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Material Science Flashcards

Sophomore Level Course for Mechanical Engineers

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3229527581eutectic-the lowest temperature at which two solids are at equilibrium w/ liquid phase0
3229527582peritectica three phase reaction where a solid phase and liquid phase transform to a single solid phase upon cooling1
3229527583AusteniteOne of the allotropes of iron, also known as gamma iron. It is formed when iron is between 912 ° and 1,394 °C and has a face-centred cubic structure. Also found in carbon steel.2
3229527584AllotropyThe ability of a substance to exist in more than one phase in the solid (or indeed, liquid and gaseous) state.3
3229527585AnnealingA heat treatment designed to soften a metal or alloy. Microstructurally, annealing is associated with recovery, recrystallization and/or grain growth.4
3229527586BainiteA non-equilibrium phase, usually in steel, which is formed by quenching from the austenite phase. The rate of quenching required is slower than that necessary to form martensite but faster than that which produce the equilibrium phase of pearlite.5
3229527587BCCBody-centered cubic packing describes a way in which atoms (considered as hard spheres) pack together to fill space. It comprises a cube of 8 atoms, with another atom at the center.6
3229527588FCCFace-centered cubic describes a way in which atoms pack together to fill space. The first layer (A) consists of an hexagonal array of atoms. The next layer (B) sits in the hollows of the first layer. The third layer (C) does not duplicate either A or B layer, giving an ABCABC... structure.7
3229527589FatigueThe failure of a structure subjected to repeated loading at stress levels below those required to cause general yielding. The process of fatigue may involve the initiation and growth of cracks from stress concentrations. However, the initiation stage is often by-passed since micro-cracks are usually introduced into a structure during processing.8
3229527590S-N curveA graph plotting stress amplitude, S versus number of cycles to failure, N for a fatigue test. Some materials, notably low carbon steels exhibit a fatigue limit, below which stress, failure never occurs. More commonly, no such limit exists and an endurance limit must be defined as the stress required to cause failure after 108 cycles.9
3229527591FerritePure iron up to 912 ºC has a bcc structure and is known as alpha ferrite. Between 1394 ºC and the melting point of iron the bcc structure is now known as delta ferrite. Also found in carbon steel.10
3229527592Fick's first law of diffusionStates that the rate of diffusion, or flux, J of a species is proportional to the concentration gradient.11
3229527593allotropythe possibility of the existence of two or more different crystal structures for a substance (generally an elemental solid)12
3229527594amorphous(adj.) shapeless, without definite form; of no particular type or character; without organization, unity, or cohesion13
3229527595anionA negatively charged ion14
3229527596anisotropyhaving a different value when measured in different directions15
3229527597atomic packing factor (APF)the volume of atoms in a selected unit cell divided by the volume of the unit cell16
3229527598Bragg's lawnλ=2dsinΘ17
3229527599cationA positively charged ion18
3229527600coordination numberThe number of immediately adjacent (i.e. touching) atoms to a given atom is called the:19
3229527601crystallineA solid that is made up of crystals in which particles are arranged in a regular, repeating pattern20
3229527602crystal structureThe arrangement of the atoms in a material into a regular repeatable lattice.21
3229527603crystal systemany of the seven groups (cubic, hexagonal, rhombohedral, tetragonal, orthorhombic, monoclinic, and triclinic) of crystals22
3229527604grain boundaryThe interface separating two adjoining grains having different crystallographic orientations.23
3229527605hexagonal close-packed (HCP)most common non-cubic bravais lattice, 6 atoms form a hexagon on both the top and bottom and a single atom positioned in the center between the two hexagonal rings24
3229527606isotropicHaving the same property in all directions.25
3229527607lattice parametersthe edge lengths and angles of a unit cell26
3229527608Miller indicesA shorthand notation to describe certain crystallographic directions and planes in a material. Denoted by [ ] brackets. A negative number is represented by a bar over the number.27
3229527609octahedral positionthe void space among close-packed, hard-sphere atoms or ions for which there are six nearest neighbors; an octahedron (double pyramid) is circumscribed by lines constructed from centers of adjacent spheres28
3229527610tetrahedral positioninterstitial position where the atoms surrounding the interstitial atom forms a tetrahedron29
3229527611unit cellA simple arrangement of atoms or molecules which is repeated to develop a solid crystal structure is called unit cell.30
3229527612alternating copolymerAlternating sequence of monomers31
3229527613atactic configurationa type of polymer chain configuration (stereoisomer) wherein side groups are randomly positioned on one side of the chain or the other32
