机械工程材料双语课件第二章
机械工程专业英语Unit 2
the physical properties. 因为某些微量元素，尤其是碳，极大地影响物理性能，所以必须了
解对钢的分析。 ➢ Alloy steels owe their properties to the presence of one or more
elements other than carbon, namely nickel, chromium,
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 .
铁碳图中靠近铁素体区和含碳量高于2%的那些部分对工程师 而言不重要，因此将它们去掉。如图2.1所示的简化铁碳图将焦点 集中在共析区，这对理解钢的性能和处理是十分有用的。
1、be of sth. 拥有，具有 2、focus on 致力于，对…予以注意，把焦点集中于…，focus…on 把…集中/聚焦到…，be focused on 集中/聚焦到... 3、be useful in 在…方面有用
材料工程专业英语 UNIT SIX-LESSON TWO
parameter 参数，参量
coordination 相互位置
surface finish 表面光洁度
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
(c)The degree of coincidence of the real parameters obtained after a part is manufactured, with the parameters defined in part design, represents the manufacturing quality of the part. For the convenience of analysis, the degree of coincidence between the real macro-geometrical parameters (dimension, shape and coordination) of a part obtained after machining, and those specified in part design is defined as machining accuracy. The degree of coincidence between the real micro-geometrical parameters (surface finish) and the parameters of the physic-mechanical properties of part surfaces, obtained after machining a part, with those specified in part design is defined as surface quality. Other physical and chemical parameters are involved only in some special cases.
机械工程专业英语教程第2版Lesson 2
Rotary Motion. The motion that is commonly transmitted is rotary motion. This type of motion may be produced with hand tools or power tools. Rotary motion is required to drill holes, turn parts in a lathe, mill surfaces, or drive a generator or fan belt.[4] 4. rotary motion 意为“回转运动”。全句可译为： 钻孔、在车床上车削零件、铣平面、驱动发电机或风扇的 带等都需要回转运动。
2012-2-4
《机械工程专业英语教程》
9
Harmonic and Intermittent Motion.[6] Any simple vibration, such as the regular back-and-forth movement of the end of a pendulum, is simple harmonic motion.[7] 6. harmonic and intermittent motion 意为谐和运动和间歇运 动”。 7. simple harmonic motion 意为“简谐运动”。全句可译 为 ： 任何简单的振动，例如摆的下端有规律的往复运动是简 谐运动。
2012-2-4
《机械工程专业英语教程》
8
Rectilinear Motion. The feed of a tool on a lathe, the cutting of steel on a power saw, or the shaping of materials are all situations in which rectilinear or straight line motion produces work. In each of these situations a part or mechanism is used to change rotary motion to straight line motion. The screw of a micrometer and the threads in a nut are still other applications where the direction of motion is changed from rotary to rectilinear.[5] 5. the screw of a micrometer 意为“千分尺中的螺杆”全句 可译为： 千分尺中的螺杆和螺母中的螺纹是把运动方向从转动变 为直线的另外一些应用实例。
机械工程材料双语课件2)
密排面 数量 密排方向 数量
体心立方晶格 {110} 6
<111>Fra bibliotek4面心立方晶格 {111} 4
<110>
6
密排六方晶格 六方底面 1 底面对角线 3
密
• closed-packed planes
排
底面对角线
六
and orientations of
方
六方底面
晶
the three ordinary
格
crystal lattices
体
面
心
心
立
立
方
方
晶
晶
格
格
密
• 三种常见晶格的密
排
底面对角线
六
排面和密排方向
六方底面
方 晶
格
体
面
心
心
立
立
方
方
晶
晶
格
格
体心立方(110)面 面心立方(111)面 密排六方底面
Stack sequence of the closed-packed plane in face centered cubic crystal lattice and closed-packed hexagonal crystal lattice Stack sequence of closed-packed hexagonal crystal lattice is ABABAB… Stack sequence of face centered cubic crystal lattice is ABCABCABC…
晶格常数：a
原子半径：r 2 a
4 原子个数：4 配位数： 12 致密度：0.74 常见金属： -Fe、Ni、Al、Cu、Pb、Au等
《机械工程专业英语》李光布饶锡新Lesson2CarbonandAlloySteel..
