粉末冶金原理課件11制備

Powder

Metallurgy

PrinciplePowder

Metallurgy

Research

Institute2007Particle

Science

and

Engineering粉末冶金原理(課程分布)

40學時教學方式:

雙語講學

Chinese/English課程內(nèi)容:

Part

I

Powder

fabrication

粉體制備

PartⅡ

Powder

characterization

性能How

do

the

powders

fabricate？Main

methods

to

fabricate

powdersWhat physic-chemical

phenomenon

could

beobserved

during

powder

fabrication？Which

method

is

suitable

to

sphere

particles？How

about

the

particle

morphologies？How

can

we

obtain

the

high

purity？What

takes

place

during

the

powder

fabri.?Which

condition

to

control

the

particle

size?What

can

we

do?

related

powder

makings.ContinuersWhat

are

the

microstructures

of

the

particles?What

is

the

apparent

density

of

the

powders?Which

equipment

can

measure

the

fine

particles?課時安排Talking

arrangements霧化制粉快速冷凝化學沉積電解制粉還原制粉Atomization

4hrsRSTRapidsolidification

4hrsChemistry

precipitation4hrsElectrical

fabrication

4hrsReduction

8hrs序言

Introduction

2hrsPartⅠ粉末制備28hrs機械研磨

Mechanical

grinding

4hrs參考書籍:ReferencesPowder

Metallurgy

Science粉末冶金原理 黃培云

P/M.

Principle考核成績

Score

作業(yè)30%

卷面考試70%Part

Ⅱ4hrs粉末性能

12hrs顆粒結構Particle

microstructure

4hrs粒度分布Particlesizeanddistribution比表面

Specific

surface

2hrs考試

Testing

2hrs (closebook)What

is

Powder

MetallurgyPowder

metallurgyStudy

of

the

processing

of

metal

powders,including

the

fabrication,

characterization,and

conversionof

metalpowders

intousefulengineering

components.Studyofthe

basiclaws

andmechanisms

ofpowder

fabri.,

powder

compaction,sinteringand

surfacetreatments.R&D

ofnovel

materialsandproducts.Powder

MetallurgyProcessingpowderMicrostructureChemistryPackingSizeShapeFabricationtoolingprocessingMoldRollExtrudeSinterForgeHot

presstestingpropertiesDensityDuctilityMagneticStrengthConductivityMicrostructurePowder

Metallurgy

Processing粉末冶金材料和制品的工藝流程舉例原料粉末其它添加劑熱壓松裝燒結粉漿燒注混合壓制等靜壓制軋制擠壓燒結燒結預燒結燒縮浸滲

熱處理

電鍍高溫燒結 復壓 精整鍛造 軋制

擠壓 燒結鍛打 復燒（浸油）熱處理拉絲粉末冶金成品Reasons

for

using

powder

metallurgycostproecisionproductivityEconomic(example:automobilegears)Captiverefractoryreactive(example:tungstenlampfilaments)Uniquealloysmicrostructures(example:stainlesssteel

filters

)Ideal

Applications(example:poroustantalum

capacitors)Iron

and

steelAluminumCopperNickelTungstenStainiess

steelTin0.001

0.01

0.1

1Relative

ProductionThe

futureofpowdermetallurgyA

comparison

of

the

relative

production

for

somecommon

metal

powders,logarithmic

scale.High

volume

production

of

precise,

high

qualitystructural

parts

from

ferrous

alloys;Consolidation

of

high

performance

materials,where

full

density

and

reliability

are

primaryconcerns;Fabrication

of

difficulty

to

process

materials,where

fully

dense

high

performance

alloys

can

befabricated

with

uniform

microstructure;Further

considerations

1Further

considerations

2Economic

consolidation

of

special

alloys,

typicallycomposites

containing

mixed

phase;Synthesis

of

non

equilibrium

materials

such

asamorphous,

microcrystalline,

or

some

special

alloys;Processing

of

complex

parts

with

unique

ingredients(組元）or

uncommon

shapes.粉末冶金發(fā)展History

and

development

of

P/M歷史部分:武器,生活用具,藝術建筑Weapon,

life

facilities,

arts-construction,

etc.現(xiàn)代部分:硬質合金,高溫材料,汽車部件,軍事工程Cement

carbide,

refractory

materials,

automobile

parts,equipments

in

defensive,

civilization

products,

etc.目前,

粉末冶金最發(fā)達的國家瑞典(Sweden)硬質合金工業(yè)非常發(fā)達Hoganess,

建立許多子公司,

Be

number

one其次是北美(North

American)和西歐(western

European)

