Production and consumption of aluminum powders (review)  

Microsoft Academic Search

UDC 621.762 The prod, ration of powder products of aluminum and its alloys (medium and very fine powders, pastes, granules) is one of the fastest growing areas of international aluminum metallurgy. In terms of volume of production, the output of aluminum powders and pastes is second after iron powders. World pro~iuction of powder aluminum products annually during the period 1993-1996

O. S. Nichiporenko

1997-01-01

303

Steric stabilization of nonaqueous silicon slips. I - Control of particle agglomeration and packing. II - Pressure casting of powder compacts  

NASA Technical Reports Server (NTRS)

The application of steric stabilization to control particle agglomeration and packing of silicon powder in benzene and trichloroethylene is reported. The results provide useful guidelines for controlling unfavorable particle-particle interactions during nonaqueous processing of silicon-based ceramic materials. The application of steric stabilization to the control and improvement of green processing of nonaqueous silicon slips in pressure consolidation is also demonstrated.

Kerkar, Awdhoot V.; Henderson, Robert J. M.; Feke, Donald L.

1990-01-01

304

Analysis of powdered tungsten carbide hard-metal precursors and cemented compact tungsten carbides using laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS) has been applied to the direct analysis of powdered tungsten carbide hard-metal precursors and cemented tungsten carbides. The aim of this work was to examine the possibility of quantitative determination of the niobium, titanium, tantalum and cobalt. The investigated samples were in the form of pellets, pressed with and without binder (powdered silver) and in the form of cemented tungsten carbides. The pellets were prepared by pressing the powdered material in a hydraulic press. Cemented tungsten carbides were embedded in resin for easier manipulation. Several lasers and detection systems were utilized. The Nd:YAG laser working at a basic wavelength of 1064 nm and fourth-harmonic frequency of 266 nm with a gated photomultiplier or ICCD detector HORIBA JY was used for the determination of niobium which was chosen as a model element. Different types of surrounding gases (air, He, Ar) were investigated for analysis. The ICCD detector DICAM PRO with Mechelle 7500 spectrometer with ArF laser (193 nm) and KrF laser (248 nm) were employed for the determination of niobium, titanium, tantalum and cobalt in samples under air atmosphere. Good calibration curves were obtained for Nb, Ti, and Ta (coefficients of determination r2 > 0.96). Acceptable calibration curves were acquired for the determination of cobalt (coefficient of determination r2 = 0.7994) but only for the cemented samples. In the case of powdered carbide precursors, the calibration for cobalt was found to be problematic.

Novotný, K.; Sta?ková, A.; Häkkänen, H.; Korppi-Tommola, J.; Otruba, V.; Kanický, V.

2007-12-01

305

Laws of vibrational compaction of difficultly deformable powder materials: 1. Theory of dynamical behavior of unbonded granular media  

Microsoft Academic Search

A model is proposed to describe the behavior of an arbitrarily loaded granular medium. The model is based on known results of the theory of irreversible deformation of self-poured media, and the kinetic theory of dense gases. The model is used to describe the process of vibrational compaction.

Yu. A. Ivlev; A. L. Maksimenko; P. P. Malyushevskii; E. K. Miroshnichenko

1996-01-01

306

Mechanical Behavior of Powder Particle on the Applied Vibration  

Microsoft Academic Search

Powder is the popular state of material for the many parts of industries. In the powder metallurgy, it is important to know the powder behavior under applied stress for the accurate design and good quality assurance. But the mechanical behaviors of it has not been well known. We consider this is from the difficulty of handling powder numerically. To investigate

Shigeyuki Tamura; Tatsuhiko Aizawa; Junji Kihara

1993-01-01

307

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

308

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

309

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

310

Compaction of TiH sub 1. 65 \\/KClO sub 4 pyrotechnic powder during confined burn  

Microsoft Academic Search

The burning behavior of titanium subhydride potassium perchlorate (TiH{sub 1.65}\\/KClOâ) is currently under investigation. The research is presently aimed at studying the dynamic compaction of the material as a confined cylindrical charge of the pyrotechnic burns. Flash radiography equipment, optical fibers, and piezoelectric pressure transducers are used to study this phenomenon. The length to diameter ratio of the test charge

S. L. Hingorani-Norenberg; A. Razani; M. Shahinpoor

1990-01-01

311

Modeling the uniaxial compaction of pharmaceutical powders using the mechanical properties of single crystals. II: Brittle materials.  

PubMed

A model is presented which uses the hardness and elastic moduli of brittle crystals, determined using the Vickers microindentation test, to predict the uniaxial compaction behavior of compacts. A general approach first developed in the materials science field to predict the densification of particulate matter under hydrostatic loading was followed. Modifications to account for the effects of particle geometry and the closed-die loading conditions were considered. The model predicted the densification behavior of sucrose and adipic acid. It did not predict the densification of acetaminophen as well; however, the discrepancy between the experimental and predicted values may arise either from error associated with the evaluation of the elastic modulus using the microindentation test or from error in calculating the relative density of compacts which were observed to have partially laminated. The effects of error both in the hardness value and in the ratio of punch to die-wall stress on the predictive capability of the model were also discussed briefly. PMID:2338639

Duncan-Hewitt, W C; Weatherly, G C

1990-03-01

312

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

313

Development of a Power Metallurgy Superalloy for Use at 1800-2000 F (980-1090 C).  

National Technical Information Service (NTIS)

A program was conducted to develop a powder metallurgy nickel-base superalloy for 1800-2000 F (980-1090 C) temperature applications. The feasibility of a unique concept for alloying carbon into a superalloy powder matrix and achieving both grain growth an...

C. S. Kortovich

1973-01-01

314

Powder processing and properties of zircon-reinforced Al13.5Si2.5Mg alloy composites  

Microsoft Academic Search

Zircon, ZrSiO4, is a thermally stable mineral requiring expensive and energy-intensive process to reduce. Owing to its abundance, high hardness,\\u000a excellent abrasion\\/wear resistance, and low coefficient of thermal expansion, a low-cost alternative use of the mineral for\\u000a medium-strength tribology was investigated. The present study has developed a conventional low-cost, double-compaction powder\\u000a metallurgy route in the synthesis of Al-13.5Si-2.5Mg alloy reinforced

J. U. Ejiofor; B. A. Okorie; R. G. Reddy

1997-01-01

315

Powder processing and properties of zircon-reinforced Al13.5Si2.5Mg alloy composites  

Microsoft Academic Search

Zircon, ZrSiO4, is a thermally stable mineral requiring expensive and energy-intensive process to reduce. Owing to its abundance, high hardness, excellent abrasion\\/wear resistance, and low coefficient of thermal expansion, a low-cost alternative use of the mineral for medium-strength tribology was investigated. The present study has developed a conventional low-cost, double-compaction powder metallurgy route in the synthesis of Al-13.5Si-2.5Mg alloy reinforced

J. U. Ejiofo; B. A. Okorie; R. G. Reddy

1997-01-01

316

Experimental Equipment for Powder Processing.  

National Technical Information Service (NTIS)

To increasing the safety factor of the space vehicles, Perspirable Skin, a new designed Thermal Protection System (TPS) was proposed by bio-mimicking the process of human sweating. Powder Metallurgy (P/M) was considered to be the best candidate method to ...

P. Kwon

2009-01-01

317

Infiltration Kinetics of Aluminum in Silicon Carbide Compacts.  

National Technical Information Service (NTIS)

Although metal matrix composites have been fabricated by various techniques, the most successful are solid state processes such as powder metallurgy and diffusion bonding. Liquid metal processes such as compucasting, pultrusion, and infiltration, while le...

G. R. Edwards D. L. Olson

1987-01-01

318

SHS metallurgy of nickel-based alloying compositions for the manufacture of high-temperature steels  

NASA Astrophysics Data System (ADS)

The possibility of producing multicomponent master alloys with low-melting-point (Mg) and refractory (Ni, Mo, W) metals, which are used for the manufacture of high-temperature alloys in metallurgy, by SHS metallurgy is studied. The experiments are performed at a high inert gas pressure in a reactor. Highly exothermic powder mixtures of nickel oxide, molybdenum, tungsten, elementary magnesium, and elementary aluminum are used for synthesis. The experimental results demonstrate a strong effect of the ratio of the reagent masses, the gas pressure, and the magnesium and aluminum particle sizes on the laws of synthesis and the formation of the composition and microstructure of the end products.

Miloserdov, P. A.; Gorshkov, V. A.; Yukhvid, V. I.

2013-09-01

319

The Rules of Ferrous Metallurgy  

PubMed Central

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

2010-01-01

320

The equal channel angular pressing of magnesium and magnesium alloy powders  

Microsoft Academic Search

Applications for magnesium powders have generally been restricted to the area of pyrotechnology, but with improved safety\\u000a measures and novel processing technologies there are now more opportunities opening up for magnesium powder metallurgy components.\\u000a Conventional powder metallurgy involving liquid phase sintering may not be a viable option, however, due to the high reactivity\\u000a of molten magnesium in air. Solid-state consolidation

M. Moss; R. Lapovok; C. J. Bettles

2007-01-01

321

Microstructure, mechanical properties and oxidation behavior of Nb–Si–Al and Nb–Si–N powder compacts prepared by spark plasma sintering  

Microsoft Academic Search

First tentative Nb–Si–Al and Nb–Si–N ternary phase diagrams were constructed by investigating microstructures of spark plasma sintered compacts of these systems. The microstructure, mechanical properties and oxidation behavior of compacts with some different compositions in the two systems were then examined. Nb3Si5Al2 matrix compact showed extremely good oxidation resistance at 1573 K, although the compact showed poor oxidation resistance at

T. Murakami; S. Sasaki; K. Ichikawa; A. Kitahara

2001-01-01

322

Combustibility of titanium powders  

NASA Technical Reports Server (NTRS)

The combustion of compact samples was studied; the mechanism of autoignition is defined. Several studies are made of the combustibility of titanium using 50 samples. The data provide a clear idea of the combustibility of titanium powders.

Popov, Ye. I.; Poyarkov, V. G.; Finayev, Yu. A.

1989-01-01

323

Nonferrous Metallurgy, 1963, Vol. 6, No. 2.  