Lesson 2 Carbon and Alloy SteelTEXTSteel is probably the most widely used material for machine elements because of its properties of high strength, high stiffness, durability and relative ease of fabrication. The term steel refers to and alloy of iron, carbon, manganese and one or more other significant elements. Carbon has a very strong effect on the strength, hardness and ductility of any steel alloy. The other elements affect hardenability, toughness, corrosion resistance, machinability and strength retention at high temperatures. The primary alloying elements present in the various alloy steels are sulfur, phosphorus, silicon, nickel, chromium, molybdenum and vanadium.1.Importance of CarbonAlthough most steel alloys contain less than 1.0% carbon, it is included in the designation because of its effect on the properties of steel. As Figure 1.2illustrates, the last tow digits indicate carbon content n hundredths of a percent.As carbon content increases, strength and hardness also increase under the same conditions of processing and heat treatment. Since ductility decreases withincreasing carbon content, selecting suitable steel involves some compromisebetween strength and ductility.As a rough classification scheme, a low-carbon steel is one having fewer than30 points of carbon (0.30%). These steels have relatively low strength but goodformability. In machine element applications where high strength is not required, low-carbon steels are frequently specified. If wear is a potential problem,low-carbon steels can be carburized to increase the carbon content in the veryouter surface of the part and to improve the combination of properties.Medium-carbon steels contain 30 to 50 points of carbon (0.30%-0.50%).Most machine elements having moderate to high strength requirements withfairly good ductility and moderate hardness requirements come from this group.High-carbon steels have 50 to 95 points of carbon (0.50%-0.95%). The high carbon content provides better wear properties suitable for applications requiringdurable cutting edges and for applications where surfaces are subjected to constant abrasion. Tools, knives, chisels, and many agricultural implement components are among these uses.2.Stainless SteelsThe term stainless steel characterizes the high level of corrosion resistance. To be classified as a stainless steel, the alloy must have a chromium content of at least 10%. Most have 12% to 18% chromium.The three main groups of stainless steels are austenitic, ferritic, and martensitic. Austenitic stainless steels fall into the AISI 200 and 300 series. They are general-purpose grades with moderate strength. Most are not heat-treatable, and their final properties are determined by the amount of working. These alloys are nonmagnetic and are typically used in food processing equipment.Ferritic stainless steels belong to the AISI 400 series, designated as 405, 409, 430, 446, and so on. They are magnetic and perform well at elevated temperatures, from 1300℉to 1900℉(700℃-1040℃). They are notheat-treatable, but they can be cold-worked to improve properties. Typical applications include