材料概论英文版 武汉理工大学.doc

精品文档Material: Solids used by man kind to produce items which constitute the support for his living environmentCharacteristics of materialsu Have certain compositions; u Can be processed; u With certain shape and color; u Can be used and reused or recycled.u 特点: p 具有一定的成分和配比；p 可成型加工；p 保持一定形状和外观；p 具有使用价值并可回收再利用。材料性能的决定因素u 组成材料的各元素的原子结构，u 原子间的相互作用、相互结合，u 原子或分子在空间的排列分布和运动规律,u 原子集合体的形貌特征。Classification of materialsu Atomic structures u Nature of chemical bonds:p Metallic bond 金属键p Ionic bond 离子键p Covalent bond 共价键 p Secondary bond 次价键p Van der Waals bond 范德华力p Hydrogen bond 氢 键Classification:u metals and their alloys:- metallic bondingu Organic polymers: Covalent bonding & secondary bondingu Ceramics: Ionic bonding & covalent bondingMetals and their alloys:u are good conductors of heat and electricity;u are opaque to visible light;u are hard, rigid;u can undergo plastic deformationu have a high melting temperature (Tm). Organic polymers:u made up of long-chain molecules;u are electrical and thermal insulators;u are light and easily formable; u the best-known organic polymers are:p poly (vinyl chloride) (聚氯乙烯，PVC);p polyethylene (聚乙烯，PE);p polystyrene (聚苯乙烯，PS)。Composite materials: Are constituted by two or more different materials with specific properties. Glass fiber reinforced resins: lightweight composites with high mechanical strength Concrete: an agglomeration of cement, sand and gravelMechanical properties:p The behavior of materials deformed by a set of forces.p 弹性 Elasticity p 塑性 Plasticity p 强度 Strength p 硬度 Hardness p 韧性 Toughnessp 疲劳特性 Fatigue behavior p 耐磨性 Abrasion resistancePhysical properties:u The behavior of materials subjected to the action of temperature, electric or magnetic fields, or light.p 电性能 Electric propertiesp 磁性能 Magnetic propertiesp 热性能 Thermal propertiesp 光性能 Optical propertiesChemical properties:u The behavior of material in a reactive environment.u 抗腐蚀能力 Corrosion resistancep Atmospherically, p Chemically (salts, acid, alkali) Materials Engineering:u Concerned with p Manufacturing, p Transformation p Shapingp Processing. The three most common crystal structures of metals arep Body-centered cubic structure, p Face-centered cubic structure,p Hexagonal close-packed structure Production of steel:u Pig iron contains too much carbon and too many impurities to be used directly in most applications.u It must be converted to steel in one of several types of converters. These converters may differ in appearance, but they do the same thing: p burn off the carbon in the iron. p Impurities are removed as gases and in the slag.p Phosphorus and sulfur are reduced to less than 0.05 percent of the steel. p Manganese content is reduced to an amount from 0.2 to 2.0 percent; p Silicon is reduced to an amount from 0.01 to 3.5 percent.Three primary ores arep magnetite, p hematite,p taconite铸铁概念：cast iron, essentially an alloy of iron, carbon and silicon, is composed of iron and from 2 to 6.67 percent carbon, plus manganese, sulfur, and phosphorus, and shaped by being cast in a mold. The types and properties of cast iron ； white cast iron( hard , brittle ) , gray cast iron (brittle ,withstand large compressive loads but small tensile loads ), alloy cast iron , nodular or ductile cast iron (good castability ,toughness, good wear resistance ,low melting point ,and hardenability ), malleable cast iron (strength ,toughness, ductility ,and machinability)Stainless Steel :l Ferritic l Martensitic l Austeniticl PH Alloysadvantages of using Al: one-third of the weight of steel ;good thermal and electrical conductivity ;high strength-to-weight ratio ;can be given a hard surface by anodizing and hard coating ;most alloys are weldable ;will not rust ;high reflectivity ;can be die cast ;easily machined ;good formability; nonmagnetic ;nontoxic and one third of the stiffness of steel.Magnesium:1.The lightest of all structural metals 2.Specific gravity:1.753. Magnesium weighs 1.5 times less than an equal volume of aluminum and 4 times less than zinc. 4.High strength, stiffness, dimensional stability, 5.High strength-to-weight