【正文】 g through this temperature.隨著富碳部分的形成，剩余奧氏體含碳量減少，在727℃(1341℉)時(shí)達(dá)到共析組織。 Hypereutectoid steels are steels that contain greater than the eutectoid amount of carbon. When such steel cools, as shown in zz’ of the process is similar to the hypoeutectoid case, except that the primary or proeutectoid phase is now cementite instead of ferrite. 過(guò)共析鋼是含碳量大于共析量的鋼。At 727℃(1341℉), the austenite is of eutectoid position (% carbon) and further cooling transforms the remaining austenite to pearlite. The resulting structure is a mixture of primary or proeutectoid ferrite (ferrite that formed above the eutectoid reaction) and regions of pearlite.在727℃(1341℉)時(shí)，奧氏體為共析組成(%)，再冷卻剩余的奧氏體就轉(zhuǎn)化為珠光體。At high temperatures, the material is entirely austenite, but upon cooling enters a region where the stable phases are ferrite and austenite. Tieline and levellaw calculations show that lowcarbon ferrite nucleates and grows, leaving the remaining austenite richer in carbon.在較高溫度時(shí)，這種材料全部是奧氏體，但隨著冷卻就進(jìn)入到鐵素體和奧氏體穩(wěn)定狀態(tài)的區(qū)域。 Steels having less than the eutectoid amount of carbon (less than %) are known as hypoeutectoid steels. Consider now the transformation of such a material represented by cooling along line yy’ in . 含碳量少于共析體(%)的鋼稱(chēng)為亞共析鋼。通過(guò)打磨并在弱硝酸酒精溶液中蝕刻制備的樣本顯示出由緩慢冷卻形成的交互層狀的薄片結(jié)構(gòu)。本質(zhì)上，%的碳→%的碳+%的碳。 The iron wants to change from the FCC austenite structure to the BCC ferrite structure, but the ferrite can only contain % carbon in solid solution. 鐵需要從面心立方體奧氏體結(jié)構(gòu)轉(zhuǎn)變?yōu)轶w心立方體鐵素體結(jié)構(gòu)，%的碳。在較高溫度時(shí)，只存在奧氏體，%的碳溶解在鐵里形成固溶體。Control of this reaction, which arises due to the drastically different carbon solubility of austenite and ferrite, enables a wide range of properties to be achieved through heat treatment.控制這一由于奧氏體和鐵素體的碳溶解性完全不同而產(chǎn)生的反應(yīng)，使得通過(guò)熱處理能獲得很大范圍的特性。這對(duì)理解鋼的性能和處理是十分有用的。? A Simplified Ironcarbon Diagram簡(jiǎn)化鐵碳狀態(tài)圖 If we focus only on the materials normally known as steels, a simplified diagram is often used. 如果只把注意力集中于一般所說(shuō)的鋼上，經(jīng)常要用到簡(jiǎn)化鐵碳狀態(tài)圖。 The following discussion applies principally to the heat treatment of ordinary mercial steels known as plain carbon steels. With this process the rate of cooling is the controlling factor, rapid cooling from above the critical range results in hard structure, whereas very slow cooling produces the opposite effect. 下列討論主要針對(duì)被稱(chēng)為普通碳鋼的工業(yè)用鋼而言。 Alloy steel owe their properties to the presence of one or more elements other than carbon, namely nickel, chromium, manganese, molybdenum, tungsten, silicon, vanadium, and copper. Because of their improved physical properties they are used mercially in many ways not possible with carbon steels. 合金鋼的性質(zhì)取決于其所含有的除碳以外的一種或多種元素，如鎳、鉻、錳、鉬、鎢、硅、釩和銅。With the proper heat treatment internal stresses may be removed, grain size reduced, toughness increased, or a hard surface produced on a ductile interior. The analysis of the steel must be known because small percentages of certain elements, notably carbon, greatly affect the physical properties.使用合適的熱處理可以去除內(nèi)應(yīng)力、細(xì)化晶粒、增加韌性或在柔軟材料上覆蓋堅(jiān)硬的表面。