heat exchanger tubing, petroleum refining equipment, automotive trim, furnace parts, and chemical equipment.Martensitic stainless steels are also members of the AISI 400 series, including 403, 410, 414, 416, 420, 431 and 440 types. They are magnetic, can be heat-treated, and have higher strength than the AISI 200 and 300 series, while retaining good toughness. Typical uses include turbine engine parts, cutlery, scissors, pump parts, valve parts, surgical instruments, aircraft fittings, and marine hardware.3.Structural SteelsMost structural steels are designated by ASTM numbers established by American Society for Testing and Materials. The most common grade is ASTMA36, which has a minimum yield point of 36000 psi (248MPa) and is very ductile. It is basically a low-carbon, hot-rolled steel available in sheet, plate, bar, and structural shapes, such as wide-flange beams, American standard beams, channelsand angles.Most wide-flange beams are currently made using ASTM A992 structural steel, which has a yield point of 50 ksi to 65 ksi and a minimum tensile strength of 65 ksi. An additional requirement is that the maximum ratio of the yield point to the tensile strength is 0.85. This is a highly ductile steel, having a minimum of 21% elongation in a 2.00-inch gage length. Using this steel instead of the lower strength ASTM A36 steel typically allows smaller, lighter structural members at little or no additional cost.Hollow structural sections (HSS) are typically made from ASTM A500 steel that is cold-formed and either welded or made seamless. Included are round tubes and square rectangular shapes. There are different strength grades can bespecified. Some of these HSS products are made from ASTM A501 hot-formed steel having properties similar to the ASTM A36 hot-rolled steel.Many higher-strength grades of structural steel are available for use in construction, vehicular, and machine applications. They provide yield points in the range from 42 000 psi to 10 000 psi (290 MPa-700MPa).4.Tool SteelsTool steels refers to a group of steels typically used for cutting tools, punches, dies, shearing blades, chisels and similar uses. The numerous varieties of toolsteel materials have been classified into seven general types. Whereas most uses of tool steels are related to the field of manufacturing engineering, they are also pertinent to machine design where the ability to maintain a keen edge underabrasive conditions is required. Also, some tool steels have rather high shockresistance which may be desirable in machine components such as parts formechanical clutches, pawls, blades, guides for moving materials and clamps.READING MATERIALThe final properties of steels are dramatically affected by the way the steels are produced. Some processes involve mechanical working, such as rolling toa particular shape or drawing through the dies. In machine design, many bar-shaped parts, shafts, wire and structural members are produced in these ways. But most machine parts, particularly those carrying heavy loads, are heat-treated to produce high strength with acceptable toughness and ductility.Carbon steel