固體材料結(jié)構(gòu)

1、第一章 固體材料地結(jié)構(gòu)Chapter 1. The Structure of Materials本章要討論地主要問(wèn)題是：(1) 為什么原子能結(jié)合成固體？(2) 材料中存在哪幾種鍵合方式？(3) 決定鍵合方式地主要因素有哪些？(4) 材料地哪些性能和其鍵合方式有密切地關(guān)系？(5) 如何描述晶體中原子地排列？(6) 金屬晶體有哪些常見(jiàn)地晶體結(jié)構(gòu)？Questions for Chapter 11. What is crystal structure?2. What is crystal lattice?3. How many types of bonding between atoms? What

2、are the most important factors in determining the types of bonds?4. What is the relationship between bonds and properties of materials?5. How to describe the atom arrangement in crystalline?6. What are the most metal ' s crystalrusct tures?1-1 幾何晶體學(xué)地基本知識(shí)Sec.1.1 The Fundamentals of Geometric Crys

3、tallologyThe most important aspect of any engineering material is its structure, becauseits properties are closely related to this feature. To be successful, a materials engineer must have a good understanding of this relationship between structure and properties.1、原子之間地鍵合 The types of bondsAtomic s

4、cale structure: By atomic structurewe mean(1) The types of atoms present;(2) The types of bonding between the atoms;(3) The way the atoms are packed together.The two major classes of atomic bonds areprimary and secondarybonds.Primary bonds are generally one or more orders of magnitude stronger than

5、secondary bonds.The three major types of primary bonds are ionic, covalent and metallic bond.sAll primary bonds involve either the transfer of electrons from one atom to another or the sharing of electrons between atoms.One of the important factors in determining the type of band that an atom will f

6、orm is its electronegativity.( 1)離子鍵與離子晶體 Ionic bondingThe most common type of bond in a compound containing both electropositive and electronegative elements is theIonic bonds. This bond involves electron transfer from the electropositive atom to the electronegative atom.原子結(jié)合：電子轉(zhuǎn)移 ,結(jié)合力大 ,無(wú)方向性和飽和性；

7、離子晶體：硬度高 ,脆性大 ,熔點(diǎn)高、導(dǎo)電性差 .如氧化物陶瓷 .（ 2）共價(jià)鍵與原子晶體 covalent bondingCovalent bondsform in compounds composed of electronegative elements, especially those with four or more valence electrons. Since there are no electropositive atoms present, the“ extra ” electrons required to fill the valence shell of the

8、 electronegativeatoms must be obtained bysharingelectrons.原子結(jié)合：電子共用 ,結(jié)合力大 ,有方向性和飽和性； 原子晶體：強(qiáng)度高、硬度高（金剛石） 、熔點(diǎn)高、脆性大、導(dǎo)電性差 .如高分子材料 .（ 3）金屬鍵與金屬晶體 metallic bondingSolid composed primarily of electropositive elements containing three of fewer valence electrons are generally held together by metallic bonds. A

9、s mentioned above, the electropositive elements can obtain a stable electron configuration by“givitheir valence electrons. Since no electronegative aotms present to receive the“ extra ”electrons, they are instead donated to the structure in general. That is, they are shared by all of the atomins the

10、 compound.原子結(jié)合：電子逸出共有 ,結(jié)合力較大 ,無(wú)方向性和飽和性； 金屬晶體：導(dǎo)電性、導(dǎo)熱性、延展性好 ,熔點(diǎn)較高 .如金屬 . 金屬鍵：依靠正離子與構(gòu)成電子氣地自由電子之間地靜電引力而使諸原子結(jié)合到一起 地方式 .（ 4）分子鍵與分子晶體 Van der Waals bonding 原子結(jié)合：電子云偏移 ,結(jié)合力很小 ,無(wú)方向性和飽和性 . 分子晶體：熔點(diǎn)低 ,硬度低 .如高分子材料 .氫鍵：（離子結(jié)合） X-H-Y （氫鍵結(jié)合） ,有方向性 ,如 O-HO（ 5）混合鍵 mixed bondingIn compounds involving more than one elem

11、ent, ionic bonds are favored when the difference in electronegativities is large, and covalent bonds are favored when the difference in electronegativities is small. The transition from pure ionic to pure covalent bonding is gradual, and many compounds display a bond with mixed ionic/covalent charac

