材料科学与工程概述(原文)matscience

Materials Science and Engineering Overview The Field - Preparation - Day In The Life - Earnings -Employment - Industries - Development -Career Path Forecast - Professional OrganizationsMaterials Science and Engineering (MSE) is a field ofengineering that encompasses the spectrum of materials typesand how to use them in manufacturing. Materials span therange: metals, ceramics, polymers (plastics), semiconductors,and combinations of materials called composites. We live in aworld that is both dependent upon and limited by materials.Everything we see and use is made of materials: cars,airplanes, computers, refrigerators, microwave ovens, TVs,dishes, silverware, athletic equipment of all types, and evenbiomedical devices such as replacement joints and limbs. All of these require materials specifically tailored for their application. Specific properties are required that result from carefully selecting the materials and from controlling the manufacturing processes used to convert the basic materials into the final engineered product. Exciting new product developments frequently are possible only through new materials and/or processing. New materials technologies developed through engineering and science will continue to make startling changes in our lives in the 21st century, and people in Materials Science and Engineering will continue to be key in these changes and advances. These engineers deal with the science and technology of producing materials that have properties and shapes suitable for practical use. Activities of these engineers range from primary materials production, including recycling, through the design and development of new materials to the reliable and economical manufacturing for the final product. Such activities are found commonly in industries such as aerospace, transportation, electronics, energy conversion, and biomedical systems. The future will bring ever-increasing challenges and opportunities for new materials and better processing. Materials are evolving faster today than at any time in history. New and improved materials are an "underpinning technology" - one which can stimulate innovation and product improvement. High quality products result from improved processing and more emphasis will be placed on reclaiming and recycling. For these many reasons, most surveys name the materials field as one of the careers with excellent future opportunities.The FieldCD-ROMs, like everything around us, are made of materials. So are dessert plates, basketballs, car engines, telephones, and audiocassettes. Therefore the work done under the heading of Materials Science Engineering has an unprecedented impact on our quality of life. Although the field deals with materials, it encompasses an incredible diversity of topics and problems constituting the four elements of the field -- processing, structure, properties, and performance.MaterialsHistory is measured by innovations in materials. Developments in metals like iron and bronze enabled advances in civilization thousands of years ago, a synergy which continues today in the fiber optics that have created the World Wide Web and in the development of biomaterials that mimic living tissue. As you explore the field it may be useful to become familiar with some generic categories of materials.MetalsMetals are materials that are normally combinations of "metallic elements". Theseelements, when combined, usually have electrons that are non-localized and as aconsequence have generic types of properties. Metals usually are good conductors of heat and electricity. They are also quite strong but deformable and tend to have alustrous look when polished.CeramicsCeramics are generally compounds between metallic and nonmetallic elements andinclude such compounds as oxides, nitrides, and carbides. Typically they are insulating and resistant to high temperatures and harsh environments.PlasticsPlastics, also known as polymers, are generally organic compounds based upon carbon and hydrogen. They are very large molecular structures. Usually they are low densityand are not stable at high temperatures.SemiconductorsSemiconductors have electrical properties intermediate between metallic conductorsand ceramic insulators. Electrical properties are strongly dependent upon smallamounts of impurities.CompositesComposites consist of more than one material type. Fiberglass, a combination of glass and a polymer, is an example. Concrete and plywood are other familiar composites.Many new combinations include ceramic fibers in metal or polymer matrix. ProcessingProcessing refers to the way in which a material is achieved. Advances in technology have made it possible to create a material atomic layer by atomic layer. There are four general categories which may be useful to know: solidification processing, powder processing, deposition processing, and deformation processing.Solidification ProcessingMost metals are formed by creating an alloy in the molten state, where it is relativelyeasy to mix the components. This process is also utilized for glasses and somepolymers. Once the proper temperature and composition have been achieved, the melt is cast. Castings can be divided into two types, depending on the subsequentprocessing steps. The first type is shape casting, which takes advantage of the fluidity of liquid metal to form complex shapes directly. Because of the