ratio. Magnesium alloys havep relatively high thermal and electrical conductivities; p good energy absorption characteristics;p Nonmagnetic propertiesThe four types of stresses: ductility, tensile strength, proportional limit, elastic limit, modulus of elasticity, resilience, yield point, yield strength, ultimate strength, and breaking strengthFour basic types of stresses : tensile, compressive, shear ,torsion (拉力，压力，剪切力，扭转力)Metals and nonmetalsu Ability to donate electrons and form a positive ion; u Crystalline structure grain structure; u High thermal and electrical conductivity; u Ability to be deformed plastically, and u Metallic luster or reflectivityCrystalline unit structuresu Body-centered cubic (BCC) u Face-centered cubic (FCC) u Hexagonal close-packed (HCP) u Cubic u Body-centered tetragonal u Rhombohedral There are several factors that may speed the corrosion process. Among these factors arep an increase in temperature, p the presence of certain gases, p environmental factors such as acid rain, p metal fatigue, p cold working/forming,p and other similar factors Ceramic compounds: Can be defined as inorganic compounds made by heating clay or other mineral matter to a high temperature at which they partially melt and bond togetherCeramics Classificationp traditional ceramics: derived and processed from clay or nonclay minerals including refractories（耐火材料), white wares, cement(水泥), porcelain(瓷器), and structural clay ceramics. p advanced ceramics: high purity, better mechanical, electrical, magnetic, and optical properties Nature of Ceramicsu Crystalline solids composed of metallic and nonmetallic materialsu Ceramics are crystal structures made of metallic ions and Inorganic materials u Bonding is either partially or completely ionic. u Variables include p The magnitude of the electrical charge on the ions;p The relative size of the ionsProperties of Ceramicsu Corrosion resistance, chemical inertness, thermal shock resistance wear-resistanceu Electrical properties: solid electrolytes in experimental batteries and fuel cellsu Other uses: include automotive sensors, packaging for integrated circuits, electronic/optical devices, fiber optics, microchips, and magnetic headsPorosity and Densityu Mass density, which uses the mass of a material divided by its volume refers to this theoretical densityu Atomic weight is a major factor in determining the density of a materialu Close-packed metals are more dense than open-structured materialsu The optimum density of spherical particles can be reached by varying the size distribution of particles to permit smaller particles (50 nm or less) to locate in the interstices (空隙) of the larger ones. Ceramic Processingu Traditional Processingp structural clay products and the whitewares. p Formation Drying Firingu Advanced Ceramic Processing1.制备工艺：不再以熔炉为主要烧结工具, 如真空烧结、气氛烧结、热压烧结、气压烧结等。2.性能：高强度、高硬度、耐腐蚀、导电、绝缘以及磁、电、光、生物相容性等。Classification of glasses according to compositionsu Oxide glassesu Chalcogenide Glasses (硫属化物玻璃) u Thioborate glasses (B2S3) (硫硼玻璃)u Halide glasses (BeF2, ZnCl2 etc.) (卤化物玻璃)u Heavy metal fluoride glasses (ZrF4) (重金属氟化玻璃)u Oxy-halide glasses (氧卤玻璃)u Oxynitride glasses (氧氮玻璃)u Metallic glasses (金属玻璃)u Glass-like Carbon (玻璃碳)u Silica and silicate glasses (硅酸盐玻璃） u B2O3 and borate glasses (硼酸盐玻璃）u GeO2 and germanate glasses （锗酸盐玻璃）u P2O5 and phosphate glasses （磷酸盐玻璃）u Complex oxide glasses The glass transition is the region of temperatures where the properties of a cooled liquid continuously change from being “liquid-like” to “solid-likeProperties of glassu Density p The density of most glasses is dependent upon its thermal history and decreases with temperaturep Glasses cooled at various rates from above the annealing point will differ in density with the more rapidly cooled glasses having a lower density u Hardness p Glasses are brittle in a macroscopic scale, but they can flow under shear stresses in a microscopic scale p Hardness is a property closely related to the mechanical strength of a glass and to its low temperature viscosity u Hardness p Glasses are brittle in a macroscopic scale, but