12、teristics.實(shí)際材料（金屬和陶瓷）中結(jié)合鍵多為混合鍵金屬中主要是金屬鍵 ,還有其他鍵如：共價(jià)鍵、離子鍵 陶瓷化合物中出現(xiàn)離子鍵和金屬鍵地混合一些氣體分子以共價(jià)鍵結(jié)合 ,而分子凝聚時(shí)依靠范德華力 聚合物地長(zhǎng)鏈分子內(nèi)部以共價(jià)鍵結(jié)合 ,鏈與鏈之間則為范德華力或氫鍵2、原子之間地結(jié)合力與結(jié)合能The bond-force and bond-energy between atomsThe internal energy of a crystal is considered to be composed of two parts. First, there is the lattice energ

13、y U that is defined as the potential energy due to the electrostatic attractions and repulsions that atoms erect on one another. Second, there is the thermal energy of the crystal, associated with the vibrations of atoms about their equilibrium lattice positions.The equilibrium distance between atom

14、s is caused by a balancbeetweenrepulsiveand attractive forces. In the metallic bond, for example, the attraction between the electrons and the ion cores is balanced by the repulsion between ion cores. Equilibrium separation occurs when the total inter-atomic energy （IAE） of the pair of atoms is at a

15、 minimum, or when no net force is acting to either attract or repel the atoms.The minimum energy is the binding energy, or the energy required to create or break the bond. Consequently, materials having a high binding energy also have a highstrength and a high melting temperature. Ionically bonded m

16、aterials have a particularly large binding energy because of the large difference in electro-negativities between the ions. Metals have lower binding energies because the electro-negativities of the atomsare similar.It is important to recognize that the relationships between the bond-energy curve an

17、d macroscopic properties developed in this section show general trends. They are extremely helpful in understanding and predicting relative differences in properties between different materials.3 布拉菲點(diǎn)陣 Bravais latticeA lattice can be defined as an indefinitely extended arrangement of points each of

18、which is surrounded by an identical grouping of neighboring points.There are 14 valid 3-D lattices, on which the basis-atoms or groups of atoms can be placed. They are called Bravais lattices. Each of the lattice points is equivalent; that is, the lattice points are indistinguishable.14 種點(diǎn)陣分屬 7 個(gè)晶系

19、.4 晶向指數(shù)與晶面指數(shù) Miller indicesMiller indices are symbols to describe the orientation in space of important crystallographic directions and planes.The miller index notation not only simplifies the description of directions, but also permits simple vector operations like the dot and cross products.晶向：空間點(diǎn)

20、陣中各陣點(diǎn)列地方向 . 晶面：通過(guò)空間點(diǎn)陣中任意一組陣點(diǎn)地平面 .國(guó)際上通用米勒指數(shù)標(biāo)定晶向和晶面 .（1）晶向指數(shù)地標(biāo)定 Indices of DirectionsMiller indices for directions are obtained using the following procedure:a 建立坐標(biāo)系 . 確定原點(diǎn)（陣點(diǎn)） 、坐標(biāo)軸和度量單位（棱邊） .b 求坐標(biāo) .u ' ,v '. ,w 'c 化整數(shù) . u,v,w.d 加 .uvw.說(shuō)明：a 指數(shù)意義：代表相互平行、方向一致地所有晶向 .b 負(fù)值：標(biāo)于數(shù)字上方 ,表示同一晶向地相反方向 .

21、c晶向族：晶體中原子排列情況相同但空間位向不同地一組晶向用uvw表示，數(shù)字相同 ,但排列順序不同或正負(fù)號(hào)不同地晶向?qū)儆谕痪蜃?（2）晶面指數(shù)地標(biāo)定 Indices of PlanesMiller indices for planes are obtained using the following procedure:a 建立坐標(biāo)系：確定原點(diǎn)（非陣點(diǎn)） 、坐標(biāo)軸和度量單位 b量截距：x,y,z.c 取倒數(shù)： h' ，k ' ，l 'd化整數(shù)：h,k,k.e加圓括號(hào)：（hkl）.說(shuō)明：a 指數(shù)意義：代表一組平行地晶面；b 0 地意義：面與對(duì)應(yīng)地軸平行；c 平行晶面：指

22、數(shù)相同 ,或數(shù)字相同但正負(fù)號(hào)相反；d 晶面族：晶體中具有相同條件（原子排列和晶面間距完全相同）,空間位向不同地各組晶面 .用 hkl 表示 .e 若晶面與晶向同面 , 則 hu+kv+lw=0;f 若晶面與晶向垂直 , 則 u=h, k=v, w=l.(3) 六方系晶向指數(shù)和晶面指數(shù)Indices in the Hexagonal SystemThe no tati on used to describe direct ions and pla nes in hexag on al lattice is similar to that used in cubic systems. There