。德國的粉末冶金工業(yè)也是處于世界前列-

工具鋼.,tooling

steel.美國的粉末冶金公司主要產(chǎn)品用戶是汽車制造商

producer，汽車工業(yè)auto

vehicle

industry發(fā)達，帶動了

美國的粉末冶金工業(yè)發(fā)展，這是因為發(fā)達的汽車工業(yè)，大量a

huge

of

application

用粉末冶金部件。SametoAmerican，日本Japan的汽車工業(yè)的發(fā)展帶動了粉末冶金工業(yè)發(fā)展。Different

to

China與中國不一樣，the

western

countriesand

Japan西方或日本的粉末冶金工業(yè)是由兩部分構成

conbined

by

two

part制粉公司：制備各種粉末：Companies

to

fabricate

andsupply

powders制品公司：買進粉末，制備零部件：Companiestofabricate

final

parts能夠大量節(jié)約材料、lowcast無切削、lesscuting少切削，普通鑄造合金切削量在30-50%，粉末冶金產(chǎn)品可少于

5%。Less

or

absent

cutting

machining.“Net

shaping”能夠大量節(jié)省能源energy

saving能夠大量節(jié)省勞動labor

saving能夠制備其他方法不能制備的材料

specific

materialsand/or

products能夠制備其他方法難以生產(chǎn)的零部件the

material

andpart

that

are

difficultly

to

be

produced

by

other

methods粉末冶金技術的優(yōu)越性與局限性

advantages

and

limitation粉末冶金的特點particularly

points能生產(chǎn)用普通熔煉方法無法生產(chǎn)的具有特殊性能的材料；ability

to

produce

materials

which

cannot

be

produced

by

other

method.①

Porous

materials

and

products,

parts

within

lubricants②

Refractory

metals

such

as

tungsten,

molybdenum,

etc③

Pesudo-alloys,

such

as,

tungsten-copper

alloys④

Composite

materials,

such

as

316

ss

+

bioceramic⑤

Nano-crystalline,

sub-micrometer

crystalline

grain

metal⑥

Special

functional

materials

and

products,

such

asmagnetic

products,

supper

alloys

applied

in

airo-industry.Powder

metallurgy

disadvantages

and

limitationRather

lower

mechanical

properties,

for

their

pores

in

partsSize

and

morphological

limitation,

for

press

machine.Rather

lower

wrought

properties,

for

the

products

maycontain

oxide

that

induce

materials

brittle.Rather

small

industry

background

compared

with

castingand

conventional

materials

industry,

such

iron

and

steelproduced

on

big

scale.1+1>2,

new

materials

and

high

performancePowder

metallurgy

plus

conventional

material

processing粉末冶金新技術Novel

techniques

of

powder

metallurgy快速原形制備技術,RSP粉末注射成形、PIM快速冷凝技術獲得非晶粉末、RST粉末濺射成形、powder

spray

forming機械合金化技術、MA溫壓成形技術,Worm

Comp.納米粉末技術,Namo-Tech等靜壓成形-燒結技術,ISP-sintering高性能材料研發(fā)，等等.A

Interest

ComparisonMetal

powders:

109

kg/yearIndustry

minerals:

300

times

109

kg/yearCoffee,

tea,

and

tobacco:

1010

kg/yearPowder

metallurgy

is

a

prolonged

growth

phase;Iron

and

steel,

aluminum,

copper,

nickel,

andtungsten

are

the

main

consumption,

worldwide.Automobile

industryGear

partsMechanical

industryP/M

Industry

–200520032004Iron

&

Steel442,799473,804Stainless

Steel8,900

(E)9,350

(E)Copper

&Copper

Base22,63225,204Aluminum50,000

(E)50,000

(E)Molybdenum2,500

(E)2,600

(E)Tungsten3,000

(E)3,500

(E)Tungsten

Carbide5,263

(R)5,891

(R)Nickel10,057

(R)10,110

(R)Tin9351,077546,086

st*581,536

st*(E)

Estimate (R)

Revised*1st=0.9078mt鐵基結構合金的高精度highprecise﹑高質量highquality﹑大數(shù)量產(chǎn)品。致密高性能材料，主要是理想的密度和牢固性full

density

andreliability。難加工材料的制造，difficulty

to

process

materials全密度具有統(tǒng)一微觀結構的高性能合金。4）特殊合金，主要為包含有多相的組分multi-compositescontainingmixedphase，通過增強密度的工藝來制造。