bar and sheet forms are usually delivered in the as-rolling condition, that is, they are rolled at an elevated temperature that eases the rolling process. The rolling can also be done cold to improve strength and surface finish. Cold-drawn bar and wire have the highest strength of the forms, along with a very good surface finish. However, when a material is designated to be as-rolled, it should be assumed that it was hot-rolled.1.Heat TreatingHeat treating is the process in which steel is modified its properties by different elevated temperatures. Of the several processes available, those most used for machine steels are annealing, normalizing, through-hardening (quench and temper), and case hardening.Figure 1.3 shows the temperature-time cycles for these heat treating processes. The symbol RT indicates normal room temperature, and LC refers to the lower critical temperature at which the ferrite transformation begins during the heating of the steel. At the upper critical temperature (UC), the transformation is complete. These temperatures vary with the composition of the steel. For most medium-carbon (0.30%—0.50%) steels. UC is approximately 1 500°F(822℃). References giving detailed heat treating process data should be consulted.1)AnnealingFull annealing (Figure 1.3(a)) is performed by heating the steel above the upper critical temperature and holding it until the composition is uniform. Then the steel is cooled very slowly in the furnace until its temperature is below the lower critical temperature. Slow cooling to room temperature outside the furnace completes the process. This treatment produces a soft, low-strength form of the material, free of significant internal stresses. Parts are frequentlycold-formed or machined in the annealed condition.Stress relief annealing (Figure 1.3 (b)) is often used following welding, machining, or cold forming to relieve residual stresses and thereby minimize subsequent distortion. The steel is heated to approximately 1 000 °F to 1 200 °℉(540℃—650℃), held to achieve uniformity, and then slowly cooled in still air to room temperature.NormalizingNormalizing (Figure 1.3 (c)) is similar to annealing, but at a higher temperature, above the transformation range where austenite is formed, approximately 1 600 ℉(870℃). The result is a uniform internal structure in the steel and somewhat higher strength than annealing produces. Machinability and toughness are usually improved over the as-rolled condition.2.Through-Hardening and Quenching and TemperingThrough-hardening (Figure 1.3(d)) is accomplished by heating the steel to above the transformation range where austenite forms and then rapidly cooling it in a quenching medium. The rapid cooling causes the formation of martensite, the hard and strong form of steel. The properties of the martensite forms depend on the alloy’s composition. An alloy containing a minim um of 80% of its structure in the martensite form over the entire cross section has high hardenability. This is an important property to look for when selecting a requiring high strength and hardness steel. The common quenching media are