Uci Engr 54 Exam 2 Gust

Front 1

How does primary (transient) creep change?

Back 1

Creep rate decreases.

Front 2

How does secondary creep change?

Back 2

The creep rate is constant.

Front 3

How does tertiary creep change?

Back 3

The creep rate increases.

Front 4

What are the x and y axes of a graph of the mechanical or failure characteristics of metals?

Back 4

Time and strain, respectively.

Front 5

What are the consequences of either increasing stress or temperature?

Back 5

The rupture lifetime diminishes, and the steady creep rate increases.

Front 6

Above about what temperature does creep become an important failure mechanism for a metal?

Back 6

at 40% of the melting point of the material, T_m

Front 7

What four metallurgical/processing techniques are employed to enhance the creep resistance of metal alloys?

Back 7

unidirectional solidification of allows, increasing the grain size or producing a grain structure with a preferred orientation, dispersion strengthening by using an insoluble second phase and solid solution alloying

Front 8

The heating of a homogenous and isotropic rod of solid material for which axial motion is restrained, results in which type of thermal stresses?

Back 8

compressive

Front 9

What conditions must an alloy meet to have complete solid solubility?

Back 9

similar atom size, similar electonegativities, same valence, same structure for A and B and A and B don't form intermediate chemical compounds

Front 10

What is the solidus line in a phase diagram?

Back 10

The border between which an alloy switches between a solid and a solid-liquid solution.

Front 11

What is the solvus in a phase diagram?

Back 11

This border, from which an alloy switches between a mixed phase solution and single phase solution, denotes the solubility limit.

Front 12

What is a eutectic structure?

Back 12

This microconstituent, that is not a phase, is stable at room temperature because diffusion is very slow.

Front 13

What is precipitation hardening (strength hardening, age hardening?)

Back 13

This process creates a dense and fine dispersion of precipitated particles in a matrix of deformable metal.

Front 14

What are precipitated particles?

Back 14

These particles act as obstacles to dislocation motion.

Front 15

What is a non-equilibrium structure?

Back 15

The structure of an alloy consists of supersaturated solid solution.

Front 16

What is a quenching medium?

Back 16

Water or oil is typically the medium that is used to rapidly cool material to a lower temperature in the process of precipitation hardening.

Front 17

What is a supersaturated solid solution?

Back 17

This solid solution has a phase in which there is the same amount of metal B as in the overall composition rather than the equilibrium amount.

Front 18

What is natural aging?

Back 18

This process uses room temperature.

Front 19

What is artificial aging?

Back 19

This process uses a temperature that is usually 15-25% of the difference between room and solutionizing temperature.

Front 20

What is aging?

Back 20

This process is necessary to finely disperse precipitate forms that lower the energy state of the material.

Front 21

What is the principle difference between wrought and cast alloys?

Back 21

Wrought alloys are ductile enough so as to be hot or cold worked during fabrication, where as cast alloys are brittle to the degree that shaping by deformation is not possible and they must be fabricated by casting.

Front 22

What is gray cast iron?

Back 22

This metal or alloy is most suitable for for milling machine base.

Front 23

What is stainless steel?

Back 23

This metal or alloy is most suitable for walls of a steam boiler. It has excellent corrosion resistance and contains more than 11%wt Cr.

Front 24

What is titanium alloy?

Back 24

This metal or alloy is most suitable for high speed aircraft.

Front 25

What is tool steel?

Back 25

This metal or alloy is most suitable for a drill bit.

Front 26

What is aluminum?

Back 26

This metal or alloy is most suitable for a cryogenic (very low temperature) container.

Front 27

What is magnesium?

Back 27

This metal or alloy is most suitable for pyrotechnics (i.e. fireworks or flares.)

Front 28

What is platinum?

Back 28

This metal or alloy is most suitable for high temperature furnace elements to be used in oxidizing environments.

Front 29

What are the primary constituents of brass?

Back 29

Copper and Zinc

Front 30

Which type of nonferrous alloy is amenable to mechanical deformation?

Back 30

wrought

Front 31

What are desirable characteristics of the noble metals?

Back 31

high electrical conductivities, oxidation resistance and high ductilities

Front 32

What are mechanical properties characteristic of the refractory metals?