complexity of their part geometries, these castings generally cannot be worked mechanically to a significantdegree. Therefore any changes in microstructure or properties must either be achieved first during solidification or through subsequent heat treatments.Powder ProcessingPowder processing involves consolidation, or packing, of particulate to form a `greenbody'. Densification follows, usually by sintering. There are two basic methods ofconsolidating powders: either dry powder can be compacted in a die, a process known as dry-pressing, or the particles can be suspended in a liquid and then filtered against the walls of a porous mold in a process known as slip-casting or filter pressing. Bulkceramics are usually processed in powder form since their high melting points and low formability prohibit other types of processing. Metals and polymers can also beprocessed from powders.Deposition ProcessingDeposition processing modifies a surface chemically, usually by depositing a chemical vapor or ions onto a surface. It is used in semiconductor processing and for decorative or protective coatings. Vapor source methods require a vacuum to transport thegaseous source of atoms to the surface for deposition. Common vapor sources arethermal evaporation (similar to boiling water to create steam), sputtering (usingenergetic ions to bombard a source and create the gas state), or laser light (ablates, or removes, atoms from surface to create the gaseous state). Other sources use carrier media such as electrochemical mixtures (ions in a solution transported by an electrical field to the surface for depositions) or spray coating (ions or small particles transported by gases, liquids, and/or electrical field).Deformation ProcessingOne of the most common processes is the deformation of a solid to create a desiredshape. A large force is generally used to accomplish the deformation, and manytechniques heat the material in order to reduce the force necessary to deform it.Sometimes a mold is used to define the shape. Forging, an old method that heated the metal and deformed the metal by hammer blows is still used today, albeit with multi-ton hammers. Rolling to reduce the thickness of a plate is another common process. Some glasses when heated can be formed with tools or molds. Other common methods, like drilling to make holes, or milling, are machining versions of the deformation process. StructureStructure refers to the arrangement of a material's components from an atomic to a macro scale. Understanding the structure of a substance is key to understanding the state or condition of a material, information which is then correlated with the processing of the material in tandem with its properties. Understanding these relationships is an intrinsic part of materials science engineering, as it allows engineers to manipulate the properties of a material. PropertiesDoes a material need to be strong and heat-resistant, yet lightweight? Whether you're talking about a fork or the space shuttle, products have specific requirements which necessitate the use of materials with unique properties. Materials engineers must frequently reconcile the desired properties of a material with its structural state to ensure compatibility with its selected processing. Typical properties of interest may be classified into:Mechanical Properties: Tensile strength, fracture toughness, fatigue strength, creep strength, hardnessElectrical Properties: Conductivity or resistivity, ionic conductivity, semiconductorconductivity (mobility of holes and electrons)Magnetic Properties: Magnetic susceptibility, Curie Temperature, Neel Temperature, saturation magnetizationOptical and Dielectric Properties: Polarization, capacitance, permittivity, refractiveindex, absorptionThermal Properties: Coefficient of thermal expansion, heat capacity, thermalconductivityEnvironmental Related Properties: Corrosion behavior, wear behavior PerformanceThe evaluation of performance is an integral part of the field. The analysis of failed products is often used to obtain feedback on processing and its control as well as to assist in the initial selection of the material and in the stages of processing. Testing also ensures that the product meets performance requirements. In many products the control of its processing is closely associated with some property test and/or a structural characterization.PreparationPreparation for a career in materials engineering can begin as early ashigh school, and need not be limited to a course of `materials' study.There are many kinds of programs, degrees, and disciplines that willenable you to pursue a career in the field.Pre-CollegeIt is highly recommended that while in high school you take themaximum amount of college preparatory mathematics, laboratorysciences, and English offered. If choices are possible, those courseshighly dependent upon knowledge and reasoning should takeprecedence over courses in which the emphasis is on manual skill.Students should try to take all the physical sciences and mathematicscourses offered at their school. In addition, students should takeadvantage of all available opportunities to develop their communicationskills. Study of a language other than English is desirable. Talk to your guidance counselor about requirements at the university of your choiceCollege ProgramsMost major universities have academic BS degree granting