water, brine, and special mineral oils. The selection of a quenching medium depends on the required cooling rate. Most machine steels use either oil or water quenching.Tempering is usually performed immediately after quenching and involves reheating the steel from a temperature of 400℉to 1 300℉(200℃—700℃) and then slowly cooling it in air to room temperature. This process modifies the steel’s properties. Tensile strength and yield strength decrease with increasing tempering temperature, whereas ductility improves, as indicated by an increase in the percent elongation. Thus, the designer can tailor the propertiesof the steel to meet specific requirements. Furthermore, the steel in its as-quenched condition has high internal stresses and is usually quite brittle. Machine parts should normally be tempered at 700 ℉(370℃) or higher after quenching.(a)full annealing (b) stress relief annealing(c) normalizing (d) quenching and tempering(through-hardening)Figure 1. 3 Heat treatments for steels3. Case HardeningIn many cases, many parts require only moderate strength although the durface must have a very high hardness. In gear teeth, for example, high surface hardness is necessary to resist wearing as the mating teeth come into contact several million times during the expected life of the gears. At each contact, a high stress happens at the surface of the teeth. In this condition, case hardening is used. The surface (or case) of the part is given a high hardness to a depth of perhaps 0.010 in to 0.040 in (0.25 mm—1.00 mm), although the interior of the part (the core) is affected only slightly, if at all. Theadvantage of surface hardening is that as the surface receives the required wear-resisting hardness, the core of the part remains in a more ductile form which is resistant to impact and fatigue. The most used processes of case hardening are flame hardening, induction hardening, carburizing, nitriding, cyaniding, carbo-nitriding.。
机械工程材料ppt课件
1,纯铁(重要特性是结晶过程具有同素
目 录 异构转变 );
2, 铁素体 :是碳溶于α-Fe中形成的固
上一页 溶体，常用符号“α”或“F”表示。
下一页
3,奥氏体 :奥氏体是碳溶于γ-Fe中形
成的固溶体，用“γ”或“A”表示。
4,渗碳体:是铁与碳的稳定化合物Fe3C，
退出
其碳的质量分数为6.69％。 渗碳体在高温下可以分解形成石墨态的自
第3章 合金的相结构与二元合金相图
目录
上一页 下一页 退出
• 3.1 合金的相结构 • 3.2 匀晶相图 • 3.3 共晶相图 • 3.4 合金的性能与相图的关系
2020/11/4
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常见心律失常心电图诊断的误区诺如 病毒感 染的防 控知识 介绍责 任那些 事浅谈 用人单 位承担 的社会 保险法 律责任 和案例 分析现 代农业 示范工 程设施 红地球 葡萄栽 培培训 材料
4.3 铁碳合金的平衡结晶过程及组织
目
录
•
铁碳合金按其碳的质量分数及室温平衡组织 分为三大类，即工业纯铁、钢和铸铁。
• 4.3.1 工业纯铁: (Wc<0．0218％)室温平衡组织
上一页 为铁素体加少量Fe3CⅢ;
下一页 • 4.3.2 共析钢 :室温平衡组织为珠光体 ; • 4.3.3 亚共析钢 :在室温下的组织由先共析铁素
再结晶 • 第3章 合金的相结构与二
元合金相图 • 第4章 铁碳合金 • 第5章 钢的热处理 • 第6章 合金钢 • 第7章 铸铁
• 第8章 有色金属及其合金 • 第9章 非金属材料 • 第10章 纳米材料与功能材料 • 第11章 铸造 • 第12章 金属压力加工 • 第13章 焊接 • 第14章 机械零件的选材及工
机械工程材料第二章金属塑性变形与再结晶
4. 再结晶与重结晶
相同点：晶粒形核、长大的过程。
不同点： （1）再结晶转变前后的晶格类型没有发生变化， 重结晶时晶格类型发生改变。 （2）再结晶是对冷塑性变形的金属而言的，没有 发生冷塑性变形的金属不存在再结晶问题。
三、晶粒长大 再结晶刚刚完成后的晶粒是无畸变的等轴晶粒， 如果继续升高温度或延长保温时间，晶粒之间就 会通过晶界的迁移相互吞并而长大。
➢ 产生残余应力。
（二）其他性能
塑性变形影响金属的物理、化学性能， 如电阻增大，导磁率下降，耐腐蚀性能 降低。 密度、导热系数下降。
三、残余应力（约占变形功的10％）
（一）宏观内应力（第一类内应力） 原因：由工件不同部位的宏观变形不均匀而引起的。 作用范围：作用于整个工件。
金属棒弯曲变形后 的残余应力
正火组织
带状组织
金属冷拉拔后 的残余应力
（二）微观内应力（第二类内应力） 原因：晶粒或亚晶粒之间的变形不均匀引起的。 作用范围：与晶粒尺寸相当。
