材料科学基础
Fundamental of Materials
Prof,Tian Min Bo
Tel,62795426, 62772851
E-mail,tmb@mail.tsinghua.edu.cn
Department of Material Science and Engineering
Tsinghua University,Beijing 100084
Lesson ten
§ 3.6 Intermetallic Compounds
(Intermetallic Phases)
? Ⅰ,Future
1,The structure of AmBn differs from those of
either A or B
2,Its composition is variable to more or less
extension
3,Mixed bonding
4,Intermediate properties
? Ⅱ,Formation
A→←B
The property of AmBn is between that of A and B.
? Ⅲ,Factor governing the structure
of,compounds”.
1) Electrochemical factor (X)
2) Electron concentration (e/a)
3) Size factor
Metal Nonmetal Metalloid
§ 3.7 Normal Valence Compounds
Ⅰ,Definition:
If the number of valence electrons of the
cation is sufficient to complete octahedron of the
anion,the compound is called the normal
valence compounds.
Example,CmAn
meC＝ n(8－ eA)
sometimes,m(eC－ eCC)＝ n(8－ eA－ eAA)
? Ⅱ,Classification
according to structure
1,NaCl and CaF2 types
NaCl:
(Mg Ca Sr Ba)(Se Te)
(Mn Pb Sn)(Se Te)
CaF2:
PtSn2 PtIn2 Pt2P
Anti-CaF2:
Mg2(Si Ge Sn Pb) Cu2Se Li3AlN2
LiMg(N As Sb Bi) AgMgAs
2,Diamond,Zinc blende,Wurtzite types
Zinc blende:
(Be Zn Ca Hg)(S Se Te)
(Al Ga In)(P As Sb)
Wurtzite:
(Zn Cd Mn)S
(Cd Mn)Se
3,NiAs structure
Example:
(Cr Fe Co Ni)(S Se Sb)
(Fe Co)Te
(Mn Fe Ni Pt Cn)Sn
Ni(As Sb Bi)
Structure
c41
c43
? Normal state —— Ni, As = 1, 1
? When Ni does not full fill octahedral interspaces
Ni, As < 1, 1
? Extreme state,Ni occupy trigonal interspaces
Ni, As > 1, 1
4,Electron Phase
(Electron compounds)
For Alloys of IB or transition metals,and B
group metals phases with sane or similar
structure occur at approximately some electron
concentration(e/a) these alloys are therefore
called as electron compounds
§ 3.8 Electron Phases
(Hume-Rothery phases)
Feature:
⑴ Identical on similar structure occur at
approximately the same electron concentration,
e/a.
For example:
CuZn, β
Cu5Zn8, γ
CuZn3, ε(HCP)
β,(2+1)/2 = 21/14
γ,21/13
ε,21/12
⑵ Components
IB or transition metal＋ metals in B group
⑶ Composition range is related to e/a
⑷ Metallic character
§ 3.9 Size Factor Compounds
? Ⅰ,Interstitial phases
(Interstitial compounds)
Condition A >> B
B,H (0.46),B (0.97),C (0.77),N (0.71)
1,Simple interstitial compound structure
59.0?
A
B
r
r A,Transition metals
B,Interstitial elements (H,B,C,N)
2,Complex structure
59.0?
A
B
r
r
M3C,(Fe3C),M23C6,M6C
properties of interstitial compounds
⑴ Some metallic properties
⑵ Hard and brittle
⑶ For size factor compounds
? Ⅱ, Three principles for the structure
1,space-filling principle:
Atoms tend to fill the space as closely as
possible
2,Symmetry principle:
Atoms tend to build a configuration of high
symmetry
3,Principle of multi-dimensional connection
? Ⅲ,Intermetallic compounds
Examples:
1,Laves phases
MgCu2 MgZn2 MgNi2 ar
da
B
B
8
2
42
?
?
A原子
B原子
22 5.1
2
3 ??
B
A
r
r
16)CuMg(12)MgMg(4CN:Mgf o r
12)CuCu(6)MgCu(6CN:Cuf o r
?????
?????
2,phase?
A Cr Mo W V
B Mn Fe Co Ni
3,Topologically close-packed phase
7a t o me le c t r o n s ?
Examples and Discussions
Exercise
Thank you !
