【正文】 that “ceramic” must also be crystalline. 陶瓷通常被概括地定義為無機(jī)的非金屬材料。同樣，在鋼里加一些鉻能減緩它的生銹過程，但也將使它較脆。加一些其它金屬能影響密度、強(qiáng)度、斷裂韌性、塑性變形、導(dǎo)電以及耐環(huán)境退化等性能。沒有光子能通過金屬。由于電子能導(dǎo)熱和導(dǎo)電，所以金屬適合做好的烹飪鍋和電線。 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. 金屬的原子連結(jié)對(duì)它們的特性也有影響。 However, sometimes we can take advantage of plastic deformation. The crumple zones in a car absorb energy by undergoing plastic deformation before they ，有時(shí)我們也能利用塑性變形。作為工程師，設(shè)計(jì)時(shí)通常要使材料在正常條件下不變形。橄欖球運(yùn)動(dòng)員據(jù)此相信他的面罩不會(huì)裂成碎片。 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. 斷裂韌性可以描述為材料防止斷裂特別是出現(xiàn)缺陷時(shí)不斷裂的能力。 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 通常由較大原子序數(shù)原子構(gòu)成， 例如金或鉛。 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 pared to polymers. 金屬有哪些重要特性？密度定義為材料的質(zhì)量與其體積之比。 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. 某些金屬合金，例如鋁基合金，其密度低，可用于航空航天以節(jié)省燃料。金屬合金的例子有：不銹鋼是一種鐵、鎳和鉻的合金，以 及金飾品通常含有金鎳合金。 and gold jewelry which usually contains an alloy of gold and 。例如電線中的銅和制造烹飪箔及飲料罐的鋁。在極低的溫度下，某些金屬和金屬化合物能轉(zhuǎn)變成超導(dǎo)體。許多金屬具有高強(qiáng)度、高剛性以及良好的延展性。 Engineering materials may be further subdivided into: ① Metal ② Ceramics ③ Composite ④Polymers, ：①金屬材料②陶瓷材料③復(fù)合材料 ④聚合材料，等等。那些用于加工制造并成為產(chǎn)品組成部分的就是工程材料。他們也把材料分為有機(jī)材料 (曾經(jīng)有生命的 )和無機(jī)材料 (從未有生命的 )。 1 UNIT 1 ADVANCED ENGINEERING MATERIALS....................................................................................... 2 UNIT 2 HEAT TREATMENT OF METALS .................................................................................................... 7 UNIT 3 CASTING PROCESSES .................................................................................................................... 15 UNIT 4 FORGING PROCESSES ................................................................................................................... 22 UNIT 5 POWDER METALLURGY ............................................................................................................... 26 UNIT 6 INJECTION MOLDING ................................................................................................................... 32 UNIT 7 METAL CUTTING ........................................................................................................................... 39 UNIT 8 GRINDING ....................................................................................................................................... 45 UNIT 9 LAPPING POLISHING .................................................................................................................... 49 UNIT 10 SURFACE ENGINEERING ............................................................................................................ 52 UNIT 12 DRILLING AND MILLING............................................................................................................ 64 UNIT 13 JIGS AND FIXTURES.................................................................................................................... 68 UNIT 14 LIMIT AND TOLERANCES .......................................................................................................... 72 特種加工工藝（Ⅰ、Ⅱ） .............................................................................................................................. 77 2 UNIT 1 Advanced Engineering Materials Types of Materials 材料的類型 Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into anic (once living) and inanic (never living) ?？茖W(xué)家常根據(jù)狀態(tài)將材料分為：固體、液體或氣體。 For ind