（三）点阵畸变（第三类内应力）80-90%
原因：晶体缺陷而引起的畸变应力。 作用范围：约几百到几千个原子范围内。
金属强化 主要原因
➢第一类、第二类残余应力： 弊：对金属材料的性二、塑性变形对金属性能的影响
（一）力学性能 加工硬化（形变强化）:随着冷塑性变形量 的增加，金属的强度、硬度升高，塑性、韧 性下降的现象。
工业纯铜
45钢
➢加工硬化是强化金属的重要手段之一。
对于不能热处理强化的金属和合金尤为重要。
链条板的轧制
材料为Q345（16Mn) 钢 的自行车链条经过五 次轧制，厚度由3.5mm压缩到1.2mm，总变形 量为65%。
原始横截面积的百分比。
Ψ=
机械工程材料第2章
零件
热锻
机加工
零件
冷轧、拔、冲
（机加工）
零件
2.1.1 材料凝固与结晶的条件
（1）熔融液体的粘度（内因）——是材料
内部结合键性质和结构情况的宏观表征，其大小表 示了液体中发生相对运动的难易程度。
聚合物粘度大，不易结晶；金属粘度小，一般为
金属晶体
（2）冷却速度（外因）——冷速越大，则在
单位时间内逸散的热量越多，熔体温度降得越低， 而又直接关系其中原子或分子的扩散能力。
单晶体与多晶体示意图
金属锑锭的组织示意图
2.2 二元相图的基本类型
有关相图的基本概念： 合金状态 一定条件下合金有哪几个相组成 相变 临界点 相变的温度 相图 反映在平衡条件下，合金的状态同温度、
成分之间关系的图形。
2.2.1 相图的建立
热分析法建立Cu-Ni 二元合金相图的过程
用热分析法建立Cu-Ni相图
2.化学变质处理 3.增强液体流动法
2.4.2 定向凝固技术
单晶体的制备
1.尖端形核法 2.垂直提拉法
做无差错能手，向零缺陷迈进。20.12. 220.12. 2Wedn esday , December 02, 2020
天长地久有时尽，9000推行无绝期。1 7:27:28 17:27:2 817:27 12/2/20 20 5:27:28 PM
形成条件：固态为有限固溶体，发生共晶反应。
1. 相图分析
（1）共晶相图的形成
（2）相区与基本相 （3）特性线与特性点
MEN水平线——共晶线(三相区)
LE 183℃M N
2.典型合金的平衡结晶过程
（1）有限固溶体合金Ⅰ （2）共晶成分的合金Ⅱ （3）亚共晶成分合金Ⅲ （4）过共晶成分合金Ⅳ
机械工程材料概述PPT(共 72张)
§2-4 其他工程材料及应用
复习：
工程材料的分类
铸铁
黑色金属 碳钢
金属材料
合金钢
铝合金 有色金属 铜合金
其它有色金属
塑料 高分子材料 橡胶
非金属材料 陶瓷材料 合成纤维
复合材料
新授： §2-4 其他工程材料及应用
一、有色金属及硬质合金
1、有色金属 ——指黑色金属（钢铁）以外的所有 金属及其合金，也称为非铁金属。
HPb59-1：表示平均含铜量为59%、含铅量为1%的特殊黄铜。
常用牌号有HPb63-3、HAl60-1-1、HSn62-1、 HFe59-1-1、ZCuZn38Mn2Pb2、ZCuZn16Si4等，主要 用于船舶及化工零件，如冷凝管、齿轮、螺旋桨、 轴承、衬套及阀体等。
2)青铜 ——除黄铜和白铜外的其他铜合金。 牌号：Q 元素符号数字-数字
常用硬铝合金如 飞机翼梁(腹板为
硬铝合金)
LY11 (2A11)、 LY12
(2A12)等，用于制造
冲压件、模锻件和铆
接件，如螺旋桨、梁、
铆钉等。
③ 超硬铝合金
——属Al-Zn-Mg-Cu系 合金，并含有少量Cr和Mn。
热态塑性好，但耐蚀性差。
常用合金有 LC4 (7A04 )、LC9 (7A09 ) 飞 等，主要用于工作温度 机
形成的，分别称锌白铜、锰白铜、铝白铜等。
其耐蚀性、强度和塑性高，成本低。
常用牌号如BMn40-1.5(康铜)、BMn43-0.5(考铜)。
用于制造精密机械、仪表零件及
医疗器械等。
康铜热偶
白铜型材
（2）铝及铝合金
①纯铝 纯铝具有银白色金属光泽，密度小，熔点低,
机械工程材料 第二章 金属的晶体结构与结晶
均匀长大
树枝状长大
2-2
晶粒度
实际金属结晶后形成多晶体，晶粒的大小对力学性能影响很大。 晶粒细小金属强度、塑性、韧性好，且晶粒愈细小，性能愈好。
标准晶粒度共分八级， 一级最粗，八级最细。 通过100倍显微镜下的 晶粒大小与标准图对 照来评级。
2-2
• 影响晶粒度的因素
• （1）结晶过程中的形核速度N（形核率） • （2）长大速度G（长大率）
面心立方晶 格
912 °C α - Fe
体心立方晶 格
1600
温 度
1500 1400
1300
1200
1100
1000
900
800
700 600 500
1534℃ 1394℃
体心立方晶格
δ - Fe
γ - Fe
γ - Fe
912℃
纯铁的冷却曲线
α – Fe
体心立方晶 格
时间
由于纯铁具有同素异构转变的特性，因此，生产中才有可能通过 不同的热处理工艺来改变钢铁的组织和性能。
2-3
• 铁碳合金—碳钢+铸铁，是工业应用最广的合金。 含碳量为0.0218% ~2.11%的称钢 含碳量为 2.11%~ 6.69%的称铸铁。 Fe、C为组元，称为黑色金属。 Fe-C合金除Fe和C外，还含有少量Mn 、Si 、P 、 S 、 N 、O等元素，这些元素称为杂质。
2-3
• 铁和碳可形成一系列稳定化合物： Fe3C、 Fe2C、 FeC。 • 含碳量大于Fe3C成分（6.69%）时，合金太脆，已无实用价值。 • 实际所讨论的铁碳合金相图是Fe- Fe3C相图。
2-2
物质从液态到固态的转变过程称为凝固。 材料的凝固分为两种类型：
机械工程英语Unit2 Heat Treatment of Metals
Unit 2Heat Treatment of Metals金属材料的热处理The understanding of heat treatment is embraced拥抱，接受by the broader广泛的study of metallurgy冶金学.热处理的认识是被冶金学广泛接受的。
Metallurgy is the physics, chemistry, and engineering related to metals from ore extraction矿石提炼to the final product. 冶金学是物理学，化学和金属从矿石提炼到最终产品的工程学Heat treatmentis the operation of heating and cooling a metal in its solidstate固态to change its physical properties. 热处理是为了改变金属的物理特性，在固态下将其加热和冷却。
Accordingto the procedure used, steel can be hardened to对……变得无动于衷，抵抗resist cutting action and abrasion磨损, or it can be softened to permit machining. 通过热处理，金属可以抵抗切割和磨损，也可以变得柔软，便于加工。
