材料导论总结

Module 1:1-1Understand the following terms (a) engineering materials: a term often loosely used to define most materials that go into products and systems.(b) engineering materials technology: covers fields of applied science related to materials, materials processing(处理，加工), and the many engineering specialties（特性）dealing with materials, such as research and development, design, manufacturing, construction, and maintenance（维护，保持）.(c) materials: the matter of the universe which have properties that make them useful in structures, machines, devices(装置), products and systems.(d) materials science:(e) materials engineering: deals with the synthesis（合成）and used of knowledge in properties, processing and behavior, prepare, modify（修饰）, and apply materials to specific needs.(f) materials science and engineering: a major field of study, which involves the generation and application of knowledge relating the composition(构成), structure（结构）, and processing of materials to their properties and uses.(g) properties: describes the behavior of materials when subjected to some external force or condition.1-5Understand the two terms,Life Cycle Analysis (LCA) : products to determine their impact on the global environment. and Life Cycle Inventory (LCI);what in the main purpose of LCA?Dealing with the materials and processes involved in products in terms of cost and environmental impacts.1-11What is the difference between design for assembly and design for disassembly?Design for assembly（装配）emphasizes(着重) easy product assembly by robots and other automated equipment; Design for disassembly is a concept that places recycling at the beginning or design stage of the materials cycle to ensure that waste going into municipal landfills will be minimized.1-14How can the stage of recycling/disposal become the first stage in the materials cycle? 1-18Understand the terms of metals, alloys and powdered metals.Metals are elements that can be defined by their properties, such as ductility(延展性), toughness（韧性）, malleability（可锻性）, electrical and heat conductivity（导热系数）, and thermal expansion（热膨胀）.Alloy（合金）consists（由组成）of metal elements combined with other elements.Powdered metals: alloying of metals involves melting(融化) the main ingredients（材料）together so that on cooling, the metal alloy is generally a nonporous（无孔的）solid.1-19List the subgroups（子组）of metallics.Ferrous, Nonferrous and Powdered metal1-20Give some examples for ferrous metals and nonferrous metals.Ferrous(黑色金属): Iron, Steel, Cast ironNonferrous（有色金属）: Cooper, Aluminum, TinPowdered metals（粉末金属）: Sintered（烧结的）steel, Sintered brass（黄铜）1-21 Describe the main stages in preparing powdered metals1-26List the two types of plastics regarding processing method, and give some examples for each type.Thermosets （热固）: epoxy（环氧树脂）, phenolic（酚醛树脂）, and polyurethane（聚氨酯）.Thermoplastics: acrylics（丙烯酸树脂）, nylon and polyethylene（聚乙烯）.1-32List the typical properties of ceramics（陶瓷）.Hard, brittle, stiff and have high melting points.1-33What type of chemical bonds existing in ceramics?Ionic bonds and covalent bonding1-49Understand the following terms;(a) catalyst(催化剂): a substance that enters into a chemical reaction in such a way as to make the reaction go faster without itself being consumed.(b) stoichiometry（化学计量数）: the branch of chemistry that deals with calculation of mass implied in chemical equations.(c) factor of safety（安全系数）: defined as the ratio of unnormal operation conditions(d) allowable stress(许用应力) (or design, working, safe stress): the maximum level of stress that a part will be permitted（允许）to endure under operation conditions. Module 2:2-2What is matter（物质）? Anything that has mass and occupies volume.List the four states in which matter exists.Liquid, Solid, Gas and Plasma（等离子体）2-7Describe the atomic structure（原子结构）, and exemplify（示例）the standard notation （标准符号）for expressing the composition of nucleus.Proton, Neutron, Electron, …..2-9What is the Valence Electron(价电子)? Describe its influences on the chemical properties of an element and on the formation（构造）of chemical bonding.Valence Electron: Those electrons that occupy the outermost ring or shell from the nucleus.Valenceis the capacity of an element to combine with other elements.2-10Explain the following terms: ionization（离子化）, ionization potential（电离势能）, electronegativity（电负性）, electron affinity（电子亲和性）, electron configuration（电子排布）.Ionization: the process of pulling away (removing) or adding valence electrons from a balanced or neutral atom.Ionization potential: the energy required to cause the loss of a valence electron. Electronegativity: the degree to which an atom attracts electrons.Electron affinity: the same as electronegativityElectron configuration: the manner in which the electrons of an atom distribute themselves in the ground, or lowest energy, state2-11Describe the electron structure with Classical Theory and Quantum Mechanical Theory （量子力学）, listing four quantum（量子数）numbers to characterize（描绘）an electron as to its size, shape and spatial orientation（空间环境）.Classical Theory: the position of electrons in relation to the nucleus of an atom must be described in terms of a probability distribution（概率分布）rather than by the precisely determined value（精确值）.Quantum Mechanical Theory: the basis for a new branch of physics.