Liquid phase sintering of mechanically alloyed supersaturated iron-copper powders

Sintering

CONSTITUTIVE EQUATION POWDER COMPACTION INCORPORATING POWDER

MODELLING OF DENSIFICATION DURING ACTIVATED SOLID STATE SINTERING J.L. Johnson, State Tram

K.M. German

University,

USA).

CHARACTERISTICS

(Pennsylvania Metall.

Mater.

A, Vol 27A, No 2, 1996, 441-450.

The role of grain boundary segregating species in enhancing solid state sintering was discussed W

with

with reference to a model for

transition

Modifications

elements

to

added.

three-stage

theory are suggested.

classical

It is shown

that the

second and third stages overlap according to the amount of closed porosity. Mean curvature curvature

theory is used to estimate pore during the intermediate stage of

sintering. modrlled

In the final stage pores are on corners of a tetrakaidehedron

and

on the square

location small

facets.

on densification and

grain

Effect

of pore

is shown

boundary

FOR

to

mobility

be

is a

M.A.E. Saleh, S. Shima (Kyoto University, Kyoto, Japan). J. Japan Sot. Pounder Pozr,der Metall., Vol 41, No 12, 1994, 1541. 1546. (In English.) Influence of powder characteristics on tap density, compressibility, densilication mechanisms and density distribution is discussed. Attempts to relate powder properties to constitutive behaviour during compaction are described with the object of improving existing constitutive equations. Experiments on Cu are used to show that the effects of particle shape is small within a small range of particle sizes but not within a wide range. SURFACETOPOGRAPHYOF COMPACTED

AGGREGATES

OPTIMIZATION

~

OF COMPACTION

Shenyang, China). Acta Mater., Vol 44, No 3, 1996, 1211-1221. Deformation structures in ball milled Cu were investigated. Shear bands and mechanical twins were observed. Formation of twins was discussed with respect to the Venables model and shear stresses. Randomly oriented nm scale subgrains are explained on the basis of formation on shear bands. STRUCTURE

AND PROPERTIES

COPPER-ALUMINIUM SINTERED

OF

ALLOY

AFTER

INTERNAL

OXIDATION T. Sugui et al. (Academia Sinica, Shenyang, China). PM Technol., Vol 13, No 4, 1995, 289-293. (In Chinese.) Investigations on wear and corrosion properties of Cu-AlzOs materials, made by internal oxidation of Al in Cu-Al alloys are described. The Al,O,l is reported to form at grain boundaries and within grains and

CONDITIONS

increases

N. Ozkan, B.J. Rriscoe (Imperial College, London, IJK). Powder Technol., Vol 86, No 2, 1996, 201-207. Surface topography of die pressed cylinders of AlzO:l, made from agglomerated powders was investigated as functions of pressure, aspect ratio and breakdown of agglomerates at the compact/die interface using a laser profilometer. Agglomerates started to break at low pressures and surface pores closed at high pressures. Deformation at curved surfaces varied with position from top to bottom of the compact.

Iron and steel

wear and corrosion

resistance.

greater factor. The model allows pore/grain boundary

separation

experimentally

to

measured

match

grain

sizes.

Dilatometer experiments were performed on pure W and W alloyed with small amounts

of Co 7Fe , Ni and Pd.

MODERN

METHODS

TEMPERATURE FURNACES M. Dolezal

OF

REGULATION

(PRAMET, Sumperk,

IN PM

Czechoslo-

vakia). Pokrokg Praskove Metalurgie, 4, 1995, 24-36. (In Czech.) Problems and control

No 3/

of temperature measurement in PM are discussed with

reference to sensors current application.

and The

developing

integrated

indicated. validated.

Methods

controllers possibility

control are

in of

systems

proposed

is and

Fundamentals PROJECTED

AREAS

OF ELLIPSOIDS

AND CYLINDERS G.T. Vickers field, IJK).

(University Powder

of Sheffield,

Wchnol.,

Shef-

Vol 86, No 2,

1996, 195-200. It is noted that in measuring particle size, volume and concentration by laser diffraction the powder is often assumed to be spherical but for other shapes projected areas have a range of values, This is examined from a statistical viewpoint for ellipsoids, cylinders.

for axes with ratios 1:2:8 and for Graphs of distribution functions

are presented.

38

MPR October

1996

Aluminium PRODUCTION

AND PROPERTIES

OF

AMORPHOUS ALUMINIUM ALLOY MADE BY GAS ATOMIZATION C.H. Bae et al. (National University of Technology, Pusan, Korea) J. Korean Inst. Metals, Vol 33, No 8, 1995, 1069-1074. (In Korean.) Investigations to determine optimum composition of an Al-Ni-Ce-Mg alloy are described. Al-Gat’%;Ni-4!%Ce-4%Mg was produced and He atomized powder and melt spun ribbon. The powder was extruded at 450°C and a tensile strength of 750 MPd with 7.5’% elongation is reported.

