Electric discharge compaction of metal powders

Literature Powder production

p.36

Pressing

p.36

Sintering

p.36

Fundamentals

P.37

Aluminium

P.37

Iron and steel

P.37

Coatings

P.37

Laser machining

P.37

For copies of full papers you are recommended authors,

to contact individual

use the Interlibrary

Loan

system or, for conference

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Literature. review Production of ZrO, microspheres and microshells by electro-dispersion precipitation from aqueous solutions of ZrCl, is described. The process uses an organic liquid and NH, and requires control of PH. A is presented. model for the process Simulations to describe the effects of NH, concentration were carried out. Good agreement between experiment and simulation is reported.

Production and characteristics of AgO-CuOcomposite powders H.D.Giicksman

et al. (DuPont, Wilmington, USA.) Powder Technol., Vol I JO, No 1-2, 2000, 76-81.

Powder production Insights into variables in water atomization of iron B.Bergquist. (L&d University of Technology, L.&d, Sweden.) Powder Me~~l.,Vo~42, Nu4,1999,331-342.

Effects of surfactants on surface tension and viscosity of liquids are noted. A study of effects on characteristics of water atomized Fe powders, using a wide range of material and process parameters, is described. It is reported that addition of S reduces particle size due to reduction in surface tension. Increased water pressure reduced powder density, lowered flowability and reduced swelling during sintering. A model is proposed. Addition of Al reduced standard deviation in particle size distribution and increased %C.

Wet chemical synthesis of BaTiO, from titanium dioxide microspheres M.Z.C.Hu et al. (Oak RidgeNationat Lab, USA.) Powder Tech&.,

Oak Ridge,

VolJ10, No i-2, 2000,2-14.

is reported that a low-temperature hydrothermal method for preparation of pure, controlled uniformly sized, ultrafine and nanocystalline BaTiO, powder, from 30, microspheres and Ba(OH), solution, had been developed. Reactants and products were characterized. The BaTiO, had a thermally stable cubic structure. It

Synthesis and modelling of production of zirconia by electro-dispersion precipitation N.T.Hanis et al. (University of Marykmd, USA.) Powder Technot., Vol 110, No l-2, 2oo0, f5-21.

36

MPR June

2001

It is reported that spray pyrolysis of Cu-Ag nitrate solutions had been used to make AgO-CuO composite powders. Stages in the process are described: evaporation of water, melting and decomposition, first of Cu nitrate followed by Ag nitrate, to give the oxides. The powders are shown to contain well-dispersed Ag and Cu oxides. Particle morphology varied with composition in the range 60 to 95%Ag. The method may be applicable to metal and alloy powder production,

Ni powders from aqueous slurries R.Mureno et al. (CSIC. Madrid, Spain.) Advanced Mater., Vol12, No 16, 2oo0, f192-1195. It is reported that a novel method of making metal powders had arisen from a study of rheological properties of aqueous metal suspensions. Porous Ni parts had been made. The binder used, carrageen, is considered to be a suitable binder for injection and gel casting, at low cost.

Pressing Rubber isostatic pressing M.Sagarua et al. (IntennewlIics Co Ltd, Kyaw, Jopan.) Mater. Design, Vol21, 2000,243-249.

Rubber isostatic pressing of magnetic and other powders is reviewed. The process involves filling a rubber mould with the powder which is then die pressed. A new filling technique, air tapping and grid separation is reported. This is shown to allow application of

0026-0657/01/$-see

RIP to a wide range of metallic and non-metallic powder materials.

Enhanced densification of metal powders by transformation mismatch plasticity C.Sckuk et al. (Northwestern University, Evanston, USA.1 Acta Mater., Vo 48, No 8, 2000, 1639-1653. Ti powder was hot pressed, isothermally at 980 “C, in the B phase field, and with thermal cycling between 860 and 980 “C, in the I# phase field. Den&cation was enhanced by the thermal cycling. This is attributed to transformation mismatch plasticity between phases. The experimental results are shown to agree with models for powder densification. Similar conclusions were reached for Ti powder with 1, 5 or 10~01% ZrG, even though ZrG, inhibited densification.