National Technical Information Service (NTIS)

Reports of Russian research on nonferrous metallurgy are presented. Topics include: (1) multiface drilling; (2) power engineering by multispeed squirrel-cage motors; (3) high speed flotation; (4) ore classification; (5) flotational properties of columbite...

1964-01-01

324

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

National Technical Information Service (NTIS)

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) extru...

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

1990-01-01

325

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

326

Cold hydrostatic extrusion of powder metallurgy processed superconducting materials  

SciTech Connect

Hydrostatically extruded multifilamentary composites of Cu-Nb, Cu-Nb with a central tin core and Nb-Al were directly drawn to fine wires without intermediate annealing. Uniform deformation was observed throughout the process. Cu-Nb composite wires were Sn plated for external diffusion. Overall critical current densities of better than 10/sup 4/ A/cm/sup 2/ at 16 T were achieved for Nb/sub 3/Sn-Cu composite wires with nominal areal reductions of 2000.

Pourrahimi, S.; Thieme, C.L.H.; Foner, S.; Murphy, R.J.

1983-12-01

327

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 1350°C) 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

328

The imaging performance of compact Lu{sub 2}O{sub 3}:Eu powdered phosphor screens: Monte Carlo simulation for applications in mammography  

SciTech Connect

In medical mammographic imaging systems, one type of detector configuration, often referred to as indirect detectors, is based on a scintillator layer (phosphor screen) that converts the x-ray radiation into optical signal. The indirect detector performance may be optimized either by improving the structural parameters of the screen or by employing new phosphor materials with improved physical characteristics (e.g., x-ray absorption efficiency, intrinsic conversion efficiency, emitted light spectrum). Lu{sub 2}O{sub 3}:Eu is a relatively new phosphor material that exhibits improved scintillating properties indicating a promising material for mammographic applications. In this article, a custom validated Monte Carlo program was used in order to examine the performance of compact Lu{sub 2}O{sub 3}:Eu powdered phosphor screens under diagnostic mammography conditions (x-ray spectra: 28 kV Mo, 0.030 mm Mo and 32 kV W, 0.050 mm Rh). Lu{sub 2}O{sub 3}:Eu screens of coating weight in the range between 20 and 40 mg/cm{sup 2} were examined. The Monte Carlo code was based on a model using Mie-scattering theory for the description of light propagation within the phosphor. The overall performance of Lu{sub 2}O{sub 3}:Eu powdered phosphor screens was investigated in terms of the (i) quantum detection efficiency, (ii) luminescence efficiency, (iii) compatibility with optical sensors, (iv) modulation transfer function, (v) the Swank factor, and (vi) zero-frequency detective quantum efficiency. Results were compared to the traditional rare-earth Gd{sub 2}O{sub 2}S:Tb phosphor material. The increased packing density and therefore the light extinction properties of Lu{sub 2}O{sub 3}:Eu phosphor were found to improve the x-ray absorption (approximately up to 21% and 16% at 40 mg/cm{sup 2} for Mo and W x-ray spectra, respectively), the spatial resolution (approximately 2.6 and 2.4 cycles/mm at 40 mg/cm{sup 2} for Mo and W x-ray spectra, respectively), as well as the zero-frequency detective quantum efficiency (approximately up to 8% and 18% at 20 mg/cm{sup 2} for Mo and W x-ray spectra, respectively) of the screens in comparison to the Gd{sub 2}O{sub 2}S:Tb screens. Data obtained by the simulations indicate that certain optical properties of Lu{sub 2}O{sub 3}:Eu make this material a promising phosphor which, under appropriate conditions, could be considered for use in x-ray mammography imagers.

Liaparinos, P. F.; Kandarakis, I. S. [Department of Medical Instruments Technology, Technological Educational Institute, 122 10 Athens (Greece)

2009-06-15

329

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

330

Welding Metallurgy of Aluminium for Radiation Tube of Reactor.  

National Technical Information Service (NTIS)

The metallurgy of TIG weldment in aluminium alloy was examined based on physical metallurgy characteristics. The presence of weld defects have been detected by x-ray radiographic and metallographic methods. The lack of penetration in the aluminium weldmen...

Mohamad Harun Abdul Aziz Mohamad Zailee Dollah Azlan Samah Jasmin Baba

1986-01-01

331

Creep behavior of consolidated rapidly solidified Type 304 stainless steel powder containing helium  

Microsoft Academic Search

An investigation on the creep behavior of extrusion consolidated Type 304 SS powder containing approximately 7 appM helium was performed. The helium was entrapped during powder processing by centrifugal atomization (CA) and retained through consolidation. In comparison with a wrought ingot metallurgy (I\\/M) reference of Type 304 SS, the CA SS extruded powder material showed considerable creep resistance with nearly

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

1987-01-01

332

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

333

Powder and particulate production of metallic alloys  

NASA Technical Reports Server (NTRS)

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

Grant, N. J.

1982-01-01

334

TiNi synthesis from elemental powder components  

NASA Astrophysics Data System (ADS)

Commercially, the shape memory alloy TiNi is produced by either vacuum induction melting or by vacuum arc remelting of the pure metal ingots. Powder metallurgy techniques provide an alternative fabrication route but problems arise achieving chemical homogeneity. In this study TiNi compacts were cold pressed from the blended elemental powders and sintered in vacuum for varying times at temperatures from 800 degree(s)C to 1000 degree(s)C. Two heating rates were used, 5 K/min and 10 K/min. A TiNi microstructure could be produced after annealing at 1000 degree(s)C for 6 hrs, although some TiNi3 was still observed. This is likely to be difficult to completely remove as TiNi3 is thermodynamically more stable than TiNi. Thus, homogenization is unlikely to be completed by solid-state diffusion processes. The martensitic B19' structure was observed to be highly oriented after processing.

Hey, Janet C.; Jardine, A. Peter

1994-05-01

335

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

336

Powder magnetoresistance (invited)  

NASA Astrophysics Data System (ADS)

Magnetoresistance observed in pressed powder compacts of half-metallic ferromagnetic oxides is reviewed. The main, isotropic negative magnetoresistance, which exceeds 50% in CrO2 at low temperature, is due to alignment of the the ferromagnetic moments of contiguous ferromagnetic grains. The effect is related to interparticle tunelling and shows hysteresis similar to that of the bulk magnetization. Spin-dependent Coulomb blocade observed in the smallest particles. There is also, an anisotropic magnetoresistance of up to 1% and a high-field increase in conductivity of order 1%/T in the powder compacts.

Coey, J. M. D.

1999-04-01

337

Microstructural development during consolidation of rapidly solidified Al-Fe-V-Si powder by VHP, extrusion and rolling  

Microsoft Academic Search

The rapid solidification of powder results in a high cooling rate which leads to microstructural refinement and extended solid solubility of alloying elements and thereby precipitation of fine dispersive phases during powder solidification and consolidation. During the last decade considerable research work has been done in the development of high temperature powder metallurgy aluminum alloys capable of competing with titanium

Y. Wang; G. W. Lorimer; F. R. Sale

1994-01-01

338

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

339

Electrical conductivity of carbonaceous powders  

Microsoft Academic Search

The present paper deals with the electrical conductivity of a number of carbonaceous powders undergoing a low compaction. It is shown that the contributions to the conductivity of such samples are too numerous and too complex to be solved exactly. Hence, several criteria are proposed in order to quantify the behaviour of moderately compressed powders, and thus derive several useful

A. Celzard; J. F. Marêché; F. Payot; G. Furdin

2002-01-01

340

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

341

Powder-Metallurgical Bearings For Turbopumps  

NASA Technical Reports Server (NTRS)

Bearings fabricated by powder metallurgy developed for use in machines subjected to extremes of temperature, rolling-contact cyclic stresses, and oxidizing or otherwise corrosive fluids. Bearings also extend operating lives of other machines in which bearings required to resist extreme thermal, mechanical, and chemical stresses. One alloy exhibiting outstanding properties was MRC-2001. Resistance to fatigue, stress corrosion cracking, and wear found superior to that of 440C stainless steel.

Bhat, B. N.; Humphries, T. S.; Thom, R. L.; Moxson, V.; Friedman, G. I.; Dolan, F. J.; Shipley, R. J.

1993-01-01

342

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

343

Applying Massively Parallel Kinetic Monte Carlo Methods to Simulate Grain Growth and Sintering in Powdered Metals.  

National Technical Information Service (NTIS)

Kinetic Monte Carlo (KMC) simulation methods were utilized to study the grain growth and sintering of nanocrystalline metal compacts. Sintering is the process used to fabricate materials from powders by densifying the powder compact at elevated temperatur...

A. M. Hay

2011-01-01

344

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

345

Mechanisms of Corrosion Fatigue in High Strength I/M (Ingot Metallurgy) and P/M (Powder Metallurgy) Aluminum Alloys.  

National Technical Information Service (NTIS)

High strength aluminum alloys are employed extensively in the primary structure of current and projected Air Force and civilian aircraft. The service lives and reliability of these aircrafts depend to a great extent on the corrosion fatigue resistance of ...

R. P. Wei P. S. Pao

1984-01-01

346

Magnetic inductor based on nanosize amorphous metal powder  

Microsoft Academic Search

Amorphous metal powders with sizes from 20–50nm 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. O’Reilly

2007-01-01

347

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

348

Reaction phase-forming and mechanical properties of Fe[sub 3]Al produced from elemental powders  

SciTech Connect

The Fe[sub 3]Al-based intermetallics can be produced by several conventional processing routes. However, there are applications where the powder metallurgy (P/M) process offers a better or the only route for producing these materials. A refined microstructure of the P/M products is beneficial for improving mechanical properties of the Fe[sub 3]Al-based intermetallics. Conventional P/M processing routes utilize mostly the prealloyed powders and consolidation is conducted by sintering, hot isostatic pressing (HIP) or hot extrusion. These methods involve generally processing steps and are, therefore, rather expensive. Reactive sintering, as an alternative fabrication method, is one of the novel and attractive processes. It is a method to obtain dense intermetallic compounds and intermetallic matrix composites from elemental powders using a self-sustaining reaction. This process, also known as combustion process, offers advantages over conventional processing methods including the use of less expensive, readily available, and easily compacted elemental powder, lower processing temperatures and shorter processing times, in short, low cost and energy savings. On the other hand, the reaction process of elemental iron-aluminium mixtures has a particular problem, i.e., a high porosity of the products due to extensive swelling. In order to achieve near-full density, the reactive sintering process should be assisted by an external pressure. In this case, reactive sintering is conducted in a HIP unit or a hot press. One should also appreciate that reactive hipping may provide near-net shape components which is important for reducing the cost because most of the intermetallics are hard-to-fabricate materials. This study describes the preparation of a binary Fe[sub 3]Al intermetallic compound by in-situ reaction phase-forming/consolidation from elemental powders, its mechanical properties, and a comparison of these properties with those of conventionally processed materials.