With the proper heat treatment internal stresses内应力may be removed , grain size晶粒reduced, toughness increased, or a hard surface produced on a ductile柔软的interior. 通过适当的热处理，内应力消失，晶粒变小，韧性增强，或者柔软的物体使得表面变硬。
机械工程材料课件(ppt)
内部原子的排列是否有规则； 晶体有固定的熔点，而非晶体没有固定的熔点； 晶体具有各向异性，而非晶体呈各向同性。
晶体 非晶体
第一节 金属的晶体结构 二、金属的晶体结构 1.金属晶体结构的基本概念
第一节 金属的晶体结构 二、金属的晶体结构 1.金属晶体结构的基本概念 晶格—假设通过原子结点的中心划出许多空间直线所形成的空间格架。 晶胞—能反映晶格特征的最小组成单元。 晶格常数—晶胞的三个棱边的长度a,b,c
晶格常数：底面边长a， 底面间距c， c/a=1.633 原子半径：a/2 原子个数：6 配位数：12 致密度：0.74 常见金属： Be、Mg、Zn、Cd、 - Ti等
密排六方晶格
r四=0.29 r原子 r八=0.15 r原子
r四=0.225 r原子 r八=0.414 r原子
r四=0.225 r原子 r八=0.414 r原子
第二章 金属材料的基础知识
机械工程材料课件 (ppt)
SDUST
机械工程材料
优选机械工ቤተ መጻሕፍቲ ባይዱ材料课件
第一节 金属的晶体结构 第二节 合金的相结构 第三节 纯金属的结晶 第四节 合金的结晶 第五节 铁-碳合金相图
第一节 金属的晶体结构 一、晶体与非晶体 晶体：凡内部原子呈规则排列的物质称为晶体。
非晶体：凡内部原子无规则排列的物质称为非晶体。
α-Fe等
体心立方晶格
第一节 金属的晶体结构
二、金属的晶体结构
2.典型的晶体结构
面心立方晶格
晶格常数：a(a=b=c) 原子半径： 原子个数：4 配位数：12 致密度：0.74 常见金属： -Fe、Cu、Al、Ni、Au、 Ag、Pt等
面心立方晶格
第一节 金属的晶体结构 二、金属的晶体结构 2.典型的晶体结构 密排六方晶格
机械工程材料双语教学PPT讲解
1.2.5 Fatigue Strength 疲劳强度
3）疲劳断裂的特点
① 断裂时的应力远低于材料静载下的抗拉强度，甚至屈服强度,
疲劳断裂属低应力脆断；
② 断裂是突然发生的，不产生明显的塑性变形，是一种无预兆、
突然发生的断裂，因此危险性极大。 4）疲劳断裂的基本过程
① 裂纹产生：材料本身的缺陷和 结构等原因，使零件受力时局部产生应 力集中，形成疲劳裂纹源，达到一定条 件时，产生裂纹。
韧性向脆性的转变
In these materials the fracture behaviors is ductile at high tem-
perature and brittle at low temperature.
22
1.2.4 Toughness 韧性 冲击韧性 a. 一般来说，低碳钢和低强度钢的韧脆转变温度较低且比较 明显;而高碳钢和高强度钢看不出明显的韧脆转变温度 b. 为避免脆性破坏，多采用0.20% C以下的低碳钢。钢中加 入锰、镍等元索，可使韧脆转变温度降低。
低碳钢的拉伸图
屈服点（S） ：如继续增大外力，超过s点时，拉伸曲线上就出现 了近似水平的线段，此时试棒所受外力虽不再增加，但变形却继 续增加，这种现象称为“屈服”，S点称为屈服点。
7
（一）屈服强度（σ s ）
材料产生屈服现象时的应力为材料的屈服强度，单位为MPa
s
Fs A
(MPa)
Fs——试棒产生屈服时所承受的最大外力(N) A——试棒原始截面面积(mm2)
3
1.2.1 Elastic Deformation 弹性变形 • Young’s Modulus (Elastic Modulus) 弹性模量
UNIT-2(机械专业英语)PPT课件
2021/3/12
3
例1：Control Center, Smoking Free.
控制中心，吸烟自由。 正确：控制中心，严禁吸烟。
例2：A dog driver stop the rotation of the wheel.
狗驾驶员使轮子停转。 正确：止动器使轮子停止旋转。
例3：The importance of computer in the use of manufacturing can not be overestimated.
翻译不是简单的或是原封不动的照搬原文的表达形式，而是有 意的选择与原文作用相等的语言手段来表达原意。
翻译的一种创造性的语言活动，是一种艺术。
2021/3/12
6
（一） 翻译的标准——信、达、雅
译文应忠于原文
例如： 1）In certain cases friction is an absolute necessity. 在一定的场合下摩擦是绝对必要的。 2）A roughing cut is usually to be followed by a finishing cut. 粗切之后通常还要精切。
忠实于原文不是照搬原文形式，应避免逐字死译，损坏原意。
2021/3/12
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译文的语言应通顺，要符合汉语的规范。
The foundation of the machine should not be constructed at a place of conspicuous temperature change, due to direct sunshine, excessive heat or vibration, or at a place contaminated with soil or dust particles.
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Fatigue strength
§2 Iron-carbon phase diagram
铁碳合金相图
Phase and Phase diagrams （相与相图）
•Phase：a region that differs in its state, microstructure， and /or composition from another region.
两组元在液态下无限溶解，固态下有限 溶解的二元合金相图。
The characteristics of eutectic system （共晶相图特点）：
eutectic reaction(共晶反应)
Eutectic reaction equation
共晶反应式
Eutectic system
（共晶相图）
Toughness What’s the relationship between the
value of ak and toughness? ak ↑，toughness↑
Questions for you
4. When a metal is subjected to repetitive stresses ， even when the stress is much lower than that which the metal can withstand under a static stress, the metal will fail to work. What do we call this phenomenon?