These

will

often

be

fabricated

by

enhanceddensification.5）非平衡nonequilibrium材料的合成例如suchsamorphous非晶，micro-crystalline,or

metastable

alloys微晶和亞穩(wěn)合金。6）具有獨特組分或不常用形狀的特殊附件的工藝。粉末冶金未來The

future

of

the

powder

metllurgy30,00025,00020,00015,00010,0005,00001990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004*1

st

=0.9087

mtP/M

Parts Other

Usesst*Copper

and

Copper

base

powder

in

North

AmericaCopper

and

copper-base

powder

in

2004

increased

11.3%

andcopper

powder

base

parts

increased

7%.International

iron

and

steel

powder

Metal

powder

in2004

increased

by

6.5%

to

527,918(mt),

figure

Ironpowder

increased

7%

over

2003

to

430,119mt.1000000900000800000700000600000500000400000300000200000100000Europe**JapanNorthAmericanSt**1st=0.907801994

1996

1998

2000

2002

2004**Reflects

P/M

grade

powders

only

Sourse:MPIF,JPMA,EPMAincludes

stainless

steels

after

1996International

copper

and

copper

basepowders

in

200410000200003000040000019942004Europe**JapanNorthAmerican*st60000500001996

1998

2000

2002**reflects

P/M

grade

powders

only*1st=0.9078source:MPIF,JPMA,EPMAP/M

parts

content

in

a

typical

vehicleNorth

AmericaJapanEurope19807.7kg(17lb)3.03kg(6.7lb)2.5kg(5.5lb)19858.6kg(19lb)3.78kg(8.3lb)19878.8kg(19.5lb)4.3kg(9.5lb)3.2kg(7lb)199010.9kg(24lb)5.55kg(12.21lb)4.1kg(9lb)199412.2kg(27lb)6.64kg(14.6lb)5.7kg(12.5lb)199512.7kg(28lb)6.7kg(14.8lb)6.1kg(13.46lb)199714kg(31lb)6.52kg(14.41lb)199814.9kg(33lb)6.65kg(14.6lb)7.02kg(15.5lb)199915.6kg(34.5lb)7.17kg(15.8lb)7.4kg(16.3lb)200016.3kg(36lb)8.2kg(18lb)200117kg(37.5lb)7.3kg(16lb)8.1kg(17.8lb)200217.7kg(39lb)7.6kg(16.7lb)8.3kg(18.3lb)200318.4kg(40.5lb)8.0kg(17.6lb)8.7kg(19lb)200419.5kg(43lb)9.0kg(19.8lb)North

America

copper

and

copper

base

powder*1

st

=0.9087

mtP/M

Parts Other

Usesst*30,00025,00020,00015,00010,0005,00001990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004Stainless

steel

powder

increased

5%

to

an

estimated8,488

mt.Tungsten

powder

increased

16%

to

3,177

mt

andtungsten

carbide

powder

increased

almost

12%.Although

there

are

about

10

companies

makingaluminum

P/M

parts,

two

players

dominated

the

marketin

North

America.European

iron

and

steel

powder

in

2004

fared

betterthan

North

America,

increasing

by

8.8%

to

172,952mt.Increases

in

iron

powder

in

Japan

did

not

match

NorthAmerica.Estimate

that

that

the

iron

powder

market

now

exceeds908，000mtImpact

of

ChinaIn

the

last

several

years,

China

poses

both

acompetitive

threat

and

potentially

huge

opportunity.It

has

an

estimated

680

P/M

part

makers,

but

onlyabout

five

of

these

are

considered

capable

of

makinghigh

quality

P/M

parts.The

Chinese

P/M

parts

industry

is

experiencing

anestimated

19%

annual

growth

rate.The

typical

passenger

car

in

China

contains

about4.7kg

of

P/M

parts.China

produced

about

85000mt

of

P/M

parts.Chinese

P/M

industry

will

undoubtedly

increase

itsquality

capability

as

more

funds

are

invested,particularly

by

Western

companies.Currentlyrepresentingmore

than

20

non-Chinesethe

U.S,

Europe,

Japan,

Korea,firmsandTaiwan

have

P/M

plants

in

China

mainland.On

the

other

hand,

China

is

beginning

to

impact

theEuropean

automotive

market,

selling

inexpensive

cars.Chapter

2

粉末制備方法Powder

fabrication

methods物理機械法Physic-Mechanical

Protocol機械研磨法制備粉末Milling高溫霧化法制備粉末Atomization物理化學法制備粉末氧化物還原法制備粉末reduction

of

metallic

oxides氣相沉積法制備粉末precipitation

from

atmosphere

phase液相沉積法制備粉末precipitation

from

liquid

phase電解法制備粉末electrolytic

fabrication

techniques

fromthe

electrode納米及超細粉末制備技術nano/ultro

fine

powder

preparation從過程的實質來看，大體上可以歸納為兩大類，即物理機械法mechanical和物理化學physio-chemical法粉末的生產(chǎn)方法很多，從工業(yè)規(guī)模industrialscale而言，應用最廣泛pervasive