they can flow under shear stresses in a microscopic scale p Hardness is a property closely related to the mechanical strength of a glass and to its low temperature viscosity u Brittleness p One of the main causes of this loss of strength is the presence of surface defects p The stress will concentrate over only a few inter-atomic bonds at the apex (顶点) of the crack p If the glass is cooled too rapidly it does not have time to release stresses set up within it during cooling. These stresses are “frozen-in” and can cause the glass to shatter(粉碎) when it becomes a solid. u Optical Properties p The refractive index depends upon the wavelength of light, the density, temperature, thermal history, stress, and composition of the glass p Glasses of higher refractive index have greater dispersion. The higher the index, the more the dispersion tends to increase with decreasing wavelength p The refractive index of a glass and its change with the composition and heat treatment are of primary importance for optical glasses Polymers are macromolecules built up by the linking together of large numbers of much smaller molecules. Elastomers, Fibers, and Plasticsp The small molecules that combine with each other to form polymer molecules are termed monomers（单体）.p The reactions by which they combine are termed polymerizations（聚合）. Chain polymerization consists of a sequence of three steps： Initiation reaction (birth) Propagation reaction (growth) Termination reaction (death)Control of Tm and Tg1.Thus a highly flexible chain has a low Tg, which increases as the rigidity of the chain becomes greater. 2.Similarly, strong intermolecular forces tend to raise Tg and also increase crystallinity.General consideration u The chemical level. p This deals with information on the fine structure, namely what type of monomer constitutes the chain and whether more than one type of monomer is used (copolymer),u The architectural aspects. p These are concerned with the chain as a whole, and now we are required to ask such questions as:u is the polymer linear, branched, or crosslinked; u what distribution of chain lengths exist; u what is the chain conformation and rigidity？ Mechanical Properties u Modulus. The resistance to deformation as measured by the initial stress divided by L / L. u Ultimate Strength or Tensile Strength. The stress required to rupture the sample. u Ultimate Elongation. The extent of elongation at the point where the sample ruptures. u Elastic Elongation. The elasticity as measured by the extent of reversible elongation. u Polymers vary widely in their mechanical behavior depending on the degree of crystallinity, degree of crosslinking, and the values of Tg and Tm. 1. High strength and low extensibility are obtained in polymers by having various combinations of high degrees of crystallinity or crosslinking or rigid chains (characterized by high Tg). 2. High extensibility and low strength in polymers are synonymous with low degrees of crystallinity and crosslinking and low Tg values. 3. The temperature limits of utility of a polymer are governed by its Tg and/or Tm. Strength is lost at or near Tg for an amorphous polymer and at or near Tm for a crystalline polymer. u Different polymers are synthesized to yield various mechanical behaviors by the appropriate combinations of crystallinity, crosslinking, Tg, and Tm. 1. Depending on the particular combination, a specific polymer will be used as a fiber, flexible plastic, rigid plastic, or elastomer. u Commonly encountered articles that typify these uses of polymers are clothing and rope (fiber), packaging films and seat covers (flexible plastic), eyeglass lenses and housings for appliances (rigid plastic), and rubber bands and tires (elastomer). The Definition of composite: A composite is a combined material created by the synthetic assembly of two or more components a selected filler or reinforcing agent and a compatible matrix（基体） binder (i.e., a resin) in order to obtain specific characteristics and properties.复合材料定义：由两种或两种以上组分，通常一种是填料或增强材料，另一种是与之相容的基体粘结材料结合而成，以获得最佳或特殊性能的一种材料。on the basis of the form of th