Back 32

high strengths and high melting temperatures

Front 33

What are Molybdenum, Tungsten, Tantalum and Niobium?

Back 33

These metals are refractory metals.

Front 34

What are Iron, Nickel and Cobalt?

Back 34

These metals are the primary superalloy metals.

Front 35

What is yield strength?

Back 35

The magnitude of the applied stress must at least exceed this strength during metal forming operations.

Front 36

increases hardenability

Back 36

How does increasing carbon content influence the hardenability of a steel?

Front 37

What is hardenability?

Back 37

This characteristic is a material's ability to form martensite throughout the entirety of a piece.

Front 38

true

Back 38

For crystalline ceramics, plastic deformation occurs by the motion of dislocations. (T/F)

Front 39

What are Tungsten carbide, Aluminum oxide, Silica sand, Silicon carbide and Diamond?

Back 39

These materials are used as abrasive ceramics.

Front 40

What are high temperature stability, high toughness, and high wear resistance?

Back 40

These properties are required for abrasive ceramics.

Front 41

What are iron and its alloys?

Back 41

These metals account for 90% of the world's production of metals.

Front 42

What is an iron-carbide system?

Back 42

This system has the combined benefits of good strength, toughness and ductility at relatively low cost.

Front 43

What is the reason for the common use of the Fe-Fe3C phase diagram?

Back 43

High carbon content alloys are not useful for most applications.

Front 44

What is ferrite?

Back 44

This alpha phase is an interstitial solid solution of carbon in BCC iron ((delta r)/r is large,) its maxium solubility of carbon in BCC iron is 0.022 weight percent carbon at 727 degrees Celsius and .008 percent weight carbon at room temperature, and this material is soft and ductile.

Front 45

What is austentite?

Back 45

This gamma phase is an interstitial solid solution of carbon in FCC iron, and its maximum solubility of carbon in FCC iron is 2.14% weight carbon at 1147 degrees Celsius and .76% weight carbon at 727 degrees Celsius.

Front 46

What is cementite (Fe3C?)

Back 46

This metastable phase (not equilibrium phase on phase diagram but stable at room temperature) is a stoichiometric , intermetallic, hard and brittle compound with a composition of 6.7% weight carbon and 93.3% wt iron.

Front 47

What is wrought iron?

Back 47

This soft and easy to form alloy has less than. 008% weight carbon and is used for pipes, certain gates and nails.

Front 48

What are steels?

Back 48

This alloy has between .008% and 2.14% weight carbon (in practice, typically less than 1%.)

Front 49

What is cast iron?

Back 49

This hard, brittle alloy fabricated by melting and casting with 2.14% to 6.7% weight carbon is used for engine blocks, high temperature gears and valves (applications depend on additional alloying elements.)

Front 50

What is the eutectoid reaction in an iron carbide system?

Back 50

This reaction occurs at 727 degrees Celsius with .76% weight Carbon.

Front 51

What is pearlite?

Back 51

This eutectoid microconstituent composed of cementite and ferrite is a lamellar structure that looks like mother of pearl under a microscope and has properties that lie between those of soft, ductile ferrite and hard, brittle cementite. It also needs carbon diffusion to occur, and its transformation is dependent on time and temperature.

Front 52

What is a hypoeutectoid?

Back 52

This structure has a carbon content between .22% and .76% which is less than that of the eutectoid.

Front 53

What is a hypereutectoid?

Back 53

This structure has a carbon content between .76% and 2.14% which is more than that of the eutectoid.

Front 54

What are austentite stabilizers?

Back 54

These elements - Mn, Ni, Co, N, Cu, Zn - lower the eutectoid temperature.

Front 55

What are ferrite stabilizers?

Back 55

These elements - Si, Cr, Mo, W, V, Ti, Al - raise the eutectoid temperature.

Front 56

What are reasons for alloys?

Back 56

These reasons are solid solution strengthening, increasing corrosion resistance and forming carbides (high hardness and T strength.)

Front 57

What is heat treatment of steels?

Back 57

This process can create different mechanical properties by varying heating/cooling temperatures.

Front 58

What is coarse pearlite?

Back 58

This eutectoid microconstituent is formed by rapidly cooling steel to just below the eutectoid temperature and holding it there. It has thick lamellar layers (fast diffusion of carbon.)

Front 59

What is fine pearlite?