3229527614block copolymeridentical repeat units are clustered in blocks along the chain33
3229527615branched polymera polymer having a molecular structure of secondary chains that extend from the primary main chains34
3229527616copolymera polymer consisting of two or more different monomers35
3229527617crosslinked polymerPermanently bonded, tangled polymers. A crosslinked polymer can never melt. Most flexible and is the most dense polymer36
3229527618degree of polymerizationnumber of repeating units within the chain37
3229527619isotactic configurationa type of polymer chain configuration (stereoisomer) wherein all side groups are positioned on the same side of the chain molecule38
3229527620linear polymerpolymer in which the molecules form long chains without branches or cross-linked structures39
3229527621molecular weightThe molecular weight of a compound is the sum of the atomic weights of all atoms in the molecule.40
3229527622monomerA simple molecule that can combine with other like or unlike molecules to make a polymer41
3229527623network polymerA polymer in which monomers are connected in a three-dimensional cross-linked network.42
3229527624polymerA compound consisting of repeated linked monomers.43
3229527625random copolymerA copolymer in which different monomers are linked in no particular order.44
3229527626syndiotacticIn polymers, an orientation where the side groups alternate in a regular pattern from side to side along the backbone of the polymer.45
3229527627thermoplastic polymerA polymer that can be melted and solidified multiple times. Conversely, heat-set elastomers and thermosets undergo a crosslinking reaction upon heating to form a 3-D covalently bonded network and cannot be remelted. Thermoplastics include PE, PP, PVC, PS, PMMA, PVDC, PET, PC, Nylon, and Kevlar. A semi crystalline polymeric material that softens when heated and hardens when cooled. While in the softened state, articles may be formed by molding or extrusion46
3229527628thermosetting polymerpolymers that undergo a chemical reaction to produce a rigid cross-linked network47
3229527629alloyA COMBINATION; A MIXTURE OF TWO OR MORE METALS48
3229527630atom percent(at%) the number of moles of an element in relation to the total moles of the elements in the alloy49
3229527631Burgers vectorThe direction and magnitude of the slip caused by a single dislocation50
3229527632dislocation linethe line extending along the extra partial plane of atoms in an edge dislocation51
3229527633edge dislocationa line defect; a slip of the part of crystal over an atomic plane relative to another part is perpedicular to this plane.52
3229527634Frenkel defectpoint defect found in ceramic materials that occurs when a cation diffuses into an interstitial site on the lattice53
3229527635interstitial solid solutiona solid solution wherein relatively small solute atoms occupy interstitial positions between the solvent or host atoms.54
3229527636microstructurethe structural features of an alloy that can be seen under a microscope (ex: grain and phase structure)55
3229527637point defecta flaw in the structure of a material that occurs at a single site in the lattice, such as vacancies, substitutions, and interstitial defects56
3229527638scanning electron microscope (SEM)A microscope that is especially useful for the detailed study of the surface of a specimen; electron beams scan the surface of the sample, which is usually coated with a thin film of gold, allowing electrons on the surface to be deleted and translated into an image; result is a 3D topographic image57
3229527639Schottky defectsmall cation and anion vacancy clusters that are formed in ionic solids. The cation to anion ration in these clusters is adjusted to maintain electroneutrality.58
3229527640screw dislocationa line defect in which the Burgers vector is parallel to the dislocation line59
3229527641self-interstitialAtom crowded into an interstitial site, that under normal circumstances normally isn't occupied.60
3229527642solid solutionIs a metallic substance that is composed of two or more metallic elements.61
3229527643soluteA substance that is dissolved in a solution.62
3229527644solventThe dissolving agent of a solution63
3229527645substitutional solid solutionA solution where a solute atom replaces a host atom on a lattice site in a crystal64
3229527646vacancyType of point defect where there is a vacant lattice site65
3229527647weight percentmass of one component divided by the total mass of the mixture, multiplied by 100%66
3229527648activation energyEnergy needed to get a reaction started67
3229527649carburizingproduces a high carbon layer on the surface of a metal by exposing the metal to a carbon-containing atmosphere at elevated temperatures, such that carbon atoms diffuse into the surface of the metal.68
3229527650concentration gradientA difference in the concentration of a substance across a distance69
3229527651concentration profilecurve of the concentration v. position graph70
3229527652diffusionMovement of molecules from an area of higher concentration to an area of lower concentration.71