Zhuang, L.Z.; Buekenhout, L. (Delft Univ. of Technology (Netherlands). Lab. for Materials Science); Duszczyk, J. (Industrial Materials Technology, Niklaas (Belgium))

1994-04-01

349

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

350

Hot Isostatic Pressing of Ceramic Powder Compacts.  

National Technical Information Service (NTIS)

The densification of aluminum oxide in hot isostatic pressing has been studied in detail. Methods for calculating maps of densification rate as function of temperature and applied pressure have been developed. A new mechanism, interface-reaction-controlle...

J. K. McCoy A. J. Markworth

1986-01-01

351

Hot Isostatic Pressing of Ceramic Powder Compacts.  

National Technical Information Service (NTIS)

Several mechanisms contribute to the densification of ceramics during HIP. These can potentially be related to the kinetics of densification by the use of mechanism maps and a predictive methodology derived for determining parameter selection during HIP. ...

R. R. Wills J. K. McCoy A. J. Markworth L. G. McCoy L. E. Muttart

1983-01-01

352

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

NASA Astrophysics Data System (ADS)

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

Newell, Kenneth James

353

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 1270°C 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

354

Hydrodynamic Modeling and Explosive Compaction of Ceramics.  

National Technical Information Service (NTIS)

High-density ceramics with high-strength microstructure were achieved by explosive compaction. Well-characterized Al sub 2 O sub 3 , AlN, and boron powders were explosively compacted in both cylindrical and flat plate geometries. In cylindrical geometries...

C. Hoenig A. Holt M. Finger W. Kuhl

1977-01-01

355

Structure improvement of milk powder for chocolate processing  

Microsoft Academic Search

A mechanical–thermal treatment was applied to improve processing suitability of spray-dried milk powders for milk chocolate manufacture. Skimmed and whole milk powder were treated in a twin-screw extruder at 75°C. A die was not installed to avoid compacting of powder. Results of sorption tests confirmed that the amorphous lactose in the powders was re-crystallized due to this treatment. Powder particles

Knut Franke; Katrin Heinzelmann

2008-01-01

356

Spark plasma sintering of hydroxyapatite powders  

Microsoft Academic Search

Dense hydroxyapatite (HA) compacts have been successfully fabricated by a spark plasma sintering (SPS). The sintering behavior of HA powders at different temperatures ranging from 850°C to 1100°C was studied. Results showed that spark plasma sintering resulted in rapid densification to near theoretical density. The HA compact was homogeneously sintered at 950°C in a short sintering duration of 5min, while

Y. W. Gu; N. H. Loh; K. A. Khor; S. B. Tor; P. Cheang

2002-01-01

357

Powder particle bonding behavior during plastic working  

Microsoft Academic Search

The existence is demonstrated of a single curve describing the bond strength in powder compacts as a function of the specific regenerated surface, which is independent of the method of formation of the latter. At lower compaction temperatures, the single curve of sbi\\/s\\/bmax curve shifts downwards. This is due to the contact surfaces interacting through active centers, as a result

B. A. Aref'ev; V. V. Kuleshov; V. M. Panovko

1990-01-01

358

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

Federal Register 2010, 2011, 2012, 2013

...Subcommittees on Thermal Hydraulic Phenomena and Materials, Metallurgy and Reactor Fuels; Notice of Meeting The Joint ACRS Subcommittees on Thermal Hydraulic Phenomena and Materials, Metallurgy and Reactor Fuels will hold a meeting on February...

2013-02-05

359

Fluidized reduction of oxides on fine metal powders without sintering  

NASA Technical Reports Server (NTRS)

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

Hayashi, T.

1985-01-01

360

Sintering behaviour of Y 2O 3 powders prepared by the polymer complex solution method  

Microsoft Academic Search

High purity fine Y2O3 powder has been prepared by a polymer complex solution method using polyethylene glycol as the complexant of Y3+ cations. Powder morphology and compacts prepared from three different powder characteristics have been studied. SEM observations were used to know the agglomeration degree of the powders, and the uniformity of powder compacts, and the Hg-porosimetry results to investigate

P Durán; J Tartaj; C Moure

2002-01-01

361

Microstructural and mechanical analysis of carbon nanotube reinforced magnesium alloy powder composites  

Microsoft Academic Search

Carbon nanotube (CNT) is an effective reinforcement used to improve the mechanical and thermal responses of metal matrix composites. It is, however, obvious that segregation of CNTs due to their strong van der Waals forces will produce material defects, decreasing the material properties. An advanced powder metallurgy process that disperses un-bundled nanotubes has been developed, and it is applied to

Katsuyoshi Kondoh; Hiroyuki Fukuda; Junko Umeda; Hisashi Imai; Bunshi Fugetsu; Morinobu Endo

2010-01-01

362

The effect of temperature of magnetic pulsed compaction on the characteristics of nanostructured aluminum compacts  

Microsoft Academic Search

Magnetic pulse compaction (MPC) allows one to maintain a nanostructured state in nano powder metallic compacts and to achieve\\u000a near theoretical density. In this study, nano Al powders of about 80 nm in diameter were prepared with the Pulse Wire Evaporation\\u000a (PWE) method and passivated with a thin Al2O3 layer on a surface about 2 nm thick to prevent further

Geun Hee Lee; Chang Kyu Rhee; Whung Whoe Kim; Victor V. Ivanov

2003-01-01

363

Statistical Analysis of Modified Drucker-Prager Cap Model Parameters for Application to Modeling Die Compaction  

Microsoft Academic Search

Many soil constitutive models have been studied for their applicability to the powder compaction simulation process. However most of the parameters to define these models are determined by high- pressure hydrostatic compression and triaxial tests requiring a high pressure setup. This limits the industrial usability of these simulations to determine density gradients in compacted powder parts for different powders. In

Gautam S. Wagle; Renata S. Engel; Ravi Bollina; Randall M. German

364

A constitutive model for sintering of granulated ceramic powders  

Microsoft Academic Search

Sintering behavior of granulated powder is investigated to develop a constitutive model for deformation analysis of ceramic\\u000a powder compacts during sintering. Spray-dried alumina is compacted by CIPing (cold isostatic pressing) and sintered at various\\u000a temperatures. Shrinkage and the change in grain size of the compacts during sintering are revealed in relation to the inhomogeneous\\u000a microstructure consisting of fractured and unfractured

K. Shinagawa; Y. Hirashima

1998-01-01

365

UâOâ powder from uranyl-loaded cation exchange resin  

Microsoft Academic Search

UâOâ 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-UâOâ 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

366

Sinter-hardening of Ni-Mo pre-alloyed powders with tungsten addition  

Microsoft Academic Search

Purpose: Purpose of this paper was to present the benefits of powder metallurgy technology and development of sinter-hardening process. The mechanical properties, focusing in particular on hardness and wear resistance, of two different carbon levels pre-alloyed steel powders processed with sinter-hardening method, were described. Microstructure characteristic of produced sinter-hardened Ni-Mo steels with increasing amount of tungsten (from 0 to 0.3%

L. A. Dobrza?ski a; J. Otr?ba; M. Actis Grande; M. Rosso

367

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

ERIC Educational Resources Information Center

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

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

368

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

ERIC Educational Resources Information Center

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

Shapley, Deborah

1975-01-01

369

Science and Technical Progress in Non-Ferrous Metallurgy.  

National Technical Information Service (NTIS)

The attainments of science in the field of non-ferrous metallurgy are discussed. The basic results of work in branches for 1966-1970 and for the first year of the ninth Five-year Plan are given. The book covers questions of adopting new processes and equi...

P. F. Lomako

1973-01-01

370

Explicit finite element method simulation of consolidation of monolithic and composite powders  

Microsoft Academic Search

The explicit finite element method (FEM) has been used to simulate the compaction of monolithic and composite powder compacts.\\u000a It is concluded that with the proper FEM model and appropriate loading speed, explicit FEM can be used to simulate powder\\u000a compaction with satisfactory accuracy. The simulated pressure-density curves for four periodic powders are in reasonable agreement\\u000a with experiments using model

X. J. Xin; P. Jayaraman; G. Jiang; R. H. Wagoner; G. S. Daehn

2002-01-01

371

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

372

Dynamic densification behavior of nanoiron powders under shock compression  

NASA Astrophysics Data System (ADS)

The dynamic densification behavior of nanoiron powder (~25 nm particle size) prepressed to ~35% and ~45% of solid density was determined based on measurements of shock input stress and wave velocity by using piezoelectric stress gauges. The experimentally determined shock densification response is observed to be sensitive to the initial density (or porosity) of prepressed nanoiron powder compacts. Hugoniot measurements show an obvious densification-distension transition at ~2 GPa for the ~35% dense and ~6 GPa for the ~45% dense powder compacts. The densification and shock compression responses of the nanoiron powders are also calculated by using isobaric and isochoric models. Correlations of the model calculations with the measured data indicate that the shock Hugoniot of nanoiron powders cannot be correctly described by the currently available analytical models that are otherwise capable of predicting the Hugoniot of highly porous materials (prepressed compacts) of micron-sized powders.

Dai, C. D.; Eakins, D. E.; Thadhani, N. N.

2008-05-01

373

Sol-Gel Synthesis and Densification of Aluminoborosilicate Powders. Part 2: Densification.  

National Technical Information Service (NTIS)

Aluminoborosilicate (ABS) powders, high in alumina content, were synthesized by the sol-gel process utilizing four different methods of synthesis. The effect of these methods on the densification behavior of ABS powder compacts was studied. Five regions o...