Back 59

This eutectoid microconstituent is formed by rapidly cooling steel below the eutectoid temperature and holding it there. It has thin lamellar layers (slow diffusion of carbon.) It is stronger, harder and less ductile than its other form because it has more phase boundaries to impede dislocation motion.) It is also harder and stronger than austentite.

Front 60

What is bainite?

Back 60

This microconstituent forms at temperatures below the temperature for pearlite formation and forms needles or plates.

Front 61

What is speroidite?

Back 61

This microconstituent forms if alloy with pearlite or bainite structure is heated to just below eutectoid temperature and held for a long time.

Front 62

What is martensite?

Back 62

This microconstituent forms if steel is cooled rapidly enough (quenched) to prevent carbon diffusion. Its transformation is only dependent on temperature (independent of time) -> athermal transformation. It has a plate-like or needle-like appearance and a body centered tetragonal (BCT) structure. It is the hardest and strongest of all microconstituents. Its ductility is negligible (very brittle.) Its properties are related to interstitial carbon atoms hindering dislocation movement (solid solution strengthening) and the few slips systems in its BCT structure.

Front 63

What is tempered martensite?

Back 63

This microconstituent enhances ductility and toughness by relieving internal stresses in material without compromising much strength. It must be held at an elevated temperature and forms alpha structures with very fine particles of ferrite (reverts to BCC structure.) Tempering it for a very long time eventually leads to spheroidite.

Front 64

What are plain carbon steels?

Back 64

These materials contain carbon and .3 -.95%wt Mn (only residual concentrations of other impurities.)

Front 65

What are low carbons steels?

Back 65

These materials contain less than .25%wt carbon and are soft and weak with good ductility and toughness. Their strengthening is achieved by cold working (can't form martensite.) They are the least expensive of their class to produce and used for fenders, nails, wires and pipes.

Front 66

What are medium carbon steels?

Back 66

These materials contain .25-.6%wt carbon and are stronger than its lower carbon class. It has low ductility, toughness and hardenability and is used for gears, axles, bolts and shafts.

Front 67

What are high carbon steels?

Back 67

These materials contain between .6-1.4%wt carbon, are the hardest, strongest and least ductile of their class and use and used for knives, saw blades, chisels and hammers.

Front 68

What are alloy steels?

Back 68

These materials are created by adding elements to improve properties of their plain carbon class.

Front 69

What are high strength, low allow steels?

Back 69

These materials have less than 10%wt alloying additions. They have Cu, V, Ni and Mo added to their low carbon class to increase strength and corrosion resistance.

Front 70

What are heat treatable steels?

Back 70

These materials have Cr, Ni and Mo added to their medium carbon class to increase hardenability.

Front 71

What are tool and die steels?

Back 71

These materials have Cr, V, W and Mo added to their high carbon class to form very hard and wear-resistant carbides.

Front 72

What is ferritic stainless steel?

Back 72

This material contains very little carbon and 12-30%wt Cr, is strengthened by cold working and used for high temperature valves, combustion chambers and range hoods.

Front 73

What is austentitic stainless steel?

Back 73

This materials contains very little carbon, 16-25%wt Cr and 7-20%wt Ni, is strengthened by cold working, has the highest corrosion resistance of its class and is used for signs, wires and food processing equipment.

Front 74

What is martensitic stainless steel?

Back 74

This material contains .15-1%wt carbon and 12-17%wt Cr, is quenched to form martensite, has a composition chosen to optimize strength and hardness (has lowest corrosion resistance of its class) and is used for cutlery, bearings and surgical tools.

Front 75

What are ceramic materials?

Back 75

These materials are inorganic, non-metallic, (include glass) and consist of metallic ???

Front 76

What are tradition ceramics?

Back 76

These materials are made from clay, silica and feldspar and used for bricks, tiles and electrical porcelain.

Front 77

What are engineering ceramics?

Back 77

These materials are pure or nearly pure compounds (oxides, carbides and nitrides) and used for structural, optical, electrical and biological applications.

Front 78

What is an amorphous ceramic structure?

Back 78

Glass has this structure.

Front 79

What is a crystalline ceramic structure?

Back 79

This structure is determined by the size of ions (cation and anions) and magnitude of electrical charge on the ions (must maintain charge neutrality.)