3229527653diffusion coefficienta factor that determines the rate of net movement of a substance by diffusion, it is a property that depends on the particle size of the substance and the nature of the medium in which diffusion is occurring.72
3229527654diffusion fluxhow fast the foreign mass can transfer across and area J=M/At73
3229527655driving forceA force that tends to encourage change in a particular direction.74
3229527656Fick's first lawuse for steady state diffusion; net flux (#atoms/area-time) of molecules of material A diffusing in the x-direction (dx) because of a concentration gradient (dCa/dx)--> A can diffuse through material B.75
3229527657Fick's second lawdescribes the diffusion of atoms when the concentration is changed with time76
3229527658interstitial diffusionatoms migrate from an interstitial position to a neighboring one that is empty , this occurs more rapidly than vacancy diffusion because interstitial atoms are smaller and more mobile77
3229527659self-diffusionthe mechanism by which a species diffuses in itself78
3229527660steady-state diffusiondiffusion flux does not change with time79
3229527661vacancy diffusionone mechanism involves the interchange of an atom from a normal lattice position to an adjacent vacant lattice site or vacancy80
3229527662ductilityAbility of a material to stretch or deform under a load without breaking:81
3229527663elastic deformationOccurs when an object changes shape because of a stress is being applied, but snaps back into shape when the stress is removed.82
3229527664elastomera material that can undergo a substantial change in shape via stretching, bending, or compression and return to its original shape upon release of the distorting force83
3229527665engineering strainthe change in length of sample divided by the original length of the sample84
3229527666engineering stressAverage force divided by the original cross-sectional area.85
3229527667flexural strengththe amount of flexural stress a material can withstand before breaking. measured through the bend test.86
3229527668hardness-Refers to various properties of matter in the solid phase that give it a high resistance to its shape changing when force is applied87
3229527669modulus of elasticitya coefficient of elasticity of a material, expressing the ratio between a unit stress and the corresponding unit strain caused by the stress, as derived from Hooke's law and represented by the slope of the straight-line portion of the stress-strain diagram (coefficient of elasticity)88
3229527670plastic deformationOccurs when a material deforms, or changes shape, as a stress is applied and remains in the new shape when the stress is released.89
3229527671proportional limitPoint at which the deformation is no longer directly proportional to the applied force. Hooke's Law no longer applies90
3229527672safe stressA stress used for design purposes; for ductile metals, it is the yield strength divided by a factor of safety.91
3229527673Ultimate tensile strengthMaximum stress which can be applied to a material before failure92
3229527674toughnessMechanical property of a material that indicates the ability of the material to handle overloading before it fractures.93
3229527675true strainstrain measure in which increments in strain are based on current dimensions of the structure94
3229527676true stressa ratio of the force applied to a sample and the instantaneous cross-sectional area of the sample95
3229527677viscoelasticityproperty deforms slowly with load and returns originial shape slowly with removal of load96
3229527678yield strengthpoint a which, when exceeded, a material will no longer completely return to its original shape after removing the applied load97
3229527679cold workingpermanent deformation of metals and alloys below the temperature at which a strain-free microstructure is produced continuously98
3229527680critical resolved shear stressStress required to cause slip in pure metal single crystal. Depends on crystal structure, atomic bonding characteristics, temp, orientation of slip plane99
3229527681grain growththe third step in the formation of crystallites, which is dependent on temperature and can be described using the arrhenius equation100
3229527682recrystallizationIs the formation of a new set of strain-free and equiaxed grains (i.e. having approximately equal dimensions in all directions) that have low dislocation densities and characterization of period-worked condition.101
3229527683recrystallization temperatureThe temperature at which atomic mobility is sufficient to affect mechanical properties as a result of recrystallization.102
3229527684resolved shear stressA material property that depends on angles fie and lambda, where lambda is the angle between the slip direction and force axis and fie is the angle between the normal direction of the slip plane.103
3229527685slip systemcomposed of both the slip plane and the slip directions104
3229527686solid-solution strengtheningalloying metals with impurity atoms that go into either substitutional or intersitital solid solution in order to strengthen or harden105
3229527687strain hardeningthe increase in hardness and strength of a ductile metal as it is plastically deformed below its recrystallization temperature.106
3229527688viscosityA liquid's resistance to flowing107
