-
Types of Materials
材料的类型
Materials may be grouped in several
ways.
Scientists often classify
materials by their state: solid, liquid,
or gas. They also separate them into
organic (once living)
and inorganic
(never living) materials.
材料可以按多种方法分类。科学家
常根据状态将材料
分为：固体、液体或气体。他们也把材料分为有机材料
(
曾经
有生命的
)
和无机材料
(
从未有生命的
)
。
For industrial
purposes, materials are divided into
engineering materials or nonengineering
materials.
Engineering materials are
those used in manufacture and
become
parts of products.
就工业效用而言，材料被分为工程
材料和非工程材料。
那些用于加工制造并成为产品组成部分的就是工程材料。
Nonengineering
materials are the chemicals, fuels, lubricants,
and other materials used in the
manufacturing process,
which do not
become part of the product.
非工程材料则是化学品、
燃料、润滑剂以及其它用于加工制造
过程但不成为产品组成部分的材料。
Engineering
materials may be further subdivided
into:
①
Metal
②
Ceramics
③
Composite
④
Polymers, etc.
工程材
料还能进一步细分为：①金属材料②陶瓷材料
③复合材料
④聚合材料，等等。
Metals
and Metal Alloys
金属和金属合金
Metals are
elements that generally have good
electrical and thermal conductivity.
Many metals have high
strength, high
stiffness, and have good ductility.
金属就
是通常具有良好导电性和导热性的元素。
许多金
属具有高强度、
高硬度以及良好的延展性。
Some metals, such as iron, cobalt and
nickel, are magnetic.
At low
temperatures, some metals and intermetallic
compounds become superconductors.
某些金属能被磁化，例如铁、钴和镍。在极低的温度下，某些
金属和金属化
合物能转变成超导体。
What is the
difference between an alloy and a pure
metal? Pure metals are elements which
come from a
particular area of the
periodic table. Examples of pure
metals
include copper in electrical wires and aluminum in
cooking foil and beverage cans.
合金与纯金属的区别是什么？纯金属是在元素周期表
中占据特定位置
的元素。例如电线中的铜和制造烹饪箔及饮
料罐的铝。
Alloys contain more than
one metallic element. Their
properties
can be changed by changing the elements
present in the alloy. Examples of metal
alloys include
stainless steel which is
an alloy of iron, nickel, and
chromium;
and gold jewelry which usually contains an alloy
of gold and nickel.
合金包含不止一种
金属元素。合金的性质能通过改变其中存在
的元素而改变。金属合金的例子有：不锈钢是
一种铁、镍、
铬的合金，以及金饰品通常含有金镍合金。
Why are metals
and alloys used? Many metals and
alloys
have high densities and are used in applications
which require a high mass-to-volume
ratio.
为什么要使用金属和合金？许多金属和合金具有高密
度，因此被用在需要较高质量体积比的场合。
Some metal alloys, such as those based
on aluminum, have
low densities and are
used in aerospace applications for
fuel
economy. Many alloys also have high fracture
toughness, which means they can
withstand impact and
are durable.
某些金属合金，例如铝基合金，其密度低，可用于航空航天以
节约燃料。许
多合金还具有高断裂韧性，这意味着它们能经
得起冲击并且是耐用的。
< br>
What are some important properties of
metals?
Density
is defined as a material’s mass divided
by
its volume. Most metals have
relatively high densities,
especially
compared to polymers.
金属有哪些重要特性？
密度
定义
为材料的质量与其体积之比。大多数金属密
度相对较高，尤其是和聚合物相比较而言。<
/p>
Materials with
high densities often contain atoms with high
atomic numbers, such as gold or lead.
However, some
metals such as aluminum
or magnesium have low densities,
and
are used in applications that require other
metallic
properties but also require
low weight.
高密度材料通常由较大原子序数原子构成，
< br>例如金和铅。
然而，
诸如铝和镁之类的一些金属则具有低
密度，并被用于既需要
金属特性又要求重量轻的场合。
Fracture
toughness
can be described as a
material’s ability to avoid fracture,
especially when a flaw is
introduced.
Metals can generally contain nicks and dents
without weakening very much, and are
impact resistant. A
football player
counts on this when he trusts that his
facemask won’t shatter.
