Metallic Materials

1. 1
An Introduction to Metallic
Materials
波音客机

2. 2
We should grasp…
 What is a metal?
 What is an alloy?
 What are the differences between their
properities?
 Explain solid solution and intermetallic
compound.

3. 3
New Words & Expressions from
Part1
 roam[rəum]
 graphite['græfait]
 malleable['mæliəbl]
 ductile[‘dʌktail]
 soluble[‘sɔljubl]
 chromium[‘krəumjəm]
 transition[træn‘ziʒən ]
 shell[ʃel]
 v.漫游，闲逛，徜徉 ；
 n.漫步，漫游，徘徊
 n.石墨
 a.有伸延性的，可锻的
 a.易延展的，柔软的
 a.可溶解的，可溶的
 n.铬
 n.转换，跃迁，过渡
 n.壳，外壳

4. 4
Translation I
 The outmost layer of electrons
最外层电子
 Free election gas
自由电子气
 Electrical conductivity
电导率，电导性
 Plain-carbon steel
普通碳素钢
 Solid solution
固溶体，固溶液，固体溶液

5. 5
Translation II
 Intermetallic compound
金属间化合物
 Metallic material
金属材料
 Strainless steel
不锈钢
 Solute
溶质
 Solvent
溶剂
 Periodic table
元素周期表
 Electronegativity
电负性
 Transition metal
过渡金属
 Crystal structure
晶体结构

6. 6
What is a Metal?
 Q: What is a Metal?
 A: Metal is consisted of positive centers
(or ions) sitting in a “gas ” of free-electrons.
It tends to be good electrical conductors.

7. 7
What is an Alloy?
 Q: What is an Alloy?
 A: An alloy consists of a mixture of a pure
metal and one or more other elements
which can be metals or non-metal.
 Q: What are the differences between their
properties?
 A:Alloys are usually less malleable and
ductile than pure metals and the tend to
have lower melting points.

8. 8
Solid Solutions
 In many cases ,metals are quite soluble in
other metals .For example, solid copper
and solid nickel are fully soluble in each
other.

9. 9
 This type of perfect solid solubility is a
side effect of having free electrons. Since
the electrons are free to move, the exact
number of valence electrons possessed
by any given atom shouldn’t matter.

10. 10
 So a “solid-solution” is that one metal
serves as the solvent and the other as the
other as the solute, although in a case
like copper and nickel where these are
mutually soluble at all compositions the
terms solvent and solute can be a little
misleading .

11. 11
 For example, the
figure in the right
is Au-Ag phase
diagram, below
fusiform area is
solid solutions.

12. 12
Intermetallic Compounds
 Not all metals are soluble in other metals,
thus, produced another new phase called
“intermetallic compounds”, such as nickel
will dissolve some aluminum, so that at
low aluminum contents a solid solution is
produced. But if larger amounts of
aluminum are added, then produce
intermetallic compounds.

13. 13
 Some of these compounds have a very
well defined composition, such as Ni3Al.
 Others have quite a wide range of
composition, such as NiAl.
Nickel Aluminum Alloy

14. 14
Three types of circumstances of
intermetallic compounds forming
 The first circumstance: size difference.
 The second circumstance: a large
difference in electronegativity.
 The third circumstance: certain ratios of
the number of valence electrons to the
number of atoms in a structure.

15. 15
Hume-Rothery Rule
 Hume-Rothery Rule 1:Atomic Size Factor (the 15%)
Rule.
 Extensive substitutional solid solution occurs only if
the relative difference between the atomic diameters
(radii) of the two species is less than 15%. If the
difference > 15%, the solubility is limited.Comparing
the atomic radii of solids that form solid solutions,
theempirical rule given by Hume-Rothery is given as：
Mismatch= %
15
100 






 
solvent
solvent
solute
r
r
r

16. 16
 Hume-Rothery Rule 2:Crystal Structure Rule :
For appreciable solid solubility, the crystal structures
of the two elements must be identical.
 Hume-Rothery Rule 3: Valency Rule :
A metal will dissolve a metal of higher valency to a
greater extent than one of lower valency. The solute
and solvent atoms should typically have the same
valence in order to achieve maximum solubility.
 Hume-Rothery Rule 4: The Electronegativity Rule :
Electronegativity difference close to 0 gives
maximum solubility. The more electropositive one
element and the more electronegative the other, the
greater is the likelihood that they will form an
intermetallic compound instead of a substitutional solid
solution. The solute and the solvent should lie
relatively close in the electrochemical series.

17. 17
休姆－罗瑟里（Hume－Rothery）规律
（1）形成合金的元素原子半径之差超过14％～15％，则
固溶度极为有限；若尺寸差小于15％，尺寸因素成为次
要的影响因素，固溶度由其他影响因素确定，这就是知
名的15％规律。
（2）两组元只有具有相同的晶体结构才能形成无限（或
连续）固溶体。
（3）两元素的固溶度与它们的原子价有关，高价元素在
低价元素中的固溶度大于低价元素在高价元素中的固溶
度；
（4）如果合金组元的负电性相差很大，固溶度就极小。

18. 18
各式各样的合金
磁
性
合
金
镍铬合金烤瓷牙 铜中间合金

19. 19
金属外壳
锆石合金 铜乌合金

20. 20
 1. Given that many of the compounds
formed in alloys are size factor or electron
compounds,these do not follow the rules
of valency.
 在合金中，许多化合物是按比例组合或是
电子化合物，不能很好的遵循价键理论。