used

method的是還原法

reducing、霧化法和電解而氣相沉淀法vapor

decomposition

和液相l(xiāng)iquidprecipitation沉淀法在特殊應用時亦很重要。從材質范圍來看typeofthematerials，不僅使用金屬粉末、也使用合金alloying粉末、金屬化合物粉末、ceramics；從粉末外形shape來看，要求使用各種形狀的粉末，如生產(chǎn)過濾器時filter，就要求球形粉末；sphericalmorphology,

spherical

particles從粉末粒度來看，要求各種粒度的粉末，從粒度為500~1000um的粗粉末到粒度small

than0.1um的超細粉末superfine

powders。（1）從固態(tài)金屬與合金制取金屬與合金粉末的有機械粉碎法和電化腐蝕法；electricalerosion在固態(tài)下制取粉末的方法包括（2）從固態(tài)金屬氧化物及鹽類制取金屬與合金粉末的有還原法；從金屬和非金屬粉末non-metallicpowders、金屬氧化物和非金屬粉末制取金屬化合物粉末的有還原-化合法。

Reducing-chemistrycombined.（1）從金屬蒸氣冷凝制取金屬粉末的蒸氣冷凝法；

consolidationfrom

metal

steam在氣態(tài)制備粉末的方法包括（2）從氣態(tài)金屬羥基物離解制取金屬、合金以及包覆粉末的羥基物熱離解法;

carbonyl

vapordecomposition。Coated

particles（1）從液態(tài)金屬與合金制備金屬與合金粉末的霧化法；（2）從金屬鹽溶液置換substitution和還原金屬、合金以及包覆粉末的置換法

substitution、溶液氫還原法；liquidhydrogenreduction（3）從金屬鹽溶液

電解制金屬與合金粉末的水溶液電解法

liquid

electrolytic；從金屬熔鹽電解制金屬和金屬化合物粉末的熔鹽電解法。Meltsaltelectrolysis在液態(tài)下制備粉末的方法包括Chapter

3

機械研磨Mechanical

Milling利用機械力將金屬或其它材料破碎制取粉末的方法應用非常Pervasive廣泛:Suitable

for

脆性粉末制備Brittle

powders陶瓷粉末Ceramic

powder,碳鋼Carbon

steel,陶瓷粉末:Hard

alloying

硬質合金;Mixing

and

Blending

混合及合批;機械能—粉末顆表面轉化

Mechanical

E-Surface

E

Transformation缺點Disadvantages化學臟化chemicalContamination,dust,Oil油西方:高碳鋼high

carbon

steels

and牙科粉末dental

powder銀汞合金dental

amalgam

powder鋁粉Aluminum

Powder機械夾雜Machining

Impurities最簡單的方法(Simplest

method),最簡單的設備

(Simplest

Equi.),

最有效(Most

effect)有方法之一.也是能量效能利用率低的方法,能量利用率<10%.Small

than

10%percentBalls

球MaterialsCyindrical

jar

球磨桶僅需要干dry濕wet研磨規(guī)律:Grinding

Mechanism球磨如圖示過程:A

jar

mill

such

as

diagrammed

in

figure.(a)

Low

speed,

(b)

suitable

speed,

(

c)

high

rotation

speed至少有四種作用力在破碎粉末:沖擊：Colliding剪切：Shearing壓縮：Compressing磨研：Grinding這些都能形成破碎作用.Crush

Particles.那么破碎脆性brittle粉末所需要沖擊colliding力應力與缺陷結構defect和裂紋擴展敏感程度相關.A

view

of

the

action

in

a

jar

mill,

the

impact

ofthe

falling

balls

grinds

the

material

into

powderSEM

of

milled

niobium

powder,prepared

by

hydriding,

milling,

and

vacuumdehydriding leading

to

an

angular

particle

shape公式:Crack

tip

radusCrack

propagation

擴展grinding

efficiency

is

regulated

by

ball

movement

includingcolliding，sliping，friction，compression.