3229527689vulcanizationprocess of treating rubber or rubberlike materials with sulphur at great heat to improve elasticity and strength or to harden them108
3229527690brittle fracturefracture that occurs by rapid crack propagation and without appreciable macroscopic deformation109
3229527691Charpy testimpact test in which the standard specimen contains a notch where an impact occurs to complete a three-point bending110
3229527692creepTHE GRADUAL, PERMANENT DEFORMATION OF A BODY PRODUCED BY CONTINUED APPLICATION OF A LOAD111
3229527693ductile fracturea mode of fracture that is attended by extensive gross plastic deformation112
3229527694ductile-to-brittle transitionthe transition from ductile to brittle behavior with a decrease in temperature exhibited by some low-strength steel (BCC) alloys; the temperature range over which the transition occurs is determined by Charpy and Izod impact test113
3229527695fatigue lifethe number of stress cycles that will cause a fatigue failure at some specified stress amplitude114
3229527696fatigue limitstress below which there is no fatigue failure whatever the number of cycles115
3229527697fatigue strengthThe stress to which a metal can be subjected for a specified number of cyclic changes of stress.116
3229527698fracture mechanicsstudy of crack growth leading to material failure117
3229527699fracture toughnessCritical Value of stress-intensity factor that causes failure of the plane KIC =Y*σ*√ (π*crack length)118
3229527700impact energya measure of the energy absorbed during the fracture of a specimen of standard dimensions and geometry when subjected to very rapid (impact) loading; Charpy and Izod impact tests are used to measure this parameter, which is important in assessing the ductile-to-brittle transition behavior of a material119
3229527701intergranular fracturea fracture that follows the grains of the material. If the material has multiple lattice organizations, when one lattice ends and another begins, the fracture changes direction to follow the new grain. This results in a fairly jagged looking fracture with bumpy edges.120
3229527702stress raiserA small flaw (internal or surface) or a structural discontinuity at which an applied tensile stress will be amplified and from which cracks may propagate121
3229527703transgranular fracturea fracture that follows the edges of lattices in a granular material, ignoring the grains in the individual lattices. This results in a fairly smooth looking fracture with less sharp edges than one that follows the changing grains.122
3229527704solidus linealloys are entirely solid for temperatures and compositions below this curve123
3229527705solubility limitmaximum amount of solute that may be added to dissolve in a solution without forming a new phase.124
3229527706terminal solid solutionA solid solution that exists over a composition range extending to either composition extremity of a binary phase diagram.125
3229527707austeniteat 912 the ferrite turns into austenite and has FCC structure, more carbon is soluble126
3229527708cementitethe intermetallic compound Fe3C, a hard and brittle substance127
3229527709eutectic reactionupon cooling one liquid phase is transformed into two solid phases128
3229527710eutectic structureA two-phase micro-structure resulting from the solidification of a liquid having the eutectic composition; the phases exist as lamellae that alternate with one another129
3229527711eutectoid reactionSolid phase transforms to two different solid phases.130
3229527712ferritean interstitial solid solution of carbon in BCC iron131
3229527713free energyEnergy that is available to do work132
3229527714hypereutectoid alloyAn alloy with a greater concentration of solute than an alloy system that displays a eutectoid (to right in diagram)133
3229527715hypoeutectoid alloyAn alloy with a smaller concentration of solute than an alloy system that displays a eutectoid (to left in diagram)134
3229527716intermediate solid solutiona solid solution or phase having a composition range that does not extend to either of the pure components of the system135
3229527717intermetallic compoundcompound resulting from when atoms of the alloying element interact with the atoms of the base metal in definite proportions and in definite geometric relationships136
3229527718invariant pointany spot on a phase diagram where three phase are in equilibrium137
3229527719isomorphousHaving the same structure. When applied to a phase diagram, indicating that the solid phase has the same structure and hence complete solubility at every composition.138
3229527720lever rulemechanical analog for the mass balance with which one can calculate the amount of each phase present in a two phase microstructure139
3229527721liquidus lineline on a phase diagram above which only liquid exists at equilibrium140
3229527722pearlitea two phase microstructure of alternate ferrite and cementite lamellae occurring in some steels- forms by the decompositions of austenite141
3229527723peritectic reactionA reaction in which a solid and a liquid upon cooling at the peritectic temperature and composition, transform into a different solid. Ex: L+ S1 -> S2142
3229527724phaseAny part of a sample with uniform composition and properties143