---the idea that light is quantized—that it is made up of discrete（离散）amounts of energy.Four quantum numbers:1.shells or principle energy levels;2.sublevel, subshell（亚层）or orbital（轨道）;3.the number of energy states for each subshell;4.the electron spin（电子自旋）moment.2-13Exemplify the relationship that can be used to determine the maximum number of electrons at any energy level.2*n^22-19What is the Chemical Bonding? What are the groups and subgroups of the chemical bounding?Chemical bonding: explained simply as the end product of the interaction（相互作用）of the electrical forces of attraction and repulsion（排斥）between oppositely charged or similarly charged particles（带电粒子）of matter.Groups: Primary bonding（主价键）and secondary bondingSubgroups: Primary bonding: covalent bonding, ionic bonding, metallic bonding; Secondary Bonding: hydrogen boning, van der waals forces2-20Understand the terms: (a) chemical bonding;(b) covalent or shared electron-pair bonding;(c) triple covalent: one in which two atoms share three of their electrons with each other.(d) ionic bonding; some elements actually swap or transfer electrons to other elements(e) metallic bonding; these are shielded from the strong attractive forces of the positive nucleus by the inner electrons and thus they bond to the nucleus relatively weakly(f) polar molecule: both the positive and negative charges are localized within the molecule(g) nonpolar molecule; each atom shares the bonding electrons equally, producing an electrical charge distribution that is symmetrical about a line joining the two nuclei(j) hydrogen bond. The oxygen atom, having a slight negative charge, attracts a positive hydrogen atom belonging to an adjacent water molecule2-21What key word can be used to describe covalent bonding, ionic bonding, and metallic bonding?Ionic bonding：electron swappingCovalent bonding: electron sharingMetallic bonding: electron swarming2-23How is the hydrogen bond formed?The covalent bonds between the hydrogen and oxygen atoms in a water molecule, being polar, result in an asymmetrical charge distribution. The oxygen atom, having a slight negative charge, attracts a positive hydrogen atom belonging to an adjacent water molecule and forms a hydrogen bond.Exemplify the contributions of hydrogen bond to the properties and behavior of polymeric materials.The hydrogen bond affects the properties and behavior of materials. In thermoplastics, the hydrogen bond joins long, chainlike molecules to each other. These relatively weak bonds can be easily loosened or broken by heating, permitting flow(流动) to take place.2-24List the two forms of microstructure（微观结构）of solid. What is the difference between them in terms of atomic arrangement?Amorphous（无定型的）: contains no repetitious（重复的）pattern of atom locations to any extent（范围）.Crystalline（晶体）: possesses（控制）an ordered, three-dimensional（三维的）, geometric arrangement that repeats itself.2-26Define the terms: unit cells（晶胞）, space lattices（空间点阵）, and intercepts.Unite cell: used to describe the basic building block or basic geometric arrangement of atoms in a crystal.Space lattices: repeat the unit cell in all three dimensions, you create a crystalline structure with a definite pattern. This larger pattern of atoms in a single crystal is known as a space lattices.Intercepts: The sides of the box, labeled a, b, c, are the lattice parameters（晶格参数）in x, y, and z directions, respectively. These distances are also known as intercepts.2-27What are the seven crystal systems? How many space lattices can atoms form?1. simple cubic unit cell:2. body-centered cubic;3. face-centered cubic;4. body-centered tetragonal（四边）crystal lattice unit cell;5. hexagonal（六边）crystal system;6. close-packed hexagonal crystal lattice unit cell7. orthorhombic （正交晶）and monoclinic unit cell2-28Describe the intercepts of cubic, tetragonal, and hexagonal crystal systems.Cubic: a=b=cTetragonal: a=b≠cHexagonal: a=a≠c2-29What are the three basic cubic crystal systems? What are