J. Bull G. Selvaduray D. Leiser

1992-01-01

374

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

375

Microstructure of Nb–Al powders consolidated by spark plasma sintering process  

Microsoft Academic Search

Mechanically alloyed and blended Nb–Al, Nb–Al–W, Nb–Al–Mo and Nb–Al–N powders were sintered by a spark plasma sintering process and the microstructure and mechanical properties of compacts were investigated. Fully-densed Nb–Al compacts are obtained when sintering temperature is higher than 1773 K, although the microstructure of compacts consolidated from blended elemental powders is much coarser than that of compacts consolidated from

T Murakami; A Kitahara; Y Koga; M Kawahara; H Inui; M Yamaguchi

1997-01-01

376

Mesoscale Simulations of Power Compaction  

SciTech Connect

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

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

2009-08-06

377

Powder diffraction.  

National Technical Information Service (NTIS)

the importance of x-ray powder diffraction as an analytical tool for phase identification of materials was first pointed out by Debye and Scherrer in Germany and, quite independently, by Hull in the US. Three distinct periods of evolution lead to ubiquito...

M. Hart

1995-01-01

378

Powder diffraction  

Microsoft Academic Search

The powder diffraction method, by using conventional X-ray sources, was devised independently in 1916 by Debye and Scherrer in Germany and in 1917 by Hull in the United States. The technique developed steadily and, half a century later, the `traditional' applications, such as phase identification, the determination of accurate unit-cell dimensions and the analysis of structural imperfections, were well established.

J. Ian Langford; Daniel Louër

1996-01-01

379

Powder diffraction  

SciTech Connect

the importance of x-ray powder diffraction as an analytical tool for phase identification of materials was first pointed out by Debye and Scherrer in Germany and, quite independently, by Hull in the US. Three distinct periods of evolution lead to ubiquitous application in many fields of science and technology. In the first period, until the mid-1940`s, applications were and developed covering broad categories of materials including inorganic materials, minerals, ceramics, metals, alloys, organic materials and polymers. During this formative period, the concept of quantitative phase analysis was demonstrated. In the second period there followed the blossoming of technology and commercial instruments became widely used. The history is well summarized by Parrish and by Langford and Loueer. By 1980 there were probably 10,000 powder diffractometers in routine use, making it the most widely used of all x-ray crystallographic instruments. In the third, present, period data bases became firmly established and sophisticated pattern fitting and recognition software made many aspects of powder diffraction analysis routine. High resolution, tunable powder diffractometers were developed at sources of synchrotron radiation. The tunability of the spectrum made it possible to exploit all the subtleties of x-ray spectroscopy in diffraction experiments.

Hart, M.

1995-12-31

380

A laboratory means to produce tough aluminum sheet from powder  

NASA Technical Reports Server (NTRS)

The rapid solidification of aluminum alloys as powder and the subsequent fabrication processes can be used to develop and tailor alloys to satisfy specific aerospace design requirements, including high strength and toughness. Laboratory procedures to produce aluminum powder-metallurgy (PM) materials are efficient but require evidence that the laboratory methods used can produce a product with superior properties. This paper describes laboratory equipment and procedures which can be used to produce tough aluminum PM sheet. The processing of a 2124 + 0.9 percent Zr aluminum alloy powder is used as an example. The fully hardened sheet product is evaluated in terms of properties and microstructure. The key features of the vacuum hot press pressing operation used to consolidate the powder are described. The 2124 + 0.9 percent Zr - T8 temper aluminum sheet produced was both strong (460-490 MPa yield strength) and tough (Kahn Tear unit-propagation- energy values over three times those typical for ingot metallurgy 2024-T81). Both the longitudinal and longitudinal-transverse directions of the sheet were tested. The microstructure was well refined with subgrains of one or two micrometers. Fine dispersoids of Al3Zr in the precipitate free regions adjacent to boundaries are believed to contribute to the improved toughness.

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

1990-01-01

381

Reaction phase-forming and mechanical properties of Fe[sub 3]Al produced from elemental powders  

Microsoft Academic Search

The Fe[sub 3]Al-based intermetallics can be produced by several conventional processing routes. However, there are applications where the powder metallurgy (P\\/M) process offers a better or the only route for producing these materials. A refined microstructure of the P\\/M products is beneficial for improving mechanical properties of the Fe[sub 3]Al-based intermetallics. Conventional P\\/M processing routes utilize mostly the prealloyed powders

L. Z. Zhuang; L. Buekenhout; J. Duszczyk

1994-01-01

382

Cairo to Cape: The Spread of Metallurgy Through Eastern and Southern Africa  

Microsoft Academic Search

This article traces the beginnings of metallurgy in the eastern half of the African continent, focusing on three regions:\\u000a (1) Egypt and Nubia; (2) the Great Lakes region of Central and East Africa; and (3) southern Africa. Metallurgy was not practiced\\u000a much beyond the Nile valley until the first millennium BC, when copper, bronze and iron metallurgy began in Ethiopia

David Killick

2009-01-01

383

Powder metal technologies and applications  

SciTech Connect

This volume is: (1) a completely updated and expanded edition in all areas of powder production, sampling, characterization, shaping, consolidation, sintering, quality control, machining, heat treating, and P/M applications; (2) single source for practical engineering information on sintering practices, tool design, P/M metallography, dimensional control, part design, powders, binders, lubricants, and the processing, properties, and performance of P/M materials in different production technologies and applications; (3) comprehensive coverage of P/M technologies and applications including warm compaction, injection molding, rapid prototyping, thermal spray forming, reactive sintering, and P/M gears, bearings, high-performance parts, composites, machine parts, electric contacts, magnetic materials, metallic foams, hardfacing powders, automotive parts, and more.

Eisen, W.B.; Ferguson, B.L.; German, R.M.; Iacocca, R.; Lee, P.W.; Madan, D.; Moyer, K.; Sanderow, H.; Trudel, Y. [eds.

1998-12-31

384

Synthesis and processing of monosized oxide powders  

DOEpatents

Uniform-size, high-purity, spherical oxide powders are formed by hydrolysis of alkoxide precursors in dilute alcoholic solutions. Under controlled conditions (concentrations of 0.03 to 0.2 M alkoxide and 0.2 to 1.5 M water, for example) oxide particles on the order of about 0.05 to 0.7 microns can be produced. Methods of doping such powders and forming sinterable compacts are also disclosed. 6 figs.

Barringer, E.A.; Fegley, M.B. Jr.; Bowen, H.K.

1985-09-24

385

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

Microsoft Academic Search

Overview;\\u000a;\\u000aFast 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.

Sean M. McDeavitt

2011-01-01

386

Evaluation of powder metallurgy plates made by Sylvania Electric Products, Inc.  

SciTech Connect

These plates, numbered 13129, 13130, 13133, 13137, and 13146 were fabricated by Sylvania Electric Products, Inc., and were received at the Savannah plant in February, 1956. All of the plates were of the wide, ribless design. A summary of the data obtained by Sylvania on these and on {open_quotes}companion{close_quotes} plates is given in Table I, and a summary of the data obtained upon examining the plates at the Savannah River Laboratory is contained in Table II.

Not Available

1994-09-01

387

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

388

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

389

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

NASA Technical Reports Server (NTRS)

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

Domack, Marcia S.

1987-01-01

390

Technological Advancement in Electrical Discharge Machining with Powder Metallurgy Processed Electrodes: A Review  

Microsoft Academic Search

Electrical discharge machining (EDM) is a well-established machining option for processing hard materials with complex geometrical shapes which are extremely difficult-to-machine by conventional machining processes. These hard materials find applications where lower surface cracks, wear resistance, corrosion resistance, etc. are desirable surface properties. In recent years, research has been carried out to determine the possibility of employing electrode as feed

Naveen Beri; Sachin Maheshwari; Chitra Sharma; Anil Kumar

2010-01-01

391

Developments of a powder-metallurgy, MZC copper-alloy, water-cooled gas turbine component  

Microsoft Academic Search

The Department of Energy of the Federal Government has sponsored a technology development and verification testing program.\\u000a This work is in support of an advanced, watercooled gas turbine firing at 2600 ‡F (1427 ‡C). As part of this turbine, strong\\u000a emphasis has been placed on the design and testing of a composite firststage nozzle. One of the materials making up

L. G. Peterson

1984-01-01

392

The effect of zirconium addition on microstructure and properties of ball milled and hot compacted powder of Al–12 wt% Zn–3 wt% Mg–1.5 wt% Cu alloy  

Microsoft Academic Search

Elemental powders of the composition Al–12wt% Zn–3wt% Mg–1.5wt% Cu with addition of 1 and 2wt% Zr were ball milled in a planetary high-energy ball mill and then hot pressed in vacuum under 600MPa pressure at 380°C. The effect of ball milling and hot pressing on the microstructure was investigated by means of X-ray diffraction measurements (XRD), light microscopy, analytical and

Lidia Lity?ska-Dobrzy?ska; Jan Dutkiewicz; Wojciech Maziarz; Anna Góral

2011-01-01

393

Tantalum powder consolidation, modeling and properties  

SciTech Connect

A systematic approach was taken to investigate the consolidation of tantalum powders. The effects of sinter time, temperature and ramp rate; hot isostatic pressing (HIP) temperature and time; and powder oxygen content on consolidation density, kinetics, microstructure, crystallographic texture, and mechanical properties have been evaluated. In general, higher temperatures and longer hold times resulted in higher density compacts with larger grain sizes for both sintering and HIP`ing. HIP`ed compacts were consistently higher in density than sintered products. The higher oxygen content powders resulted in finer grained, higher density HIP`ed products than the low oxygen powders. Texture analysis showed that the isostatically processed powder products demonstrated a near random texture. This resulted in isotropic properties in the final product. Mechanical testing results showed that the HIP`ed powder products had consistently higher flow stresses than conventionally produced plates, and the sintered compacts were comparable to the plate material. A micromechanics model (Ashby HIP model) has been employed to predict the mechanisms active in the consolidation processes of cold isostatic pressing (CIP), HIP and sintering. This model also predicts the density of the end product and whether grain growth should be expected under the applied processing conditions.

Bingert, S.R.; Vargas, V.D.; Sheinberg, H.C.