3229527725phase diagramA graphic representation of the equilibria among the solid, and liquid phases of a substance as a function of temperature and weight percent.144
3229527726phase equilibriumequilibrium as it applies to a system where there are more than one phase.145
3229527727solidus lineThe line across the phase diagram below which all material is solid.146
3229527728solubility limitmaximum amount of solute that will dissolve in a given amount of solvent147
3229527729solvus linelines defining border between the pure solid phase and a blend of two solid phases on a phase diagram148
3229527730terminal solid solutionA solid solution that exists over a composition range extending to either composition extremity of a binary phase diagram.149
3229527731tie lineA horizontal line that extends across a two phase region at a particular temperature and intersects with the solubility limits of each phase in the two phase region.150
3229527732alloy steela form of steel containing carbon plus other metals such as chromium, cobalt, manganese, and molybdenum151
3229527733coarse pearlitethick layers of alpha-ferrite and Fe3C phases; at high temperatures high diffusion rates --> thick lamelle (layers); at low temperatures low diffusion rates --> thin lamelle152
3229527734fine pearlitethin alternating layers of cementite and pearlite and forms at low temperatures; diffusion rate is slower; harder and stronger than coarse pearlite, less ductile153
3229527735glass transition temperaturetemp at which a polymer changes from a rigid to rubbery structure; a feature of non-crystalline materials154
3229527736isothermal transformation diagramfigure used to summarize the time needed to complete a specific phase transformation as a function of temperature for a given material155
3229527737martensitehard and brittle steel structure formed after severe quenching.156
3229527738nucleationNucleation is the onset of a phase transition in a small region such as with the formation of a bubble or of a crystal from a liquid.157
3229527739overagingduring precipitation hardening, aging beyond the point at which strength and hardness are at their maxima158
3229527740phase transformationA change in the number and/or character of the phases that constitute the microstructure of an alloy.159
3229527741precipitation hardeningstrength and hardness increased by the formation of extremely small uniformly dispersed particles of a second phase within the original matrix, accomplished by heat treatments.160
3229527742precipitation heat treatmentA heat treatment used to precipitate a new phase from a supersaturated solid solution. For precipitation hardening it is termed artificial aging161
3229527743solution heat treatmentfirst step in age hardening that involves heating until one phase has completely dissolved the other162
3229527744spheroiditeproduct of austenitic transfomation; formed when steel alloy with either pearlitic or bainitc microstructures is heated to and left at temperature below eutectoid for 18-24 hours; sphere-like particle163
3229527745supercoolingWhen you cool something below its normal freezing point164
3229527746atomic mass unit (amu)a unit used to measure the mass of particles in atoms165
3229527747atomic numberNumber of protons in the nucleus166
3229527748Bohr atomic modelAtoms described as electrons orbiting the nucleus in well defined paths.167
3229527749bonding energyNet energy of attraction (or repulsion) as a function of separation distance between two atoms or ions168
3229527750covalent bondA chemical bond that involves sharing a pair of electrons between atoms in a molecule169
3229527751electron configurationthe arrangement of electrons in an atom170
3229527752electronegativethe ability of an atom of an element to attract electrons when the atoms is in a compound171
3229527753electropositiveWhen something is not at all electronegative. In fact, it tends to lose electrons rather than to gain them. Elements that are electropositive are generally to the left and bottom of the periodic table.172
3229527754hydrogen bondA type of weak chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule.173
3229527755ionic bondA chemical bond resulting from the attraction between oppositely charged ions.174
3229527756metallic bondA bond formed by the attraction between positively charged metal ions and the electrons around them.175
3229527757periodic tableA table that shows the elements, their atomic number, symbol, and average atomic mass; elements with similar chemical properties are grouped together.176
3229527758primary bondionic bonds, covalent bonds, metallic bonds177
3229527759secondary bondThese are uneven distribution of electrons around an atom or molecule the charge can be permanent or temporary weak or strong178
3229527760valence electronThe electrons in the outermost shell (main energy level) of an atom; these are the electrons involved in forming bonds.179
3229527761van der Waals bondformed when the fluctuating electrostatic charge in adjacent atoms of different molecules produces a weak electrostatic force between the molecules. Also present as a secondary bond between the long-chain molecules of polymers. Ice is an example.180

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