粉末研磨綜合有沖擊,滑動,摩擦與壓縮,研磨效果與球體運動方式相關d

=

(2Er

/

D)1/

2d

:沖擊應力E:材料彈模.Elastic

Modalusr:缺陷尺寸.Defect.裂紋尖端曲率半徑,裂紋擴展D:粉末尺寸.Partide

Size式表明:Large

particles

require

less

impact

stress

tofracture.粗顆粒粉末只需要小的沖擊應力,隨粉末顆粒直徑變小,沖擊應力增大.如果我們知道初始粒度(顆粒尺寸)initial

ParticleSize當要研磨到所需粒度時,需要多少能量可以由一個simplerelationship去估計(estimating)需要的能量.d

=(2Er

/

D)1/

2D1D22

1g:

一個常數(shù)

a

constanta:

指數(shù)

between

1

and

2這是一個經(jīng)驗工式, a--經(jīng)驗系數(shù).球磨效應影響因素,Factors

to…干/濕. Dry/wet,

脆性/還原性

Brittle/Ductile,Plastic/Rigid粉末粒度Particle

Size球體尺寸Ball

Size旋轉速度:Jar

Rotation

on

speed.W

=

g(D-a

-

D-a

)計算:一青銅粉末Boron

Powder

40um,5小時到

20

um,若磨到10um需要多少時間.假設一立方形納米顆粒晶粒,晶界寬度Width約1.2nm,

如果該晶粒中有20%原子是處于晶界上,估計該晶粒Size.EstimateTotal

energy

change

during

milling由顆粒尺寸變化與總能關系:W

=

g(D-a

-

D-a

)f

iDf

研磨粒度;

Di初始粒度

a=2作業(yè)

1

、

復合粉末材料,

屈服強度(yieldingstrength)與第二相關系如下:求:第二相粉末為200nm時,材料的屈服強度,第二相為球形.Sphere

shape

powderParticle

size(mm)ds(MPa)6.4905.91183.61602.8186Decide

ball

的運動Jar

旋轉速度最為重要.Behavior球體受力分析:suppose:

only

one

Ball

只有一個球的情況.P:離心力Centrifuge

ForceG:重力G

ForceP1:向心力

A1:臨界點R:筒體半徑V:

線速度A:

落點Falling

pointRotation

of

small

steel

ball

and

force

action球磨的基本規(guī)律Basic

regulation

of

mill球在滾筒中的基本狀態(tài)轉速慢，

瀉落狀態(tài)，摩擦效果grinding轉速快，

拋落狀態(tài)，摩擦,撞擊破碎轉速快，

拋落狀態(tài)，撞擊破碎colliding假設:we

supposethat只一個球，only

one

ball,球直徑比桶直徑小球受到兩個力作用，Two

force

acting

on

the

ballP

：離心力centrifuge

forceG

：重力gravityV

：線速度linear

velocity

of

the

small

ball.球的受力分析在拋落點平衡時（A點）：二力相等，P＝P’，P

=

magm

=

Gv

2a

=RP

=

G

·

cosaG v

2? =

G

cosag

RP

=

ma

=v

2cosa

=gR所以Relation

of

linear

speed

and

rotate

speed

isv

=

2pRn

=

pRn60

30Force

action

on

the

small

steel

ball

include

centrifuge

andgravity

force,

suppose

only

one

ball

in

the

jar.Thus，

the

critical

rotation

speed

isp

2

Rn2cosa

=g

3022以g＝9.8m/s

代入得：n2

Rcosa

=900v

2cosa

=gR代入得臨界狀態(tài)

當轉速加快，球不落下，球轉到最高點A1點，此時在這臨界狀態(tài)下，a

=

0n

2

R=

cosa

=

1900轉/分R

30

42.4Dn臨界＝

=D，

the

diameter

of

thejarIn

fact，in

order

to

obtain

the

efficiency

ground

theexperienced

working

rotation

speed

should

lower

than

thecritical

speed，and

the

experienced

working

speed：工作經(jīng)驗表示：n＝0.6n臨界時，可制取細粉fine

particlesn＝0.75n臨界時，一般只能制取較粗的粉末coarse

particlesn

=

0.75n臨界

=

0.75

·

42.4

/

D

=

32

/

D轉/

分

1

D

18 24

d

￡

1

~影響球磨效果的因素factors

to

influence

milling

efficiencya、球料比：ratio

of

powder

and

balls，一般粉末填滿球體之間的間隙b、球體直徑：diameter

of

the

balls選擇范圍c、研磨介質：medium

空氣、protective

atmosphere

，lessen

oxidation，alcohol，

gas，avoiding

assemble（團聚）componentsegeration成分偏析，and

dust（粉塵飛揚）研磨介質:the

excellent

action

of

the

groundmedium：Protective.