Front 80

What is a rock-salt structure?

Back 80

This AX structure (AX structure: A=cation X=anion) has two interpenetrating FCC lattices and a coordination number of six for both cations and anions. NaCl, MgO, LiF and FeO have this structure.

Front 81

What is a cesium chloride structure?

Back 81

This AX structure is simple cubic (not BCC because ions are different types and has a coordination number of eight for both anions and cations. CsCl, CsBr, TiCl and TiBr have this structure.

Front 82

What is a zinc blende structure?

Back 82

This AX structure has anions that form the FCC structure and cations that occupy half of tetrahedral sites. Its coordination number is for both cations and anions is four. It is covalently bonded. ZnS, SiC, GaAs and CdS (many semiconductors) have this structure.

Front 83

What is a perovskite structure?

Back 83

This ABX3 structure has cations A with a coordination of 12, cations B with a coordination number of 6 and anions with a coordination number of 6. CaTiO3, BaTiO3, SrTiO3, CaZrO3 and LaAlO3 have this structure.

Front 84

What is a Frenkel point defect?

Back 84

This defect is when a cation moves to an interstitial site while still maintaining charge neutrality.

Front 85

What is Schottky point defect?

Back 85

This defect occurs when a missing cation and anion are missing.

Front 86

What is a flexural test?

Back 86

This method is used to determine the strength of ceramics. There are two types the three point and the four point. It is used more commonly than the tensile test with ceramics because it is difficult to make and handle ceramic tensile specimens.

Front 87

What is dislocation motion?

Back 87

This mechanism of plastic deformation is the same in ceramics as in metals.

Front 88

What are the reasons the small plastic deformation in ceramics?

Back 88

There are few slip systems (slip planes and slip directions) and low dislocation densities because of the charge neutrality requirement.

Front 89

What is a brittle fracture?

Back 89

This fracture allows little plastic deformation because the fracture strength depends on the flaw size.

Front 90

What are ways to increase fracture strength?

Back 90

Using the material in compression does not allow cracks to grow. The flaw size can be decreased by using fibers rather than bulk ceramic (smaller flaws in fiber because of smaller diameter.)

Front 91

What is the creep behavior in ceramics?

Back 91

At elevated temperature plastic deformation is time dependent. There is high resistance because of their high melting temperatures. This resistance can also be increased by increasing the grain size. It can be enhanced by adding a viscous grain boundary phase (add low melting temperature glass phase during powder processing of ceramics.)

Front 92

What are applications of refractory ceramics?

Back 92

These materials are used for heating elements, crucibles and furnace components.

Front 93

What are abrasive ceramics?

Back 93

These materials have high hardness and wear resistance. Diamond is the hardest but most expensive. SiC, WC, Al2O3 and SiO2 are often used as this material.

Front 94

What is the application of cement?

Back 94

This material is used to bind aggregates chemically such as sand and gravel to create concrete.

Front 95

What are heat engines?

Back 95

Ceramics have advantage over metals in these applications because of higher operating temperature, wear resistance, corrosion resistance and lower density. The drawback for this application is the brittle fracture of ceramics (researching to improve Kic.) Si3N4, SiC and ZrO2 look promising.

Front 96

What is electronic packaging?

Back 96

In this application ceramics are used for heat dissipation and electrical insulation in packaging of integrated circuits (becoming increasingly more important with miniaturization of electronics.) BN, SiC and AlN are often used in this application.

Front 97

What are piezoelectric ceramics?

Back 97

These materials convert electrical energy into mechanical energy and vice versa, are used in microphones, sonar detectors and strain gauges and include BaTiO3, PbTiO3, PbZrO3, PZT and quartz.

Front 98

What are microelectromechanical systems (MEMS?)

Back 98

These devices are integrated systems combining both electrical and mechanical components, fabricated on Si using IC processing technologies (research being done on ceramics that are tougher, more refractory and more inert than Si.) Its applications include microsensors and microactuators. It is currently being used as an accelerometer in air bag systems in cars (collision detector.)

Front 99

What are ceramic ball bearings?

Back 99

These materials have the advantage of being used at higher speeds, less noisy, longer life and corrosion resistance. The challenge is in the their processing/fabrication. Its uses include inline skates, bicycles, high speed dental drills, surgical saws and food processing equipment.