Copper

ADDITION

OF HIGH SPEED

STEEL

POWDERS

ON PROPERTIES

AND

STRUCTURE

OF SINTERED

STEEL

Z. Guoli et al. (Northeastern IJniversity, Shenyang, China). PM Technol., Vol 13, No 4, 1995, 285-288. (In Chinese.) The effects of adding HSS powder on the structure and properties of sintered steels were investigated. The optimum amount added was 20%. Hardness, retained austenite and martensite were reported as functions of the amount of HSS added. Martensite was ;hown to form in the interconnected areas and Fe particles.

between

prior

HSS

CHARACTERISTIC OF WARM COMPACTED ANCORDENSE H. Fenglin China). 294-302.

(Powder

powder reported high

Co, Beijing,

Vol 13, No 4, 1995,

(In Chinese.)

Experiences materials

Metallurgy

PM Technol.,

in the use of Ancordense

are with

described.

This

polymeric

additions.

that

strength

warm parts

is a steel

compaction after

single

It is yielded

pressing

and sintering. LIQUID

PHASE

SINTERING

OF

DEFORMATION STRUCTURES MILLED COPPER

IN BALL

MECHANICALLY ALLOYED SUPERSATURATED IRON-COPPER POWDERS

H.Q.

Sciences,

H. Goto et al. (Kyushi University, Fukuoka,

Ye

et

al.

(Academy

of

.Japan). J. Jupun Inst. M&ul.s, Vol 59, No 12, 1995, 1278-1285. (In *Japanese.)

temperature. For specimens 1 mm thick by 1-4 mm wide size had little effect. For

confirmed. optimize

Liquid phase sintering of supersaturated solid solution Fe,- (10 to 33)wt%Cu powders, mechanically alloyed from elemental powders, was investigated. The MA powders were hard and were annealed prior to compaction and sin&ring. Up to 25%Cu, the MA powder was single

specimen thickness 0.3 mm critical temperature was reduced and critical stress lowered slightly.

tensile strength

and high creep resistance.

INTERACTION AND MOLTEN

BETWEEN TUNGSTEN COPPER-SILICON

bodycentred

SINTERED

Cu oozes and

cubic

pl1ase. During

sintering

rearrangement the

attained

of

the

alloy.

The

98”<, density

and

Fe

particle

25%Cu

EFFECT

the

?Fe

J. Takata, h’. Kawai (Kobc

in

0.84,C-O.75”~,Zn stearate endothermic functions

gas

dew point.

when

were

of heating

Fc-Bwt:Cu-

and cooling

Decreased

heating

shrinkage and decrease in caused swelling. Compacts carburizing

and

expanded on cooling. transfer model, to phenomena, is proposed. CONSOLIDATION

sintered

investigated

and carbon these

A. lnoue

PI nl. (Tohoku

.Japan)

J. Japan

Metall.,

Vol

42,

No

40-46.

(In

compacts and 1.6

nanocrystalline powders

GPd

compacts which

are

properties.

Reduction and carburization of W from minerals was investigated and optimum conditions

for

production

established.

The

potential

S.B. Prima

machining

of electrode

et al. Pwoshkwayu

Mc&&~r-

ternary

system

Ti-Nb-Ni

The system is shown to number of pseudo-binary

eutectics and prritectics. The existence 01 a ternary compound, ‘fi:,(i%,Nb),, was not, confirmed.

SIZE ON

by liquid phase sintering, of W heavy alloys are

Applications, high damping

RECRYSTALLIZED Y.Hiraoka, T.IIoshika

BASED

The role of Th and ThO, aditives in enhancing the properties of W base materials

is discussed.

radioactivity Research to including

It is noted that the

of Th develop

presents problems. alternatives to Th,

La or CezO:j dopants,

GRAIN STRUCTURE

et ccl. (Kyushi Inst of Technology, Japan)

J.

Japan

grain and tensile

effects

of

E. Rergmann

(Balzrrs

Int. .I. Refructory

used

3-dimensional delamination, creep

the

and

control

development

Institue.

electron

of

high

Examples

W. Putz et al. (Technical

of the extent

of interlocking

Austria).

from liquid N to ambient

are derived.

is a large

grain

rate where

boundary

RADIO

grain

characteristic there

density

are given.

GROWTH OF DIAMOND IN AN ELECTRODELESS CAPACITIVE FREQUENCY DISCHARGE

bend tests and

current

hybrid processes.

of

in creep

bombardment.,

shape, tests were

prevention

Increase

is discussed which may bc

plasmas. The hot filament can also drive CVD reactions and there is a possibility of

Parameters

stress

IiSA).