10
Fundamental of Materials
Prof,Tian Min Bo
Tel,62795426, 62772851
E-mail,tmb@mail.tsinghua.edu.cn
Department of Material Science and Engineering
Tsinghua University,Beijing 100084
Lesson ten
§ 3.6 Intermetallic Compounds
(Intermetallic Phases)
? Ⅰ,Future
1,The structure of AmBn differs from those of
either A or B
2,Its composition is variable to more or less
extension
3,Mixed bonding
4,Intermediate properties
? Ⅱ,Formation
A→←B
The property of AmBn is between that of A and B.
? Ⅲ,Factor governing the structure
of,compounds”.
1) Electrochemical factor (X)
2) Electron concentration (e/a)
3) Size factor
Metal Nonmetal Metalloid
§ 3.7 Normal Valence Compounds
Ⅰ,Definition:
If the number of valence electrons of the
cation is sufficient to complete octahedron of the
anion,the compound is called the normal
valence compounds.
Example,CmAn
meC＝ n(8－ eA)
sometimes,m(eC－ eCC)＝ n(8－ eA－ eAA)
? Ⅱ,Classification
according to structure
1,NaCl and CaF2 types
NaCl:
(Mg Ca Sr Ba)(Se Te)
(Mn Pb Sn)(Se Te)
CaF2:
PtSn2 PtIn2 Pt2P
Anti-CaF2:
Mg2(Si Ge Sn Pb) Cu2Se Li3AlN2
LiMg(N As Sb Bi) AgMgAs
2,Diamond,Zinc blende,Wurtzite types
Zinc blende:
(Be Zn Ca Hg)(S Se Te)
(Al Ga In)(P As Sb)
Wurtzite:
(Zn Cd Mn)S
(Cd Mn)Se
3,NiAs structure
Example:
(Cr Fe Co Ni)(S Se Sb)
(Fe Co)Te
(Mn Fe Ni Pt Cn)Sn
Ni(As Sb Bi)
Structure
c41
c43
? Normal state —— Ni, As = 1, 1
? When Ni does not full fill octahedral interspaces
Ni, As < 1, 1
? Extreme state,Ni occupy trigonal interspaces
Ni, As > 1, 1
4,Electron Phase
(Electron compounds)
For Alloys of IB or transition metals,and B
group metals phases with sane or similar
structure occur at approximately some electron
concentration(e/a) these alloys are therefore
called as electron compounds
§ 3.8 Electron Phases
(Hume-Rothery phases)
Feature:
⑴ Identical on similar structure occur at
approximately the same electron concentration,
e/a.
For example:
CuZn, β
Cu5Zn8, γ
CuZn3, ε(HCP)
β,(2+1)/2 = 21/14
γ,21/13
ε,21/12
⑵ Components
IB or transition metal＋ metals in B group
⑶ Composition range is related to e/a
⑷ Metallic character
§ 3.9 Size Factor Compounds
? Ⅰ,Interstitial phases
(Interstitial compounds)
Condition A >> B
B,H (0.46),B (0.97),C (0.77),N (0.71)
1,Simple interstitial compound structure
59.0?
A
B
r
r A,Transition metals
B,Interstitial elements (H,B,C,N)
2,Complex structure
59.0?
A
B
r
r
M3C,(Fe3C),M23C6,M6C
properties of interstitial compounds
⑴ Some metallic properties
⑵ Hard and brittle
⑶ For size factor compounds
? Ⅱ, Three principles for the structure
1,space-filling principle:
Atoms tend to fill the space as closely as
possible
2,Symmetry principle:
Atoms tend to build a configuration of high
symmetry
3,Principle of multi-dimensional connection
? Ⅲ,Intermetallic compounds
Examples:
1,Laves phases
MgCu2 MgZn2 MgNi2 ar
da
B
B
8
2
42
?
?
A原子
B原子
22 5.1
2
3 ??
B
A
r
r
16)CuMg(12)MgMg(4CN:Mgf o r
12)CuCu(6)MgCu(6CN:Cuf o r
?????
?????
2,phase?
A Cr Mo W V
B Mn Fe Co Ni
3,Topologically close-packed phase
7a t o me le c t r o n s ?
Examples and Discussions
Exercise
Thank you !
10