21. 21
 2.Whereas the chemical formula of an
ionic compound , like NaCl or Al2O3 can
be predicted easily from the compound’s
position in the periodic table ,this is not the
case for many intermetallic compounds.
 换句话说，尽管像氯化钠，氧化铝的价键
可以通过他们在元素周期表的位置进行预
测，但却不能解释合金中金属元素的成健
方式。

22. 22
 3.Thus,knowing from their position in the
periodic table that Na wants to from Na+
ions and chlorine wants to from Cl- ions
explans why an ionic compound with a
formula NaCl is observed.
从元素周期表可以知道，钠有变成钠离子
的趋势，氯有变成氯离子的趋势，这就解
释了氯化钠的形成。

23. 23
4.In contrast,this dosen’t explain why a carbide
with a formula Cr23C6 is formed in stainless
steels.
然而，这却解释不了Cr23C6在钢铁中的成健方
式。

24. 24
 5.The precipitation of Cr23C6 is a big
problem when stainless steels are welded.
这样 Cr23C6 成为钢铁焊接的大问题
 高铬高碳冷作钢

25. 25
 6.Cr23C6 forms in the “heat affected
zone”around the weld (this region is
heated but not melted during welding).
 在“受热区”的Cr23C6遍布在焊接点周围
（这个区域在焊接的时候受热但不熔化）

26. 26
 7.The formation of this chromium-rich
phase pulls chromium out of solution in the
surrounding iron.
 富铬相的结构，使铬在离子溶液的氛围之外。

27. 27
 8. This in turn,prevents the formation of a
protective layer of Cr2O3 on the surface of
the stainless steel and so the stainless
steel is no longer stainless,but instead
suffers from catastrophic localized
corrosion.
 这样，就保护了钢铁表面氧化铬保护层的
结构，从而钢铁不再是单纯的铁，而是可
以抗局部严重腐蚀的物质。

28. 28
 9.Consider a different example,NiAl is an
electron compound which froms due to
having a “magic” 1.5 valence electrons per
atom (this magic number isn’t really magic ,
but is a results of deviations from the free
electron model).
 另外一个不同的例子，NiAl是具有“魔法”
的化合物因为其中每个原子都是1.5价的
（神奇的不是数字本身，而是1.5价不符合
自由电子模型）。

29. 29
 10.There is one nickel atom and one
aluminum atom in NiAl and the valency of
nickel is two and that of aluminum is
three.given that (2+3)/2=2.5 this doesn’t
seem like 1.5 valence electons per atom .
 一个镍原子和一个铝原子构成了NiAl，从
价键理论看，镍是二价，铝是三价。照这
样，应该平均每个原子有2.5个价电子，与
实际上每个原子1.5个价电子不同。
8 2
:3d 4s
Ni 2 3
:3 3
Al s p

30. 30
 11.However ,as a transition metal ,nickel is
able to act as if it does nor have a valency
by “hiding”electrons in the emply states in
the shell.thus , effectively ,there are
(0+3)/2=1.5 valence electrons per atom in
NiAl.
 镍作为一种过渡金属，可以将外层电子
“隐藏”在次外电子层的空轨道，看起来
没有价电子。所以，铝镍合金中，每个原
子有1.5个价电子。

31. 31
 合金的组成多种多样，可分为混合物合金，固溶体
合金和金属化合物合金等类型。
 铋镉合金是一种混合物合金，合金由两种金属的晶
粒相互间混合，紧密作用而得。这种合金有低共熔
点的特征，类似于某些盐的水溶液使水在低于零度
时才结冰一样。
 铜镍合金是固溶体合金，由一种金属原子进入另一
种金属的晶胞空隙而形成的。
 我们上面所讲的铝镍合金是金属化合物合金，这类
合金原子以金属键相互作用，不遵守化合价规则。
这类合金比任意组分的纯金属硬度都要强，但却降
低了可塑性。

32. 32
 12.Even in cases where intermetallic formation
does not occur ,there may not be perfect solid-
solubility ,if tow metals have different crystal
structures then at some intermediate
composition there will have to be a change from
the crystal structure of one metal to that of the
other .
 即使两种金属形成的晶体没有缺陷，也不
能说明它们能形成完美的固溶体，如果两
种金属有不同的晶格结构，必须在介质中
改变一种金属的晶格结构，使其与另外一
种金属的晶格结构相适应

33. 33
 13.In such a case the result would be ,on
gradually changing the composition of an
alloy from pure metal A(froming the a-
phase )to pure metal B (froming the b-
phase)
 为了形成这种晶格，逐渐将合金从A（α相）
变到B（β相）。

34. 34
 Single-phase a soild-solution;
 Two-phase mixture of a soild-solution and
b soild-sulition;
 Single-phase b solid-solution.
 α单相固溶体
 α单相固溶体与β单相固溶体混合
 β单相固溶体

35. 35
Think about….
 Q: Give examples to explain soild solution
and intermetallic compound?
 A: For example, nickel will dissolve some
aluminum,so that at low aluminum
contents a solid solution is
produced.However,if larger amounts of
aluminum are added,then a series of
intermetallic compounds(for example
Ni3Al and NiAl) are produced.

36. 36
Do you still remember?
 roam[rəum]
 graphite['græfait]
 malleable['mæliəbl]
 ductile[‘dʌktail]
 soluble[‘sɔljubl]
 chromium[‘krəumjəm]
 transition[træn‘ziʒən ]
 shell[ʃel]
 v.漫游，闲逛，徜徉 ；
 n.漫步，漫游，徘徊
 n.石墨
 a.有伸延性的，可锻的
 a.易延展的，柔软的
 a.可溶解的，可溶的
 n.铬
 n.转换，跃迁，过渡
 n.壳，外壳