ch07-应变硬化与退火-E-2解读课件.ppt

1、11The Science and Engineering of Materials, 4th ed 2003Donald R. Askeland Pradeep P. PhulChapter 7 Strain Hardening and Annealing 应变硬化应变硬化(加工硬化加工硬化)与退火与退火2 /472Introduction to Chapter 1 The tetrahedron of materials science and engineering 材料科学与工程四面体材料科学与工程四面体 3 /473Review of knowledge 知识回顾知识回顾Chapte

2、r 1 Introduction to Materials Science and Engineering 绪论绪论Chapter 2 Atomic Structure 原子结构原子结构Chapter 3 Atomic and Ionic Arrangements 原子和离子的排列原子和离子的排列Chapter 4 Imperfections in the Atomic and Ionic Arrangements 原子和离子排列中的缺陷原子和离子排列中的缺陷Chapter 5 Atom and Ion Movements in Materials 材料中原子和离子的运动材料中原子和离子的运动

3、Chapter 6 Mechanical Properties and Behavior 机械性质与行为机械性质与行为4 /474Objectives of Chapter 7第七章目标第七章目标o To learn how the strength of metals and alloys is influenced by mechanical processing and heat treatments. 学习机械加工和热处理如何影响金属和合金的强度。学习机械加工和热处理如何影响金属和合金的强度。o To learn how to enhance the strength of metal

4、s and alloys using cold working. 学习如何利用冷加工提高金属和合金的强度学习如何利用冷加工提高金属和合金的强度o To learn how to enhance ductility using annealing heat treatment. 学习如何利用退火提高展延性学习如何利用退火提高展延性5 /475Chapter Outline本章概要本章概要o7.1 Relationship of Cold Working to the Stress-Strain Curve 冷加工与应力冷加工与应力-应变曲线的关联应变曲线的关联o7.2 Strain-Harden

5、ing Mechanisms 应变硬化的机理应变硬化的机理o7.3 Properties versus Percent Cold Work（%CW） 性质与性质与%CWo7.4 Microstructure, Texture Strengthening, and Residual Stresses 微观结构，织构强化，残余应力微观结构，织构强化，残余应力o7.5 Characteristics of Cold Working 冷加工的特性冷加工的特性o7.6 The Three Stages of Annealing 退火的三个阶段退火的三个阶段o7.7 Control of Annealin

6、g 退火的控制退火的控制o7.8 Annealing and Materials Processing 退火和材料处理退火和材料处理o7.9 Hot Working 热加工热加工o7.10 Superplastic Forming (SPF) 超塑性成型超塑性成型6 /476 Section 7.1 Relationship of Cold Working to the Stress-Strain Curve冷加工与应力冷加工与应力-应变曲线的关联应变曲线的关联 o Strain hardening 应变硬化应变硬化o Strain hardening exponent (n) 应变硬化指数（

7、应变硬化指数（n）7 /477应变硬化应变硬化 Strain hardening 金属材料在再结晶温度以下塑性变形时强度和硬度升高，而塑性和韧性金属材料在再结晶温度以下塑性变形时强度和硬度升高，而塑性和韧性降低的现象。又称冷作硬化。产生原因是，金属在塑性变形时，晶粒发生滑降低的现象。又称冷作硬化。产生原因是，金属在塑性变形时，晶粒发生滑移，出现位错的缠结，使晶粒拉长、破碎和纤维化，金属内部产生了残余应移，出现位错的缠结，使晶粒拉长、破碎和纤维化，金属内部产生了残余应力等。加工硬化的程度通常用加工后与加工前表面层显微硬度的比值和硬化力等。加工硬化的程度通常用加工后与加工前表面层显微硬度的比值和硬