programs in one of the specialty areas of Materials Science and Engineering. The majority of undergraduate programs provide a survey across the spectrum of materials. Other programs focus in one particular class of materials like Ceramics, Metallurgy, or Polymers.A few universities only have graduate programs. Graduate programs are open to people with bachelors degrees in the field as well as those from other more general areas of science andengineering. Specific areas of expertise in each program are dependent upon the faculty in that program. The average program is staffed by 15 faculty members. Programs range in faculty size from less than ten members to near forty. No single program covers the entire field due its breadth and the typically modest number of faculty members.Accredited ProgramsThose interested in a career in materials engineering should consider reviewing engineering programs that are accredited by the Accreditation Board for Engineering and Technology, Inc. (ABET). ABET accreditation is based on an evaluation of an engineering program's student achievement, program improvement, faculty, curricular content, facilities, and institutional commitment. The following is a partial list of universities offering accredited degree programs in materials engineering, including materials, ceramic, and metallurgical programs.Materials Programs•The University of Akron•University of Alabama at Birmingham•Alfred University•Arizona State University•University of Arizona•Auburn University•Brown University•California Polytechnic State University, San Luis Obispo•University of California, Davis•University of California, Irvine•University of California, Los Angeles•Carnegie Mellon University•Case Western Reserve University•University of Cincinnati•Colorado School of Mines•Cornell University•Drexel University•University of Florida•Georgia Institute of Technology•University of Illinois at Urbana-Champaign•Illinois Institute of Technology•Iowa State University•The Johns Hopkins University•University of Kentucky•Lehigh University•University of Maryland College Park•Massachusetts Institute of Technology•Michigan State University•Michigan Technological University•University of Michigan•University of Minnesota-Twin Cities•Montana Tech of the University ofMontana•New Mexico Institute of Mining andTechnology•North Carolina State University at Raleigh •Northwestern University•The Ohio State University Ceramic Programs•Alfred University•Clemson University•University of Missouri-Rolla•Pennsylvania State Univers ity•Rutgers, The State Universityof New JerseyMetallurgical Programs•The University of Alabama•Colorado School of Mines•University of Idaho•University of Missouri-Rolla•Montana Tech of the University of Montana•University of Nevada-Reno•The Ohio State University•University of Pittsburgh•South Dakota School of Mines and Technology•University of Texas at El Paso•University•Pennsylvania State University•University of Pennsylvania•University of Pittsburgh•Purdue University at West Lafayette•Rensselaer Polytechnic Institute•San Jose State University•University of Tennessee at Knoxville•University of Texas at El Paso•University of Utah•Virginia Polytechnic Institute and StateUniversity•Washington State University•University of Washington•Winona State University•University of Wisconsin-Madison•University of Wisconsin-Milwaukee•Wright State UniversityCourseworkA materials program serves a dual purpose: it providestechnical information and instills a thought processcharacteristic of the engineering discipline. All programsintegrate the four elements of the field (properties,structure, processing, and performance) through theseveral classes of materials (ceramics, electronicmaterials, metals, polymers, composites). Specializedcurricula synthesize one class of materials with theelements of the field, in a Ceramic Engineering or Metallurgical Engineering program, for example. In most programs, however, a core curriculum is incorporated with courses addressing the scientific principles relating to the properties and behavior of materials, as well as the structure (atomic configurations), characterization, and processing of materials. Engineering design courses focus on the performance of materials in applications and emphasize devising new materials, components, systems, or processes to meet particular objectives. Most engineering programs develop from a mathematical base coupled with aspects of chemistry or physics. MST, however, builds almost equally upon chemistry and physics and includes an increasing influence of biology. Communications, social issues, and the humanities are also incorporated in order to provide individuals the requisite breadth to be able to place technical problems in the context of tomorrow’s world.ConcentrationsDegrees are granted in several specializations and concentrations, including materials, metals, minerals, ceramics, and polymers. Within these study programs, one can emphasize areas such as processing, structure-property relationships, electronic properties, and chemical and environmental effects.Graduate SchoolMany students continue their studies to earn an advanced degree, a master's (MS) degree or a doctoral (Ph.D./D.Sc.) degree. They do this either directly after earning the BS degree or after some work experience. An MS degree generally can be earned within two years after the BS degree. The