their abbreviations（缩写）?Simple cubic—scBody-centered cubic---bccFace-centered cubic---fcc2-37【polymorphism（多态性）, allotropy（同素异形）, atomic packing factor（原子堆积因数) ）Understand the terms: coordination number（配位数）, polymorphism, allotropy, atomic packing factor and void fraction（空隙率）.Coordination number (CN): to describe how many atoms are touching each other in a group of coordinated atoms.Polymorphism: the phenomenon that elements that exist in more than one crystal structure, depending primarily on the temperature.Allotropy: the same as polymorphismAtomic packing factor: the ratio of the volume of atoms present in a crystal to the volume of the unit cell.Void fraction:2-39What is the difference in the crystal structures of polymorphic and allotropic(同素异形materials?Polymorphic materials: don’t possess this reverse(颠倒) phenomenon.Allotropic materials: can, after changing to one structure, reverse the phenomenon and return to its previous（早先的）structure.2-42Describe the long-range-order（长程有序）materials and short-range-order materials.Long-range-order materials: the orderly arrangement of atoms extends throughout the entire materials, forming a regular grid like lattice（栅格）or pattern（模式）.Short-range-order materials: their order is limited to an atom’s nearest neighboring atoms.2-45What are crystal impurities（杂质）and crystal defects（缺陷）?Crystalimpurities: there is some disorder in the atomic structure brought about by something other than impurity atoms.Crystal defects: a disorder of the crystal structure, which is brought about by some mechanism such as thermal agitation(剧烈振动) of the crystal during its formation, the effects of gravity, or the result of high-energy radiation（辐射）.2-46Group, subgroup the crystal imperfections. List two crystal impurities and three crystal defects.Group:Crystalimpurities & crystal defectsSubgroup: Crystal impurities: a mixture; diffusion（扩散）; the doping（掺杂质）; Crystal defects: point defects; line defects and area defects2-47What are substitutional solid solutions(置换固溶体) and interstitial（填隙式固溶体）solid solutions? What are the conditions on which the two solid solutions form?Substitutional solid solutions: the solute atoms replace some of the solvent atoms in a crystal structure of the solvent.Interstitial solid solutions: if impurity atoms take up sites in the lattice structure（晶格）that are normally unfilled or unoccupied（空闲）by the solvent atoms, they form an interstitial solid solution.2-48Define the terms: solution, solvent, solute, mixture, solid solution, alloy, plastic alloy, diffusion, and vacancy（空白）.Solution: a homogeneous（均匀的）mixture of chemically distinct（独特的）substances that forms a phase.Solvent: the substance present in the greatest proportion.Solute: the other substance or substances present.Mixture: a material that has no fixed composition and contains more than one phase.Solid solution: simply a solution in the solid state that consists of two kinds of atoms combined in one type of space lattice.Alloy: a combination of a metal and one or more other elements forming either a mixture or a solid solution.Plastic alloy: blends(混合) of polymers or copolymers（共聚）with other polymers or elastomers(弹性体).2-61What are the functions of grain boundaries（晶界）?Grain boundaries with different orientations（方向）of grains and grain growth in two dimensions（规模）. Remember that a solid contains crystals, each having the same lattice structure. What is different between the individual grains is the orientation of that structure within each grain.2-62Understand the terms: long-range-order materials, short-range-order materials, point defect, dislocation, and are defect.Long-range-order materialsShort-range-order materialsPoint defect: only affect the small volume of the crystal surrounding a single lattice site.Dislocation: a line array of atoms along which there is some imperfection in the bonding of the atoms that causes distortion（变形）of the crystal structure.3-1 Understand the following terms:(a) Physical properties (b)Chemical properties (c)Mechanical properties (d)Stress(e)Strain (f)Deformation (g)Young’s modulus (h)Elastic deformation (i)Plastic deformation (a) Physical properties : Physical properties involve no change in the composition of the material.(b) Chemical properties: Chemical properties are associated with the transformation of one material into another.(c) Mechanical properties(机械性能): a measure of a material's ability to carry or resist mechanical forces or stresses(d) Stress : stress, defined as the resistance offered by a material to external forces or loads, is measured in terms of the force exerted per area .