Densification in long cylindrical compacts of iron mixed with fine iron powder T.Nakagawa,

S.Takahashi.

N~r~~~~, &an.)

(Nihon

University,

J. Jpn Sot. Powder~o~der Met&.,

Vol47, No 1, 2000, 52-57. (In 1apanese.J It is reported that long hollow cylindrical compacts, with a thin wall, had been pressed by single action tooling from Fe powders with additions of lOwt%fine Fe powder, l%Zn stearate and 1% micro-wax. Green densities up to 88% were attained in a length of 40 mm with a 3% variation in density. The sintered tube had a radial crushing strength of 400 MPa.

Sintering Electric discharge compaction of metal powders P.K.Rajagop&net al. (BhubbaAtomicResemck Cenme, Mzunbai, India.) Mater. Science/Engineering A, Vol 280, 2000, 289-293. It is noted that conventional pressing and sintering or hot pressing may cause unacceptable grain growth in metals and alloys. A study of electric discharge sintering is described. A high pulse of current is passed through powder under pressure in a die for a few milliseconds. The requirements for densification of Ti, Sn and Zn were investigated.

front matter 0 ZOOI Elsevier Science Ltd. All rights reserved.

Improvements

in density

and

structure

are

reported.

Behaviour of metal powder during hot forming - experimental simulation with lead powder

‘4 study of the effects

pressures

at

various

at various

temperatures

uniaxial radial and

and strain

compression stress

strain that

rates using

pressing

Behaviour

rates

results

can be applied similar

die

measurement.

high

reported

and is

with at low

described.

It

from the model

to any industrial

morphological

Critical

process

m terms

of break

optimum

smtering.

with

rheological

Mechanical properties of Fe-Cr prepared by mechanical alloying

Effects

were deter-

Elemental

parameters

are isolated

mechanically

oxides

sure,

up of surface

and

for various

on sintering

of

strength

creased

with

Enhanced blenders

mixing

in double

cone The effect of up to l’%Mg on stntering 12’~~Si-l%Sn-O.l5’%Fe

performances one

regard

two

conventional

with a deflector particles,

of

and

plate to enhance

were compared to rotation

the

other

and

that denslfication

to reduction

axial

with

or radial

Effect of tin on nitriding of rapidly solidified aluminium alloy powder

The

effect

was constructed.

reported

to enhance

single

The

using plate

rate by a factor

is of

25:l.

Influence of induced anisotropy powder based materials N.Bontchwu Bufgann.)

et

al.

(Academy

Int. J. Mech.

Development erence

of

Sofia.

LOl 42, 2000,

anisotropy

of metal powders to a model

methods.

which

Simulations

ing are described. density

during

is discussed

of cotnpaction

distrtbutions

593-

PM hot forging. obeys

a

Velocity,

Ing particle

surfaces

and

are considered. thermo-mechanical model

was

automotive

The

rate

complete coupling

validated connecting

www.metaI-powder.net

against rod.

thus preventing

amount

formation

of AlN formed depended and specific

0

Elemental compacted

and 620 “C. The

ence

to alloy

includes The of

an

mixtures sintered

in the

E Furan

composition,

I

Duane,

J Bnnhnrt.

It is reported been stance

dia-

of liquid

et

al

(Trchmon.

i Acta

coating inner

Halfa.

coatings

were

based

on the

that

Al

that evolves

mg to a temperature

foam

I.mxl.)

Materialz.

reaction

the coating activation

between

The structure

was investigated layer containing

on BN using a

grown

and found

Ti

of the

to he an

fine TiB and TiB,,

an outer layer containing

and

Ti and N. Growth

was diffrlsion

controlled

with

of an

energy of 215 kJ.tnol*‘.