断裂韧
性
可以描述为材料防止断裂特别是出现缺陷时
不断裂的能力。金
属一般能在有缺口和凹痕的情况下不显著
削弱，并且能抵抗冲击。橄榄球运动员据此相信
他的面罩不
会裂成碎片。
Plastic deformation
is the
ability of bend or deform
before
breaking. As engineers, we usually design
materials
so that they don’t deform
under normal conditions. You
don’t want
your car to lean to the east after a strong west
wind.
塑性变形
就是在断裂前弯曲或变形的能力。作为工程
师，设计时通常要使材料在正常条件下不变形
。没有人愿意
一阵强烈的西风过后自己的汽车向东倾斜。
However, sometimes we can
take advantage of plastic
deformation.
The crumple zones in a car absorb energy by
undergoing plastic deformation before
they break.
然而，有时我们也能利用塑性变形。汽车上压皱的区域在它们
断裂前通过经历塑性变形来吸收能量。
The atomic bonding of metals also
affects their
properties. In metals,
the outer valence electrons are
shared
among all atoms, and are free to travel
everywhere.
Since electrons conduct
heat and electricity, metals make
good
cooking pans and electrical wires.
金属的
原子连结对它们的特性也有影响。在金属内部，
原子的外层阶电子由所有原子共享并能到
处自由移动。由于
电子能导热和导电，
所以用金属可以制造好的
烹饪锅和电线。
It is
impossible to see through metals, since these
valence
electrons absorb any photons of
light which reach the metal.
No photons
pass through.
因为这些阶电子吸收到达金属的光子，所以透过金属不可
能看
得见。没有光子能通过金属。
Alloys
are
compounds consisting of more than one
metal. Adding other metals can affect
the density, strength,
fracture
toughness, plastic deformation, electrical
conductivity and environmental
degradation.
合金
是由一种以上金属组成的混合物
。加一些其它金
属能影响密度、强度、断裂韧性、塑性变形、导电性以及环
境侵蚀。
For
example, adding a small amount of iron to aluminum
will
make it stronger. Also, adding
some chromium to steel will
slow the
rusting process, but will make it more brittle.
例如，往铝里加少量铁可使其更强。同样，在钢里加一些铬能
减缓它
的生锈过程，但也将使它更脆。
Ceramics and
Glasses
陶瓷和玻璃
A ceramic is
often broadly defined as any inorganic
nonmetallic
material
．
By this
definition, ceramic materials
would
also include glasses; however, many materials
scientists add the stipulation that
“ceramic” mus
t also be
crystalline.
陶瓷通常被概括地定义为无机的非金属材料。照此定
义，陶瓷材料也应包括玻璃；然而许多材料科学家添加了
“
陶
瓷
”
必须同时是晶体物组
成的约定。
A glass is an
inorganic nonmetallic material that does
not have a crystalline structure. Such
materials are said to
be amorphous.
玻璃是
没有晶体状结构的无机非金属材料。
这种材料被
称为非结晶质材
料。
Properties of
Ceramics and Glasses
Some of the
useful properties of ceramics and
glasses include high melting
temperature, low density, high
strength, stiffness, hardness, wear
resistance, and
corrosion resistance.
陶瓷和玻璃的特性
高熔点、低密度、高强度、高刚度
、高硬度、高耐磨性
和抗腐蚀性是陶瓷和玻璃的一些有用特性。
Many ceramics are good
electrical and thermal insulators.
Some
ceramics have special properties: some ceramics
are
magnetic
materials; some are
piezoelectric
materials; and
a few special
ceramics are
superconductors at very low
temperatures. Ceramics and
glasses have
one major drawback: they are brittle.
许
多陶瓷都是电和热的良绝缘体。某些陶瓷还具有一些特殊性
能：有些是磁性材料，有些是
压电材料，还有些特殊陶瓷在
极低温度下是超导体。陶瓷和玻璃都有一个主要的缺点：它
们容易破碎。
Ceramics are not typically formed from
the melt.
This is because most ceramics
will crack extensively (i.e.
form a
powder) upon cooling from the liquid
state.
陶瓷一般不是由熔化形成的。
因为大多数陶瓷在从液态
冷却时将会完全破碎
(
即形成粉末
)
。
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