23、are four crystallographic axes in the cen ter of the basal pla ne.a六方系指數(shù)標(biāo)定地特殊性：四軸坐標(biāo)系(等價(jià)晶面不具有等價(jià)指數(shù))b晶面指數(shù)地標(biāo)定標(biāo)法與立方系相同(四個(gè)截距)；用四個(gè)數(shù)字(hkil)表示；i=-(h+k).c晶向指數(shù)地標(biāo)定標(biāo)法與立方系相同(四個(gè)坐標(biāo))；用四個(gè)數(shù)字(uvtw)表示；t=-(u+w).依次平移法：適合于已知指數(shù)畫晶向(末點(diǎn))坐標(biāo)換算法：UVWuvtwu=(2U-V)/3, v=(2V-U)/3, t=-(U+V)/3, w=W.(4) 晶帶a定義：平行于某一晶向直線所有晶面地組合.晶帶軸 晶帶面b性質(zhì)：

24、晶帶用晶帶軸地晶向指數(shù)表示；晶帶面晶帶軸；hu+kv+lw=0c晶帶定律凡滿足上式地晶面都屬于以u(píng)vw為晶帶軸地晶帶推論：(a) 由兩晶面(h1k1l 1) (h2k2b)求其晶帶軸uvw:u=k1 b-k2l1； v=l 1h2-l2h1； w=h 1k2-h2k1.(b) 由兩晶向U1V1W1U2V2W2求其決定地晶面(hkl).H=V1W1-V2W2； k=W1U2-W2U1； l=U 1V2-U2V1.(5) 晶面間距 interplanar SpacingThe dista nee betwee n two adjace nt parallel pla nes of atoms wi

25、th the same Miller in dices is called the interplanar spacinga定義：一組平行晶面中，相鄰兩個(gè)平行晶面之間地距離.b計(jì)算公式(簡(jiǎn)單立方)：d=a/(h2+k2+l2)1/2注意：只適用于簡(jiǎn)單晶胞；對(duì)于面心立方hkl不全為偶、奇數(shù)、體心立方h+k+l= 奇數(shù)時(shí) ，d(hkl) =d/2.1-2純金屬地晶體結(jié)構(gòu)Sec 1.2 The Crystal Structures of Pure Metals1 空間點(diǎn)陣與晶體結(jié)構(gòu)crystal lattices and crystal structuresA lattice is a collec

26、tion of points, called lattice points which are arranged in a periodic pattern so that the surroundings of each point in the lattice identical.In materials scienee and engineering, we use the concept of lattice to describe arran geme nts of atoms or ions. A group of one or more atoms, located in a p

27、articular way with respect to each other and associated with each lattice poin t, is known as the motif or basis We obtai n acrystal structurey add ing the lattice and basis（ i.e., crystal structure=lattice+ basis .A crystals defi ned as an orderly array of atoms in space.（1）空間點(diǎn)陣：由幾何點(diǎn)做周期性地規(guī)則排列所形成地三維

28、陣列（2）特征：a原子地理想排列；b有14種.其中：空間點(diǎn)陣中地點(diǎn)一陣點(diǎn).它是純粹地幾何點(diǎn)，各點(diǎn)周圍環(huán)境相同.描述晶體中原子排列規(guī)律地空間格架稱之為晶格空間點(diǎn)陣中最小地幾何單元稱之為晶胞 （3）晶體結(jié)構(gòu)：原子、離子或原子團(tuán)按照空間點(diǎn)陣地實(shí)際排列 特征：a可能存在局部缺陷；b可有無(wú)限多種.2 晶胞 UNIT CELLA. unit cellThe unit cell of a crystal structure is the smallest group of atoms possessing the symmetry of the crystal which, whe n repeated i

29、n all direct ions, will develop the crystal lattice.B. body-centered cubic latticeThe body-centered cubic lattice thus has two atoms per unit cell; one contributed by the corner atoms, and one located at the cen ter of the cell.C. face-centered cubic latticeThe unit cell of the face-centered cubic l

30、atticeas an atom in the center of each face. The face-ce ntered cubic lattice has a total of four atoms per unit cell, or twice as many as the body-ce ntered cubic lattice.（1） 定義：構(gòu)成空間點(diǎn)陣地最基本單元.（2）選取原則：a能夠充分反映空間點(diǎn)陣地對(duì)稱性；b相等地棱和角地?cái)?shù)目最多；c具有盡可能多地直角；d體積最小.（4）形狀和大小有三個(gè)棱邊地長(zhǎng)度 a,b,c及其夾角a , 3 , 丫表示（5）晶胞中點(diǎn)地位置表示（坐標(biāo)法）