1996-10-01

394

Compact magnetograph  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

395

76 FR 64344 - Amended Record of Decision for the Nuclear Facility Portion of the Chemistry and Metallurgy...  

Federal Register 2010, 2011, 2012, 2013

...Chemistry and Metallurgy Research Building Replacement Project at Los...Chemistry and Metallurgy Research Building Replacement (CMRR) Project...Replacing the aging CMR Building with a new facility that incorporates...and groundwater quality; ecological resources; cultural and...

2011-10-18

396

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) [Sayville, NY

1982-01-01

397

Compaction of AWBA Fuel Pellets Without Binders (AWBA Development Program).  

National Technical Information Service (NTIS)

Highly active oxide fuel powders, composed of UO sub 2 , UO sub 2 -ThO sub 2 , or ThO sub 2 , were compacted into ultra-high density pellets without the use of binders. The objective of the study was to select the optimum die lubricant for compacting thes...

R. G. R. Johnson

1982-01-01

398

Characteristic variation of spark plasma-sintered Ta compacts  

Microsoft Academic Search

In the present study, we applied the SPS process to obtain a tantalum (Ta) compact for a sputtering target. Sintered Ta compacts were characterized with respect to microstructure, relative density, Vickers hardness and phase composition of the inside and the surface. By radio frequency (RF) thermal plasma treatment, a spherical ultra-fine Ta powder was obtained; however, the oxygen content increased

Gue-Serb Cho; Jung-Kyu Lim; Kyeong-Hwan Choe; Seung-Yong Shin

2010-01-01

399

Characteristic variation of spark plasma-sintered Ta compacts  

NASA Astrophysics Data System (ADS)

In the present study, we applied the SPS process to obtain a tantalum (Ta) compact for a sputtering target. Sintered Ta compacts were characterized with respect to microstructure, relative density, Vickers hardness and phase composition of the inside and the surface. By radio frequency (RF) thermal plasma treatment, a spherical ultra-fine Ta powder was obtained; however, the oxygen content increased due to severe passivation during powder handling. Higher sintering temperature and the RF plasma treatment increased the densification of the sintered compact and also the Vickers hardness. From XRD analysis, only Ta was identified in the cross section of compacts, and TaC formed by the reaction between Ta and the graphite mould was found in the surface of the compacts. The evacuation of the chamber and the reduction by the graphite mould promote the purification of the compact.

Cho, Gue-Serb; Lim, Jung-Kyu; Choe, Kyeong-Hwan; Shin, Seung-Yong

2010-05-01

400

Effect of powder calcination on the sintering of hydroxyapatite.  

PubMed

The sintering behaviour of synthesized HA powder that was calcined at various temperatures ranging from 700 degrees C to 1000 degrees C was investigated in terms of phase stability, bulk density, Young's modulus and Vickers hardness. The calcination treatment resulted in higher crystallinity of the starting HA powder. Decomposition of HA phase to form secondary phases was not observed in all the calcined powders. The results also indicated that powder calcination (up to 900 degrees C) prior to sintering has negligible effect on the sinterability of the HA compacts. However, powder calcined at 1000 degrees C was found to be detrimental to the properties of sintered hydroxyapatite bioceramics. PMID:19024997

Tan, C Y; Ramesh, S; Aw, K L; Yeo, W H; Hamdi, M; Sopyan, I

2008-07-01

401

Metallurgy in the Laboratory: Preparation of Pure Antimony  

NASA Astrophysics Data System (ADS)

Very few procedures have appeared in the literature for the preparation of small amounts of pure metals or metalloids in an undergraduate laboratory. The preparation of pure antimony is readily accomplished on a laboratory scale by the high-temperature reduction of antimony trioxide with potassium cyanide. The product is obtained in almost quantitative yield (up to 98%) using a procedure that is simple, inexpensive, and quick. This experiment also illustrates the basic principles of metallurgy and introduces students to an element whose chemistry is seldom discussed in general or inorganic chemistry classes.

O'Klatner, Brooke L.; Rabinovich, Daniel

2000-02-01

402

University of Cambridge Department Of Materials Science and Metallurgy  

NSDL National Science Digital Library

The University of Cambridge Department Of Materials Science and Metallurgy page offers information on current research ranging from the creation of new materials to improving existing materials. Considered "one of the leading materials science departments in the world," the department's research page points to more detailed pages outlining the work of seventeen groups. Research within the groups includes atomistic simulation, composites and coatings, device materials, high temperature stability of materials, materials chemistry, and the like. A special search feature allows users to easily locate information on research in progress by investigator, research topic, and supporting agency. Also available online are grant reports from the Engineering and Physical Sciences Research Council.

403

Ceramic Powders  

NASA Technical Reports Server (NTRS)

In developing its product line of specialty ceramic powders and related products for government and industrial customers, including companies in the oil, automotive, electronics and nuclear industries, Advanced Refractory Technologies sought technical assistance from NERAC, Inc. in specific areas of ceramic materials and silicon technology, and for assistance in identifying possible applications of these materials in government programs and in the automotive and electronics industry. NERAC conducted a computerized search of several data bases and provided extensive information in the subject areas requested. NERAC's assistance resulted in transfer of technologies that helped ART staff develop a unique method for manufacture of ceramic materials to precise customer specifications.

1984-01-01

404

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

405

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 1350°C) 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

406

SemiSolid Metal Powder Forming of Ti-Sn Alloys & Their Metal Matrix Composites  

Microsoft Academic Search

The Semi-Solid Metal Powder Form- ing (SSMPF) involves mixing elemental Ti and Sn powders followed by compacting the mixture under predetermined pressures and tempera- tures. At compacting temperatures, the Sn is melted and forced to fill up the gaps formed by the Ti particles to form a near 100% dense green part. During alloying process at an appro- priate temperature,

Q. F. Li; S. X. Zhang; M. K. Ho; S. F. Pook; J. M. S. Yong

407

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

408

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

409

The effect of contact torques on porosity of cohesive powders  

Microsoft Academic Search

The porosity of uniaxially compacted cohesive powders depends on the applied stress (including gravity). The case, where these stresses are weak, is considered. The compaction results in a porosity which is a function of sliding, rolling and torsion friction. By contact dynamics simulations it is shown that the influences of contact torques (static rolling and torsion friction) on the porosity

Guido Bartels; Tamás Unger; Dirk Kadau; Dietrich E. Wolf; János Kertész

2005-01-01

410

T Strip Properties Fabricated by Powder Rolling Method  

NASA Astrophysics Data System (ADS)

In the present study, the characteristics of the Ti powders fabricated by Hydride-Dehydride (HDH) were analyzed in terms of particle shape, size and size distribution. Ti powders were subjected to roll compaction and their microstructure and green densities were evaluated in terms of particle size, powder morphology, roll gap and rolling speed. Effects of blending elements having different powder sizes on densification properties were analyzed. The strip thickness was proportional to the roll gap up to 0.9 mm and the density of titanium strip was decreased with the increase in roll gap. As the roll speed increased, the strip density and thickness were decreased by using -200 mesh Ti powder. However, the effect of rolling speed for -400 mesh Ti powder was not greater than that of -200 mesh powder. The highest density by 93% was achieved by using -400 mesh Ti powder at 0.1 mm roll gap, however edge cracks and alligator cracks were occurred.

Hong, Jae-Keun; Lee, Chae-Hun; Kim, Jeoung-Han; Yeom, Jong-Taek; Park, Nho-Kwang

411

Structure analysis of surface layer on passivated magnesium powders  

Microsoft Academic Search

The combustion-time of the passivated magnesium powders as desulfurizer was determined to be about 15.7 s, much higher than that of non-passivated magnesium powders. The surface layer of the passivated magnesium powders was studied by using SEM, XRD and AES. It is uniform and compact and no obvious holes or cracks have been found from the SEM micrographs. The result of

Junlin Huang; Jianfeng F. Wan; Chaoying Xie; Jinsong Chen; Chuanjiang Long

2007-01-01

412

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

413

Obtaining and sintering yttria stabilized zirconia (YSZ) powders from alkoxides  

Microsoft Academic Search

Amorphous zirconia ceramics powders containing 3 and 6 mol% yttria were prepared by controlled hydrolysis of alkoxides. Characterization of these powders was carried away by Thermal Analysis, X-ray Diffraction, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX™). The calcination temperature was optimized for compaction at a temperature ranging from 500–800°C. 3% molar YSZ powders from alkoxide, that attained

C. Barrera-Solano; C. Jiménez-Solís; N. Rosa-Fox; L. Esquivias

1994-01-01

414

An investigation on the compressibility of aluminum\\/nano-alumina composite powder prepared by blending and mechanical milling  

Microsoft Academic Search

The densification response of aluminum powder reinforced with 5vol.% nanometric alumina particles (35nm) during uniaxial compaction in a rigid die was studied. The composite powder was prepared by blending and mechanical milling procedures. To determine the effect of the reinforcement nanoparticles on the compressibility of aluminum powder, monolithic Al powder, i.e. without the addition of alumina, was also examined. It

Z. Razavi Hesabi; H. R. Hafizpour; A. Simchi

2007-01-01

415

Canning Of Powdered Metal For Hot Isostatic Pressing  

NASA Technical Reports Server (NTRS)

Quality of specimen enhanced by improved canning process. Method developed for canning specimens for hot isostatic pressing. Specimen placed inside refractory-metal ring, then sandwiched between two refractory-metal face sheets. Assembly placed inside die, then positioned in vacuum hot press. Heated to set temperature at prescribed vacuum to burn off all of binder in specimen. Advantages: powder-metallurgy composite totally purged of binder sealed in can in single operation, maintains size, shape, and uniformity of specimen. Weld region does not recrystallize, and little possibility of cracking.

Juhas, John J.