1230-1236.

carried nut on fine W wires with respect to fracture. Interlocking grains are considered to have two roles in enhancing creep resistance

to

fracture.

critical

Ltd, Florida,

triode etching and throwing power, activated reactive ion deposition and

boundary

to measure

tools

Mrtwls Hard Muter., Volol

transition

&point

arc

HIGH CURRENT DENSITY PLASMA PROCESSES WITH DIFFERENT VAPOUR SOURCES

PVL) using t,he hot filament

WIRES

(ITniversity of Science,

size on ductile/brittle

penetrators.

with regard to the processes

OF FINE PM

MOLYBDENUM

of

is described.

OF INTERLOCKING

12, 1995,

(In Japanese.)

balance uses, dies

14, No 1:3, 1996, 167.172. OPTIMIZATION

Met&s,

Okayama, dapan). J. Japan Sot. Powder Powder Metull., Vol42, No 1, 1996, 108-l 12.

energy

including capa&y

47.

Kitakyushi, OF

are

Z. Ludynski, W. Novak (OKRIT, Warsaw, Poland.) M&u/. Pmszkow, Vol 28, so 3:4, 1995. 24.28. (In l’olish.)

discussed.

Vol 59, No (In Japanese.)

in MO sheet is described.

alloying

PROCESS ENGINEERING AND PROPERTIES OF TUNGSTEN HEAVY ALLOYS

weights,

TO THORIUM

IN TUNGSTEN

are

for electro-erosion

electrospark

Product,ion, and properties

ALTERNATIVES

WC

was

investigated by metallography, thermal analysis and electron and X-ray probe techniques. contain a

materials and

of

for production

discussed.

yiyu, No 3/4, 1995, 48-54. (In Russian.)

TUNGSTEN

TRANSITION

used

I.V. Sokol et al. Poroshkomyn M&tlhrryiyu. No 3;4, 1995, 114-l 17. (In Kussian.)

Coatings on hardmetal

powders

investigation

RAW TUNGSTEN

PHASE RELATIONSHIPS IN TITANIUMNICKEL-NIOBIUM ALLOYS

The

phase

OF ELECTRODE FROM

1’. Paschen. J. Met&s, F’ol 48, No 1, 1996, 45.

1, 1995,

DUCTILE-BRITTLE

were

pore sizes were smaller in than in vacuum sintered

PRODUCTION MATERIALS MINERALS

liquid

and MO- (c’u.Si).

and kinctir outlined.

OF SPECIMEN

and temperatures

is

Titanium

K. Tanoue

An

It

to analyze

of W- (Cu,Si)

MATERIALS

Molybdenum

specimen

determined.

are used

sintering

ADDITIVES

to have good magnetic

EFFECT

by

above

are discussed.

Sendai,

4.4 Gl’a to make nanocrystalline

amorphous

10%. Kinetics of the reaction

Powdrr

maps are presented for amorphous and nanocrystalline powders. 3 GPa was required to dens@ amorphous powders,

reported

Ta

capsule free HIP or vacuum sintering are described. Shrinkage, porosity and pore were

silicide forms on the W at Si contents Results

of

C11-Si,

It is rc>ported that

Powdrr

Densification of Fe-&-B powders, by hot pressing, was investigated. Uensification

from nanocrystalline

W and molten

University,

SW.

.Japanese.)

dense

sintering

Tungsten

POWDERS

BY HOT PRESSING

make

of

OF AMORPHOUS

IRON-ZIRCONIUM-BORON

from

(In Japanese.)

Investigations

rate caused cooling rate contracted

heating,

Nagoya,

Inst. Mrtuls, \‘ol 59, No

in as

rates and

A new explain

University,

(Nagoya

J. Japun

reported that IIIP material specimens.

(In Japanese.) changes

rt al.

characteristics

J. .Japan SW. Powder Pmc~drr Vol 41, No 12. 1994, 1553-1559.

Dimensional

T. Oki

12, 1996, 12861291.

Steel, Takasago,

between

at 1200 C, was studied.

grain

CONDITIONS ON DIMENSIONAL CHANGE IN IRON BASE COMPACTS

to

Reaction

TANTALUM

Japan).

OF HEATING/COOLING

during

VP. Titov ef al. Poroshkomyn Mr~tullw~iyu, No 3. 4, 1995. 29 32. (In Russian.)

OF POROUS

alloy

size was less than %O/tm even after 1 hour sintering at 1100 C.

Mrtall.,

CHARACTERISTICS

on to the ;/Fe grain boundaries

densifies

Japan)

Tantalum

It is considered possible to the structure for both high

area

is

University, Vienna,

Int. J. Rej+actory

Met&s Hrwd Mater., Vol 14, No 1:‘3, 1996, 173-178. It is reported

that plasma

assisted

MPR October

1996

CVD

39