8、化层深度来表示。层深度来表示。 加工硬化给金属件的进一步加工带来困难。如在冷轧钢板的过程中会愈加工硬化给金属件的进一步加工带来困难。如在冷轧钢板的过程中会愈轧愈硬以致轧不动，因而需在加工过程中安排中间退火，通过加热消除其加轧愈硬以致轧不动，因而需在加工过程中安排中间退火，通过加热消除其加工硬化。又如在切削加工中使工件表层脆而硬，从而加速刀具磨损、增大切工硬化。又如在切削加工中使工件表层脆而硬，从而加速刀具磨损、增大切削力等。但有利的一面是，它可提高金属的强度、硬度和耐磨性，特别是对削力等。但有利的一面是，它可提高金属的强度、硬度和耐磨性，特别是对于那些不能以热处理方法提高强度的纯金属和某些合金

9、尤为重要。如冷拉高于那些不能以热处理方法提高强度的纯金属和某些合金尤为重要。如冷拉高强度钢丝和冷卷弹簧等，就是利用冷加工变形来提高其强度和弹性极限。又强度钢丝和冷卷弹簧等，就是利用冷加工变形来提高其强度和弹性极限。又如坦克和拖拉机的履带、破碎机的颚板以及铁路的道岔等也是利用加工硬化如坦克和拖拉机的履带、破碎机的颚板以及铁路的道岔等也是利用加工硬化来提高其硬度和耐磨性的。来提高其硬度和耐磨性的。 8 /478Figure 7.2 Manufacturing processes that make use of cold working as well as hot working. Common

10、 metalworking methods冷加工及热加工过冷加工及热加工过程。普通的金属加程。普通的金属加工方式。工方式。Forging 锻造锻造Extruding挤压挤压Drawing拉拔拉拔Stamping冲压冲压Rolling 轧制轧制9 /479Strain hardening exponent (n)应变硬化指数（应变硬化指数（n） 在金属材料拉伸真应力应变曲线上的均匀塑性变形阶在金属材料拉伸真应力应变曲线上的均匀塑性变形阶段关系式段关系式 ： =k n （：真应力，：真应力， ：真应变）：真应变） 应变硬化指数应变硬化指数n反映了金属材料抵抗继续塑性变形的反映了金属材料抵抗继续塑性

11、变形的能力，是表征金属材料应变硬化的性能指标。能力，是表征金属材料应变硬化的性能指标。 在极限情况下，在极限情况下，n1，表示材料为完全理想的弹性，表示材料为完全理想的弹性体，体， 与与 成正比关系；成正比关系； n0时，时， k常数，表示材料没有应变硬化能常数，表示材料没有应变硬化能力，例如室温下产生再结晶的软金属及已受强烈应变硬力，例如室温下产生再结晶的软金属及已受强烈应变硬化的材料。大多数金属的化的材料。大多数金属的n值在值在0.10.5之间。之间。10 /47102003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson

12、 Learning is a trademark used herein under license.Figure 7.3 The true stress-true strain curves for metals with large and small strain-hardening exponents. Larger degrees of strengthening are obtained for a given strain for the metal with the larger n具有大的和小的应变硬化具有大的和小的应变硬化指数（指数（n）的金属的真应）的金属的真应力力-应变

13、曲线，当应变给定应变曲线，当应变给定时，具有较大时，具有较大n的金属的的金属的应变硬化程度更大。应变硬化程度更大。ln =lnK+n ln 11 /4711典型金属和合金的应变硬化指数和强度系数典型金属和合金的应变硬化指数和强度系数磅力/英寸2(psi)= psi=磅力磅力/英寸英寸2钛钛钼钼奥氏体不锈钢奥氏体不锈钢淬火和回火中碳钢淬火和回火中碳钢退火合金钢退火合金钢12 /4712Section 7.2 Strain-Hardening Mechanisms 应变硬化的机理应变硬化的机理o Frank-Read source - A pinned dislocation that, unde

14、r an applied stress, produces additional dislocations. This mechanism is at least partly responsible for strain hardening. 弗兰克弗兰克-瑞德源瑞德源 一个被钉住的位错，在外加应力的作用下，引起一个被钉住的位错，在外加应力的作用下，引起额外的位错。这一机制至少是引起应变硬化的部分原因。额外的位错。这一机制至少是引起应变硬化的部分原因。o Thermoplastics - A class of polymers that consist of large, long spag