1989-01-01

416

Detonation synthesized nanodiamond powder for the preparation of porous polycrystalline micron powders  

Microsoft Academic Search

Characteristics and properties of detonation-synthesized nanodiamond (UDD) powder and polycrystalline micron (PDD) powders produced by high pressure–high temperature sintering of detonation-synthesized diamond and a subsequent crushing of the resulting compacts have been described.It has been shown that during the sintering in the diamond stability region the phase composition of the superhard material under study changes and the grain secondary recrystallization

G. P. Bogatyreva; M. N. Voloshin; V. I. Padalko

2008-01-01

417

Numerical simulation of powder flow field on coaxial powder nozzle in laser metal direct manufacturing  

Microsoft Academic Search

In the laser metal direct manufacturing, gas–solid two-phase flow theory is adopted to simulate the flow field of powders\\u000a in coaxial nozzle to fabricate complex parts of compact structure. The separate model in FLUENT is used to evaluate the concentration\\u000a distribution rule and the focusing characteristics of the powder flow field. The results indicate that the focal concentrations\\u000a of the

Anfeng Zhang; Dichen Li; Zhimin Zhou; Gangxian Zhu; Bingheng Lu

2010-01-01

418

The mysterious world of plutonium metallurgy: Past and future  

SciTech Connect

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

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

1998-12-31

419

High-temperature deformation behavior of aluminum alloys produced from centrifugally-atomized powders  

Microsoft Academic Search

Powder metallurgy (P\\/M) aluminum alloys have been expected to have extended application in the production of such items as automobile, aeroplane and machine parts. P\\/M AlAl?10mass%Mg and hyper-eutectic Al?Si alloys have been produced using a centrifugal-atomization process, which is one of the rapid-solidification techniques, and the possibility of superplastic deformation has been investigated because the components required have become of

T. Satoh; K. Okimoto; S. Nishida

1997-01-01

420

UâOâ powder from uranyl-loaded cation exchange resin  

Microsoft Academic Search

Large batches of UâOâ, suitable for powder metallurgy fabrication of Al-UâOâ 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

421

UâOâ powder from uranyl-loaded cation exchange resin  

Microsoft Academic Search

Production-size batches of UâOâ, suitable for powder metallurgy fabrication of Al-UâOâ 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

422

Simulation Study for Complex Shaped Pressing of Ceramic Powder  

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

423

Exploring Baking Powder  

NSDL National Science Digital Library

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

Kessler, James H.; Galvan, Patricia M.

2007-01-01

424

A combined experimental–numerical study of the compaction behavior of NaCl  

Microsoft Academic Search

The compaction behavior of NaCl as a model substance is investigated by an integrated experimental and computational approach. The method for characterization of this granular material employs convenient experiments: load–displacement measurements of compaction; measurements of strain on outer circumference of an elastic tubular die; load on bottom and top of the powder compact, as well as compressive strength tests. Related

Steffen Brinckmann; Guofeng Gao; Thomas Siegmund

2009-01-01

425

A study of the coefficients in yield functions modeling metal powder deformation  

Microsoft Academic Search

In the past, several phenomenological constitutive models have been proposed for modeling the compaction processes of sintered metal powders on the basis of continuum mechanics. Compared with the sintered metal powders, the loose metal powders behave very differently in many aspects and therefore need a different constitutive model. In this paper, we study such a constitutive model and the approach

T. C. Tszeng; W. T. Wu

1996-01-01

426

Compact spaces, compact cardinals, and elementary submodels  

Microsoft Academic Search

If M is an elementary submodel and X a topological space, then XM denotes the set X?M given the topology generated by the open subsets of X which are members of M. Call a compact space squashable iff for some M, XM is compact and XM?X. The first supercompact cardinal is the least ? such that all compact X with

Kenneth Kunen

2003-01-01

427

Powder treatment process  

DOEpatents

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

Weyand, John D. (Greensburg, PA) [Greensburg, PA

1988-01-01

428

Powder treatment process  

DOEpatents

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

Weyand, J.D.

1988-02-09

429

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

430

The welding metallurgy of Custom Age 625 PLUS alloy  

SciTech Connect

The authors discuss the welding metallurgy (solidification behavior, mechanical properties of weld metal, and susceptibility to fusion zone hot cracking) of Carpenter Custom Age 625 PLUS alloy. This alloy solidifies to a nickel austenitic matrix with the formation of a Nb-rich {gamma}/Laves terminal solidification constituent. The low Si and C concentrations in combination with a lower Nb content (3.4wt-%) in this alloy result in a relatively small volume fraction of eutectic constituent relative to that previously observed in Alloy 718. Because of the low volume fraction of eutectic constituent, this alloy has better weldability than Alloy 718. In addition to Laves phase, {gamma} was observed adjacent to Laves phase {gamma} was observed adjacent to Laves in the fusion zone microstructure of the new alloy. Weld metal strengths approximately equal to aged wrought product can be achieved by direct aging of welds.

Cieslak, M.J.; Headley, T.J. (Sandia National Labs., Alburquerque, NM (US)); Frank, R.B. (Carpenter Technology Corp., Reading, PA (US))

1989-12-01

431

Process for synthesizing compounds from elemental powders and product  

DOEpatents

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

Rabin, Barry H. (Idaho Falls, ID); Wright, Richard N. (Idaho Falls, ID)

1993-01-01

432

Polymer quenched prealloyed metal powder  

DOEpatents

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

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

2001-01-01

433

Sintering Aids in the Consolidation of Boron Carbide (B4C) by the Plasma Pressure Compaction (PC) Method  

Microsoft Academic Search

Boron carbide (B4C) powder has been densified by a novel method of powder consolidation known as Plasma Pressure Compaction (PC). The PC technique allows for rapid consolidation of powder by Joule heating of the powder bed. Powder is placed in graphite dies, and uniaxial pressure and low-voltage, high-amperage (10 V, 5000 amps maximum) direct current are applied to achieve densification. Pure

Bradley R. Klotz; Kyu C. Cho; Robert J. Dowding

2004-01-01

434

POWDERS FOR EXTINGUISHING FIRES  

Microsoft Academic Search

The development of a powder suitable for extinguishing fires of burning ; U, Pu, or Th is described. The powder consists of a mixture of powdered ; inorganic chlorides and\\/or fluorides inert towards the bunning metal. The ; mixture has a melting point below the melting point of the burning metal such ; that fusion of the powder takes place

Cope

1963-01-01

435

Resin-Powder Dispenser  

NASA Technical Reports Server (NTRS)

Resin-powder dispenser used at NASA's Langley Research Center for processing of composite-material prepregs. Dispenser evenly distributes powder (resin polymer and other matrix materials in powder form) onto wet uncured prepregs. Provides versatility in distribution of solid resin in prepreg operation. Used wherever there is requirement for even, continuous distribution of small amount of powder.

Standfield, Clarence E.

1994-01-01

436

NMT-7 APPROACH TO WASTE MANAGEMENT AT LOS ALAMOS NATIONAL LABORATORY'S CHEMISTRY AND METALLURGY RESEARCH FACILITY  

Microsoft Academic Search

The Chemistry and Metallurgy Research (CMR) Facility at Los Alamos National Laboratory (LANL) is a 550,000-square-foot building that was constructed in 1952, to house research and experimental facilities for analytical chemistry, plutonium and uranium chemistry, metallurgy, engineering design and drafting, electronics, and other support functions. Operations conducted within this diverse facility generate significant volumes of a wide range of hazardous,

Edward D. Derr; Ronald E. Wieneke

2000-01-01

437

Characterization of Fine Powders  

NASA Astrophysics Data System (ADS)

Fine powders are used in many applications and across many industries such as powdered paints and pigments, ceramics, petrochemicals, plastics, pharmaceuticals, and bulk and fine chemicals, to name a few. In addition, fine powders must often be handled as a waste by-product, such as ash generated in combustion and gasification processes. In order to correctly design a process and process equipment for application and handling of powders, especially fine powders, it is essential to understand how the powder would behave. Many characterization techniques are available for determining the flow properties of powders; however, care must be taken in selecting the most appropriate technique(s).

Krantz, Matthew; Zhang, Hui; Zhu, Jesse

438

Preparation of titanium diboride powder  

SciTech Connect

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

Brynestad, J.; Bamberger, C.E.

1985-03-05

439

Consolidation of nanostructured metal powders by rapid forging: Processing, modeling, and subsequent mechanical behavior  

Microsoft Academic Search

Fe-10Cu powders containing 20-nm grains were produced by attritor milling of elemental powders in argon. A rapid powder forging\\u000a technique was developed to consolidate the powders into fully dense compacts while maintaining nanoscale grain sizes. Grain\\u000a growth during the consolidation was controlled by reducing the time of exposure at elevated temperature to a few minutes or\\u000a less, a technique which

G. R. Shaik; W. W. Milligan

1997-01-01

440

Consolidation of nanostructured metal powders by rapid forging: Processing, modeling, and subsequent mechanical behavior  

Microsoft Academic Search

Fe?10Cu powders containing 20-nm grains were produced by attritor milling of elemental powders in argon. A rapid powder forging\\u000a technique was developed to consolidate the powders into fully dense compacts while maintaining nanoscale grain sizes. Grain\\u000a growth during the consolidation was controlled by reducing the time of exposure at elevated temperature to a few minutes or\\u000a less, a technique which

G. R. Shaik; W. W. Milligan

1997-01-01

441

Influence of ceramic powders of different characteristics on particle packing structure and sintering behaviour  

Microsoft Academic Search

Ytteria-stabilized zirconia powders from different sources were used to investigate powder packing characteristics and subsequent\\u000a sintering behaviour. Powders of different levels of agglomeration were controlled by varying degrees of ball-milling, followed\\u000a by shaping through colloidal casting. Experimental findings revealed that the average pore diameter of the powder compacts\\u000a appears to be a good representative of the whole pore structure of

Dean-Mo Liu; Jiang-Tsair Lin

1999-01-01

442

Microstructural Development in Al-Si Powder During Rapid Solidification  

SciTech Connect

Powder metallurgy has become an increasingly important form of metal processing because of its ability to produce materials with superior mechanical properties. These properties are due in part to the unique and often desirable microstructures which arise as a result of the extreme levels of undercooling achieved, especially in the finest size powder, and the subsequent rapid solidification which occurs. A better understanding of the fundamental processes of nucleation and growth is required to further exploit the potential of rapid solidification processing. Aluminum-silicon, an alloy of significant industrial importance, was chosen as a model for simple eutectic systems displaying an unfaceted/faceted interface and skewed coupled eutectic growth zone, Al-Si powder produced by high pressure gas atomization was studied to determine the relationship between microstructure and alloy composition as a function of powder size and atomization gas. Critical experimental measurements of hypereutectic (Si-rich) compositions were used to determine undercooling and interface velocity, based on the theoretical models which are available. Solidification conditions were analyzed as a function of particle diameter and distance from nucleation site. A revised microstructural map is proposed which allows the prediction of particle morphology based on temperature and composition. It is hoped that this work, by providing enhanced understanding of the processes which govern the development of the solidification morphology of gas atomized powder, will eventually allow for better control of processing conditions so that particle microstructures can be optimized for specific applications.