doctoral degree, which typically involves four plus years of study and research beyond the BS degree, is usually completed by those interested in careers in research and/or teaching. Depending on an individual's career goals, the BS degreemay also be followed by study in such fields as businessadministration, management, medicine, and law.Study AbroadStudying abroad can be an exciting and rewarding experience.Materials Science & Engineering careers may take you overseas orat least offer you the opportunity to work with internationalcorporations. Information on studying abroad may be obtained fromuniversity counselors. For more information, visit:o Institute of International Education: o Resource for Study Abroad: o Council of International Educational Exchange: o Association for International Practical Training: Day in the LifeFrom cellular phones to artificial hip joints to lightweight bicycles,materials engineers work to develop products that improve lives.Materials engineers bring advances in the auto, aerospace,construction, manufacturing, electronics, computer, andtelecommunications industries by developing new or improved metals,plastics, ceramics, semiconductors and composites. They work toincrease the strength of steel, toughen ceramics, lower the cost ofcomposites and make faster computer circuits. Materials are involvedin almost every engineering product, and materials engineers areneeded to select the best material, improve its properties, lower itsprocessing cost and increase its durability.Career TracksThere can be many tracks within a career. A materials engineer mightbegin in a technical area such as manufacturing or research anddevelopment, and then move into a management, sales, marketing, or a consulting role, depending on interest and ability.Teamwork & EnvironmentIn a manufacturing operation most tasks are conducted by cross-functional teams of people. Materials engineers are generally part of a support group integral to these teams for various functions -- from design concept through manufacturing processes to final product evaluations.SkillsIn addition to the technical and problem-solving skills requisite for a career in the field, the so-called `soft skills' will play a significant role in your success. Leadership abilities, teamwork, communication skills, flexibility, goal orientation, as well as the capacity for organization, all figure prominently in a career.AlternativesBecause of their training and skills, materials engineers make strong candidates for jobs not traditionally associated with engineering: sales, training, law, medicine, insurance, real estate, publishing, finance, technical service, and government.DiversityOpportunities exist for a wide range of people with a spectrumof backgrounds. A recent survey shows a changing distributionof people in the field over the past twenty years. Much of thischange was the result of people becoming aware of theopportunities in the field.Organizational SizeEach work environment is unique. Factors like a company's size may impact your career. Over half of the people polled in a recent survey of the field work in large companies (more than 1000 people). However, a growing number of materials engineers are finding positions in small companies.EarningsEarnings for engineers vary significantly by specialty, industry,and education. Even so, as a group, engineers earn some ofthe highest average starting salaries among those holdingbachelor's degrees.Starting SalaryAccording to a 2005 salary survey by the National Associationof Colleges and Employers, bachelor's degree candidates inmaterials engineering received starting salary offers averaging $50,982 a year.Variation in median earnings and in the earnings distributions for engineers in the various branches of engineering also is significant. For aerospace engineers, earnings distributions by percentile in May 2004 are shown in the following tabulation.Specialty 10%25%50%75%90%$101,120 Materials $44,130$53,510$67,110$83,830EmploymentAccording to the U.S. Bureau of Labor Statistics, materials engineersheld about 21,000 jobs in 2004. This represents 1.5% of the 1.4million jobs held by engineers in the U.S. in 2004.Materials engineers are involved in the development, processing, andtesting of the materials used to create a range of products, fromcomputer chips and television screens to golf clubs and snow skis.They work with metals, ceramics, plastics, semiconductors, andcomposites to create new materials that meet certain mechanical,electrical, and chemical requirements. They also are involved inselecting materials for new applications. Materials engineers havedeveloped the ability to create and then study materials at an atomiclevel, using advanced processes to replicate the characteristics ofmaterials and their components with computers. Most materials engineers specialize in a particular material. For example, metallurgical engineers specialize in metals such as steel, and ceramic engineers develop ceramic materials and the processes for making ceramic materials into useful products such as glassware or fiber optic communication lines. EmployersThe following is a partial list of employers of materials scientists and engineers:•3M Company•Advanced Magnetics, Inc.•Advanced Micro Devices.•AK Steel Corp.•Alcan Aluminum•ALCOA•Allegheny Ludlum Corp.