15、hetti-like molecules that are intertwined (e.g., polyethylene, nylon, PET, etc.). 热塑性塑料热塑性塑料 一类由长链大分子相互缠绕组成的聚合物（例如，聚一类由长链大分子相互缠绕组成的聚合物（例如，聚乙烯，尼龙，聚对苯二甲酸乙二酯等。）乙烯，尼龙，聚对苯二甲酸乙二酯等。）13 /4713Figure 7.5 The Frank-Read source can generate dislocations. (a) A dislocation is pinned at its ends by lattice defect

16、s. (b) As the dislocation continues to move, the dislocation bows, eventually bending back on itself. (c) finally the dislocation loop forms, and (d) a new dislocation is created. (e) Electron micrograph of a Frank-Read source (330,000). 弗兰克弗兰克-瑞德源能产生位错。瑞德源能产生位错。(a)一一个位错被它两端的晶格缺陷固定。个位错被它两端的晶格缺陷固定。(b

17、)当位错连续运动，该位错变成弓当位错连续运动，该位错变成弓形，最终折回。形，最终折回。(c)最后该位错成环最后该位错成环形。形。(d)形成新的位错。形成新的位错。(e)弗兰克弗兰克-瑞德源的电镜照片（瑞德源的电镜照片（330000倍）倍）14 /47142003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Figure 7.6 In an undeformed thermoplastic polymer tensile ba

18、r, (a) the polymer chains are randomly oriented. (b) When a stress is applied, a neck develops as chains become aligned locally. The neck continues to grow until the chains in the entire gage length have aligned. (c) The strength of the polymer is increased在一个未变形的热塑性塑料拉在一个未变形的热塑性塑料拉力试棒中，力试棒中，(a)聚合物分

19、子链聚合物分子链是随机取向的。是随机取向的。(b)当施加应当施加应力后，因分子链局部定向排列力后，因分子链局部定向排列从而形成细颈。细颈增长直到从而形成细颈。细颈增长直到所有分子链定向排列。所有分子链定向排列。(c)聚聚合物的强度被提高。合物的强度被提高。15 /4715Section 7.3 Properties versus Percent Cold Work 性质与性质与%CW percent cold work 的定义是冷加工前初始横截面积与的定义是冷加工前初始横截面积与冷加工后最终横截面积的变化百分比，其中包含多个中间冷加工后最终横截面积的变化百分比，其中包含多个中间过程对结果没有影

20、响。因此总的过程对结果没有影响。因此总的 percent cold work 实实际上是际上是:%CW=(t0-tf)/t0X100%16 /4716Section 7.3 Properties versus Percent Cold Work 性质与性质与%CW 2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Figure 7.7 The effect of cold work on the mechanical p

21、roperties of copper 冷加工对铜的机械性质的影响伸长率伸长率屈服强度屈服强度抗张强度抗张强度17 /4717Example 7.1 Cold Working a Copper Plate冷加工铜板冷加工铜板 A 1-cm-thick copper plate is cold-reduced to 0.50 cm, and later further reduced to 0.16 cm. Determine the total percent cold work and the tensile strength of the 0.16-cm plate. (See Figur

22、e 7.8.) 一块厚度一块厚度1cm的铜的铜板，被冷加工至板，被冷加工至0.50 cm厚，然后进一步冷加工至厚，然后进一步冷加工至0.16 cm厚。确定厚。确定0.16 cm厚的板材总的厚的板材总的%CW和拉和拉伸强度。伸强度。18 /47182003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Figure 7.8 Diagram showing the rolling of a 1-cm plate (for Exam

23、ple 7.1)轧轧1cm板的示意图板的示意图19 /4719Example 7.1 SOLUTION20 /4720Example 7.2 Design of a Cold Working Process 设计冷加工工艺设计冷加工工艺 Design a manufacturing process to produce a 0.1-cm-thick copper plate having at least 65,000 psi tensile strength, 60,000 psi yield strength, and 5% elongation.设计一个制造工艺生产拉伸强度不低于设计一个