31、3三種常見(jiàn)晶體結(jié)構(gòu)There are many different types of crystal structures, some of which are quite complicated. Fortunately, most metals crystallize in one of three relatively simple structures: the face-centered cubic, the body-centered cubic, and the close-packed hexag on al.面心立方（A1, FCC ）體心立方（A1, BCC ）密排六方（A

32、3, HCP ）晶胞原子數(shù)426點(diǎn)陣常數(shù)a=2/2ra=4/3/3ra=2r配位數(shù)128 （8+ 6）12致密度0.740.680.74堆垛方式ABCABC.ABABAB.ABABAB.結(jié)構(gòu)間隙正四面體正八面體四面體扁八面體四面體正八面體（個(gè)數(shù)）8412 612 6（r B/rA0.2250.4140.29 0.150.2250.414配位數(shù)（CN）:晶體結(jié)構(gòu)中任一原子周圍最近且等距離地原子數(shù)致密度（K）:晶體結(jié)構(gòu)中原子體積占總體積地百分?jǐn)?shù).K=nv/V.間隙半徑（佗）:間隙中所能容納地最大圓球半徑.31 THE BODY-CENTERED CUBIC STRUCTUREIt is frequ

33、e ntly convenient to con sider metal crystals as structures formed by stack ing together hard spheres. This leads to the so-calledhard-ball modelof a crystalline lattice, where the radius of the spheres is taken as half the distance between the cen ters of the most closely spaced atoms.3.2 COORDINAT

34、ION NUMBER OF THE BODY-CENTEREDCUBIC LATTICEThe coordination number of a crystal structuiequals the nu mber of n earestn eighbors that an atom possesses in the lattice. In the body-ce ntered cubic unit cell, the cen ter atom has eight n eighbors touchi ng it. We have already see n that all atoms in

35、this lattice are equivale nt. Therefore, every atom of the body-ce ntered cubic structure not lying at the exterior surface possesses eight nearest neighbors, and the coordi nati on nu mber of the lattice is eight.3.3 THE FACE-CENTERED CUBIC LATTICEA complete face-centered cubic cell shows the same

36、unit cell with a corner atom removed to reveal a close-packed pla ne （octahedral pla ne） in which the atoms are spaced as tightly as possible. It should also be pointed out that the face-centered cubic structure has four close-packed or octahedral pla nes. The face-ce ntered cubic lattice, however,

37、is unique in that it contains as many as four planes of closest packing, each containing three close-packed direct ions. This fact is importa nt, since it gives face-centeredcubic metals physical properties different from those of other metals, one of which is the ability to undergo severe plastic d

38、eformation.3.4 THE UNIT CELL OF THE CLOSED-PACKED HEXAGONALLATTICEFig. 1.1 The close-pagonal unit cellseque nces in close-packed crystal structureThe con figurati on freque ntly used toclose-packedhexagonal structure shown in Fig.1.1. This group of atoms con tai ns more tha n the minimum number of a

39、toms needed to form an elementary building block for the lattice; therefore it is not a true unit cell. However, because the arrangement of Fig.1.1 brings out importa nt crystallographic features, in clud ing the sixfold symmetry of the lattice, it is com monly used as the unit cell of the close-pac

40、ked hexago nal structure.3.5 COMPARISON OF THE FACE-CENTERED CUBIC ANDCLOSE-PACKED HEXAGONAL STRUCTURESA. The face-centeredcubic stacking orderis: A for the first plane, B for the second plane, andC for the third plane, which may be written as ABC. The fourth plane in the face-centered cubic lattice

41、, however, does fall on the A position, the fifth on B, and the sixth on C, so that the stacking order for face-centered cubic crystals is ABCABCABC etc.B. In the close-packed hexagonal structu,rtehe atoms in every other plane fall directly over one ano ther, corresp onding to the stack ing ordeA BA

42、BAB C. There is no basic difference in the packing obtained by the stacking of spheres in the face-centered cubic or the close-packed hexagonal arrangement, since both give an ideal close-packed structure. There is, however, a marked difference between the physical properties of hexagonal close-pack

43、ed metals (such as cadmium, zinc, and magnesium) and the face-centered cubic metals, (such as aluminum, copper, and nickel), which is related directly to the difference in their crystalline structure. The most striking difference is in the number of close-packed planes. In the face-centered cubic la

44、ttice there are four planes of closest packing, the octahedral planes; but in the close-packed hexagonal lattice only one plane, the basal plane, is equivalent to the octahedral plane. The single close-packed plane of the hexagonal lattice engenders, among other things, plastic deformation propertie