Amber Lynn Genau

2004-12-19

443

NanoComposite Stainless Steel Powder Technologies  

SciTech Connect

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

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

2012-07-25

444

The influence of microstructure on the sintering process in crystalline metal powders investigated by positron lifetime spectroscopy: II. Tungsten powders with different powder-particle sizes  

Microsoft Academic Search

Compacts of tungsten powder with five different powder-particle sizes (from 0953-8984\\/11\\/7\\/010\\/img7 to 0953-8984\\/11\\/7\\/010\\/img8) are subjected to pressureless sintering. We investigate the change in microstructure during the sintering process by positron lifetime spectroscopy. So as to be able to distinguish between defects having the same positron lifetime, we investigate their kinetics when the sample is annealed. In particular, we consider the

T. E. M. Staab; R. Krause-Rehberg; B. Vetter; B. Kieback; G. Lange; P. Klimanek

1999-01-01

445

Modelling Die Compaction in the Pharmaceutical Industry  

Microsoft Academic Search

This chapter presents the current state of die compaction modelling in the pharmaceutical industry. The topic is introduced\\u000a with a review of the particular features of pharmaceutical powder formulations. The operation of rotary production presses\\u000a is described together with experimental procedures developed to characterise die-fill and high-speed compression. The experimental\\u000a techniques described in Chapters 4–8 are employed to characterise the

I. Sinka; A. Cocks

446

Extrusion and mechanical properties of mixed powder and spray co-deposited Al 2014\\/SiC metal matrix composites  

Microsoft Academic Search

Al 2014\\/SiCp metal matrix composites have been produced by a powder metallurgy route that included mixing, canning, degassing and hot extrusion (300°C, 16:1). Two types of SiC (12 and 4 µm), two SiC contents (~ 10 vol. % and ~ 15 vol. %) and three different degassing temperatures (350, 400, 500 °C) were used. The degassing temperature was found to

M. H. Carvalho; T. Marcelo; H. Carvalhinhos; C. M. Sellars

1992-01-01

447

Amorphous powders of Al-Hf prepared by mechanical alloying  

SciTech Connect

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

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

1988-01-01

448

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

SciTech Connect

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

Louthan, M

2007-07-17

449

Effect of starting particle size on hot-pressing of magnesium oxide powder prepared by vapour-phase oxidation process  

Microsoft Academic Search

Effect of starting particle size on hot-pressing of magnesium oxide (MgO) powder was examined using seven kinds of MgO powders\\u000a prepared by a vapour-phase oxidation process; the average primary particle sizes were 11, 25, 32, 44, 57, 107 and 261 nm.\\u000a These compressed powders (compacts) were hot-pressed at a temperature between 900 and 1300°C. The densifications of these\\u000a compacts during

K Itatani; R Yasuda; F. Scott Howell; A Kishioka

1997-01-01

450

Powder processing and properties of zircon-reinforced Al-13.5Si-2.5Mg alloy composites  

SciTech Connect

Zircon, ZrSiO{sub 4}, is a thermally stable mineral requiring expensive and energy-intensive process to reduce. Owing to its abundance, high hardness, excellent abrasion/wear resistance, and low coefficient of thermal expansion, a low-cost alternative use of the mineral for medium-strength tribology was investigated. The present study has developed a conventional low-cost, double-compaction powder metallurgy route in the synthesis of Al-13.5Si-2.5Mg alloy reinforced with zircon. The mechanical and physical properties were determined following the development of optimum conditions of cold pressing and reaction sintering. Reinforcing the hypereutectic Al-Si alloy with 15 vol% zircon particles (size <200 {micro}m) and cold pressing at 350 MPa to near-net shape, followed by liquid-phase reaction sintering at 615 C in vacuum for 20 min, improved the ultimate tensile strength, 0.2% yield strength, and hardness of the alloy by 4, 12.8, and 88%, respectively. At values of more than 9 vol% zircon, percent elongation and the dimensional changes of the sintered composites remained virtually unchanged. At a critical volume fraction of zircon, between 0.03 and 0.05, a sharp rise in hardness was observed. Microstructural and mechanical property analysis showed that the improvement in the mechanical properties is attributable largely to the load-bearing ability and intrinsic hardness of zircon, rather than to particulate dispersion effects. A good distribution of the dispersed zircon particulates in the matrix alloy was achieved.

Ejiofor, J.U.; Reddy, R.G. [Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Metallurgical and Materials Engineering; Okorie, B.A. [Enugu State Univ. of Technology (Nigeria). Dept. of Metallurgical and Materials Engineering

1997-06-01

451

Powder processing and properties of zircon-reinforced Al-13.5Si-2.5Mg alloy composites  

NASA Astrophysics Data System (ADS)

Zircon, ZrSiO4, is a thermally stable mineral requiring expensive and energy-intensive process to reduce. Owing to its abundance, high hardness, excellent abrasion/wear resistance, and low coefficient of thermal expansion, a low-cost alternative use of the mineral for medium-strength tribology was investigated. The present study has developed a conventional low-cost, double-compaction powder metallurgy route in the synthesis of Al-13.5Si-2.5Mg alloy reinforced with zircon. The mechanical and physical properties were determined following the development of optimum conditions of cold pressing and reactionsintering. Reinforcing the hypereutectic Al-Si alloy with 15 vol% zircon particles (size < 200 µm) and cold pressing at 350 MPa to near-net shape, followed by liquid-phase reaction sintering at 615 °C in vacuum for 20 min, improved the ultimate tensile strength, 0.2 % yield strength, and hardness of the alloy by 4,12.8, and 88%, respectively. At values of more than 9 vol% zircon, percent elongation and the dimensional changes of the sintered composites remained virtually unchanged. At a critical volume fraction of zircon, between 0.03 and 0.05, a sharp rise in hardness was observed. Microstructural and mechanical property analysis showed that the improvement in the mechanical properties is attributable largely to the load-bearing ability and intrinsic hardness of zircon, rather than to particulate dispersion effects. A good distribution of the dispersed zircon particulates in the matrix alloy was achieved.

Ejiofo, J. U.; Okorie, B. A.; Reddy, R. G.

1997-06-01

452

The Compact for Education.  

ERIC Educational Resources Information Center

The Compact for Education is not yet particularly significant either for good or evil. Partly because of time and partly because of unreasonable expectations, the Compact is not yet a going concern. Enthusiasts have overestimated Compact possibilities and opponents have overestimated its dangers, so if the organization has limited rather than…

Harrington, Fred Harvey

453

Prediction of compaction curves  

Microsoft Academic Search

Compaction of soil is one of the major activities in geotechnical engineering involving earthworks. Compaction curve generally features an inverted parabolic shape and is used to find the optimum water content that maximises dry density. Since its introduction by Proctor in 1933, several researchers have provided qualitative explanations for the general shape of the compaction curve. Furthermore, there is a

Nurses Kurucuk; Australia Jayantha Kodikara; Australia Delwyn Fredlund

454

Soil Compaction and Drainage  

NSDL National Science Digital Library

This bulletin, authored by N.R. Fausey and B.H. Nolte for Ohio State University, describes soil compaction and its effect on drainage and crops in situations of surface soil compaction and deep soil compaction. Contains links to research, discussions and conclusions.

Fausey, N. R.; Nolte, B. H.

2008-02-07

455

An investigation of the influence of powder particle size on microstructure and hardness of bulk samples of tungsten carbide  

Microsoft Academic Search

Bulk tungsten carbide samples were prepared by consolidating tungsten carbide powders using plasma pressure compaction. Three different powder particle sizes were chosen and the samples were obtained by consolidating the particles under conditions of pulse and no-pulse. Microstructural observations and density measurements provide sufficient evidence for the presence of porosity even after consolidation at 1500 °C. Regardless of initial powder

T. S. Srivatsan; R. Woods; M. Petraroli; T. S. Sudarshan

2002-01-01

456

An investigation on the capability of equal channel angular pressing for consolidation of aluminum and aluminum composite powder  

Microsoft Academic Search

In this study equal channel angular pressing (ECAP) was used as a technique for consolidation of attritioned aluminum powder (45?m) with varying concentration of nano alumina powders (35nm) in tube at 200°C. The effect of ECAP on consolidation behavior of composite powder and mechanical properties of subsequent compacts are presented. It is found that ECAP has the capability of consolidating

R. Derakhshandeh. H; A. Jenabali Jahromi

2011-01-01

457

Composite powder particles  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

458

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

SciTech Connect

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

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

2000-04-24

459

Spark-plasma-sintering (SPS) of nanostructured titanium carbonitride powders  

Microsoft Academic Search

Spark-plasma-sintering (SPS) compaction experiments of nanostructured titanium carbonitride powders have been performed at 1600°C and 1800°C (sintering time = 1min). The as-received nanostructured powders have been synthesized through rapid condensation from the gas-phase (high frequency plasma). The sintering results were compared with data obtained by various conventional sintering techniques such as pressureless sintering, gas pressure sintering, and hot pressing. The

P. Angerer; L. G. Yu; K. A. Khor; G. Korb; I. Zalite

2005-01-01

460

Low temperature fabrication from nano-size ceramic powders  

SciTech Connect

The objective of the compaction process is to produce a dense green-state compact from a nanosize powder that subsequently can be sintered at high temperatures to form a dense ceramic piece. High density in the green-state after pressing is of primary importance for achieving high densities after sintering. Investigation of the compaction behavior of ceramic powders, therefore, is an important part of characterization of raw ceramic powders and evaluation of their compaction behavior, analysis of interaction between particles, and the study of microstructure of green body (unsintered) during pressure-forming processes. The compaction of nanosize ceramic particles into high density green bodies is very difficult. For the nanosize materials used in this study (amorphous Si{sub 3}N{sub 4} and {gamma} Al{sub 2}O{sub 3}), there is no evidence by TEM of partial sintering after synthesis. Nevertheless, strong aggregation forces, such as the van der Waals surface forces of attraction, exist and result in moderate precursor particle agglomeration. More importantly, these attractive surface forces, which increase in magnitude with decreasing particle size, inhibit interparticle sliding necessary for particle rearrangement to denser bodies during subsequent compaction. Attempts to produce high density green body compacts of nanosize particles, therefore, generally have been focused on overcoming these surface forces of attraction by using either dispersive fluids or high pressures with or without lubricating liquids. In the present work, the use of high pressure has been employed as a means of compacting nanosize powders to relatively high green densities.