24、制造工艺生产拉伸强度不低于65,000 psi(磅力磅力/英寸英寸2) ，屈服强度不低于屈服强度不低于60,000 psi以及断裂伸长不低于以及断裂伸长不低于 5%的的0.1cm厚度厚度的铜板。的铜板。Example 7.2 SOLUTIONTo produce the plate, a cold-rolling process would be appropriate. The original thickness of the copper plate prior to rolling can be calculated from Equation 7-4. Because there i

25、s a range of allowable cold workbetween 40% and 45%there is a range of initial plate thicknesses: 要生产这种板材，冷轧工艺是适合的。冷轧之前铜要生产这种板材，冷轧工艺是适合的。冷轧之前铜板的初始厚度可通过板的初始厚度可通过%CW计算。因为允许的计算。因为允许的%CW 在在40% 45%范围内（参见图范围内（参见图7-7），初始板材厚度范围为：），初始板材厚度范围为：21 /4721Example 7.2 SOLUTION (Continued)To produce the 0.1-cm coppe

26、r plate, we begin with a 0.167- to 0.182-cm copper plate in the softest possible condition, then cold roll the plate 40% to 45% to achieve the 0.1 cm thickness. 为生产为生产0.1-cm 的铜板，我们用尽可能软的的铜板，我们用尽可能软的0.167至至0.182cm的铜板，冷轧至的铜板，冷轧至%CW为为 40% 45%得到得到厚度为厚度为0.1cm的板材。的板材。22 /4722Section 7.4 Microstructure, Te

27、xture Strengthening, and Residual Stresses 微观结构，织构强化，残余应力微观结构，织构强化，残余应力 o Fiber texture, Sheet texture 纤维状构造，薄片状构造纤维状构造，薄片状构造o Pole figure analysis, Orientation microscopy 极图分析极图分析,取向显微术取向显微术o Residual stresses, Stress-relief anneal残余应力，消除应力退火残余应力，消除应力退火o Annealing glass, Tempered glass 玻璃退火，钢化玻璃玻璃退

28、火，钢化玻璃23 /4723Figure 7.9 The fibrous grain structure of a low carbon steel produced by cold working: (a) 10% cold work, (b) 30% cold work, (c) 60% cold work, and (d) 90% cold work (250).冷加工得到的冷加工得到的低碳钢纤维状晶粒结构低碳钢纤维状晶粒结构:(a)10%CW，(b)30%CW，(c)60%CW，(d)90%CW (250倍倍）。）。24 /47242003 Brooks/Cole, a divisio

29、n of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Figure 7.10 Anisotropic behavior in a rolled aluminum-lithium sheet material used in aerospace applications. The sketch relates the position of tensile bars to the mechanical properties that are obtained用于航空领域的轧制铝用

30、于航空领域的轧制铝-锂薄片的各锂薄片的各向异性形为。示意图所示为拉力试向异性形为。示意图所示为拉力试棒的位置与所测得的机械性能之间棒的位置与所测得的机械性能之间的关系。的关系。屈服强度抗张强度伸长率25 /4725Example 7.3 Design of a Stamping Process 冲压过程的设计冲压过程的设计One method for producing fans for cooling automotive and truck engines is to stamp the blades from cold-rolled steel sheet, then attach th

31、e blades to a “spider that holds the blades in the proper position. A number of fan blades, all produced at the same time, have failed by the initiation and propagation of a fatigue crack transverse to the axis of the blade (Figure 7.11). All other fan blades perform satisfactorily. Provide an expla

32、nation for the failure of the blades and redesign the manufacturing process to prevent these failures.一种制造用于冷却汽车和卡车发动机的风扇的方式是首先将冷轧钢一种制造用于冷却汽车和卡车发动机的风扇的方式是首先将冷轧钢板冲压成叶片，然后将叶片固定在一个板冲压成叶片，然后将叶片固定在一个“十字架十字架”上以使得叶片处上以使得叶片处于适当的位置。在同时生产的叶片中，一定数量的叶片会因为于适当的位置。在同时生产的叶片中，一定数量的叶片会因为疲劳疲劳裂纹的产生和裂纹扩展而报废，所产生的裂纹与叶片的轴垂