Anti-干磨:保護氣氛AtmosphereOxidation濕磨:保護和效率;wet

milling濕磨介質:水,乙醇等;milling

mediumwet

grind

split

濕磨尖壁作用,有利于裂紋擴展Crackpropagation減少泠焊.Decrease

cold

weldingIncreasing

the

grinding

efficiency如要產(chǎn)生Colliding

action

沖擊作用Experienced

Relation，n實=0.7~0.75n臨界如果要Colliding+Slipping

action，n實=0.6n臨界Apart

from

above

factors.

There

are:球料比:Ball:Mater

ratio

:4:1~5:1裝料比Filling

volume:0.4~0.5

packing球體直徑:10~20mmJar

diameter:

300~500mm物料性質

future

of

the

grounding

particles脆性粉末破碎，Brittle

powder延性粉末，ductile

powder，精細分層，fine

lamination，and

cold

welding.Relation

of

powder

surface

area

and

ground

time

is

follow；Sm

粉末極限研磨后的比表面積S0

粉末研磨前的比表面積S

粉末研磨后的表面積,

t

研磨時間,

k

常數(shù)氧化鋁、氧化鋯、炭化硅、鈦、鎳等都符合這種關系=

ktln

Sm

-

S0Sm

-

S缺點，Disadvantages:Contamination

臟化,Limited

particle

size,Brittle

materials

脆性材料.例1.車削粉研磨a=2.(assumed)Vacuumed

milling8hrs

Di=300μm,Df=110

μm,if

milling

to

75

μm,how

many

hrs

are

needed?8

的1.33

folds,

10.6

hrs.強化球磨:Enhanced

grindinga.

機械合金化Mechanicalalloying

Stirredmill攪拌當球體沖擊粉末,產(chǎn)生功能,功能越大,沖擊力越大,導致粉末破碎。為了提高球的沖擊速度,采用了機械合金化技術。The

input

material

goes

through

a

sequenceof

cold

welding

and

fracture

steps.

As

aconsequence

of

attrition,

the

microstructurebecomes

more

homogeneous

as

sketched

atthe

bottom

of

the

figure.A

view

of

mechanical

alloying

where

therotating

impeller

stirs

a

tank

filled

with

ballsd:

研磨介質(粉體)顆粒直徑，粉體直徑減少轉速增大,時間減少。制備彌散強化。ODS Oxide

DispersionStrengthening

Alloys.

Ni

Base,

Co

Base

,

Fe

BaseSuper

alloys.

Oxide

Particles

Sub.

micrometer

亞微米粉末。Alloying

mechanism

合金化機理:

破碎與冷焊

Fractural/cold

welding導致均勻化homogenization研磨過程所需的能量與攪拌旋轉時速度N相關:fit

=cd2

/N1/2

c:經(jīng)驗常數(shù).empirical

Constant高能球磨(Mechanical

alloying

)并不在乎粒度減少,而在乎have

finer

microstructure.

精細結構,

產(chǎn)生復合材料.result

in

Composite

materials。Fe,

Co,

Ni

base

均為韌性ductile

材料,、航空材料、高溫合金,

Super-alloys，要的是產(chǎn)生一個結構去達到性能.b.振動球磨Vibratory

Milling粉末靠沖擊Colliding碰撞,提高單位時間內(nèi)球體的碰撞次數(shù),可提高破碎效果,特別是當磨到一定程度,只要小的碰撞,即可使粉末破碎。隨著研磨的進行,

粉末平均粒度Mean

particle

size

減小,單位質量(單質體積)粉末表面積增加.

-比表面積:Specific

Surface

Area/per

unit

powder.單位時間內(nèi)球體的總沖擊數(shù)empirical

EquationR

:粉末比表面積w:振動頻率Freauncyd:球直徑d:粉末直徑t

:研磨時間e

:振動ApiplinghyR

=f(w,e,d球,d粉,d粉,t)m

:單位時間球磨體總沖擊數(shù)V:球角體積K:單位體積中球數(shù)量B:裝填系數(shù)N:振動次數(shù)/minZ:轉動一周球沖擊數(shù)E:轉動一周相鄰沖擊數(shù)m=