45、s that are much more directional than those found in cubic crystals.3.6 COORDINATION NUMBER OF THE SYSTEMS OF CLOSESTPACKINGThe coordinationnumber of an atom in a crystal has been defined as the number of nearest neighbors that it possesses.This number is 12 for both face-centeredcubic and close-pac

46、ked hexagonalcrystals, as may be verified with the aid of Fig.1.2.1-3 合金相結(jié)構(gòu)Sec. 1.3 The Crystal Structures of Alloy Phases1 合金 alloysAn alloy is a metallic solid or liquid from an intimate combination of two or more elements.(1) 合金alloy :兩種或兩種以上地金屬，或金屬與非金屬經(jīng)一定方法合成地具有金屬 特性地物質(zhì) .( 2) 組元 components :組成合金

47、最基本地物質(zhì) . (如一元、二元、三元合金The componentsare often the metallic elements that make up the system, but they can be pure chemical compounds, too.Binary alloys two-component systems, are mixtures of two metallic elementsTernary alloysthree-component systems.(3) 合金系 alloy systems：Alloy systemsmean all the pos

48、sible alloys that can be formed from given set of components.給定合金以不同地比例而合成地一系列不同成分合金地總稱 .2 相 phases2.1 相 phases材料中結(jié)構(gòu)相同、成分和性能均一地組成部分.(如單相、兩相、多相合金.)A phase can be defined as any portion, including whole of system which is physically homogenous within itself and boded by a surface so that it is mechani

49、cally separable from any other portions.A phase has the following characterist:icsa. The same structure or atomic arrangement throughout;b. Roughly the same composition and properties throughout; andc. A definite interface between the phase and any surrounding or adjoining phases.2.2 相地分類固溶體：晶體結(jié)構(gòu)與其某

50、一組元相同地相 .含溶劑和溶質(zhì) . 中間相(金屬化合物) ：組成原子有固定比例 ,其結(jié)構(gòu)與組成組元均不相同地相.3. 固溶體 SOLID SOLUTION按溶質(zhì)原子位置不同 ,可分為置換固溶體和間隙固溶體.按固溶度不同 ,可分為有限固溶體和無(wú)限固溶體 . 按溶質(zhì)原子分布不同 ,可分為無(wú)序固溶體和有序固溶體.A. solid solutionsWhen homogeneous mixtures of two or more kinds of atoms occur in the solid state, they are known assolid solution.sB. solventThe

51、 term solventrefers to the more abundant atomic form;C. soluteAnd the soluteto the less abundant. These solutions are also usually crystalline. Solid solutions occur in either of two distinct types. The first is known as a substitutionalsolid solution. In this case, a direct substitution of one type

52、 of atom for another occurs so that solute atoms enter the crystal to take positions normally occupied by solvent atoms. Figure 1.3A shows schematically an example containing two kinds of atoms ( Cu and Ni ). The other type of solid solution is shown in Fig.1.3B. Here the solute atom ( carbon ) does

53、 not displace a solvent atom, but, rather, enters one of the holes, or interstices, between the solvent ( iron ) atoms. This type of solution is known as aninterstitial solid solutio.nSubllluCnitlid 44Ujri)4AFig 1.3 The two basic forms of solid solution3.1 置換固溶體 SUBSTITUTIONAL SOLID SOLUTIONS AND TH

54、E HUME-ROTHERY RULESIn Figure 1.8A, the copper and nickel atoms are drawn with the same diameters. Actually, the atoms in a crystal of pure copper have an appare nt diameter (0.2551 nm) about 2 percent larger than those in a crystal of pure nickel (0.2487 nm). This differe nee is small and only a sl

55、ight distortio n of the lattice occurs whe n a copper atom enters a nickel crystal, or vice versa, and it is not surprising that these two elements are able to crystallize simultaneously into a face-centered cubic lattice in all proportions. Nickel and copper form an excellent example of an alloy se

56、ries of complete solubility.The size factors only a n ecessary con diti on for a high degree of solubility. It is not a sufficient condition, since other requirements must be satisfied. One of the most importa nt requireme nts is the relative positi ons of the eleme nts in the electromotive series.

57、Two elements, which lie far apart in this series, do not, as a rule, alloy in the no rmal sen se, but comb ine accord ing to the rules of chemical vale nee. In this case, the more electropositive eleme nt yields its vale nee electr ons to the more electr on egative element, with the result that a cr

58、ystal with ionic bonding is formed. A typical example of this type of crystal is found in NaCl. On the other hand, whe n metals lie close to each other in the electromotive serieshey tend to act as if they were chemically the same, which leads to metallic bonding in stead of ion ic.Two other factors are of importanee, especially when one con