33、直裂纹的产生和裂纹扩展而报废，所产生的裂纹与叶片的轴垂直(Figure 7.11) ，其它叶片的质量则令人满意。解释叶片报废的其它叶片的质量则令人满意。解释叶片报废的原因并重新设计制造过程以防止废品产生。原因并重新设计制造过程以防止废品产生。26 /47262003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Figure 7.11 Orientations of samples (for Example 7.3) 试样的方

34、位试样的方位Example 7.3 (continued)轧制方向轧制方向 想要的想要的 不想要的不想要的 27 /4727Example 7.3 SOLUTIONo The wrong type of steel may have been selected.可能选择了型号不正确的钢板。可能选择了型号不正确的钢板。o The dies used to stamp the blades from the sheet may be worn. 由钢板冲压叶片所使用的模具可能旧了。由钢板冲压叶片所使用的模具可能旧了。o The clearance between the parts of the

35、dies may be incorrect, producing defects that initiate fatigue failure. 模具各个部件之间的间隙可能不正模具各个部件之间的间隙可能不正确，产生的缺陷引起疲劳破坏。确，产生的缺陷引起疲劳破坏。o The failures could also be related to the anisotropic behavior of the steel sheet caused by rolling. 废品也可能与轧制钢板时材料产生的各向异性行为有关。废品也可能与轧制钢板时材料产生的各向异性行为有关。28 /47282003 Broo

36、ks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Figure 7.12 The compressive residual stresses can be harmful or beneficial. (a) A bending force applies a tensile stress on the top of the beam. Since there are already tensile residual stresses a

37、t the top, the load-carrying characteristics are poor. (b) The top contains compressive residual stresses. Now the load-carrying characteristics are very goods. 残余压应力可能是有害的或有益的。 (a)一个弯曲力在梁的顶部产生张应力。因为在顶部已经存在残余张应力，承载能力差。 (b)顶部存在残余压应力，承载能力非常好。29 /4729Example 7.4 Design of a Fatigue-Resistant Shaft 抗疲劳轴

38、的设计抗疲劳轴的设计Your company has produced several thousand shafts that have a fatigue strength of 20,000 psi. The shafts are subjected to high-bending loads during rotation. Your sales engineers report that the first few shafts placed into service failed in a short period of time by fatigue. Design a proc

39、ess by which the remaining shafts can be salvaged by improving their fatigue properties. 你的公司生产了数千根疲劳强度为你的公司生产了数千根疲劳强度为20,000 psi 的轴，的轴，该轴在转动过程中承受高弯曲载荷。你的经销人员报告该轴在转动过程中承受高弯曲载荷。你的经销人员报告因为疲劳最初的几根轴在短期内就损坏了，设计处理方因为疲劳最初的几根轴在短期内就损坏了，设计处理方法通过改善轴的疲劳性能来挽救剩余的轴。法通过改善轴的疲劳性能来挽救剩余的轴。30 /4730Example 7.4 SOLUTIONo

40、Increasing the strength at the surface improves the fatigue life of the shaft carburizing 提高表面强度改善轴的疲劳寿命提高表面强度改善轴的疲劳寿命-渗碳处理渗碳处理o Cold working the shaft 对对轴进行冷加工轴进行冷加工o Shot peen the shaft 轴（表面）喷丸强化轴（表面）喷丸强化喷丸强化分为一般喷丸和应力喷丸喷丸强化分为一般喷丸和应力喷丸.一般处理时一般处理时,钢板在自由状钢板在自由状态下态下,用高速钢丸打击钢板的里面用高速钢丸打击钢板的里面,使其表面产生预压应力