(e) Strain（张力）: Strain , or unit deformation（形变）, is defined as the unit change in the size or shape of material as a result of force on the material.(f) Deformation（形变）: Regardless of how small the force, a body will alter（改变）its shape when subjected to a force. In other words, the body will change its dimensions（大小）. The change in a physical dimension is called deformation.(g) Young’s modulus（杨氏模量）: Young’s modulus or elastic modulus (E) is defined as the ratio of engineering stress (σ) to engineering strain (Є) in the linear or elastic region of the stress-strain diagram（图表）.(h) Elastic deformation（弹性形变）:(i) Plastic deformation（塑性形变）:When a material is loaded with external forces in the elastic region, the material with the highest modulus value experiences the least amount of deformation or strain, which may be either elastic or plastic deformation.If the material reverts back to its normal size and shape upon removal of the load, it is elastic deformation.If the applied force or load is removed and the material is permanently deformed (changed in shape),the material is said to have undergone plastic deformation.3-5 Describe the difference between elastic and plastic deformation and give an example of each.Elastic deformation: If the material reverts back to its normal size and shape upon removal of the load, it is elastic deformation.Plastic deformation: If the applied force or load is removed and the material is permanently deformed (changed in shape),the material is said to have undergone plastic deformation.3-6 Draw a stress-strain diagram that is obtained（获得）from a tensile test（拉力实验）,a) Label（标注）at least four important properties that can be determined from the diagram;b) Indicate elastic region and plastic region; c) Indicate the area that represents the modulus of resilience（回弹模量）; d) Indicate the area that represents the modulus of toughness（韧性系数）.3-7 Name the different names of elastic modulus and relate this property to the structure and stiffness of materials.The different names of elastic modulus:The modulus of elasticity, elastic modulus, tensile modulus, Young's modulus, modulus of elasticity in tension, or coefficient of elasticity（弹性系数）.The stiffness（坚硬）of a material is defined as the ratio of the load to the deformation produced. The higher the value of Young's modulus, the stiffer（更硬的）the material. Reinforced metal composites possess greater stiffness than non-reinforced metals.3-8 Which mechanical property（机械性能）refers to the lowest stress at which plastic deformation occurs?Yield strength.(补充：yield strength 屈服强度：l The stress corresponding（与一致）to the elastic limitl The lowest stress at which plastic deformation occursl For most design, the yield strength（屈服强度）is assumed（假定）to be the same in tension as in compression（压缩）.)3-10 Which type of materials shows a little difference between yield strength and tensile strength（抗张强度）, brittle materials（脆性材料）or ductile materials（延性材料）? Brittle materials show very little difference between yield strength and tensile strength, 3-11 Which mechanical property is a measure of the energy per unit volume that the material can absorb without plastic deformation?Modulus of resilience（补充：l the area under which the straight-line portion (elastic region) of the stress-strain curvel A measure of the energy per unit volume that the material can absorb without plastic deformation.l SI unit : 1MPa)3-12 Calculate（预测）ductility（延展性）by using two methods. How to distinguish（区分）a ductile material from a brittle material with the aid of a stress-strain diagram or the value of ductility?3-13 Is the specimen（样品）that has 5% or less elongation（延展率）considered as a brittle material or ductile material?A specimen that has 5％or less elongation is considered as a brittle material3-14 Which mechanical property represents the energy per unit volume of a material required to produce fracture（断裂）under static conditions（静态条件）.Modulus of toughness.(T)(补充：l The total area under the stress-strain curve up to the point of rupture（断裂）.l Represents the energy per unit volume of a material required to produce fracture under static conditions .l3-15 Which properties of metals does the temperature affect the most?Impact resistance（抗冲击性）(effects of temperature over a wide range on the impact resistance of metals)3-16 List three common brittle fracture（脆性破坏）forms.1) Cleavage（分裂）2) Intergranular path3) Chevron pattern(具体:l cleavage：cracks propagate most rapidly along specific crystallographic planes. 开裂破裂l intergranular path : crack grows along the grain boundaries particularly when the grain boundaries are weakened by inclusions or segregation. 