Laser machining

of

L.LI, A SlocombeCUMJST, Surface Scwnce,

Inst.

Aduanced

Mater.,

VCJI 48,

matertals

Al powder

gas when heated,

with

had a sub-

and heat-

above 660 “C in an enclo-

No 154/155.

Laser ablation polymer nism

made by mixing

by reaction

Laser ablation of metal-polymer composite materials

and shrinkage.

(Fmunhofer

Gennuny

sec-

with refer-

amount

temperature

is established.

10 to 60wt%.

statistically

Kinetics and microstructure aluminium foam formation Materials, Bremen. 2000, 2349-2362

were at 600

equilibriutn

range

part.

Letters. No 43, 2000. 192-196

of liquid phase pre-

thermal

as an

final

“C in Ar. A relationshIp

and C contents

Coating of boron nitride with titanium powder

surface.

from the isothermal

were analysed

phase, sintering

rule.

phase

amounts

and were

Densities

and friction. forging

powder

of the ternary

grams

and pressure

model

Al-Si-Cu and liquid

the

Coatings

Ti base

sent were detertnined

is used to simulate

strain

The

in

was at 280 to 3 30 “C in air and sin-

was at 1350

between

tempera-

of an injection

Sn coat-

Liquid phase sintering of compacts of elemental AI-Si-Cu powders

and forg-

of anisotropy

compressibility

volumetric

powders

were investigated %C

powder and BN substrates.

It is assumed that the material

viscoplastic

of Sn. It is

tering

of

element

in the simulations.

tnodel

control

technique

Three-field formulation of finite element analysis of compressible viscoplastic powders

element

by addition

that this is due to molten

tions

A finite

of Al alloys,

com-

and the final shape of the

part are incorporated

with

was not detected.

and debinding

with ref-

uses firute

Effects

in N, is reduced

on powder composition

615.

paction

sintered

that the N content

considered of AIN.

in

of Scwncec,

Sciencea,

It is reported

of ‘XC

Cr-Mo

to

Debinding

parameter

deflector

mixing

of 1045 MPa and

attamed

steel

moulded

model

were

characteristics

aid

was assessed A

pick up N and 0 dur-

strength

ture on smtermg

material.

analysis.

de,

It is sug-

of

Dark and light glass beads were used image

time.

surfaces.

as model digital

and elongation

milling

for 100 h. (5 phase

rotation.

Mixing

by

“C for 5 min.

Control of carbon in injection moulding of Cr-Mo steel

IS enhanced

oxide films on the Al alloy particle

consolidated

axial flow of

experimentally

speed

increased

Tensile

were

of Al-

powder was mvestigat-

by adding Mg. This is attributed

double-cone

and

at 850

increased

elongation

milled

ed. It IS shown

times

gested that the powders ing milling.

powders

in Ar, at 1.33 kPa pres-

sintering

Tensile

11%

blenders,

Fe-48at’YXr alloyed

spark plasma

characteristics.

The

and morphology.

Iron and steel

properties

Effect of magnesium aluminium powder

conditions

was investi-

and microscopy.

and sintered

and process

The foam was characterized

temperatures.

material

powder

and

is

mined.

and

liquid phase sintering

by dilatometry

on green

for structure

and degassed 6061 Al alloy pow-

ed

composttion

were investigated.

conditicons

The powder was die compact-

gated

was investigated

of process

der IS described. Supersolidus of Pb powder

liquid phase sintering aluminium alloy powder

on prealloyed

Al melts and forms the foam. Effects

of alloy

Supersolidus of degassed

Fundamentals

CompactIon

sure. The

Aluminium

2000,

machining

cotnposites

is reported

Manchrsw,

L’k’.)

of metal

is descrtbed.

to be absorption

breaks election

bonds

volatization between

powder-

The

mecha-

of the laser-

energy by the metal powder, transfer the polymer,

Appl

617-621.

of heat to

of the polymer powder

particles

which and

of the metal powder by an inert gas let.

MPR June

2001

37