41、使其表面产生预压应力.以减以减少工作中钢板表面的拉应力少工作中钢板表面的拉应力,增加使用寿命增加使用寿命.应力喷丸处理是将应力喷丸处理是将钢板在一定的作用力下的预先弯曲钢板在一定的作用力下的预先弯曲,然后进行喷丸处理然后进行喷丸处理. 31 /4731Figure 7.13 Shot peen the shaft 轴轴（表面）喷丸强化（表面）喷丸强化32 /4732Section 7.5 Characteristics of Cold Working冷加工的特性冷加工的特性2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomso

42、n Learning is a trademark used herein under license.Figure 7.14 A comparison of strengthening copper by (a) cold working and (b) alloying with zinc. Note that cold working produces greater strengthening, yet has little effect on electrical conductivity.比较铜的强化效果比较铜的强化效果(a)通过冷加工强化通过冷加工强化(b)与锌形成合金强化。注意

43、冷加工导致更高的强度，与锌形成合金强化。注意冷加工导致更高的强度，但是对电导率的影响小。但是对电导率的影响小。屈服强度屈服强度33 /47332003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Figure 7.15 The wire-drawing process. The force Fd acts on both the original and final diameters. Thus, the stress p

44、roduced in the final wire is greater than that in the original. If the wire did not strain harden during drawing, the final wire would break before the original wire was drawn through the die.金属丝-拉拔加工。拉力Fd同时作用于前后两种直径的丝上，因此，作用在最终的丝上的应力要高于作用在初始丝上的应力，如果在拉拔加工过程中没有出现应变硬化，在初始丝被拉出模具之前，最终的丝就将会断裂。34 /4734Sec

45、tion 7.6 The Three Stages of Annealing 退火的三个阶段退火的三个阶段o Recovery - A low-temperature annealing heat treatment designed to eliminate residual stresses introduced during deformation without reducing the strength of the cold-worked material. 回复回复 退火热处理低温阶段，作用是退火热处理低温阶段，作用是消除变形过程中产生的残余应力，被冷加工的材料强度不降低。消除变

46、形过程中产生的残余应力，被冷加工的材料强度不降低。o Recrystallization - A medium-temperature annealing heat treatment designed to eliminate all of the effects of the strain hardening produced during cold working. 再结晶再结晶 - 退火热处理中温阶段，作用是消除冷加工过程中应变硬退火热处理中温阶段，作用是消除冷加工过程中应变硬化效果。化效果。o Grain growth - Movement of grain boundaries b

47、y diffusion in order to reduce the amount of grain boundary area. 晶粒长大晶粒长大 因扩散导致晶粒边界移动以因扩散导致晶粒边界移动以减少晶粒边界的面积。减少晶粒边界的面积。35 /4735Figure 7.16 Photomicrographs showing the effect of annealing temperature on grain size in brass. Twin boundaries can also be observed in the structures. (a) Annealed at 400o

48、C, (b) annealed at 650oC, and (c) annealed at 800oC (75). 退火处理温度对黄铜中晶粒尺寸的影响(a)400oC退火，(b)650oC退火，(c)800oC退火。36 /47362003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Figure 7.17 The effect of annealing temperature on the microstructure o

49、f cold-worked metals. (a) cold-worked, (b) after recovery, (c) after recrystallization, and (d) after grain growth.退火温度对冷加工材料微观结构的影响。(a)冷加工材料，(b)回复阶段后，(c)再结晶后，(d)晶粒长大后。37 /4737Section 7.7 Control of Annealing退火的控制退火的控制o Warm working - A term used to indicate the processing of metallic materials in a

50、 temperature range that is between those that define cold and hot working (usually a temperature between 0.3 to 0.6 of melting temperature in K). 温加工温加工 用于表示金属材料处理的术语，处理用于表示金属材料处理的术语，处理的温度是介于冷加工和热加工之间，（以的温度是介于冷加工和热加工之间，（以K为为温度单位，通常是在熔点的温度单位，通常是在熔点的0.3到到0.6倍之倍之间）。间）。38 /47382003 Brooks/Cole, a divisi