Heat treatment is the operation of heating and cooling a metal in its solid state to change its physical properties. According to the procedure used, steel can be hardened to resist cutting action and abrasion, or it can be softened to permit machining. 熱處理是將金屬在固態(tài)加熱和冷卻以改變其物理性能的操作。第二單元 The understanding of heat treatment is embraced by the broader study of metallurgy. Metallurgy is the physics, chemistry, and engineering related to metals from ore extraction to the final product. 對(duì)熱處理的理解包含于對(duì)冶金學(xué)較廣泛的研究。 Intrachain structure. The chemical structure of the chains also has a tremendous effect on the properties. Depending on the structure the polymer may be hydrophilic or hydrophobic (likes or hates water), stiff or flexible, crystalline or amorphous, reactive or unreactive. 鏈內(nèi)結(jié)構(gòu)：原子鏈的化學(xué)結(jié)構(gòu)對(duì)性能也有很大影響。 Interchain interactions. The polymer chains can be free to slide past one another (thermoplastic) or they can be connected to each other with crosslinks (thermoset or elastomer). Thermoplastics can be reformed and recycled, while thermosets and elastomers are not reworkable. 原子鏈間的相互作用：聚合物的原子鏈可以自由地彼此滑動(dòng)(熱可塑性)或通過(guò)交鍵互相連接(熱固性或彈性)。而某些特別制造的聚合物能經(jīng)受住高達(dá)300℃(572℉)的溫度。這些溫度通常決定聚合物能否使用的上限。The mechanical properties of a polymer are significantly affected by the molecular weight, with better engineering properties at higher molecular weights.聚合物的分子量極大地影響其機(jī)械性能，分子量越大，工程性能也越好。它們的強(qiáng)度通?？刹捎眉訌?qiáng)復(fù)合結(jié)構(gòu)來(lái)改善。 Some important characteristics of polymers include their size (or molecular weight), softening and melting points, crystallinity, and structure. The mechanical properties of polymers generally include low strength and high toughness. Their strength is often improved using reinforced posite structures. 聚合材料具有一些重要特性，包括尺寸(或分子量)、軟化及熔化點(diǎn)、結(jié)晶度和結(jié)構(gòu)。這種重復(fù)結(jié)構(gòu)產(chǎn)生鏈狀大分子。微粒加強(qiáng)型復(fù)合材料的一個(gè)例子是機(jī)動(dòng)車(chē)胎，它就是在聚異丁烯人造橡膠聚合物基材中加入了碳黑微粒。Particlereinforced posites Particles used for reinforcing include ceramics and glasses such as small mineral particles, metal particles such as aluminum, and amorphous materials, including polymers and carbon black.微粒加強(qiáng)型復(fù)合材料 用于加強(qiáng)的微粒包含了陶瓷和玻璃之類(lèi)的礦物微粒，鋁之類(lèi)的金屬微粒以及包括聚合物和碳黑的非結(jié)晶質(zhì)微粒。 Fibers have a very high modulus along their axis, but have a low modulus perpendicular to their axis. Fiber posite manufacturers often rotate layers of fibers to avoid directional variations in the modulus. 纖維在沿著其軸向有很高的模量，但垂直于其軸向的模量卻較低。Fiberreinforced posites are used in some of the most advanced, and therefore most expensive sports equipment, such as a timetrial racing bicycle frame which consists of carbon fibers in a thermoset polymer matrix. 纖維加強(qiáng)型復(fù)合材料用于某些最先進(jìn)也是最昂貴的運(yùn)動(dòng)設(shè)備，例如計(jì)時(shí)賽競(jìng)賽用自行車(chē)骨架就是用含碳纖維的熱固塑料基材制成的。The strong covalent bonds along the fiber’s length give them a very high modulus in this direction because to break or extend the fiber the bonds must also be broken or moved.沿著纖維長(zhǎng)度有很強(qiáng)結(jié)合力的共價(jià)結(jié)合在這個(gè)方向上給予復(fù)合材料很高的模量，因?yàn)橐獡p壞