Gonzalez, E.J.; Piermarini, G.J.; Hockey, B. [and others

1995-06-01

461

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

PubMed

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

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

2014-01-01

462

Oxide Dispersion Strengthened Iron Aluminide by CVD Coated Powders  

SciTech Connect

This I &I Category2 program developed chemical vapor deposition (CVD) of iron, aluminum and aluminum oxide coated iron powders and the availability of high temperature oxidation, corrosion and erosion resistant coating for future power generation equipment and can be used for retrofitting existing fossil-fired power plant equipment. This coating will provide enhanced life and performance of Coal-Fired Boilers components such as fire side corrosion on the outer diameter (OD) of the water wall and superheater tubing as well as on the inner diameter (ID) and OD of larger diameter headers. The program also developed a manufacturing route for readily available thermal spray powders for iron aluminide coating and fabrication of net shape component by powder metallurgy route using this CVD coated powders. This coating can also be applid on jet engine compressor blade and housing, industrial heat treating furnace fixtures, magnetic electronic parts, heating element, piping and tubing for fossil energy application and automotive application, chemical processing equipment , heat exchanger, and structural member of aircraft. The program also resulted in developing a new fabrication route of thermal spray coating and oxide dispersion strengthened (ODS) iron aluminide composites enabling more precise control over material microstructures.

Asit Biswas Andrew J. Sherman

2006-09-25

463

Shock Consolidation of Nanocrystalline Aluminum Powders for Bulk Component Formation  

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

464

Thermal conductivity of pressed powder compacts: tin oxide and alumina  

Microsoft Academic Search

Three aspects, which significantly reduce heat transfer through a polycrystalline material, are considered in this paper: porosity, grain boundary thermal resistance and the state of the grain–grain contacts. Tin oxide and alumina were chosen as model systems. Tin oxide, without a sintering additive, does not densify during thermal treatment but grain growth is not inhibited and consequently the microstructure can

C. Poulier; D. S. Smith; J. Absi

2007-01-01

465

Problems of YAG nanopowders compaction for laser ceramics  

NASA Astrophysics Data System (ADS)

Slip casting and colloidal slip casting at high pressure of yttrium aluminum garnet powders were investigated. It was found that the presence of residual pores in laser oxide ceramics was determined mainly by big size pores in the compact. The size of pore in compact is critical when it is greater than the mean size of initial particles. It was shown that formation of pores' structure in compact was controlled by appearance of quasi-particles in heavy loaded slurry. Pores concentration is critical for ceramics optical transmittance.

Bagayev, S. N.; Kaminskii, A. A.; Kopylov, Yu. L.; Kravchenko, V. B.

2011-03-01

466

The rheology and hydrodynamics of dry powder lubrication  

NASA Technical Reports Server (NTRS)

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

Heshmat, Hooshang

1991-01-01

467

Reversible DNA compaction.  

PubMed

In this review we summarize and discuss the different methods we can use to achieve reversible DNA compaction in vitro. Reversible DNA compaction is a natural process that occurs in living cells and viruses. As a result these process long sequences of DNA can be concentrated in a small volume (compacted) to be decompacted only when the information carried by the DNA is needed. In the current work we review the main artificial compacting agents looking at their suitability for decompaction. The different approaches used for decompaction are strongly influenced by the nature of the compacting agent that determines the mechanism of compaction. We focus our discussion on two main artificial compacting agents: multivalent cations and cationic surfactants that are the best known compacting agents. The reversibility of the process can be achieved by adding chemicals like divalent cations, alcohols, anionic surfactants, cyclodextrins or by changing the chemical nature of the compacting agents via pH modifications, light induced conformation changes or by redox-reactions. We stress the relevance of electrostatic interactions and self-assembly as a main approach in order to tune up the DNA conformation in order to create an on-off switch allowing a transition between coil and compact states. The recent advances to control DNA conformation in vitro, by means of molecular self-assembly, result in a better understanding of the fundamental aspects involved in the DNA behavior in vivo and serve of invaluable inspiration for the development of potential biomedical applications. PMID:24444152

González-Pérez, Alfredo

2014-01-01

468

Investigation of machining damage and tool wear resulting from drilling powder metal aluminum alloy  

SciTech Connect

This report documents the cutting of aluminum powder metallurgy (PM) parts for the North Carolina Manufacturing Extension Partnership. The parts, an aluminum powder metal formulation, were supplied by Sinter Metals Inc., of Conover, North Carolina. The intended use of the alloy is for automotive components. Machining tests were conducted at Y-12 in the machine shop of the Skills Demonstration Center in Building 9737. Testing was done on June 2 and June 3, 1997. The powder metal alloy tested is very abrasive and tends to wear craters and produce erosion effects on the chip washed face of the drills used. It also resulted in huge amounts of flank wear and degraded performance on the part of most drills. Anti-wear coatings on drills seemed to have an effect. Drills with the coating showed less wear for the same amount of cutting. The usefulness of coolants and lubricants in reducing tool wear and chipping/breakout was not investigated.

Fell, H.A. [Lockheed Martin Energy Systems, Inc., Oak Ridge, TN (United States)

1997-05-01

469

Mechanical properties of compacts and particles that control tableting success.  

PubMed

The use and limitations of linear-elasticity equations for describing mechanical properties of compacts is discussed; the limitations occur because compacts are porous, viscoelastic, nonhomogeneous, Mohr bodies. Awareness of these properties permits meaningful comparisons to be made. Ignoring limitations may result in unjustified conclusions. Special care during measuring mechanical properties of compacts is required. The mechanical criteria for a successful formulation are good flowability for powders and adequate strength without fracture for compacts. Interparticle attraction is spontaneous but particle contact numbers and size are limited by mechanical preclusion. Plastic deformation and fracture mechanics are controlling mechanisms with the magnitude of elastic constants having little effect on the successful processing. General compaction characteristics can be appraised by using combinations of properties, e.g., specific tableting indices. PMID:9294809

Hiestand, E N

1997-09-01

470

Differential compaction behaviour of roller compacted granules of clopidogrel bisulphate polymorphs.  

PubMed

In the present work, in-die and out-of-die compaction behaviour of dry-granulated powders of clopidogrel bisulphate (CLP) polymorphs, form I and form II, was investigated using a fully instrumented rotary tablet press. Each polymorph was compacted at three different roller pressures [70.3 (S1), 105.5 (S2) and 140.6 (S3)kgf/cm(2)], and obtained granules were characterized for their physico-mechanical properties. Compaction data were analyzed for out-of-die compressibility, tabletability and compactibility profiles, and in-die Heckel, Kawakita and Walker analysis. The roller compacted granules of both forms showed markedly different tabletting behaviour. Roller pressure exhibited a trend on compaction behaviour of form I granules, whereas, in case of form II, the effect was insignificant. Tabletability of the six granule batches follows the order; I_S1>I_S2>I_S3>II_S1?II_S2?II_S3. In case of form I, the reduced tabletability of the granules compacted at higher roller pressure was attributed to the decreased compressibility and plastic deformation. This was confirmed by compressibility plot and various mathematical parameters derived from Heckel (Py), Kawakita (1/b) and Walker (W) equations. The reduced tabletability of form I granules was due to 'granule hardening' during roller compaction. On the other hand, insignificant effect of roller compaction on tabletting behaviour of form II granules was attributed to brittle fragmentation. The extensive fragmentation of granules offered new 'clean' surfaces and higher contact points that negated the effect of granule hardening. PMID:24971694

Khomane, Kailas S; Bansal, Arvind K

2014-09-10

471

Explosive compaction/cladding of metal sheathed/superconducting grooved plates: FE modeling and validation  

NASA Astrophysics Data System (ADS)

Explosive compaction/cladding is a technique that combines explosive welding and compaction and is particularly effective for superconducting materials. In this paper, experimental and numerical investigations were carried out on rectangular grooved plates, filled with superconducting ceramic powder, subjected to explosive loading. The compacts are characterized in terms of SEM observations and Tc measurements, showing that the superconducting properties are maintained. The response of the metal and ceramic material during compaction is studied using finite element techniques and the dimensions of the compacts, pressure and temperature distributions during the entire process are predicted. The numerical results obtained are compared with experimental observations, leading to the validation of the 3-dimensional FE model.

Mamalis, A. G.; Vottea, I. N.; Manolakos, D. E.

2004-08-01

472

Characterization of shock-loaded nanocrystallite silicon powder  

NASA Astrophysics Data System (ADS)

Shock compactions of nanocrystallite silicon powder with an average particle size of 50 nm were performed using a propellant powder gun. A copper plate 30 mm in diameter was accelerated to a copper capsule with an infill of nanocrystallite silicon powder pressed to 40% of the theoretical maximum density. The pressure generated in silicon powder was calculated to be below 3.6 GPa. The products of shock compression were examined by X-ray diffraction (XRD) analysis and Raman spectroscopy. The shocked samples were well consolidated, but the color of the samples changed from yellow to gray. No additional peak other than the diamond structure of silicon was observed in the XRD traces and Raman spectra. The particle size of the shocked nanocrystallite silicon was larger than that of the starting powder. Such coarsening may be enhanced by shock-induced heat.

Kishimura, Hiroaki; Matsumoto, Hitoshi

2011-06-01

473

Phenomenological modeling of the compaction dynamics of shaken granular systems  

NASA Astrophysics Data System (ADS)

Granular systems such as powder or sand can compact because of shaking. Using a phenomenological decay law for the successive inverse packing fractions, we obtain the relaxation dynamics for the packing fraction recently found in the experiment by Knight et al. [Phys. Rev. E 51, 3957 (1995)] and discuss the physical implications as well as the physical origin of the proposed decay law.

Linz, Stefan J.

1996-09-01