晶粒间断裂l Chevron pattern : crack fronts propagate at different levels in the materials from a common origin.回纹状破裂3-18 How does the toughness of metals change with temperature?(TTR=transition temperature range)a) T<T critical temp :Crystalline and amorphous polymers both are brittle at low temperatures ,with corresponding low impact strength（冲击强度）.b) T within the transition temperature range :Between TTR, there is a zone in which types of failures are mixed.c) T>T critical tempAbove some critical temperature（临界温度）, failures in metals are ductile ,with a much greater absorption（吸收）of energy3-20 When a downward-acting transverse（横向）load is applied to a beam, indicate the type of stresses at the top and bottom surface of the beam.The load in this example would cause the beam to deflect（转向）, resulting in compressive stresses near the top surface and tensile stresses（张应力）at the bottom.3-21 How do many ferrous alloys（铁基合金）differ from nonferrous materials in terms of the endurance limit（疲劳极限）?For many ferrous alloys, the endurance limit is about one-half (1/2) the tensile strength of the mental .For nonferrous materials and plastics, they exhibit（展示）no fatigue limit, which means that there is no stress below which they will not fracture.3-22 Do all materials have fatigue (or endurance) limit?Non ferrous metal and some plastics exhibit no fatigue (or endurance) limit.3-24 Understand the terms fatigue limit, fatigue ratio（疲劳比）, endurance ratio（耐久比）, fatigue strength.l fatigue limit : the maximum stress that can be sustained for an infinite（无穷大） number of stress cyclesl fatigue strength : the maximum stress that can be sustained for a specified（规定的） number of cycles without fracture.l fatigue (endurance) ratio : the quotient（系数）of endurance limit to tensile strength3-26 Amaterial plastically deforms or flows very slowly under load as a function of time. What is this phenomenon called?Creep (a slow process of plastic deformation that takes place when a material is subjected to a constant condition of loading (stress) below its normal yield strength.)3-30 How is the creep rate determined? What is the expression of creep rate?•Creep rate is determined at any point by the slope（斜坡）of the curve.‚Creep r ate is expressed in percent creep strain per hour：蠕变曲线三个阶段Initial stage（原始期）<primary or transient creep> : decreasing creep rateMiddle stage<secondary creep> : constant（不变）, minimum rateFinal stage<tertiary creep> : accelerated（加速）creep rate and failure.3-32 When a circular rod is under torsion, the applied torque produces a torsional stress （扭转应力）, which type of stress is it? What is the maximum torsional stress called?Stress includes : torsional stress, shear stress（剪切应力）.The maximum torsional stress is called Torsional yield strength.3-34 Understand the terms modulus of rupture（断裂模量）, modulus of rigidity（刚性模量）, modulus of resilience（回弹模量）, and modulus of elasticity（弹性模量）.3-35 List four important hardness tests.1) The degree of penetration（压痕法）:Brinell hardness(HB)（布氏硬度）Vickers hardness(HV)（维氏硬度）Rockwell hardness(HR)（罗氏硬度）2) The resistance of scratching（划痕法）:Mohs hardness（莫氏硬度）3) The rebound of a small weight bounced off the surface of the material（回弹法）3-36 What is the difference between Brinell hardness and Vickers hardness tests?3-39 What are the major categories of properties to be considered in material selection? Which properties rank highest in importance when selecting materials for many applications?3-40What are the three tests that supply the most useful information for most applications?l Tensile test -----strengthl Impact test-------rigidityl Hardness test-------durability注释：拉伸试验----强度；冲击试验----刚度；硬度试验----耐久度3-74 What thermal effect（热效应）does a metal exhibit when it is heated deliberately （故意的）? What are the corresponding properties for describing the effects?1) Absorbs heat （吸热）specific heat（比热容）2) Expands coefficient of thermal expansion（热膨胀系数）3) Transmits heat thermal conductivity（导热系数）3-75 List the thermal expansion of the following materials in a decreasing order, i.e.: polymers, metals, covalent and ionic bonded materials.l Polymers > Metals > ionic bonded and covalent bonded3-76 Compare polymers with metals in terms of expansion coefficient and thermal conductivities.Thermal conductivities : metals >> polymersExpansion coefficient (CET): polymers >metals3-77 What are the factors influencing thermal conductivity of materials? Exemplify how they affect thermal conductivity.3-78 Does thermal conductivity of materials increases continuously with increasing temperature?Thermal conductivity (k) of materials has a varied relationship to temperature:l In some materials, k initially decreases with increasing temperature up to a certain temperature and then increases. 