（共析相图）
The eutectoid reaction takes place completely in the solid state.
Eutectoid system
（共析相图）
Explanation of some concepts(概念): • Eutectoid reactions （共析反应） • eutectoid steels(共析钢) • hypoeutectoid steels（亚共析钢 ） • hypereutectoid steels(过共析钢)
（相图类型）
• Only binary alloy phase diagrams (二 元合金相图) are discussed.
• Types: isomorphous system(匀晶相图) eutectic system （共晶相图） eutectoid system（共析相图）
Isomorphous system
A—纯Pb熔点； B—纯Sn熔点；
C—共晶点，
WSn=61.9%（共
晶成分）
温度/℃
400
A 327.5
300
200 α
100
D
Pb 10
L
L+α E 183
19.2
L+β
C
61.9
232 B
F
97.5 β
α+β G
20 30 40 50 60 70 80 90 Sn
WSn/ %
Eutectoid system
• From cooling curves of metals and alloys, equilibrium phase diagrams of alloys are constructed.
• Ways to obtain a phase diagram for an alloy:
Calculation Experiment---
相图：表征不同成分的合金在不同温度、 压力下相的存在范围的图形。说明了合金 的状态与温度、成分等之间的关系。
Application of phase diagrams（相图的用途）
Most phase diagrams are constructed by using equilibrium conditions and are used to understand and predict many aspects of the behavior of materials.
（匀晶相图）
The two components of the alloy are completely soluble in each other in both the liquid and solid states, only a single type of crystal structure exists for all compositions of the components.（Cu-Ni）
Iron-carbon alloys containing
over 6.69% carbon are too brittle to use in industry, so we only discuss part of the iron-carbon phase diagram-----the iron-iron carbide
---differential thermal analysis (差热分析)
• Take Cu-Ni phase diagram for example. It is constructed by the thermal analysis(热分析法).
Fig.2.2 Construction of Cu-Ni phase
相：具有相同化学成分、晶体结构、 聚集状态的均匀组成部分 。
Phase and Phase diagrams （相与相图）
•Phase diagrams： graphical representations(代表图形) of what
phases are present in an alloy system at various temperatures and composition.
δorψ↑， the ductility ↑
Questions for you
2. What are the two hardness tests we mentioned last class?
Brinell hardness (布氏硬度) Rockwell hardness test (洛氏硬度)
相图多是通过平衡条件下获得的，可用来 估计材料行为的很多方面。
equilibrium conditions （平衡条件）
• Cooling or heating very slow. • In most cases, equilibrium is
approached but never fully attained.
1. Crystallization and cooling curve
• Crystallization（结晶）：the process of a metal transforms from a melted liquid into a crystalline solid.
结晶：金属由液态转化为晶体的过程。 • This process can be expressed by
diagram （Cu-Ni合金相图的建立）
temp/℃
100%
70%
50%
1452
WNi=30%
c
b
a 0%
a’ 108b
a L+α
b’ a’
α
1452 c c’
time
a) 冷却曲线
Cu
30 50 70
Ni
WNi%→
b) 相图
2. Types of phase diagram
3. Iron-carbon phase diagram(铁碳合金相图)
<1>Introduction
Plain carbon steels and cast irons contain not only carbon and iron elements, but also minor amounts of other elements such as Si, Mn, S and P, etc. However, in this course, they are treated as iron-carbon binary alloys.
• Alloys: formed by two or more metals or metals & nonmetals and have metallic characteristics.
• Similar to that of pure metals, but normally there are no flats in the curves.（冷却曲线上无平台）
(Fe-Fe3C) phase diagram. Fe3C, is also called cementite,
containing 6.69% carbon.
The iron-iron carbide phase diagram is shown in Fig.2.4.
All the room temperature structures obtained under different conditions are filled in the diagram.
cooling curve(过冷曲线).
cooling curve(冷却曲线)
cooling curve of a pure metal
degree of undercooling
(过冷度)
• We must note that the above discuss is based on cooling under equilibrium co存nd在it过io冷ns度（是平金衡属条或件合下金结冷晶却的）必, 要it条’s 件a ！ theoretic cooling process.