•Alliant Techsystems •Amcast•American Superconductor •Applied Materials•Argonne National Laboratory •ASARCO, Inc.•Babcock & Wilcox•BASF Corporation•Battle Mountain Gold Company •Bayer Corp.•Beaver Valley Alloy Foundry •Bechtel•BF Goodrich•Black & Decker•Boeing Company •Brookhaven National Lab.•Cabot Corporation •Chevron Chemical •Chrysler Corporation •Cincinnati Milacron, Inc.•CMI International•Conoco •Georgia Pacific•Hewlett Packard•IBM•Ingersoll-Rand•Intel Corporation •International Paper•ITT•Johnson Controls, Inc.•Kaiser Aluminum•KB Alloys Inc.•Kennecott Corp.•Logan Clay Products•Los Alamos National Lab •LTV Steel•Lucent Technologies •Michelin•Microsoft Corporation•Mobil Corporation•Motorola•Nalco Chemical•National Science Foundation •National Starch & Chemical Co.•Nissan Motor Corporation USA •Norsk Hydro Aluminum •Nucor Corp.•PPG Industries•Procter & Gamble•Sherwin-Williams •Specialized Bicycle Components•Corning Incorporated •Crucible Materials Corp.•CSM Industries, Inc.•Cypress Semiconductor •Dalton Foundries •Deere & Company, Inc.•Dow Chemical •Eastman Chemical Co.•Eastman Kodak•Eaton Corp•EI DuPont•Exxon Chemical Company •Flint Ink Corporation •FMC Corporation•Ford Motor Company •General Electric •General Motors •Sun Microsystems •Sundstrand Aerospace •Taylor Made Golf Co.•Tensar Corporation •Texas Instruments, Inc.•Timken Co.•United States Mint •United Technologies •W.L. Gore•Wabash Alloys•Wahl Refractories •Waupaca Foundry Inc.•Westinghouse •Wheeling-Pittsburgh Steel •Wolvering Tube Co.•XeroxIndustriesVirtually all industries demand people with backgrounds inmaterials engineering. These people may be monitoringimpurities in steel destined for an assembly line, shrinking thesize of circuits to improve the reliability of a pager, or designingnew materials for a missile casing. Industries may employmaterials engineers to reduce the overall weight of a vehicle,remove limitations in power plants, or research product failuresfor a liability suit.SectorsThere are four general sectors of industry that employ materials engineers:Primary Materials ProducingThese companies provide basic materials to other companies who manufacture acomponent for a product or the end product itself. Examples are steel companies, glass companies, polymer powder producing companies, etc. Typically these are relativelylarge organizations. This sector comprises a small number of companies that support a much larger number of manufacturing businesses.ManufacturingThese companies produce a component or end product using materials from PrimaryProducing companies. This sector includes a large number of companies ranging in size from a few to thousands of employees. This sector represents many different industries: transportation, electrical/electronics, machinery, computers/office, biomaterials, durable goods, and non-durable goods.ServiceCompanies in this sector provide support for others. Employers include consulting firms, research and development organizations, construction companies, utilities, engineering services, communications companies, and research groups.OtherEducational institutions, government, legal organizations, healthcare, business services, finance, insurance, and wholesale/retail are some of the other employers of materialsengineers.Professional DevelopmentLearning is a life-long endeavor. Advances in technology areperpetually changing the tools of materials engineering, somaintaining your technical competence will be a constant pursuit. Itwill also be important to continue developing communication skills.Actively pursuing professional development opportunities in and out ofthe work environment can expand your abilities and career options.Making Yourself MarketableMaintaining technical competence is important, but the developmentof other capacities (i.e., communications skills, networking, mentoring)is just as critical. By honing these crafts you will become moremarketable.RegistrationBeing a registered professional engineer is important in those areas of the field with direct public impact, such as in consulting firms. Take the Fundamentals of Engineering (FE) Exam when a senior or immediately following graduation; this exam is a prerequisite for sitting for the PE Exam. After four years of professional experience, contact your State Board. Each board generally has a packet of information which outlines the steps to be taken by engineers to become a registered Professional Engineer. This includes the requirements engineers must fulfill to qualify as a candidate to take the Principles and Practices Examination and rules while taking the examination. Further Resources:National Society of Professional Engineers: National Council of Examiners for Engineering and Surveying: Value of NetworkingThe opportunity to meet and discuss materials successes and challenges with one's peers is invaluable toward not only project success, but also personal success. Sharing information and ideas is generally beneficial to both parties and is a hallmark of a successful engineer. Networking is the single most important cited resource for people to obtain new positions. Continuing EducationWhile you will perhaps seldom find yourself in a classroom, you must remain current in your chosen specialty. Possible forms of continuing education include: reading technical journals and publications, attending conferences, workshops or training courses, and obtaining membership in a professional society.。