例如：Iron, graphite（石墨）.l With other materials, k increases continuously with increased temperature. 例如：glass, nylon, platinum(铂金).3-79 Do insulating materials（绝缘材料）have low thermal conductivities and low thermal resistance?Insulating materials have low thermal conductivities and can retard（延缓）the transfer of heat.Module 4:4-7How is steel different from cast iron?Cast iron has between 2%~4% carbon, compared with less than 2% for steel.4-14What metal fabrication(金属加工) is realized by powder metallurgy（粉末冶金）? Sintering（烧结）4-32Which metal behaves superplasticity（超塑性）when at certain temperatures? Titanium4-34What does sintering imply?Compacted and heated to allow diffusion bonding（扩散压合）.Supplementary question:1. How much do the nonferrous metals account for among the known elements?3/42. Which form does the carbon exist in each type of cast iron?Gray Cast Iron: carbon existing in a pearlite matrix（波来体基）White Cast Iron: cementite（渗碳体）instead of graphiteNodular or Ductile Cast Iron（球墨铸铁）: spherulitic（球粒状）3. Carbon content in ironsa. Ingot iron（低碳钢）: 0.01%b. Pig iron（生铁）: 4%c. cast iron: 2%~4%d. Gray cast iron: 3.2%e. White cast iron（白口铸铁）: 3.5%f. Nodular or Ductile cast iron: 3.5%g. Malleable iron（可锻铸铁）: 2.2%Module 6:6-2What are the differences in the compositions and applications of traditional and advanced ceramics?Traditional ceramics: based primarily on natural raw materials of clay（粘土）and silicates （硅酸盐）. (used as clay products, glass and cement（水泥）)Advanced ceramics: include artifical（人造的）raw materials, exhibit specialized properties, require more sophisticated（复杂的）processing (in structural, electronic and optical aspects)6-4Briefly explain the major factors in determining the density of a material.Atomic weight; how the atoms/ions are stacked（堆放）in the microstructure.6-5(green density（生胚密度）, bulk density（体积密度）, theoretical density（理论密度）) Compare the following definitions for density:green density: the bulk density of a compact prior to its densification.bulk density: used to refer to a ceramic’s density, as opposed to that of solid material. (W D/W B)theoretical density:apparent density: W D/V A6-6(open porosity（开孔率）, closed porosity（多孔性）)Compare the definitions for open porosity, closed porosity and apparent porosity（显气孔率）.Open porosity: referring to the network of pores（气孔）that is open to the surface and into which a liquid such as water can penetrate（渗透）if the part were submerged in it. Closed porosity: refers to those pores that have become sealed within the grain structure Apparent porosity:6-14Define the term densification.Densification: referring as firing, is a process by which a particulate compact is transformed into a ceramic part that has adequate(充足) properties to satisfy the needs of a specific application.6-18Ceramic process can be simple described as consisting of two steps (a) a cool step, and (b) a hot step. What is the product for each step?Cool step: the ceramic part is formed or shaped into a “green” part or preform.Hot step: the green compact is first subjected to heat to dry up any liquid phase formed during the processing and then subjected to higher heating, known as firing, sintering, or densification.6-21Define the term refractory materials(耐火材料). Cite（引用）some refractory ceramics and some furnace with extremely high temperature.Refractory materials: one with a very high melting point and other properties that make it suitable for uses such furnace linings（炉衬）and kiln construction（窑炉）.6-27What are devitrification（不透明）and vitrification（透明）.Devitrification: slower cooling permits some crystallization in the process known as devitrification.Vitrification: opposite to devitrification, producing amorphous structures（无定型结构）.6-28(soft glasses（普通玻璃）, hard glasses（硬化玻璃）) List three common types of glass. Cite the two desirable characteristics of glasses.Soda-lime silica glass（碱石灰石英玻璃）Single-strength glassDouble-strength glassLead-alkali silica glassAluminosilicate glass （铝硅酸玻璃）Desirable characteristics: soft glasses have lower heat resistance and a higher coefficient （系数）of thermal expansion than hard glasses. Hard glasses are borosilicate（硼硅酸盐）and aluminosilicate.Supplementary question:1. What types of bonding can be found in ceramic materials?Ionic and covalent bonds2. What procedures are involved in the ceramic processing?a. Densificationb. Microwave sinteringc. hot pressing（热压烧结）d. overpressure sinteringe. hot isostatic pressing（热等静压）3. Understand the term of cementite（渗碳体）Cementite: a hard brittle iron carbide Fe3C that occurs in steel, cast iron and iron-carbon alloys.。