V·K·B·n·Z·E

次/minC.行星式球磨:增加球Colliding次數(shù)自轉+公轉Protective

Atmosphere機械合金化,攪拌:非晶,納米晶,納米particles,脆性,韌性金屬,粉末振動球磨,破碎micrometer

grade納米級,脆性粉末WC行星式球磨,納米非晶粉末.研磨過程所需要時間與粉末性質相關。同樣用比表面積表達:ln

=t:

milling

time，

k：constantSm：the

limitation

specific

areaSo：

the

initial

specific

areaSt：specific

area

at

t

time=

ktSm

-

S0Sm

-

Stm

t

mS

-S

=(S

-S

)e-ktSt

t時間specific

surface

area.0St

fi

Sm

,

t

?St

越接近SmGrinding

time

increasing.不同性質的粉末,從St

fi

Sm所需的時間不同.Powder

Metallurgy

PrinciplePowder

Metallurgy

Research

Institute2006Chapter

4.

氧化還原制粉方法Chemical

Fabrication.定義:用還原氣體(固體)或活潑金屬將氧化物還原制備粉末

的過程.(Reduction

of

Oxide

Decompose

of

a

solid

by

a

gas.)1.最簡單地.反應平衡常數(shù).Reaction

Equilibrium

ConstantK

=

PH

O

/

PH2

2氣體的分壓之比.Gas

partial

pressure

.(Ratio)FeO(s)

+

H2

(g)

fi

Fe(s)

+

H2O(g)FeO,Fe3O4,Fe的穩(wěn)定存在與分壓有關溫度升高：Fe3O4

FeO

Fe反應速率J與反應過程活化能θ,反應溫度T，氣體分壓比相關：J=Aexp（-θ/RT）A：物質常數(shù)，頻率因子frequency

factor活化能降低，反應溫度升高，提高反應速度，有利于還原進行；Metal

oxides

can

be

produced

by

H2

，

CO，

etc.O2+2H2=2H2OO2+2CO=2CO2O2+C=CO2WO3+H2=WO2+H2OWO2+2H2=W+2H2OTiCl4+2Mg=Ti+2MgCl2Reducing

agents (還原劑)a:

Gas

reducing

agents:

H2,

COb:

Solid

reductant:

C

,

metal,

alkaline

metals;The

necessary

conditions

as

reductant:還原劑對氧的親和力大于對被還原物質的親和力--熱力學thermo-dynamic

必要條件,Only

fit

thenecessary

condition,

the

reaction

can

gothrough.DiscussionFor

a

close

system,

the

equilibrium

constant,energy,

determines

the

terminal

concentrationratio

of

the

products

to

reactants,For

the

reduction

of

WO3

by

H2,

the

equilibriumconstant

K

is

given

as,K=PH2O/PH2Where

PH2

and

PH2Oare

the

partial

pressure

ofhydrogen

and

water

steam金屬物質對氧的親和力affinity氧離解壓Oxide

decomposition

pressureGoing

to

change

with

temperature，and

ingeneral，Temperature

increase，decomposition

pressure

will提高，親和力

affinity

will

decrease.Thermo

–dynamics

熱力學,必要條件.Necessary

ConditionsKinetic

–dynamics

動力學,充分條件.Complementary

condition2.還原過程基本原理熱力學基本因素,必要條件,充分條件.(1)

還原過程標準Standard

free

energyX:還原劑. XO:金屬氧化物. Me:還原金屬.系統(tǒng)中溫度一定,各物質離解壓一定,通過各物質離解壓不同,物質decomposedpressure越低,氧化物越穩(wěn)定.還原反應化學式:MeO+X=Me+OX1.金屬氧化物還原熱力學條件

Thermodynamic

condition1）、還原過程標準等壓位或自由能free

energy

(焓)的變化如果還原

反應的化學式為X-還原劑,Me-金屬氧化物,XO-金屬氧化物metaloxide每種氧化物都有各自的離解壓，離解壓越低，氧化物越穩(wěn)定MeO有離解壓，XO也有離解壓decomposedpressure，前者離解壓大于后者,MeO才能被X還原，他們的離解反應為：MeO

+

X

=

Me

+

XO(1)(2)上述金屬氧化物還原過程標準自由能變化是即ΔZ

φ(2)

<ΔZφ(1)PO2(XO)

<

PO2(MO)2MeO

=

2Me

+

O2O2

(

MeO)DZ

(1)

=

-RT

ln

KP(1)

=

-RT

ln

P2

XO

=

2

X

+

O2O2

(

XO)DZ

(2)

=

-RT

ln

KP(2)

=

-RT

ln

P2DZf

=

1

(DZf(2)

