材料物理导论ChapterSolidstructureandbasiccrystaltheory

Models

of

the

three

typical

metalliccrystal

structuresThe

number

of

atoms

in

the

unit

cellof

three

typical

metallic

crystalstructuresThe

atomic

radius

and

latticeparametersThe

stacking

manner

of

the

packed

planesof

the

typical

metallic

lattice(a)

hcp

structure(b)

fcc

structure(b)

fcc

crystal

cella)

Faced-centered

cubic

lattice(properties)The

arrangement

of

the

atoms

in

the

unit

cell:

there

isone

atom

at

each

top

of

the

8

corner

and

one

atom

ineach

center

of

the

6

faces.Lattice

parameters:

a=b=c；α=β=γ=90ºThe

number

of

atoms

in

the

unit

cell:

n=8×1/8＋6×1/2=4The

atomic

radius

R:

half

of

the

distance

between

thetwo

touched

atoms.Coordinative

number

and

density

:Coordinative

number

CN=12Density

k=0.74The

location

of

the

atoms

in

theface-centered

cubic

latticeThe

number

of

the

atoms

in

theface-centered

cubic

latticeThe

coordinative

number

of

the

atomsin

the

face-centered

cubic

latticeThe

packedplanes

of

the

face-centered

cubic

latticeTwo

types

of

interstice:tetrahedral

interstice

and

octahedral

intersticeOctahedral

interstice:

rB=0.414R，where

rB

is

theradius

of

the

interstice,

R

is

the

radius

of

the

atomand

the

number

of

the

interstice

is

4.Tetrahedral

interstice:

rB=0.225R，the

number

ofthe

interstice

is

8.The

stacking

manner:

ABCABC…or

ACBACB…Metals

with

fcc

structure:γ-Fe,

Al,

Cu,

Ni,

Au

and

Agetc.a)

Faced-centered

cubic

lattice(interstice

and

the

stacking

manner)Octahedral

interstice

of

theface-centered

cubic

latticeOctahedral

intersticeOctahedral

interstice

of

the

faced-centered

cubic

latticeTetrahedral

interstice

of

the

face-centered

cubic

latticeTetrahedral

intersticeTetrahedral

interstice

of

the

faced-centered

cubic

latticeThe

stacking

manner

of

the

atoms

inthe

face-centered

cubic

latticeb)

Body-centered

cubic

lattice(properties)The

arrangement

of

the

atoms:

there

is

one

atom

ateach

top

of

the

8

corner

and

one

atom

in

the

center

ofbody.Lattice

parameters:

a=b=c，α=β=γ=90ºThe

number

of

atoms

in

the

unit

cell:

n=8×1/8＋1=2The

radius

of

the

atom

:Coordinative

number

and

density

:Coordinative

number

CN=8Density

k=0.68The

location

of

the

atoms

in

thebody-centered

cubic

latticeThe

number

of

the

atoms

in

thebody-centered

cubic

latticeThe

packedplanes

of

the

body-centered

cubic

latticeb)

Body-centered

cubic

lattice(interstice

and

the

stacking

manner)Interstice:Tetrahedral

interstice

and

octahedral

intersticeOctahedral

interstice:

rB=0.154R(in<100>)orrB=0.633R(in<110>);

Number=6Tetrahedral

interstice:

rB=0.291R;

Number=6Stacking

manner:

ABABAB…Metals

with

bcc

structure:

α-Fe,δ-Fe,

Cr,

Mo,W

and

V

etc.Interstice

of

the

body-centeredcubic

latticeN=6N=12Octahedral

intersticeMetallic

atomsOctahedral

intersticeTetrahedral

intersticeMetallic

atomsTetrahedral

intersticec)Hexagonalclose-packed

lattice(properties)The

arrangement

of

the

atoms:

there

is

one

atom

at

eachtop

corner

of

the

hexagonal

pilar

and

three

atoms

in

thecenter

of

the

hexagonal

pilar.Lattice

parameters:

a1=a2≠a3，α=β=90º

，γ

=120ºThe

number

of

atoms

in

the

lattice：n=12×1/6＋2×1/2＋3=6The

radius

of

the

atom:

2R=a

R=a/2Coordinative

number

and

density:Coordinative

number

CN=12Density

k=0.74Thelocation

of

the

atoms

in

the

hexagonalclose-packed

latticeThe

number

of

the

atoms

in

the

hexagonalclose-packed

latticeThe

packed

planes

in

the

hexagonalclose-packed

latticeThe

coordinative

number

in

the

hexagonalclose-packed

latticec)Hexagonalclose-packed

lattice(interstice

and

the

stacking

manner)Interstice

:

complexOctahedral

interstice:

rB=0.414R,

N=6Tetrahedral

interstice:

rB=0.225R,

N=12Stacking

manner:

ABABAB…Metals

with

hcp

structure:

Mg,Zn,Be

and

Cd

etc.Octahedral

interstice

of

the

hexagonalclose-packed

latticeOctahedral

intersticeMetallic

atomsOctahedral

intersticeTetrahedral

interstice

of

the

hexagonalclose-packed

latticeTetrahedral

intersticeMetallic

atomsTetrahedral

intersticeThe

stacking

manner

of

the

atoms

in

thehexagonal

close-packed

lattice2. Multi-crystal

propertiesMulti-crystal

properties

means

that

some

metalshave

different

crystal

structures

at

differenttemperatures

and

pressures.Multi-crystal

transition

(or

allotropic

transition)means

that

the

inner

part

of

the

metal

will

transferfrom

one

structure

to

another

structure

when

theexternal

conditions

changed

(for

example,

T

and

P).For

example:3.

Anisotropy

of

the

crystalAnisotropy:

anisotropy

is

the

property

of

beingdirectionally

dependent.Crystal

grain:

particles

that

composed

of

the

crystaPolycrystal:

polycrystalline

materials

are

solids

tare

composed

of

many

crystallites

of

varying

sizeand

orientation.Crystal

grainMultiphase

alloysThe

morphology

image

of

alloys