-

DZf(1))

0The

higher

decomposed

pressure,

the

more

unstablethe

metal

oxide,

then

the

greater

the

free

energychange,

the

metal

oxide

will

be

reduced

byreductant.即XO離解反應標準自由能變化應小于MO離解

反應自由能的變化，這樣XO才比MO穩(wěn)定，這時，這時，XO的離解壓小于MO的離解壓，還原反應

正向進行。氧對X的親和力大于對Me的親和力，推廣之，對氧的親和力大于被還原的金屬時，都可以作為該金屬氧化物的還原劑。金屬氧化過程標準自由能變化與溫度的關系是：直線關系,截距A

表示在絕對零度

absolutetemperature:T=0時，形成該金屬氧化物的自由能DZ

=

A

+

BTC的氧化反應都是隨著溫度的升高而有利于C的oxidation。Water生成反應的ΔZ°－T關系線在Cu、Co、Fe、Mo、等氧化物的生成線之下，在一定條件下，H2

能還原這些氧化物。In

practice,

the

reaction

system

pressure

equal

to

1,

the

partialpressures

of

PO2

and

PH2

are

small

than

1.DZ

＜0，當T上升,隨溫度難度增加上升C

+

O2

=

CO22C

+

O2

=

2CODZ

變的越負，即[DZ

]增大，從2H

2

+

O2

=

2H

2OThermo

–dynamic

熱力學必要條件???PMO

〉PXOPMO

=PXOPMO〈PXO還原反應進行反應達到平衡反應逆向進行，金屬被氧化離解反應2MeO=2Me+O2DZ

（1）=

-RTlnkp

（1）=

-RTlnPO2（MeO）

（1）平衡常數(shù)kp（1）

=PO2（MeO）

（1），DZ

<0

反應進行2XO=2X+O2D

DZ

（2）=

-RTlnRp

（2）=

-RTlnPO2（XO）

（2）

D平衡常數(shù)kp（2）

=PO2（XO）

（2），DZ

<0

反應進行等溫條件:平衡常數(shù)用離解壓表示.T不變,以(1)-(2),并除以2,消除分數(shù),得mol數(shù),over/by

2(2)(1)(2)(1)2222(

m

)2

(

X

)=

1

[-

RT

ln

kp+

RT

ln

kp

]=

1

[-

RT

ln

PO+

RT

ln

PO

]M

eO

+

X

=

M

e

+

XO

Z

=

-

RT

ln

kp=

1

[

Z

-

Z

]Thermo-dynamiccondition：

ΔZ°

<

0ΔZ2°

<

ΔZ1°

，or還原劑離解壓PO2（X）小于金屬氧化物離解壓PO2（M）根據(jù)離解壓與反應過程自由能變量的關系，離解壓越大，該物質越不穩(wěn)定unstable，free

energy

changemore.

In

other

words,

XO離解反應change

of

standardfree

energy

is

小于MO離解反應change

of

standardfree

energy,

XO穩(wěn)定,MO離解,反應向還原方向進行.碳的氧化反應,

2C+O2=2CO與金屬氧化反應不同,溫度升高,ΔZ°變得越負,表明溫度升高,有利于上述C的氧化反應,CO在高溫(elevatedtemperature)ismorestable.CO在高溫的離解壓很小,excellent

reducing

agent.2H2+O2=2H2O在很多金屬Fe,

W,

Cu,

Co,

Ni,Mo氧化反應生成線(氧化反應自由能變化-溫度關系曲線)之下,H2O的離解壓小于這些金屬氧化物離解壓,H2O

比這些氧化物穩(wěn)定,therefore,

H2

couldreduce

these

metal

oxides.

H2

,excellent

reductant.2）實際還原過程:實際還原過程在非標準線以下below

thestandard

line，即此時PO2

標準狀態(tài)體系的分壓等于1,如FeO用CO還原,即（1）-（2）得非標準狀態(tài)22Fe

+

1

O

=

FeO2

22CO

+

1

O

=

COFeO

+

CO

=

Fe

+

CO2PDZ

=

DZ

＋RT

lnqCO2

CO＝DZ

+

RT

ln

P

PCO

CO2＝DZ

－RT

ln

P

PCO

CO2＝DZ

－4.57DT

ln

P

PPCO2qP

=

PCO（1）（2）即該還原反應與的分壓有關, related

to例如reduction

reaction

of

tungsten

oxideWO2+2H2=W+2H2OΔZ=

ΔZ

°-2

x

4.576TlnPH2/PH2OΔZ’=2